Adsorption of Crude Oil Spill from Aqueous Solution using Agro-Wastes as Adsorbents

Ever increasing and growing awareness of oil-spillage to water environment has led to the search for cost-effective unconventional remediating techniques. This study was carried out using agro-wastes (Rice Husks, Banana Peels and Groundnut Husks) adsorbents. They were activated with H3PO4 for crude oil spill removal from aqueous solution; results were analysed using atomic absorption spectroscopy. The raw agro-wastes and their activated forms were characterized by SEM. The sorption study for maximum adsorption capacity were carried out at different adsorbent concentrations, adsorbent dosage, contact time, pH and rotational speed. The experimental results were analysed using Langmuir, Freundlich, Temkin, Dubinin-Radushkevich isotherm models. The maximum average adsorption capacity (qe) for raw and activated carbon adsorbents were observed in rice husks with 0.2750 and 0.3698 mg/g respectively. The Langmuir isotherm was found to well represent the measured sorption data for the raw and activated banana peel while the remaining raw and activated adsorbents followed the Temkin isotherm. The batch adsorption data on the effect of contact time were fitted into the pseudo-first-order and pseudo-second order models. The banana peel data and its activated form were best described by the pseudo-second-order model indicating chemisorption process while the remaining adsorbents followed the pseudo-first-order model indicating physisorption process. The average removal efficiency of oil by the various adsorbents used increase in the order: (Raw: Banana Peels (50.4 %) < Groundnut Husks (56.8 %) < Rice Husks (74.4 %); Activated Carbon: Banana Peels (61.4 %) < Groundnut Husks (65.6 %) < Rice Husks (82.8 %)). Results of this study (high values of R2 and least values AARE and RMSE) revealed and confirmed that activated carbon adsorbents have better adsorption capacity than the raw forms to clean-up oil spills in aqueous solution.