One of the most serious environmental problems that can pose irreversible economical and ecological impacts is oil pollution. Different methods are used for remediation of aqueous environment contaminated by oil compounds with different viscosities in aqueous environment, including crude oil, engine oil and used (spent) oil. Rice husk samples modified by thermal treatment in nitrogen and air atmospheres at 600 for 1 h. The oil adsorption capacity was determined by weighting method. The sorbents were characterized using composition analysis (CHNSO), thermal analysis (TGA), FT-IR spectroscopy and scanning electron microscopy (SEM). The effect of various parameters including pH, contact time, particle size, initial oil concentration, adsorbent dose on adsorption were investigated. The results showed that adsorption kinetic was rapid and the kinetic data for oil sorption by three adsorbents were precisely described by pseudo-second order models. The change in the pH of oil solution from 1–10, had no effect in the adsorption of oil compounds. The decrease of particle size of the raw rice hulls, reduced oil sorption percent. However, particle size of treated adsorbents except for adsorption of used oil, had no effect on the adsorption percent of other oil compounds. Raw rice hull and rice hull ash have specific adsorption capacity for oil compounds, and after adsorption of certain oil concentration, adsorption remains constant and was not increased by addition of adsorbent amount. Pyrolyzed adsorbent had the high oil capacity. The removal of total engine oil, used oil and crude oil in water medium need 2, 3 and 5-6 times of pyrolyzed adsorbent respectively. The adsorption of crude oil and used oil samples on rice hull and rice hull ash obeyed the Freundlich isotherm models and on pyrolyzed adsorbent was fitted well by Langmuir isotherm model. But engine oil adsorption on rice hull and pyrolyzed adsorbent was described well by the Langmuir and its adsorption on rice hull ash fitted by Freundlich model. Maximum capacity of adsorption for engine oil, used oil and crude oil by pyrolyzed adsorbent was 2000, 1250 and 1000 mg/g respectively. Pyrolyzed adsorbent indicated the higher performance in comparison with rice hull ash for adsorption of three oil compounds. In general, use of rice hull as adsorbent remove the environmental pollutants as well as reduce the problems of burning and disposal of agricultural by-products. Key words : rice husk (rice hull), oil pollution, adsorption, thermal treatment, Adsorption kinetic and isotherms
