Equilibrium and Kinetic Batch Studies of Cadmium and Lead sorption using Low Cost Biosorbents

v Dedication To my sister and best friend who passed on during the course of these studies; Mrs Jessica Jaafa. Baaba Jessica you were a real big sister who showed me love and care. You inspired me to strive hard and achieve the best in life. The memory of your relationship remains fresh in my mind all the time. I beseech the Almighty to rest thy soul in eternal peace. vii Summary The trace metals cadmium and lead are contaminants that have detrimental health effects on life support systems when chronic exposure to minute quantities in environmental matrices occurs. They adsorb onto soil particles and soil organic matter which increases their retention and reduces their transmission to the soil water. When the soil is overladen or when the soil pH is lowered, trace metals vertical mobility increases and contamination of groundwater occurs through the soil solution. Conventional remediation techniques are available for reducing trace metal contaminants in effluents, wastewater, leachates, surface runoff, surface water and groundwater to allowable levels and to ensure adherence to water quality standards. The conventional remediation techniques have high installation and operational costs besides sludge disposal hazards and non-selectivity for trace metals whereas biosorption studies have shown biosorbents to be effective remediation alternatives for trace metals in minute concentrations. Studies were done to characterize and evaluate the efficiency besides the effectiveness of application of local biosorbents in remediation of selected trace metals in contaminated water. The agricultural wastes; Albizia coriaria, Erythrina abyssinica, Coffea canephora, Cyperus papyrus and Musa spp. were selected for preparation of biosorbents. Chemical treatment of biosorbents was done using sodium hydroxide and hydrogen peroxide. The characterisation of biosorbents was done using ICP-MS for inorganic contents and XRD for the surface structural constituents. The contaminated water was prepared by diluting AAS standard solutions of cadmium and lead containing 1000 mg/L to required concentrations using distilled deionized water. Equilibrium and kinetic batch studies were done to evaluate biosorbent remediation of aqueous cadmium and lead. The treated water was analysed for DOC and residual trace metal ions using the TOC analyser and ICP-MS respectively. The experimental data were fitted to kinetic models and equilibrium isotherm models. Results in these studies showed that sodium hydroxide treatment enhanced sorption intensity of the biosorbents better than peroxide treatment. A pseudo-second-order kinetic model and the Langmuir isotherm provided good fits to the biosorption data. The underlying reaction mechanism was mainly …