Modeling of adsorption process establishes mathematical relationship between the interacting process variables and process optimization is important in determining the values of factors for which the response is at maximum. In this paper, response surface methodology was employed for the modeling and optimization of adsorption of phenol onto rice husk activated carbon. Among the action variables considered are activated carbon pretreatment temperature, adsorbent dosage, and initial concentration of phenol, while the response variables are removal efficiency and adsorption capacity. Regression analysis was used to analyze the models developed. The outcome of this research showed that 99.79% and 99.81% of the variations in removal efficiency and adsorption capacity, respectively, are attributed to the three process variables considered, that is, pretreatment temperature, adsorbent dosage, and initial phenol concentration. Therefore, the models can be used to predict the interaction of the process variables. Optimization tests showed that the optimum operating conditions for the adsorption process occurred at initial solute concentration of 40.61？mg/L, pretreatment temperature of 441.46°C, adsorbent dosage 4？g, adsorption capacity of 0.9595？mg/g, and removal efficiency of 97.16%. These optimum operating conditions were experimentally validated. 1. Introduction The increase in industrial, agricultural, and domestic activities has led to the discharge of large amounts of wastewater containing toxic pollutants. The growing awareness of the adverse effects of the presence of these water pollutants has led to increased strict regulation of water pollution, hence making the treatment of wastewater generated from industrial activities a high priority [1]. Phenols are among the most common water pollutants that can cause hazards including health hazard which may lead to death. Amongst hydrocarbons present in refinery wastewater, phenol is one of the main dissolved components and it is also one of the difficult hydrocarbons to degrade biologically [2, 3]. Consequently, pollution control and management have evolved many technologies for the treatment of wastewater [4, 5]. These technologies and methodologies which differ in their performance and effectiveness include coagulation, filtration, ion exchange, sedimentation, solvent extraction, adsorption, electrodialysis, chemical oxidation, disinfection, chemical precipitation, and membrane separation [6, 7]. Among the various available technologies for water pollution control, adsorption process is considered
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