Chemistry

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Removal of heavy metals from wastewater using raw diatomite and manganese oxide-diatomite composite
(Chuka University, 2024) Mwangi Samuel King’ori
Access to clean water is a basic human right, however about 43% of the population in Kenya do not have access to clean water mainly due to water pollution. Most industries and wastewater treatment plants in the country discharge their effluents laden with heavy metals such as Cd and Pb into the environment at levels exceeding the maximum limits setup by NEMA. Pb (II) and Cd (II) ions are toxic to humans, therefore, there is a great need to remove them from wastewater before discharge into the environment. Adsorption is an effective method in remediating wastewater laden with heavy metals, but the high cost of adsorbents limits its application in developing countries such as Kenya. This study aimed at synthesizing MnO2−diatomite composite, characterizing and using both raw diatomite and MnO2−diatomite composite as low-cost adsorbents for the removal of Pb (II) and Cd (II) ions from aqueous solutions. The raw diatomite obtained from the African Diatomite Industries Limited (ADIL) in Kariandusi, Gilgil, Nakuru County, Kenya was used to prepare MnO2−diatomite composite by acid reduction of KMnO4−diatomite mixture at room temperature using 6M HCl acid. These adsorbents were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) techniques. Both raw diatomite and MnO2−diatomite composite were found to be mainly composed of silica and alumina with hydroxyl (-OH), silanol (Si-OH), siloxane (Si-O-Si) and aluminosilicate (Al-O-Si) functional groups. In addition, the adsorbents were amorphous in nature with BET surface area of 32.29m2/g for raw diatomite and 30.48m2/g for MnO2-diatomite composite. The surface area and porosity of the MnO2-diatomite composite was lower compared to raw diatomite due to the blocking of pores by MnO2 particles during the modification process. Batch adsorption experiments were carried out to optimize the effects of pH, initial metal ion concentration, contact time, adsorbent dosage and temperature on the percentage removal of Pb (II) and Cd (II) ions from single ion and binary ion solutions. For single ion studies, the optimal conditions for Pb (II) adsorption were initial metal concentration 10mg/L, contact time 60 minutes, temperature 25 oC, pH of 4 (raw diatomite) and pH of 6 (MnO2-diatomite composite) and dosage of 4g/L (raw diatomite) and 6g/L (MnO2-diatomite composite). Optimal adsorption conditions for Cd (II) were initial metal concentration 10mg/L, pH of 6, contact time 80 minutes, temperature 65 oC, adsorbent dose 6g/L (raw diatomite) and 8g/L (MnO2diatomite composite) resulting in 100% removal. Raw diatomite had higher removal efficiency of Pb (II) and Cd (II) ions compared to MnO2-diatomite composite since it had a larger surface area and porosity, therefore, it was chosen for adsorption of heavy metal ions from Pb-Cd binary mixture. For binary ion studies, optimal conditions were pH of 6, initial metal ion concentration of 10mg/L each, contact time 80 minutes, adsorbent dosage 10g/L and temperature of 65 oC. The removal efficiency of the metal ions from binary solutions was lower compared to that of single ion solutions. The order of removal of the heavy metal ions by both adsorbents was Pb (II)>Cd (II) ions. Adsorption kinetics and isotherm analysis of experimental data showed that the adsorption of Pb (II) and Cd (II) ions by the adsorbents was well described by pseudo-second order kinetic model and Langmuir isotherm model respectively. Thermodynamic parameters namely Gibbs free energy (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were evaluated and revealed that the adsorption process was feasible and spontaneous. ΔH° indicated that Pb (II) ions adsorption was exothermic process while Cd (II) adsorption was an endothermic process. Equilibrium studies demonstrated that both raw diatomite and MnO2-diatomite composite were efficient in the removal of Pb (II) and Cd (II) ions from aqueous solutions. The results of this study indicate that both raw diatomite and MnO2-diatomite composite are effective in heavy metal remediation, therefore, they should be employed as low-cost adsorbents in the treatment of industrial effluents laden with heavy metals.
Hybridized convolutional long short-term memory and support vector machines model for violence detection in surveillance footage
(Chuka University, 2024) Muiruri Samuel Muigai
There has been widespread use of Closed-circuit Television (CCTV) surveillance cameras in both public and private settings to increase security. The bitrate for an FHD (Full High Definition) camera operating at thirty frames per second (30 fps) with moderate compression is eight megabits per second (Mbps). Based on the assumption of this bitrate and a twenty-four-hour recording period, the approximate daily data output of a single FHD camera would then amount to approximately eighty-six Gigabytes (86 GB). Monitoring and analyzing all of this material footage is challenging due to the large volume of the video data. Consequently, machine learning models have been utilized to automate analysis of surveillance footages in order to detect any forms of violence. While these models have demonstrated promising outcomes, they continue to face challenges in terms of processing speed and accuracy, particularly in the extraction of spatiotemporal features. This study developed a model based on the Convolutional Long-Short-Term Memory and Support Vector Machines (ConvLSTM-SVMs) approach for detecting violence in CCTV surveillance footage. Convolutional Neural Networks (CNNs) are a type of deep neural networks that are made to handle organised grid data, like images. Long Short-Term Memory (LSTM) networks belong to the family of Recurrent Neural Networks (RNNs) and are designed for processing sequential data. Support Vector Machines (SVMs) are a type of supervised machine learning method used for tasks like regression and classification. The integration of CNNs, LSTM networks, and SVMs leverages the unique advantages of each design, resulting in a comprehensive approach. The model was developed, trained and tested using the Keras library running on TensorFlow, using an experimental research design. The impact of various hyper-parameters on the performance of the hybridized model was investigated, and the results used to optimize the model for better performance. The UCF-Crime dataset was used for model training, validation, and testing, while the RWF-2000 dataset was used for external validation. The training data was augmented to ensure the model was well trained on the wide range of violent and non-violent activities it may experience in real-world settings. The model’s performance was evaluated, and a comparative table used to compare the speed and recognition accuracy of the hybrid model against that of similar existing state of the art models. With an accuracy of 97.8%, the Conv-LSTM-SVM model demonstrated its potency in identifying violent action in surveillance footage, against 75%, 80% and 97% of the LSTM, CNN, and Convolutional Long-Short-Term Memory (Conv-LSTM) models respectively. Even though the Two-Stream Fusion CNN model demonstrated a marginally greater accuracy of 97.8%, the hybrid model demonstrated relatively higher computational efficiency with a low inference time of 36 milliseconds, and a training time of nine hours. Experimentation revealed that optimal regularization can be achieved by using a dropout rate of 0.5, learning rate of 0.001 and a batch size of 32. The Adam optimizer demonstrated the most rapid convergence, achieving experimental convergence in a span of 145 minutes. When tested on an unseen heterogeneous RWF2000 dataset, the model verified cross-domain viability with 91.3% detection accuracy without retraining. The excellent performance and efficacy in accurately identifying violent behaviour make the hybrid model a feasible tool for enhancing public safety and security in a range of surveillance scenarios.
Green synthesis, characterization and antimicrobial activities of selected Schiff bases
(Chuka University, 2024) Nyaga Jackline Njeri Nyaga
Antimicrobial resistance is a serious global health challenge with alarming rates of emergence and spread of resistant microbes necessitating the development of novel antimicrobial agents. Schiff bases, also called imines or azomethines are synthesized from the condensation of aldehydes and amines. They have multiple properties including antibacterial and antifungal properties. Synthetic procedures of Schiff bases often involve the use of catalysts and solvents. The disposal of the latter, often leads to environmental pollution hence the need for the development of novel procedures that are applicable, environmentally friendly and economically realistic. Schiff bases were synthesized through grinding (for the solid aldehydes and amines) and stirring (for liquid aldehydes and amines) techniques without the use of catalysts and solvents in this work. This led to reduced reaction times, clean products, reduced possibility of pollution, no need for extra work up in the removal of solvents and catalysts and easy handling of the reagents. Six Schiff bases were synthesized. Schiff base S1, from benzaldehyde and 4-aminophenol, S2 from 4-aminophenol and 4-nitrobenzaldehyde, S3 from 4-aminophenol and salicylaldehyde, S4 from aniline and 4-nitrobenzaldehyde, S5 from aniline and salicylaldehyde and S6 from aniline and benzaldehyde. The compounds melted at constant temperatures demonstrating their purity. Characterization of the Schiff bases was done using FT-IR, UV-VIS and NMR (proton and carbon NMR) spectroscopy. Sharp IR peaks at 1628.95- 1617.38 cm-1 in the IR spectra of the compounds confirmed the formation of the imine bond, C=N. The disappearance of the carbonyl C=O peak at around 1600 cm-1 further confirmed the conversion of the aldehydes to imines. Free O-H broad bands were observed at 3447.91- 3339.29 cm-1. In compound S3, the O-H band was shallow and broad which was attributed to keto-enol tautomerism. In the UV-Vis spectra, bands at 261.40- 287.60 nm were observed corresponding to the n–π transitions of the azomethine C=N bond. NMR peaks at 7.26- 7.54 ppm for 1H NMR and 161.15- 158.34 ppm for 13C NMR further confirmed the presence of the imine protons and imine carbon atoms respectively. The disappearance of free NH2 peaks which usually occurs at 4.00- 6.00 ppm showed that the amines had been converted to imines. The synthesized compounds were subjected to antibacterial susceptibility tests against three Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi), one Gram-positive bacteria (Staphylococcus aureus) and one fungi Candida albicans at concentrations of 500 ppm, 250 ppm and 125 ppm. The zones of inhibition developed from 7.16- 20.00 mm on all the organisms at all concentrations indicating that all the compounds were biologically active. The data was analyzed using One- Way Anova. Significant difference between the means indicated that compounds with nitro and hydroxyl substitution had greater activity against gram negative bacteria while the compound lacking the substitution had better activity against gram positive bacteria. The compounds also showed better antifungal activity against Candida albicans than the positive control. This indicated that the compounds had great potential for development of antibacterial and antifungal drugs.
Determination of Physico-Chemical Parameters and Removal of Bis(2-Ethylhexyl) Phthalate from Wastewater Using Prosopis juliflora Biochar/Carbon Nanotubes Composite Adsorbent
(Chuka University, 2024) Mutua John Mutinda
Phthalates, such as BEHP, are endocrine-disrupting compounds commonly used as plasticizers. Their presence in wastewater, often from industrial and household effluents, poses health risks including congenital anomalies, cancer, and chronic toxicity. The high cancer prevalence in Meru County has been linked to toxicants in effluent released into Kathita River, used for domestic purposes and irrigation. This is attributed to the inefficiency of the lagoon wastewater treatment technology in removing chemicals like BEHP. This study evaluates the physico-chemical properties and BEHP levels in wastewater from Meru Sewage Treatment Plant and explores the adsorption of BEHP using a Prosopis juliflora biochar/carbon nanotubes composite adsorbent. The temperature, pH, conductivity, turbidity, TDS, TSS, BOD and COD of the wastewater were determined using the standard APHA methods for wastewater, the concentrations of heavy metals using AAS while those of BEHP using HPLC. The following mean values were reported after data analysis: BEHP 0.055mg/L, Cu ND, Pb 0.042mg/L, Cd 0.0019 mg/L, COD 65.99 mg/L, TSS 29.3mg/L, TDS 639.17mg/L, turbidity 117.9FTU, conductivity 1079.9µS, pH 7.3, temperature 26oC and BOD5 65.9 mg/L; for dry season. Only pH and COD exceeded WHO limits for wastewater discharge into environment. The wet season parameter mean values were: COD 359.7mg/L, TSS 198.3mg/L, TDS 2094.2mg/L, turbidity 105FTU, conductivity 1244µS, pH 8, temperature 26 , BEHP 0.0429mg/L, Cu 0.47mg/L, Pb 0.037mg/L, Cd 0.056mg/L and BOD5 71.2mg/L. The temperature, TDS, BOD, Cu and Pb met WHO limit while conductivity, turbidity, TSS, COD and Cd exceeded. The composite adsorbent was characterized using FTIR and powder XRD. The dominant functional groups of the composite were C=O, CO2, OH-, Si-OH, C=N, MgO, CaCO3, and SiO2. The composite adsorbent was very efficient in the adsorption of BEHP with up to 96% removal in the samples at determined optimum adsorption parameters of; pH 5, temperature 24 , 15 minutes contact time and an adsorbent dose of 200 mg. The isotherm studies showed that the adsorption process was in agreement with the Freundlich isotherms with R2 value of 0.90469 while the kinetic studies revealed that BEHP adsorption followed pseudo second order model with R2 of 0.994. It was concluded that the application of biochar/CNTs composite adsorbent for the removal of BEHP from the wastewater is relatively cheaper and eco-friendly and should be applied for treatment of wastewater for irrigation and domestic use to improve water quality and minimize health risks associated with BEHP.
Determination of physicochemical parameters and estriol levels in nyeri waste water treatment plant and the adsorption of estriol using sugarcane bagassemultiwalled carbon nanotube composite
(Chuka University, 2024) Njue Jediel Mwenda
Persistent organic pollutants and endocrine disrupting substances have been found to be highly resistant to degradation. Exposure to these chemicals interferes with normal functioning of endocrine system by causing adverse effects such as cancer and impaired neurodevelopment. Waste water treatment plant mostly concentrate on removal of microorganisms leaving behind micro contaminants such as Estriol. The objective of the study was determination of physicochemical parameters and Estriol levels in Nyeri sewage treatment plant and the removal of Estriol using carbon nanotubes-sugarcane bagasse composite adsorbate. The composite was synthesized by oxidizing Multiwalled carbon nanotube in a ratio 3:1 nitric (V) acid to sulphuric (VI) acid mixture. Multiwalled carbon nanotube were then washed with deionized water and then added to a suspension of sugarcane bagasse powder in a ratio of 100:1 ,100:0.5 and 100:0.1. The characterization of the composites was done using Fourier transform infrared spectroscopy and X-ray diffraction techniques. The results showed that turbidity was higher in the dry season at 103.954 NTU compared to 46.5647 NTU in the wet season. Cd was recorded at 0.0168 mg/L during the wet season, which is significantly higher than the 0.0015 mg/L observed in dry season. Copper exhibited a concentration of 0.0833 mg/L in the wet season, which increased substantially to 1.0172 mg/L in the dry season. For Lead, the wet season value was 0.0159 mg/L, while the dry season value of 0.0050 mg/L. Dissolved Oxygen decreased markedly from 7.0617 mg/L in the wet season to 2.2396 mg/L in dry season. These differences in Pb, Cu, and DO levels were confirmed to be statistically significant p < 0.05 based on the Fisher’s LSD test with Bonferroni correction for p-value adjustment. Electrical Conductivity increased from 695.782 µS/cm in the wet season to 1056.104 µS/cm in the dry season. A t-test was conducted to compare Estriol concentrations between the wet and dry seasons at the Nyeri Water Treatment Plant. The mean Estriol concentration during the dry season was 1.444 ±0.671 Mg/L while in the wet season it was 0.982 ±0.870 Mg/L. The mean difference between the two seasons was 0.463, with a weighted standard deviation of 0.777. The optimum conditions obtained from the adsorption of Estriol were; equilibrium time 10 minutes, pH 4, maximum adsorbate concentration adsorbed at 0.1 g of composite 2 was 8 ppm. The composite that gave the best results was composite 2 (100:0.5) with 76.7% adsorption efficiency. The kinetic analysis of estriol best fitted the pseudo first order model with the rate constant for reaction as k1=−0.1−1, with an R2 value of 1.0. The analysis of adsorption isotherms for Estriol indicated that the Langmuir model provided a good model for fitting adsorption data than the Freundlich model, with a higher R² value of 0.5280 compared to 0.439 in Freundlich model. The enthalpy change (ΔH) for the process was calculated to be 26,165.44 J/mol, indicating that the adsorption is endothermic, meaning it absorbs heat from its surroundings. The entropy change (ΔS) was positive 68.85 J/mol-K suggesting an increase in disorder at the solid-liquid interface during adsorption. The Gibbs free energy change (ΔG) was negative at all the tested temperatures showing that the process naturally progresses without the need for external energy input.The findings demonstrated that sugarcane bagasse-carbon nanotube composite is a good low cost and environmentally friendly adsorbent for removal of Estriol from waste water.
Determination of physicochemical parameters and remediation of Pb (ii) using a composite of moringa oleifera seeds and kaolin clay in borehole water within Nakuru east sub county, kenya
(Chuka University, 2024) Kiprono Geofry
The contamination of borehole water in Nakuru East Sub County, primarily due to heavy metals and non-metals from natural origins and anthropogenic activities, poses significant health risks. Exposure to these contaminants, beyond the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) limits, can lead to various diseases and even death. Activities such as industrial processes, agriculture and waste disposal in the area contribute to the infiltration and leaching of toxic elements into borehole water. These toxic elements can enter the human body through ingestion, inhalation or dermal absorption. The Nakuru Water and Sanitation Service Company (NAWASSCO) operate 40 boreholes in the region; however, only 19 were functional during the sample collection, which took place in both dry and wet seasons. These boreholes supply water to Nakuru City and surrounding areas. This study aimed to determine the levels of physicochemical parameters and remediation of Pb (II) from these boreholes. Water samples were collected from six water fields: Kiundo (1 borehole), Kabatini (6 boreholes), Nairobi Road (6 boreholes), Baharini (4 boreholes), Madaraka (1 borehole) and Olbanita (1 borehole) during both seasons. The samples were analyzed for various parameters including Temperature, pH, Turbidity, Electrical Conductivity, Dissolved Oxygen, Fluoride, Lead (Pb), Cadmium (Cd) and Arsenic (As), with heavy metal concentrations measured using Flame Atomic Absorption Spectroscopy (FAAS). Results indicated that the temperature of the borehole water ranged from 23.8 to 26.4 ±0.2°C. Dissolved Oxygen levels were found to be below WHO acceptable limits in all samples. Turbidity levels ranged from 1.54 to 4.32 ±0.01 in the dry season and 0.36 to 9.30 ±0.02 in the wet season, with 36.8% of samples exceeding WHO limits in the dry season and all samples exceeding limits in the wet season. pH values were between 6.4 and 7.6 ±0.1 in the dry season and 7.0 to 7.7 ±0.2 in the wet season, mostly within WHO guidelines, except for a few boreholes that were slightly acidic. Electrical conductivity ranged from 392.0 to 823.1 ±0.1 mS/cm in the dry season and 186.7 to 350.6 ±0.2 mS/cm in the wet season; with all dry season samples above the WHO threshold of 400.0 mS/cm. Flouride had the same mean concentrations of 1.23mg/l for both the two seasons. Significant differences (P≤0.05) were noted between the physicochemical parameters and WHO standards. Correlations among parameters were observed, ranging from negative to positive (p < 0.001). Cd concentrations were below detection limits in all samples for both seasons, while Pb (II) levels exceeded the WHO limit of 0.01 mg/L in 31.6% of boreholes during the dry season and 42.1% in the wet season. Arsenic concentrations were above the WHO limit of 0.01 mg/L in both seasons. To address the contamination, a composite of Moringa oleifera seed powder obtained from Tharaka Nithi County and pure kaolin clay were used as an adsorbent for Pb (II). Characterization of the composite was conducted using Powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The adsorption study focused on Pb, revealing that the base-activated composite effectively adsorbed Pb at a dosage of 0.5 g. The adsorption data fit the Langmuir isotherm, Temkin, and Pseudo-Second-Order models. Thermodynamic studies yielded values of 25,340.57 J/mol for ΔH, 58.32 J/mol/K for ΔS and a decrease from 7.95 kJ/mol at 25°C to -3.71 kJ/mol at 225°C for ΔG. The adsorbate was effective at 83.77% in sample NR7.The results obtained indicated the urgent need for water treatment due to elevated levels of As (III) and Pb (II). The composite showed a positive effectiveness on the remediation of Pb (II), however further research should be carried out to investigate its effectives on other heavy metals remediation and outside the boreholes of the study area.
Determination and removal of selected heavy metals in treated wastewater from Ruai sewage treatment plant for possible agricultural applications
(Chuka University, 2024) Kakuta Peace Kaviti
Fresh water has become scarce and many arid and semi-arid regions in the world suffers from water shortage. Wastewater reuse remains the only reliable and potential source of water. One of the major challenges in recycling of wastewater is the presence of toxic heavy metals which are persistent and non-biodegradable and are known to affect human health. This study sought to synthesize and characterize soda lime and borosilicate waste glass and a composite of Multi-walled Carbon Nanotubes (MWCNTs)/soda lime waste glass adsorbents and utilize them for removal of Pb2+ from wastewater. Glass wastes were collected within Chuka University and MWCNTs purchased from Hongwu International Group Ltd. The adsorbents were washed, dried, functionalized with nitric-sulfuric acid mixture and characterized using FTIR. Wastewater samples were collected in Ruai wastewater treatment plant, Kenya using grab method, transferred to 250 ml plastic bottles and were transported to Chuka university for analysis in a cooler box at 4oC. Standard laboratory procedures of determining the physicochemical parameters were employed. Batch adsorption experiments were conducted to study the effect of contact time, pH, temperature, shaking speed, initial adsorbate concentration and adsorbents dosage on removal of lead (II) ions. Residual Pb2+ concentration was determined using AAS. The findings were: pH 5.5-7.9, Temperature 22.70C-26.10C, Conductivity 526.7- 1209.7µS, turbidity 73- 1000 NTU, nitrates 6.66-25.1 mg/l, Phosphorus 1.16-10.30 mg/l, BOD5 ranged from 10-480 mg/L, COD 90-980 mg/L, TSS 14-422 mg/L, and TDS 244-967 mg/L. pH, temperature, NO3-, BOD5(wet season) results met the WHO and NEMA standards for wastewater reuse in irrigation while EC, turbidity, P, COD, BOD5(dry season), TDS and TSS did not. The results of heavy metals were Ni 0.02-0.22 mg/L, Zn 0.03-1.67 mg/L, Cu 0.01-0.23 mg/L, Cd 0.01-0.05 mg/L, Fe 0.05-7.24 mg/L, Mn 0.14-2.26 mg/L, and Pb 0.04-0.78 mg/L. The levels of Zn, Cu, and Ni were within WHO and NEMA standards while Cd, Mn, Pb and Fe did not meet the threshold at some sampling points. All the metals studied met the FAO guidelines for reuse of wastewater in irrigation. Characterization of the adsorbents was done using FTIR which displayed the dominant functional groups to be silanols, hydroxyls, carboxylic and carbonyl groups. Adsorption of lead (II) ions was conducted using a composite of soda lime waste glass and multiwalled carbon nanotubes, borosilicate and soda lime waste glass. The composite and borosilicate adsorbents reported 100% adsorption of lead (II) ions while soda lime was average. Adsorption of Pb (II) ions followed Freundlich isotherms for borosilicate and soda lime adsorbents with r2 of 0.8665 and 0.9257 while Composite had a better fit in Langmuir isotherm with r2 of 0.9446. Cd (II) and Ni (II) ions did not interfere with adsorption of lead (II), but a stiff competition for the adsorption sites was observed for the case of Mn (II) ions. Regeneration efficiencies of 99.61%, 97.45%, and 99.82% were observed for borosilicate, soda lime, and composite adsorbents. The findings of this study clearly showed that soda lime waste, borosilicate waste glass and composite of soda lime waste glass/MWCNTs are effective for the removal of lead (II) ions from waste water.
Synthesis, characterization and antibacterial Properties of copper (II) complexes of schiff bases derived from benzophenone derivatives and selected anilines
(Chuka University, 2024) Kosgei Festus Kimutai
In every region of the world, antibiotic resistance is increasing to dangerously high levels. The emergence and global dissemination of new bacterial resistance threaten human beings' capacity to cure widespread infectious diseases. As antibiotics lose their effectiveness, many infections, including blood poisoning, pneumonia, and tuberculosis, become difficult to cure and occasionally incurable. Therefore, there is a pressing need to develop new antibacterial agents to address this resistance. Thus, this study entailed synthesizing, characterizing, and determining the antibacterial activities of the Schiff base and its copper (II) complexes. The Schiff base ligands were synthesized by mixing 2-hydroxy-4-methoxybenzophenone with selected anilines in a 1:1 ratio, followed by refluxing for 3-4 hours. The precipitate obtained was filtered and dried at room temperature. The Cu (II) complexes were prepared in a 2:1 ratio by treating a hot solution of Schiff base ligands dissolved ethanol with an aqueous Cu (II) chloride under 4 hours of refluxing. The synthesized compounds melted at a constant temperature, confirming that they were pure. The Schiff base ligands and their Cu (II) complexes were characterized using various analytical techniques such as Fourier Transform-Infrared (FT-IR), Ultra Violet-Visible (UV-VIS) and Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy and molar conductance measurements. The FT-IR data of the Schiff base ligands displayed the absence of NH2 and C=O, confirming the formation of azomethine group (-HC=N-) at region 1610-1631.78cm1 which shifted to lower wavelengths upon complexation with Cu (II) ions. The peak due to OH appeared at 3420-3450 cm-1 but later disappeared due to formation Cu (II) complex. The appearance of two new peaks 475.46-480.28 and 523.68581.55cm-1 in the Cu (II) complex spectra attributed to Cu-O and Cu-N, respectively. UV-vis spectra of the free ligands appeared at 40322.58-41580cm-1 due to the transition of non-bonding electrons of azomethine nitrogen. Molar conductance measurements of Cu (II) complexes range from 13.34-22.208(Scm2mol-1), while that of free ligands range from 4.86-12.58 (Scm2mol-1), confirming they were nonionic. 1H NMR analysis of free ligands in deuterated DMSO-d6 revealed the presence of the presence of OH group at δ 11.81-12.65 ppm, which disappear upon complexing with Cu (II) ions. The antibacterial sensitivity levels of the Schiff base ligands and their Cu (II) complexes were determined using the disk diffusion method. The synthesized compounds tested for antibacterial bioassay against two gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli and one gram-positive bacterium, Staphylococcus aureus, at 4 different concentrations. All synthesized compounds show antibacterial activities against all bacteria strains. The zones of inhibition ranged from 6.00- 21.00 mm. However, no test compound showed higher inhibition zones than gentamycin and amoxiclav (positive controls). Data was analyzed using Two-Way ANOVA. The results showed a significant difference (p ≤ 0.05) between the means, indicating that methyl, nitro and carboxyl groups and coordination of the ligands to Cu (II) affected antibacterial activity. Cu (II) complexes displayed higher antibacterial activity than their free ligands. It was concluded that the substituted ligands with methyl, carboxyl and nitro groups and Cu (II) complexes have promising antibacterial activity. The results suggest potential applications of Schiff base ligands obtained from benzophenone derivatives and their Cu (II) complexes as antibacterial agents.
Synthesis, characterization and antibacterial activity of Ruthenium (II) complexes of Bidentate Schiff base ligands
(Chuka University, 2024) Nyang’ate Shem Ongechi
Increased bacterial resistance to available antibiotics remains a concern globally; therefore, there is a need for novel antibiotics with unique mechanisms of action to combat multidrug-resistant organisms. This is important in ensuring that both the human and animal health is well protected. Schiff bases containing pyridine imine pharmacophore possess significant antibacterial activity. The objectives of this study were to; – Prepare ruthenium (II) complexes of bidentate Schiff base ligands – Investigate the complex formed – Perform bioassay of the prepared complexes on some selected bacterial strains. The Schiff base ligands were synthesized by reacting 4-bromoaniline, 4-aminophenol, and aniline with 2-pyridine carboxaldehyde in a 1:1 ratio, while refluxing the mixture for 3-4 hours. To obtain the respective ruthenium (II) metal and ruthenium cymene complexes, hydrated ruthenium (II) chloride and ruthenium p-cymene were combined with the Schiff base ligands in a 2:1 ratio, followed by heating for 3 hours under reflux. The characterization process of the complexes involved proton nuclear magnetic resonance spectroscopy, melting point determination, UV/VIS spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). In the FT-IR spectra, the peaks related to C=N symmetrical vibration appeared in the range of 1600 cm ¹–1620 cm ¹, which shifted as compared to the free pyridine-imine ligands (1632–1625 cm ¹), confirming the intended complex formation. The UV-vis spectra of the ligands exhibited the absorption bands in the ranges of 275-337 nm which correspond to the transition of non-bonding electrons of azomethine nitrogen. After the complexation process, it was observed that the bands corresponding to the n→π* transition for the azomethine present in the bidentate ligand shifted to the lower frequencies indicating the interaction of imine nitrogen atoms with the metal ion. The synthesized ligands and their metal complexes were evaluated for antibacterial activity against two bacterial strains: Staphylococcus aureus which is Gram-positive and Escherichia coli which is Gram-negative, by disc diffusion method with four concentrations. The zones of inhibition were between 8 - 17 millimeters, therefore did not surpass the inhibition zones of gentamicin which was used as the positive control. Statistical analysis using two-way ANOVA highlighted that there was a difference (p ≤ 0.05) in the means of the different values to some extent, suggesting that the hydroxyl and bromo groups, as well as the ability of ligands to coordinate with ruthenium (II), were responsible for mediating antibacterial activities. It was also observed that, Ruthenium (II) complexes were more active against the bacterial strains than the free Schiff base ligands. Also, complexes formed with substituted Schiff base ligands, 4-aminophenol and 4-bromoaniline exhibited higher antibacterial activity compared to complexes formed with unsubstituted Schiff base ligands. Based on these results, it can be suggested that the synthesized compounds possess potential antibacterial activity.
Synthesis, characterization and application of copper oxide-zirconia-titania ternary system for removal of methylene blue dye in waste water
(Chuka University, 2024-10) Kinuthia Miriam Wanjiru
Contamination of water sources due to the increasing industrial processes is a major threat to human health as well other living organisms. Industrial wastes are a major pollutant especially since various industries discharge their waste without any treatment or after minimal treatment. Therefore, there is need to develop remediation technique that is cost-effective, environment friendly and effective in the removal of the industrial waste that ends up in water sources. This study sought to synthesize, characterize and use copper oxide-zirconia-titania ternary oxide for removal of methylene blue dye from waste water. The ternary oxide was prepared by Pechini method. Methylene blue aqueous solution was prepared at Chuka University laboratory. Effects of pH, temperature, concentration of adsorbate, time and dosage amounts on adsorption of methylene blue dye was determined using UltravioletVisible(UV-Vis) spectrophotometer. Characterization of the adsorbent was carried out by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Powder X-ray diffraction (XRD) and Fourier transform Infrared (FT-IR) spectroscopy. SEM micrographs showed particles with non-uniform distribution and different particle sizes. Deposits onto the surface of the larger particles seemed to be uneven and porous which is characteristic of a high surface roughness, suitable for adsorption. FTIR analysis displayed functional groups such as carbonyl groups, hydroxyl groups as well as stretching vibrations of the ZrO2, CuO and TiO2. XRD analysis exhibited a single major peak revealing that the ternary oxide calcined at 500ºC was amorphous. EDS analysis showed that all the chosen areas of the analysis contained the primary elements which were zirconium, titanium, copper and oxygen Adsorption isotherm models (Langmuir, Freundlich) and Temkin and adsorption kinetic studies (pseudo-first order, pseudo-second order) were used for data analysis. The results showed that adsorption was affected by pH, temperature, initial concentration, dosage amounts and contact time. Adsorption experiments followed pseudo second order model with r2 of 0.99987.The adsorption process followed the Langmuir and Temkin isotherms with r2 of 0.90219 and 0.93641 respectively. These findings clearly show copper oxide-zirconia-titania ternary oxides can be employed as novel adsorbents to solve the problems of water and wastewater treatment.
Synthesis, characterization and antimicrobial properties of heterocyclic N, N’- bidentate ligands and their transition metal (ii) complexes
(Chuka University, 2024) Otao Kevin Nyarango Otao
Antimicrobial resistance has been named one of the greatest global threats to the health sector as many microbes are no longer susceptible to the drugs known to kill them, making diseases harder to treat or prevent. Efforts to develop new antibacterial agents with novel mechanisms of action, higher activity, and improved selectivity are crucial to address and counter antibiotic resistance. This study aimed at synthesizing and characterizing N, N’-bidentate ligands together with their copper and zinc complexes. The reaction of equimolar quantities of the selected hydrazinyl pyridazines with a diketone resulted in the formation of the expected pyrazolylpyridazines. The transition metal (II) complexes were obtained by the reaction of the metal chlorides with the synthesized ligands in the ratio 1:2. The synthesized ligands and the complexes were characterized using the melting point determination, molar conductivity measurements, FT-IR spectroscopy, UV-VIS spectroscopy, and 1H-NMR spectroscopy. The ligands melted at lower temperatures compared to the complexes (72, 141 and 148 °C for L1, L2 and L3 respectively). It was observed that the complexes decomposed in the range of 268-320 °C and that decomposition temperature was dependent on the increase in the molecular weights of the complexes. Conductivity measurements revealed that all the compounds are non-electrolytes with their conductivities in the range 8 - 20 Ω -1 cm2mol- 1. The spectral data revealed the presence of N, N’-donor groups in the aromatic rings due to the presence of –C=N- vibration bands at 1653cm-1, 1660 cm-1 and 1624 cm-1for L1, L2 and L3 respectively. Upon complexation, the bands shift to lower frequencies (1641, 1625 and 1598 cm-1 for zinc complexes of L1, L2 and L3 respectively, suggesting coordination through the N, N’-donor groups. An octahedral geometry of the complexes was proposed based on the presence of absorption bands in the wavelength range of 238 – 456 nm in the electronic spectra of the compounds. The 1H NMR revealed the presence of –C=N- with resonance peaks at ẟ = 8.2, 8.1 and 7.8 ppm for L1, L2 and L3 respectively. Upon complexation, these peaks shift downfield (8.44, 8.57 and 7.89 ppm respectively) indicating that coordination to the metal is exclusively through the N, N’ donor atoms in the ligands. Thereafter, the antimicrobial properties of the ligands and their corresponding complexes were tested using the disc diffusion method against the gram positive and gram negative bacterial strains (Escherichia coli and staphylococcus aureus) and the fungal strain (candida albicans). The diameter of inhibition was measured relative to that of the antibacterial standard (ampicillin) and the antifungal standard (fluconazole). Dimethyl sulfoxide was used as the negative control. The ligands L1, L2 and L3 had inhibition zones in the range 11-18 mm. for the complexes, inhibition zones were observed in the range 13-22 mm. The standards gave the highest inhibition zones in the range 22-28 mm. The evaluation results revealed that the transition metal (II) complexes exhibited higher antimicrobial activity than the free N, N’-donor bidentate ligands against the same bacterial strain. The increased activity of the complexes might be due to partial sharing of the positive charge of metal ion with the donor groups of the N, N’-donor bidentate ligand that increases the liposolubility of the complex across the microbial cell membrane. Based on the promising evaluation results, complexes in particular ZnL3 and CuL3 are recommended as lead compounds in the development of novel antimicrobials.
Determination of micronutrients, heavy metals and Proximate analysis of selected indigenous vegetables in Kirinyaga East Sub-County, Kirinyaga County
(Chuka University, 2025) Maina Janet Njeri
Socio-economic changes that have taken place in Africa have influenced peoples eating habits in both rural and urban set-ups. Indigenous vegetables are important for food insecurity, malnutrition reduction and therapeutics in sub-Saharan African countries. In Kirinyaga County, indigenous vegetables are underutilized or neglected due to some nutritional content are known and others unknown. Limited data exist on the precise levels of key micronutrients (e.g. iron, zinc, magnesium) in specific indigenous vegetables cultivated in Kirinyaga East Sub-County. Variability in nutrient content due to farming practices, soil types, and climatic conditions in the region has not been comprehensively studied. Leaves are the most preferred parts of indigenous vegetables for consumption. Although they have nutritional benefits, there is a need to determine the safety levels due to toxic metals in vegetables contaminated with pesticides, heavy metals and toxins leading to failure of certain organs of the human body. The study aimed to determine levels of micronutrients (calcium, iron, magnesium and zinc), heavy metals (lead and cadmium) using AAS (atomic absorption spectrometer) using and proximate analysis (ash content, moisture content, crude fat, protein content, carbohydrates and crude fiber) of selected African indigenous vegetables (African nightshade, Spider plant, Vine spinach and Pumpkin leaves) in Kirinyaga east sub county. The results revealed that African indigenous vegetables are rich in essential micronutrients. Pumpkin leaves had the highest calcium levels (14,070.81 mg/kg), spider plant showed the highest iron concentration (233.53 mg/kg), African nightshade recorded the highest zinc content (483.33 mg/kg), while vine spinach was richest in magnesium (570.87 mg/kg). Proximate analysis indicated that spider plant and African nightshade contained higher protein levels (up to 17.9%), while moisture content ranged from 82–91%. Crude fat levels were consistently low, confirming African indigenous vegetables as nutrient-dense but energy-light vegetables Cadmium and lead concentrations varied across species and locations, with African nightshade and vine spinach showing relatively higher levels. However, all values remained within WHO/FAO permissible limits, indicating that the vegetables are safe for human consumption in terms of heavy metal contamination. African indigenous vegetables have high nutritional potential and can be promoted as affordable dietary sources of essential minerals and protein to combat malnutrition.
Determination of water quality of Nguue spring and river Mutonga in Tharaka-Nithi, Kenya and evaluation of corn-cob derived carbon powder in remediation of contaminated water
(Chuka University, 2015) Mwenda Bertha Kinya
Water quality is a pressing global concern, since water pollution negatively impacts water bodies and poses severe threats to both human and aquatic life.The aim of this study was to, determine physico-chemical and bacteriological parameters of Nguue spring and river Mutonga, and compare to the limits set by WHO and KEBS. The performance of low-cost adsorbent in removal of zinc and iron from contaminated water was also evaluated. Sampling was done each at six points along the river and the spring approximately 500 metres apart, in the dry and wet season in the months of September and November 2024. The physical parameters of water such as temperature, pH, DO, TDS and EC were measured using multiparameter. Total hardness was estimated by titrimetry. Anions of NO3 - and PO4 3- were determined by UV spectrophotometric method. The heavy metals of Zn2+ and Fe3+ in water samples were determined by Atomic Absorption Spectrophotometer. In the dry season, River Mutonga recorded a temperature between 25.9-26.6 °C, pH of 7.1-7.4 , electrical conductivity was 172.8-202 µS/cm, total dissolved solids 0.838-0.886 mg/L , dissolved oxygen, 3.19-3.25 mg/l, however, total hardness 0.838-0.886 mg/L, nitrate concentrations 16.57-19.35 mg/L, while phosphate was 1.95-2.12 mg/L. Nguue Spring during the dry season exhibited a temperature of 25.9-26.5 °C, pH was 5.21-6.58 indicating slight acidity, electrical conductivity of 147.6-193.6 µS/cm and total dissolved solids 0.552-1.2 mg/L, total hardness wa 58-160 mg/L, well Similar to Mutonga River, nitrate levels 16.83-19.47 mg/L. In the wet season, River Mutonga recorded a lower temperature of 21 °C compared to the dry.4 and 6.5-8.5 respectively, indicating increased acidity in sampling point M1. Electrical conductivity 57.2-60.4 µS/cm and total dissolved solids 31.3-36.6 mg/L were markedly lower than in the dry season, reflecting dilution effects of rainfall. Dissolved oxygen was 8.72-8.92 mg/L increased substantially and was well above the WHO minimum standard 4.0 mg/l. Total hardness decreased to 87.3-122 mg/L but remained within permissible limits. Nitrate levels dropped to 7.25-12.35 mg/L, now falling within KEBS standards which is 10 mg/l, while phosphates was 2.01-2.29 mg/L remained above WHO limits 0.5 mg/L. Nguue Spring in the wet season showed a temperature of 20.5-21 °C, pH was4.210-5.724 was consistently below both WHO and KEBS ranges, suggesting acidic conditions. Electrical conductivity was 37.8-55.6 µS/cm and total dissolved solids 27.7-59.5 mg/L decreased compared to the dry season, reflecting rainwater dilution. Dissolved oxygen was 8.58-8.86 mg/L was significantly elevated and met WHO standards, total hardness was 22.6-84 mg/L remained within permissible limits. Nitrate concentration was 7.8-14.65 mg/Lwas marginally above the KEBS guideline, while phosphate was 1.95-2.23 mg/L exceeded WHO standards but was acceptable under KEBS. Batch adsorption was carried out by varying the parameters of temperature, pH, intial concentration, contact time and adsorbent dosage. The total coliforms count in Mutonga were 11-460 and 36-1100 MPN per 100 ml in dry and wet season repectively and exceeded KEBS and WHO limits. In Nguue spring the toal coliform counts were 36-1100 and 43-˃1100 MPN per 100 ml in dry and wet season respectively exceeding KEBS and WHO limits. Adsorption of zinc and iron on CCAC and CCC was successfully represented by Freundlich and Lngmuir isotherm models. Adsorption of zinc on CCAC and CCC was best described by Freundlich with KF=2.35 mg/g, n=1.387, R2=0.9359 and KF=116.84mg/g, n=0.1634, R2= 0.9497 respectively indicating a favourable multilayer adsorption on heterogenous surface. Adsorption of iron on CCAC and CCC also Freundlich gave a reasonable fit with KF=1.1498mg/g, n=0.5826, R2=0.90703 and KF=1.8034mg/g, n=0.9063, R2=0.97692 respectively
Characterization of clay samples from Murang’a, Nyeri, Embu and Tharaka Nithi Counties for adsorption of cadmium for water purification
(Chuka University, 2025) Thuo Maryrose Wandia
Heavy metal pollution, particularly cadmium (Cd² ), remains a critical environmental challenge threatening water quality, aquatic ecosystems, and human health. Cadmium is widely introduced into aquatic systems through industrial effluents, agricultural runoff, and urban discharges. This study investigated the adsorption potential of locally available clay minerals as cost-effective and sustainable remediation materials. Clay samples were collected from Gakoigo (S), Mukurwe-ini (2A) Gakindu K1, Karurina (K2) and Mbogoni (M). The clay samples were characterized using Atomic Absorption Spectroscopy (AAS), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The results from elemental analysis and ANOVA revealed difference in concentrations of iron, magnesium, sodium, and aluminum across the counties, explaining the calculated F-statistics 2.83 (p = 0.048), 3.01 (p = 0.035), 4.51 (p = 0.020), and 5.22 (p = 0.011), respectively. These constituents are vital as they assist, particularly, the samples from Mbogoni (M) and Gakoigo (S), in boosting cadmium (Cd²) adsorption. On the contrary, calcium and potassium were seen to have less influence, evidenced by their F-statistics of 2.45 (p = 0.068) and 2.13 (p = 0.080), respectively. Physicochemical water quality analysis was done from 12 rivers sites within Nairobi County, Kenya. Turbidity ranged between 2.75–95.67 NTU, exceeding WHO’s 5 NTU guideline in urban rivers due to runoff and effluent discharges. Electrical conductivity (556–1123 µS/cm) surpassed WHO limits across all sites, confirming high ionic loading, while dissolved oxygen (0.51–3.06 mg/L) was critically low, pointing to severe organic pollution. Total suspended solids (12–247 mg/L) and TDS (362–736 mg/L) were elevated in urbanized sites, further degrading aquatic health. Cadmium concentrations (0.0105–0.0498 mg/L) consistently exceeded WHO (0.003 mg/L) and KEBS (0.01 mg/L) standards, with highest levels in industrially impacted rivers, highlighting risks of bioaccumulation and human exposure. Batch adsorption studies demonstrated that pH was a key determinant, with maximum efficiency at neutrality (pH 7, 99.81% removal by K1), while acidic conditions reduced removal due to proton competition. Contact time experiments showed rapid uptake within 20 minutes, with equilibrium achieved at 40 minutes (69.16% removal by K1). Adsorbent dosage showed optimum performance at 0.1 g (99.72% removal at 8 ppm), though higher dosages reduced efficiency due to particle aggregation. Desorption confirmed strong Cd binding, indicating chemisorption via ion exchange and surface complexation. Agitation improved uptake by minimizing mass transfer resistance, with peak efficiency (92.29% by K1) at 400 rpm. Temperature exerted a negative effect, with maximum adsorption at 25 °C (97.52% by K1), confirming exothermic behavior. Isotherm modeling revealed Langmuir’s model (Qmax = 2.06 mg/g, KL = 5.44 L/mg, R² = 0.77) better fit the data compared to Freundlich (R² = 0.67), suggesting monolayer adsorption on homogeneous sites. Kinetic modeling indicated pseudo-second order (R² = 0.8496) best described the process, implying chemisorption. Thermodynamic evaluation showed that cadmium adsorption on the clay adsorbent was endothermic, with a positive enthalpy change (ΔH = 17,936.42 J/mol) and a positive entropy change (ΔS = 64.18 J/mol·K). Gibbs free energy (ΔG) remained negative across all temperatures (ΔG = 1.21 to -1.27 kJ/mol), confirming spontaneous adsorption at higher temperatures.
Synthesis, characterization and antibacterial activity Of selected schiff base ligands and their copper Complexes
(Chuka University, 2025) Tonui , Fredrich Kibet
Resistant strains of bacteria have emerged because of improper use of antibiotics and insufficient infection management, posing a serious danger to both public health and the global economy. Therefore, it has become essential to produce a new generation of antimicrobials to slow the spread of antibiotic resistance. This is by advancement of antimicrobial drugs that can specifically interact with a target site of a particular pathogen. The work described in this paper entails the synthesis, characterization and antibacterial evaluation of schiff base ligands and their Cu (II) complexes. The ligands, Ligand 1 ((E)-N,N-dimethyl1-4-((p-tolyimino)methyl)aniline) and Ligand 2 ((E)4(((2,4-dinitrophenyl)imino)methyl)-n-n-dimethylaniline), were obtained by microwave assisted condensation and then refluxed for 3 hours, the solid was filtered and rinsed with ethanol and left to dry. The copper complexes were prepared by treating a hot (40°C) solution of the ligands dissolved in ethanol with an aqueous solution of Cu (II) chloride followed by refluxing for 3 hours. Ultraviolet Visible spectroscopy and Fourier Transform Infrared Spectroscopy characterized each of the synthesized compounds. The percentage yield was at 78% for ligand 1, 62% for ligand 2, 76% for complex 1 and 81% for complex 2. The UV-Visible spectra showed two major absorption bands for the ligands, which shifted to higher and lower wavelengths for the complexes. The FTIR spectra show that the azomethine (-C=N-) stretch shifts from 1640.0 cm ¹ in the ligands to 1635.64 cm ¹ in complex 1 and 1614.42 cm ¹ in complex 2. Similarly, the carbonyl (-C-O-) stretch shifts from 1238.00 cm ¹ (Ligand 1) and 1160.00 cm¹ (Ligand 2) to lower values in complex 1 (1027.00 cm¹) and complex 2 (1141.00 cm¹), confirming metal-ligand interaction. The antibacterial sensitivity levels of the synthesized Schiff bases and the Cu (II) complexes was evaluated using disk diffusion method. The bacterial strains employed included; GramPositive staphylococcus aureus and Gram-negative Escherichia coli. The filter paper discs were deepen into concentration ranging from 10ug/ml-40ug/ml for every compound synthesized and then laid onto the surface of the discs. The average inhibition zone for the ligands was at 7.0 mm (ligand 1) and 6 mm (ligand 2) for gram negative bacteria and 10.5 mm (ligand 1) and 10.75 (ligand 2) for Gram positive bacteria. For the complexes 6.0 mm (complex 1) and 6.75 mm (complex 2) for gram negative bacteria and 9.5mm (Complex 1) and 8.75 mm (complex 2) for gram positive bacteria relative to standard gentamycin which showed activity at 24 mm for gram negative and 26 mm for gram positive bacteria. These results were relative to the literature work done, however the zones were slightly lower. From these results, it is concluded that the ligands and complexes were successfully synthesized and all these compounds showed promising activity against bacteria. To explore further potential of these compounds, further studies on other antimicrobial properties as antiviral, antifungal among others should be performed to evaluate similar performance.
Determination of water quality status, remediation and synthesis of multiwalled carbon nanotube/hydrochar composite in river Kathita, Meru, Kenya.
(Chuka University, 2025-10) Gitonga, Glory Gatwiri
Freshwater is required for life as well as several other activities such as human consumption, agricultural processes and industrial processes. Heavy metals are absorbed into water bodies through various pathways have adverse effect on the liver, kidneys, lungs, brain, and bones. This study sought to determine the physiochemical parameters, bacteriological, heavy metals and synthesize and characterize a composite of multi-walled carbon nanotubes (MWCNTs)/hydrochar of tea waste and utilize it for removal of Cu2+ ions from river Kathita. Tea wastes were collected from Meru tea factories and MWCNTs purchased from reputable suppliers. The tea waste samples were washed, dried and the MWCNTs, functionalized with sulfuric-nitric acid. The MWCNTs/hydrochar composite was characterized using FTIR and XRD. The water samples and sediments were collected in two seasons from River Kathita using grab method, transferred to 500 ml plastic bottles and transported to Chuka University Laboratory for analysis in a cooler box at 4oC. Standard methods for determining physicochemical and bacteriological parameters were employed and batch adsorption experiments were conducted to study the effect of pH, temperature, contact time, speed, initial metal concentration and dosage on adsorption of Cu 2+ ions. The remaining copper (II) ions concentration was determined using AAS. The water turbidity, electrical conductivity, dissolved oxygen, nitrogen and phosphorous content, TDS and TSS were found to be high during the wet season compared to dry season. pH registered small changes to more neutral-alkaline during the wet season. The pH, temperature, conductivity, TDS, phosphorus and nitrates were within the guidelines by WHO in both seasons. Turbidity and TDO exceeded the WHO and KEBS guidelines in both seasons which indicated high amounts of organic matter. The total coliform counts and faecal coliforms during wet season were beyond proposed standards of safe recreational or agricultural use. This was due to extensive runoff as well as sewer discharge into the water during the rainy season. (MWCNTs) and hydrochar from tea waste composite had a big removal efficiency of 96.5% under optimum conditions. From the kinetic modeling, the adsorption process obeyed pseudo-second order reaction (R² = 0.96683) trend showing that the process is chemisorption driven. There was greater fit of the adsorption equilibrium data on Langmuir isotherm model (R² = 0.99529) indicating monolayer surface coverage of Cu²⁺ ions by homogenous surface. There was a high regeneration potential of the absorbed Cu²⁺ ions being efficiently desorbed. The MWCNTs/hydrochar composite is highly effective and sustainable since it can be recycled multiple times without the loss of functionality on a significant scale. The addition of Pb²⁺ ions did not drastically influence the removal of Cu²⁺ while addition of Cd²⁺ ions and the binary solution of Pb²⁺ and Cd²⁺ caused a significant decrease in the efficiency of copper adsorption. The MWCNTs/hydrochar composite is generally a sustainable option for enhancing the quality of the polluted rivers' water.
CHARACTERIZATION AND SCREENING OF ANTIBACTERIAL PROPERTIES OF Actinomycetes FROM RIVER TANA AND LAKE ELEMENTAITA, KENYA
(Chuka University, 2023-04) SHIKUKU BONFACE OLOO
The increased prevalence of bacterial infections has been a major challenge to human with devastating high mortality and morbidity rates. This situation has been worsened by increasing antibiotic resistant strains of pathogenic bacteria, reduced effectiveness of antibiotics in the market, and the emergence of new bacterial infections. This study aimed at identification of antibacterial Actinomycetes species using biochemical and molecular methods, screening for their antibacterial secondary metabolite and determination of effect of pH, fructose, sucrose, urea and sodium nitrate on their antibacterial activities. The experiments for this study was laid out in Complete Randomized Design and replicated thrice to determine the difference between the inhibition zones (mm) of isolates against the tests organisms and effects of different levels of pH, sucrose and fructose on antbacterial properties of isolates. The resultant data ( zones of inhibition in millmetres) was analysed using One Way Analysis of Variance and Kruskal Wallis test in SAS version 9.4. A total of six antibiotic producing Actinomycetes species were isolated from river Tana and lake Elementaita and identified through morphological, biochemical and molecular methods.There was a significant (p<0.05) different antibacterial activity of Actinomycetes isolates against Staphylococcus aureus, Salmonella typhi and Escherichia coli. The thin layer chromatography profiling for secondary metabolites in extracts revealed a total of 13 different spots with each having a unique retardation factor. The GC-MS analysis of the extracts revealed 140 different metabolites which have been documented to have antibacterial properties from the six Actinomycetes isolates. There was a significant (p<0.05) effects of different levels of pH and concentration of fructose, urea and sodium nitrate on the antibacterial activity of Actinomycetes isolates against Escherichia coli. The study has revealed different secondary metabolites in unique combinations across the six Actinomycetes isolates with antibacterial activities against Staphylococcus aureus, Salmonella typhi and Escherichia coli. The findings of this study can help in developing new or alternative antibiotics that can be used for treatment of pathogenic and resistant bacteria.
PHYTOCHEMICAL ANALYSIS, IN VITRO TESTING OF ANTIBACTERIAL PROPERTIES, ANTI-INFLAMMATORY ACTIVITY, AND CYTOTOXICITY OF AQUEOUS AND DICHLOROMETHANE LEAF EXTRACTS OF Solanum incanum AND Tamarindus indica
(Chuka University, 2023-10) NGURARI SAMSON WAINAINA
The prevalence of bacterial infections and inflammatory-related diseases is increasing. As an alternative, the pharmaceutical sector is currently focusing on studying medicinal plants to generate alternative therapies for these health concerns. Solanum incanum and Tamarindus indica are among the plant species utilized in traditional medicine to address these issues. Most conventional drugs used to manage inflammation and bacterial infections have side effects, while some are expensive, hence the need to have alternative plant-based therapies. Additionally, there is limited information on the potency of Solanum incanum and Tamarindus indica, which is vital in process of commercializing its active metabolites to improve disease management. Therefore, this study analyzed phytochemicals present in aqueous and dichloromethane leaf extracts of the two plants and tested their antibacterial, anti-inflammatory, and cytotoxic properties. The phytochemical analysis was done using standard chemical tests followed by Gas Chromatography-Mass Spectroscopy of dichloromethane extracts. The antibacterial activity of the extracts was tested against Escherichia coli, Salmonella typhi, and Staphylococcus aureus using disc diffusion method, minimum inhibitory Concentration, and minimum bactericidal concentrations assays. The anti-inflammatory potency of the extracts was tested using an Erythrocyte stabilization assay, while the toxicity of the extract was tested using brine shrimp lethality tests. Phytochemical analysis indicated presence of flavonoids, tannins, saponins, phenols, and alkaloids in all the plant extracts. Additionally, the T. indica dichloromethane and S. incanum water extracts had no glycosides, while anthraquinones were absent in all the extracts. The antibacterial assay revealed significant difference in antibacterial activity between the plant extracts at different concentrations. The Minimum Inhibitory Concentrations of T. indica extracts ranged between 62.5 μg/mL and 125 μg/mL, while those of S. incanum ranged between 62.5 μg/mL and 250 μg/mL. The Minimum Bactericidal Concentration of both plants ranged between 125 μg/mL and 500 μg/mL. The S. incanum dichloromethane extracts had the highest percentage erythrocyte stabilization at 1000 μg/ml, 57.64 ±13.90%, while S. incanum water extract had the lowest stabilization at 2000 μg/ml, 19.06 ±14.43%. T. indica dichloromethane extract has the highest toxicity (LD50 of 113.57 μg/mL) while S. incanum DCM extract was the least toxic (LD50 of 2341 μg/mL). The plant extracts have demonstrated the potential of being used for therapeutic purposes after further analysis for the identification of the active compounds. Therefore, this research provides preliminary data on their antibacterial and anti-inflammatory activity and cytotoxicity of the extracts, which is foundational for further research.
SYNTHESIS AND CHARACTERIZATION OF IRISH POTATO PEELS POWDER-NANOSILICA COMPOSITE FOR THE DEGRADATION OF RHODAMINE BLUE AND DICLOFENAC
(Chuka University, 2023-10) MUTIE JOSEPH NZUKU
In today's world, finding safe drinking water has become a major concern. Many contaminants, including dyes and pharmaceuticals, are discharged directly or indirectly into bodies of water without sufficient treatment, rendering the water unsafe for human consumption. To safeguard the environment and human health, harmful toxins must be removed from wastewater. Various technologies have been used to address this issue. Adsorption on activated carbons is a widespread technique in wastewater treatment, but the exorbitant cost of ordinary activated carbons limits its use. Several agricultural waste products are currently being used inefficiently and have the potential to be transformed into important adsorbents such as composites. Because of its nano-sized inorganic filler, nano-silica has exceptional characteristics such as large surface area, mesoporous structure, biocompatibility, versatile pore size, modifiability, and polymer hybridizability over common composites. Irish potato peel powder is a natural binder that works well in composite materials. Since most composite materials are poorly distributed, this study concentrated on utilizing Irish potato peel powder and nano-silica from rice husks to produce a composite of Irish potato peel powder and nano-silica. This study aimed to synthesize, characterize and make Irish potato peel powder/nano-silica composite in the degradation of rhodamine blue and diclofenac. Silica nanoparticles were mixed with Irish potato peel powder in the ratios 1:1, 1:2, 2:1, 4:1, and 5:1, respectively. Glutaraldehyde was added to the mixture as a binder. The following functional groups was detected in the composite's Fourier Infrared spectrum: C=C, O-Si-O, and Si-OH, which corresponded to peaks at 1645.35 cm-1, 1104.29 cm-1, and 3439.23 cm-1, respectively, and are responsible for the adsorption of Rhodamine Blue and Diclofenac. The XRF analysis showed that silica accounted for a large proportion in the composite, which determined the mixing ratio of RHNS and IPPP (4:1). The composite surface area was 100.6328 m2/g, with a single point surface area of 97.4036 m2/g, according to BET-BJH surface characterization. The synthesized composite was amorphous in nature, as shown by the XRD pattern, which has a strong broad peak between 200 and 250 (2θ). The adsorption capacity of RB and DCF by the composite was optimal at pH 4 and 2, respectively, an initial concentration of 1 mg/L and 40 mg/L, respectively, an adsorbent dose of 0.1 g, and a 240 rpm stirring speed. The removal efficiency of the composite was 99.39% for DCF and 97.57% for RB. The rhodamine blue removal best fit the Freundlich isotherm in the used composite adsorbent with R2 = 0.996, while the DCF removal suited the Langmuir isotherm model the best with R2 = 0.901. The kinetic data were pseudo-second-order (R2 = 0.9989 for RB and 0.849 for DCF), which was more suitable for explaining the adsorption rate. Fineness, surface area, and vacancy concentration are all associated with better adsorption capacity.
LEVELS OF SELECTED PHTHALATES FROM WASTEWATER TREATMENT PLANTS IN LAKE VICTORIA CATCHMENT AREA AND THEIR ADSORPTION ONTO WATER HYACINTH BIOCHAR
(Chuka University, 2020-12) OGORA, ELKANAH NYAKWAMA
Endocrine disrupting chemicals (EDCs) disturb the endocrine system’s functionality causing negative effects on health in an organism and its progeny. They can interfere with natural hormone cycles in humans or animals, potentially affecting metabolism, development, reproduction and growth. Phthalates are among the many examples of EDCs, which have been used as plasticizers for longtime around the world. Due to their extensive usage, they are found in many surface waters, sludge and waste waters. The occurrence of phthalates in water, and their exposure to non-target organisms cause adverse effects such as congenital anomalies, endocrine disruption and chronic toxicity. This study determined residual levels of three phthalates namely; dimethyl phthalate (DMP), benzyl butyl phthalate, (BBP) and bis(2-ethylhexyl) phthalate (BEHP) in wastewater sampled from wastewater treatment plants (WWTPs) of Nyalenda, Homabay and Kisii during wet and dry seasons. The wastewater samples were extracted and cleaned by solid phase extraction cartridges (SPE) ready for high performance liquid chromatography (HPLC) for quantitative analysis. Most of the sites sampled had detectable levels of DMP, BBP and BEHP in wastewater. High concentrations were detected during wet season compared to dry season in all sampled sites. Nyalenda WWTP recorded the highest concentrations of phthalates than Homabay and Kisii WWTPs. The concentrations of all selected phthalates were recorded highest at the inlet sampling points from all WWTPs, in both seasons sampled. Almost all the selected phthalates were below the limit of quantification (LOQ) at the outlet sampling points of Homabay and Kisii WWTPs in both seasons. The residue levels obtained showed significant differences at 5% confidence limits with zcal for all phthalates in all WWTPs less than the critical value (Zcritical = 1.96). Therefore, the null hypothesis was rejected. Consequently, a cost-effective technique of removing DMP, BBP and BEHP from their solutions using water hyacinth biochar (WHB) as an adsorbent was investigated. A mass of 0.1 g of WHB both before and after adsorption was used for characterization process. Elemental analysis of WHB was determined using XRF (EDXRF), the XRD patterns were obtained using bruker operating with Cu Kά(λ = 1.541nm) and samples scanned in coupled TwoTheta/Theta. The FTIR spectra were obtained between 4000cm-1 and 400cm-1 using Shimadzu type. The adsorption process was done using an orbital shaker agitated at 125 rpm and residual levels determined using the HPLC. The optimum conditions obtained from the adsorption of DMP, BBP and BEHP onto WHB were as follows; equilibrium time was 25 minutes, maximum adsorbate concentration adsorbed at 0.1 g of WHB was 4 mg/L, temperature of 298 K was appropriate and 0.8 g of WHB was effective for the adsorption of above 67% of 10 mg/L of each selected phthalate. The kinetic data fitted the pseudo second order model with regression values for DMP, BBP and BEHP found to be 0.9987, 0.9984 and 0.9986, respectively. The Freundlich model demonstrated to be a good model for fitting the adsorption data, which was attributed to heterogenous distribution of charged functional groups at adsorption sites of WHB’s surface. The calculated thermodynamic parameters, namely; change in Gibb’s free energy (ΔG), change in enthalpy (ΔH) and change in entropy (ΔS) showed that the adsorption process was favorable, exothermic, spontaneous and of a physical type. This was due to the fact that all of them were negative values. Dimethyl phthalate was the most effectively removed by WHB as adsorbent. The removal efficiency decreased with increasing molecular weight of the phthalates. The findings demonstrated that WHB is a good low cost and environmentally adsorbent for removal of phthalates from water.

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