Effect of Organic and Inorganic Acid Pretreatment on Structural Properties of Rice Husk and Adsorption Mechanism of Phenol

Rice husk treated with organic and inorganic acid was tested as a low cost adsorbent for the removal of phenol from artificial wastewater in batch adsorption procedure. The physical and surface properties of the developed adsorbents were characterized using FTIR and SEM. The efficiency of these adsorbents was evaluated by varying the adsorbent doses. A comparison of organic acid (citric acid) and inorganic acids (HCL, H2SO4 and HNO3) treatment show that rice husk treated with organic acid (a weak acid) has less removal efficiency compared to inorganic acid (stronger acid) treated rice husk. This is the result of the active sites produced by citric acid. In general, removal efficiency between 40.21-59.54%, 32.11-43.87%, 31.33-40.66% and 22.42-35.41% could be achieved after treating the rice husk with H2SO4, HCl, HNO3 and citric acid, respectively; in comparison to the raw rice husk which is able to achieve 18.61-28.94% removal efficiency after 72hrs.The kinetics of phenol adsorption is found to follow the pseudo-second-order kinetic model. FTIR analysis shows that the –OH, C-H, C≡C, C-C, C=O, -CO, Si-OH and –Si-H groups contribute to the adsorption of phenol onto the surface of adsorbent.