Browsing by Author "Kimosop, Selly"

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  • Publication
    Publication
    Adsorption of Caffeine and Ciprofloxacin onto Pyrolitically Derived Water Hyacinth Biochar: Isothermal, Kinetic and Thermodynamic Studies
    (David Publishing, 2016-09-07) Ngeno, Emily; Orata, Francis; Baraza, Danstone; Shikuku, Victor; Kimosop, Selly
    Adsorption of Caffeine and Ciprofloxacin onto Pyrolitically Derived Water Hyacinth Biochar: Isothermal, Kinetic and Thermodynamic StudiesFull-Text PDFDownload XML 10 ViewsDOI:10.17265/1934-7375/2016.04.006Author(s)Emily Chelangat Ngeno, Francis Orata1, Lilechi Danstone Baraza, Victor Odhiambo Shikuku and Selly Jemutai KimosopAffiliation(s)ABSTRACTIn this work, the adsorptive features of water hyacinth (Eichhornia crassipes) derived biochar for sequestration of ciprofloxacin and caffeine from aqueous solution is reported. The isothermal behaviour, adsorption kinetics, mechanisms and thermodynamic parameters were investigated in batch mode. Langmuir and Freundlich models described the equilibrium adsorption data with regression values > 0.9. The kineticsdata obeyed the pseudo-second-order kinetic law while intraparticle pore diffusion was not the only rate controlling step. The computed thermodynamic parameters, namely change in Gibbs free energy (ΔG), change in enthalpy (ΔH) and change in entropy (ΔS) indicated that the adsorption processes were spontaneous and exothermic with less randomness. pH dependence studies depicted multi-mechanistic adsorption for both compounds and is hypothesized to involve hydrophobic interactions besides other non-coulombic interactions. The findings demonstrate that water hyacinth biochar presents an excellent low cost and environmentally benign adsorbent for mitigation of pharmaceuticals from water with a removal efficiency of above 60 % for caffeine and ciprofloxacin.KEYWORDSAdsorption, ciprofloxacin, caffeine, biochar, water hyacinth.
  • Publication
    Publication
    Caffeine and Ciprofloxacin Adsorption from Water onto Clinoptilolite: Linear Isotherms, Kinetics, Thermodynamic and Mechanistic Studies
    (South African Journal of Chemistry, 2019) Ngeno, Emily; Shikuku, Victor; Orata, Francis; Baraza, Danstone; Kimosop, Selly
    In this study, clinoptilolite was used to sequester ciprofloxacin (CIP) and caffeine (CAF), two emergent contaminants, from aqueous solution using batch equilibration method and the effects of contact time, pH, initial contaminant concentration, temperature and adsorbent dosage investigated and herein reported. The adsorption kinetics was described by the pseudo-second-order model (PSO) and pore diffusion was not the sole operative rate-controlling step as depicted by the intraparticle diffusion model. The equilibrium data were modelled using three linear forms of Langmuir equation and Freundlich model and was best fitted by the Lineweaver-Burk linearization of Langmuir equation (type-1). Linearization is shown to induce errors that may lead to discrepancies in parameter values estimation. The derived thermodynamic functions revealed the adsorption processes are exothermic, spontaneous and physical in nature. The adsorption mechanism of CIP is strongly controlled by electrostatic interactions while CAF adsorption is weakly affected by changes in pH. The findings demonstrate that clinoptilolite in its unmodified form is a potential low-cost and eco-friendly adsorbent for removal of pharmaceutically active ingredients from water.
  • Publication
    Publication
    Occurrence and Distribution of Per-and Polyfluoroalkyl Substances from Multi-Industry Sources to Water, Sediments and Plants along Nairobi River Basin, Kenya
    (MDPI, 2022-07-23) Chirikona, Flora; Quinete, Natalia; Gonzalez, Jesleen; Mutua, Gershom; Kimosop, Selly; Orata, Francis
    Per-and polyfluoroalkyl substances (PFAS) are ever-present pollutants in the environment. They are persistent and bio-accumulative with deleterious health effects on biota. This study assesses the levels of PFAS in environmental matrices along the Nairobi River, Kenya. An aggregate of 30 PFAS were determined in water, while 28 PFAS were detected in sediments and plants using solid phase extraction then liquid chromatography-mass spectrometric techniques. In water, higher levels of perfluoroundecanoic acids of up to 39.2 ng L −1 were observed. Sediment and plant samples obtained in the midstream and downstream contained higher levels of perfluorooctanoic acid of up to 39.62 and 29.33 ng g −1 , respectively. Comparably, levels of long-chain PFAS were higher in water and sediments than in plants. Sediment/water log distribution of selected PFAS ranged between 2.5 (perfluoroundecanoic acid) and 4.9 (perfluorooctane sulfonate). The level of perfluorooctane sul-fonate (1.83 ng L −1) in water is above the acceptable level in surface water posing high human health and ecological risks. The observed PFAS concentrations and distribution were attributed mainly to multi-industries located along the river, among other sources. The knowledge of PFAS occurrence and distribution in Nairobi River, Kenya, provides important information to local regulatory agencies for PFAS pollution control.