http://ir.mksu.ac.ke/handle/123456780/83 Scholarly outputs of The School of Pure and Applied Sciences 2026-04-04T12:55:59Z http://ir.mksu.ac.ke/handle/123456780/18006 Reduction and Degradation of Paraoxon in Water Using Zero-Valent Iron Nanoparticles Okello, Veronica A.; K’Owino, Isaac O.; Masika, Kevin; Shikuku, Victor O. Paraoxon is an emerging organophosphate pollutant that is commonly used as a pesticide and a drug, hence increasing the risk of contamination of water supplies. Its intensive use for vector control has led to pollutions in soil and water. Paraoxon is very toxic, with an LD50 of 2 to 30 mg/kg in rats. It can be metabolized in the body from parathion; thus, exposure can lead to serious health effects. In this study, zero valent iron (Fe◦/ZVI NPs) nanoparticles were synthesized and investigated for the degradation of Paraoxon, a chemical warfare agent and insecticide, in an aqueous solution. The effects of solution pH, initial pollutant concentration, ZVI NPs dosage and contact time on mineralization efficiency were examined. Batch experiments demonstrated that 15 mg L−1 of Paraoxon was mineralized at degradation efficiencies of 75.9%, 63.9% and 48.9% after three-hour treatment with 6.0, 4.0 and 2.0% w/v Fe◦ , respectively. The calculated kinetic rate constant kobs was 0.4791 h−1 , 0.4519 h−1 and 0.4175 h−1 after treating 10, 15 and 20 mg L−1 of Paraoxon solution with 6.0% w/v Fe, respectively. The degradation dynamics were described by the first-order kinetic law as evidenced by rate constants independent of the initial Paraoxon concentration. The degradation efficiency was strongly dependent on pH, increasing with a decrease in pH, with maximum removal at pH 4. p-nitrophenol was detected as a degradation product, suggesting cleavage of the O-P bond and hydrolysis as possible reaction processes. This study showed that Fe◦ particles have the potential for degrading Paraoxon. 2022-08-02T00:00:00Z http://ir.mksu.ac.ke/handle/123456780/18005 Synthesis of mesoporous akaganeite functionalized maize cob biochar for adsorptive abatement of carbamazepine: Kinetics, isotherms, and thermodynamics Selly, Jemutai Kimosop; Okello, Veronica A.; Shikuku, Victor O.; Orata, Francis; Getenga, Zachary M. In this work, akaganeite (β-FeO(OH)) impregnated maize cob biochar (Fe-MCB) was prepared by direct hydrolysis, and its adsorptive potential was tested against aqueous solutions of carbamazepine (CBZ), an emerging contaminant. The adsorbent was characterized by standard methods, namely XRD, SEM-EDX, FT-IR, BET surface area analysis, and VSM. Fe-MCB exhibited mesoporous textural structure with paramagnetic behavior at room temperature. The equilibrium data were modeled using the Langmuir, Freundlich, Fowler-Guggenheim and Sips isotherm models. The adsorption data were best described by Fowler-Guggenheim with an estimated maximum adsorption capacity of 81.80 mg g−1. The adsorption rate was described by the pseudo-first-order (PFO) model. The thermodynamic functions, namely enthalpy (ΔH = -6.88 kJ mol−1), negative Gibbs free energy (ΔG) values, entropy (ΔS = 26.33 J mol−1), indicated that the adsorption was exothermic, spontaneous, with the increased disorder at the solid-liquid interphase. The adsorption mechanism is thought to entail dispersive interactions. Modified maize cob biochar is a potentially techno-economic sorbent for CBZ adsorption. 2022-09-01T00:00:00Z http://ir.mksu.ac.ke/handle/123456780/18004 Performance of a horizontal well in a bounded anisotropic reservoir: Part II: Performance analysis of well length and reservoir geometry Nzomo, Timothy Kitungu; Adewole, Stephen Ezizanami; Awuor, Kennedy Otieno; Oyoo, Daniel Okang’a Evaluation of the performance of horizontal wells is an important aspect in the enhancement of their productivity. This study provides mathematical computations, and analysis for theoretical well and reservoir considerations. The study investigates how well design and reservoirs geometry affect the overall performance of a horizontal well in a completely bounded reservoir throughout its productive life. A horizontal well in a rectangular reservoir with completely sealed boundaries is considered and the effect of dimensionless well length L D , dimensionless reservoir length x eD , and dimensionless reservoir width y eD on the pressure response over a given period of production using dimensionless time t D is studied. The mathematical model used was derived using source and Green’s functions presented in part I of this study. Appropriate well and reservoir parameters are considered and the respective dimensionless parameters are computed which are then used in computing dimensionless pressure P D and its dimensionless pressure derivative P ′ D . From the computations, the results obtained are analysed in diagnostic log–log plots with a discussion of the flow periods. The results obtained indicate that an increase in dimensionless well length decreases pressure response during the infinite-acting flow at early times and during transition flows at middle time but increases the pressure response during the pseudosteady state flow at late times. The dimensionless reservoir width and length are observed not to influence dimensionless pressure response during the infinite-acting flow at early times and during the transition flows at middle time, only affecting the prevalence time of the flow periods. However it is observed that during the pseudosteady state flow at late times, dimensionless pressure response reduces with increased dimensionless reservoir length and width. 2023-06-01T00:00:00Z http://ir.mksu.ac.ke/handle/123456780/15838 Mathematical Modelling of the Effects Funding on HIV Dynamics Among Truckers and Female Sex Workers Along the Kenyan Northern Corridor Highway Kimulu, Ancent Makau; Mutuku, Winifred Nduku; Mwalili, Samuel Musili; Malonza, David; Oke, Abayomi Samuel The Southern and Eastern parts of Africa are the most hit by HIV/AIDS in the world and a huge financial commitment is required to control the spread of the disease. Of these countries, Kenya and South Africa have been able to increase prevention and treatment services due to their financial commitment to fighting the epidemic. However, studies have shown that most of the financial commitment comes from private donors and the private sectors are recently becoming reluctant to release funds. It is therefore important to ensure that the available funding is effectively utilised. Studies in 2018 show that infections occurred mostly among the key populations on the Kenyan Northern Corridor highway; such as sex workers and truckers. Moreso, transactional sex which involves cash transfer is the main mode of transmission of HIV/AIDS along the Northern corridor highway in Kenya. In this paper, we study the effect of funding on HIV transmission between truckers and female sex workers. A mathematical model with funding parameters is developed and analysed to determine the effects of funding on the HIV transmission dynamics between truckers and female sex workers. The reproduction number is obtained using the next-generation matrix and the conditions for the stability of the equilibrium points are established. The model is fed into the MATLAB ode45 solver and a numerical simulation is carried out. The results show that increasing circumcision funding reduces the rate of migration from the Susceptible class to the Infected class. Also, increasing treatment funding increases the Treatment class and reduces the overall number of AIDS-related. 2022-01-01T00:00:00Z