Browsing by Author "Aquiline Kathambi, Peter W. Njoroge, Sylvia A. Opiyo, Isaac Waweru, Benson M. Mwangi"

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    Adsorptive removal of phosphates from wetland waters using silica molyb date adsorbent
    (Journal of Emerging Technologies and Innovative Research, 2025-02) Aquiline Kathambi, Peter W. Njoroge, Sylvia A. Opiyo, Isaac Waweru, Benson M. Mwangi
    World’s most productive and valuable ecosystem is the wetlands. Quality and functions of wetlands have been affected adversely by deforestation, fertilizers, and pesticides among others. Pollution by phosphates affect aquatic life as they have serious side effects at very low levels. Silica molybdate was prepared by first chlorinating silica sand using phosphorous pentachloride (PCl5) to give chlorinated silica. Amination of chlorinated silica was done using Ethylenediamine (EDA) and later molybdate was chemically grafted to the aminated silica to yield silica molybdate. Silica molybdate was used to reduce the levels of PO4 3- residues from wetland ecosystem.. Molecular structure of the silica molybdate material was characterized using Fourier Transform Infrared (FT-IR). FT-IR results showed Adsorption bands at 854cm-1 and 542cm-1 which were attributed to Mo=O and Mo-O stretching in molybdate. Peaks observed at 1388 and 1662cm-1 were attributed with the vibration mode of Mo-OH bond and bending mode of adsorbed water. Spectra peaks observed at 542, 634.58 and 898.97 cm-1 were attributed to the adsorption of molybdate. The physical adsorption parameters which were examined using batch adsorption system were; temperature, pH, contact, time, initial concentration using sorption models, adsorption kinetics and thermodynamics. Results showed that optimum pH for biosorption of PO4 2- was 6.0, optimal contact time was 30 minutes, optimum temperature was 45 ℃. The experimental results obtained showed that the maximum phosphate adsorption of silica molybdate was achieved at 194.93mg/g at adsorption optimal conditions of pH, temperature and contact time. The phosphate removal based on silica molybdate will offer several benefits such as low cost, effectiveness and reliability to lower the levels of phosphates in wetland waters as compared to commercial activated carbon. Based on the adsorption efficiency values obtained from this study and comparing them with adsorption efficiency reported in the literature, it can be concluded that silica molybdate is super adsorbent for the removal of phosphates from wetland waters.
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    Removal of Nitrites from Wetland Waters Based on Diazonium Silica
    (American Journal of Chemistry, 2025) Aquiline Kathambi, Peter W. Njoroge, Sylvia A. Opiyo, Isaac Waweru, Benson M. Mwangi
    Diazonuim silica was prepared and used to remove nitrites in wetland waters. Raw silica was chlorinated using phosphorous pentachloride (PCl5). Chlorinated silica was further reacted with ethylenediamine (EDA) under reflux to give aminated silica. Thereafter, aminated silica was protonated to yield diazonium silica which was used as the adsorbent. The prepared diazonium silica material was characterized using Fourier Transform Infrared (FT-IR) showing bands at wavenumbers 1049 and 791 cm-1 of the anti-symmetric and symmetric stretching modes (Si-O-Si) of SiO4. The shift in spectra band of Si-O-Si from 1051cm-1 in raw silica to 1049cm-1, was attributed to diazonium silica. Additionally, a new open chain azo (N=N) group band was found in the region 1575cm-1 -1630cm-1. The physical adsorption parameters examined using batch adsorption system including: pH, initial concentration, contact time and temperature were made using sorption models, adsorption kinetics and thermodynamics. The results obtained showed 3.0 as the optimal pH for adsorption of NO2-, 303K as the optimal temperature, optimum contact time as 60 minutes and optimal initial concentration as 20ppm. The adsorption capacity of nitrites using diazonium silica adsorbent was achieved at 16.45mg/g. For sorption of nitrites in diazonuim silica, Langmuir isotherm model was obeyed according to correlation coefficient R2 = 0.97182 close to unity. Adsorption kinetics of nitrites in diazonium silica pseudo second order was best obeyed while, thermodynamic parameters revealed that the sorption of nitrites into diazonium silica was exothermic in nature. From the results obtained, diazonium silica is an efficient adsorbent for adsorption of nitrites compared to raw silica.