ABSTRACT
The research was conducted to develop adsorbent for the removal of crude oil from contaminated water. Chitosan, rice husk silica ash were successfully developed from prawn and raw rice husk waste respectively and their composite also produced. Chitosan was produced by demineralization, deproteinization and deacetylation of prawn while rice husk silica ash was produced by acid and thermal treatment of virgin rice husk. The adsorbents produced were characterized using FTIR, XRD, AAS and proximate analysis and were used to remove crude oil spill from simulated crude oil contaminated water using batch adsorption. Design Expert software 6.06 was used to design the adsorption experiment. The adsorption data were fitted Langmuir, Freundlich and Temkin isotherm. A kinetic analysis was also undertaken studies also carried out. The chitosan yield was 20.33% and the percentage rice husk ash obtained was 6.75%. The degree of deacetylation using C/N ratio and FTIR peaks were 85.70% and 86.27% respectively.FTIR and XRD analysis showed that both adsorbents produced were amorphous and could adsorbed crude oil on their surface. The effect of influencing parameters such as contact time, adsorbate concentration, adsorbent dosage and formulation ratio were studied. It was generally shown that adsorption process increases with time and adsorbate concentration and decreases with adsorbent dosage. Adsorption capacity was found to increase with increase in the concentration of chitosan in the composite formulated. The predictive models developed and optimized for adsorption capacity of chitosan, rice husk silica ash and their composite were significant with R2 value of 0.8488, 0.9384 and 0.8382 and ANOVA model results of P>F value of 0.0001, 0.0001 and 0.0017 respectively. The adsorption data obtained for rice husk silica, chitosan and the composite were better fitted byTemkin isotherm with R2 value of 0.9712, 0.9995 and 0.9999 respectively. The adsorption capacity of rice husk silica, chitosan and composite from isotherm studies were obtained to be 5.7, 18.34 and 18.85 g/g adsorbent respectively. The heat of adsorption obtained from Temkin isotherm studies were generally low of value -67.55,-52.55 and -50.9 kJ/molindicating physisosorption of adsorbents to the crude oil.For the kinetic studies, the pseudo-second order model suitably described the removal of crude oil by rice husk silica, chitosan and composite with R2 value 1.0, 0.9995 and 0.9999 respectively