Oxalic Acid Modified Rice Hull as a Sorbent for Methylene Blue Removal

The potential of oxalic acid modified rice husk (ORH) to adsorb Methylene Blue (MB) from aqueous solution was investigated under various experimental conditions. Parameters studied included pH, initial dye concentrations, contact time, sorption isotherm, agitation rate and adsorbent dosage. A comparison study on the percentage uptake of natural rice husk and oxalic acid modified rice husk on MB dye showed that oxalic acid modified rice husk gave better removal efficiency. The percentage of dye uptake increased with increasing of pH and contact time. The optimum pH for MB removal was recorded at the range of pH 4 to pH 10 and the adsorption equilibrium was achieved after the first one and a half hours of contact time. From the kinetic study, the adsorption process correlated well with pseudo-second order kinetics equation. The experimental data were fitted into different isotherm model equations and the results revealed that the system under studied is better explained by Langmuir isotherm as compared to Freundlich isotherm. The maximum sorption capacity of ORH for MB was 29.15 mg/g.