Abstract:
An attempt on the use of rice husk ash (RHA), an agricultural waste, as an adsorbent for the adsorption of humic acids from water was studied. Preliminary studies have been shown the feasibility of rice husk ash for humic acids removal from water. The adsorbents were characterized for its various phisico-chemical properties. Batch studies were performed to evaluate the influences of various experimental parameters such as contact time, pH and initial concentration on the adsorption of humic acids. Optimum conditions for humic acids adsorption were found as follows, 60 min equilibrium time and initial pH 3.0. Equilibrium data obtained have been found to agree with both Langmuir and Freundlich equations. The maximum adsorption capacity of rice husk ash was 2.7 mg/g, at pH 6.0. In addition, rice husk ash was modified with 3-aminopropyltriethoxysilane. Again, the adsorption behavior of the modified rice husk ash (RHA-NH[subscript 2]) was studied. Optimum conditions for humic acids adsorption were found to be 30 min equilibrium time and initial pH in the range of 3.0-4.0. The results showed that the adsorption capacity of the modified rice husk ash was higher than that of rice husk ash. Experimental data fitted well into the Langmuir equation and the maximum adsorption capacity was 8.2 mg/g, at pH 6.0. The column method was also performed. It was found that the prepared rice husk ash can be used in both batch and column methods for water treatment. The comparative efficiency of rice husk ash and commercial activated carbon to adsorb humic acids from water was studied. The result showed that adsorption efficiency of the new rice husk ash adsorbents was not significantly different from commercial activated carbon. The adsorbents were applied for humic acids removal from surface water.
