Efficiency Comparison of Conventional and Modified Rice Husk Ash in the Removal of Phenol from Aqueous Solutions: Isotherm, Kinetics and Thermodynamics Studies

Objectives Phenol is known as a toxic and carcinogen compound in the environment. It also produces unpleasant taste and odor in water reservoirs. In this study, the efficiencies of modified and conventional rice husk ashes as low-cost adsorbents were compared regarding phenol removal from aqueous solutions.
Methods This study is an interventional laboratory research in which, at first carbonized rice husk was prepared at a temperature of 450°C. Then, to improve rice husk ash adsorption capacity, NH4CL was used for its modification. Then, the effects of physiochemical factors (pH, contact time, phenol concentration and adsorbent dose) on phenol removal were studied.
Results Findings showed that the phenol removal by modified and conventional rice husk ash was 94.85% and 52.8%, respectively. The adsorption process for both adsorbents followed Freundlich isotherm (R2≥ 0. 99) and the pseudo-second order model (R2>0.99). Maximum adsorption capacity based on Langmuir model for the modified and conventional husk rice ashes were 66.6 mg/g and 4.7 mg/g, respectively.
Conclusion Results indicated that efficiency of modified husk rice ash was more than that of the conventional type in phenol removal, causing less adsorbent consuming in the industrial treatment plants. Therefore, because of its availability and easy modification, it can be used in water and wastewater technology for phenol removal.