Characterization and adsorption behaviour of anthill for the removal of anionic dye from aqueous solution

Abstract

The use of commercial adsorbents for the removal of dye from aqueous environment is expensive. Anthill could serve as alternative and cheap adsorbent in treating coloured effluents. However, this study focused on adsorption of dye from aqueous solution by anthill via batch mode process. The anthill was thermally activated at 900 °C for 2 h and then characterized using various techniques. The 2k factorial experimental design in Design Expert Software version 11 was employed for the optimization of adsorption process variables, which include initial dye concentration, contact time, adsorbent dosage and pH. Experimental data were evaluated using Langmuir and Freundlich models. The main effect analysis showed that adsorbent dosage contributes significantly to the adsorption of CR as much as 38.48%, while initial dye concentration contributes the least to the process as low as 0.00066%. The obtained data revealed that the maximum dye uptake was achieved under the optimized factor combination of adsorbent dosage of 0.5 g, contact time of 120 min, medium pH of 4 and initial CR concentration of 50 mg/L. Equilibrium adsorption isotherm and kinetic analyses revealed that Freundlich isotherm and pseudo-second-order model fitted well to the experimental data. The value of Freundlich exponent (n = 1.11) indicated that the adsorption process was favourable. The work showed that anthill material is a promising adsorbent for removing dyes from aqueous solution.