Performances of conventional activated carbon and low-cost adsorbent from clay and mineral coal in decolorization of AO7 solution

The adsorption of acid orange 7 (AO7) from aqueous solution by activated carbon (AC) as a commercial adsorbent, and mineral coal (MC) and natural clay (Cl) as a low-cost and natural adsorbent was investigated. The study was carried out under various conditions, such as the average adsorbent particle size, adsorbent dosage, contact time, pH, initial dye concentration, temperature and effect of surfactant. The adsorption was particle size dependent with a high adsorption of AO7 by MC which has the smallest particle size. The variation of adsorbent dosage allowed finding the optimal dose. Adsorption kinetic data were properly fitted with the pseudo-second order kinetic model. The good fitting was obtained with the Langmuir model (R-2 = 0.99). It shows a maximum layer adsorption capacity of 182 mg/g by MC, 278 mg/g by AC and 403 mg/g by Cl at 25 degrees C. The adsorption increased with an increase in the pH. From pH = 7, the equilibrium was stabilized and was unchanged in basic range using any adsorbent.