Investigating the Kinetics and Potentials of Acid-Activated Bentonite Clay from Gewane, Afar, Ethiopia, for Adsorption of Congo Red Dye
摘要
The study aimed to investigate the kinetics and potentials of activated Na-bentonite for Congo red adsorption. First, the raw bentonite was collected, ground, sieved, and activated using sulfuric acid, and then, an adsorption study was conducted. The acid activation was carried out using sulfuric acid solutions of various concentrations in the range of 0.05–0.5 M at different temperatures: 30, 60, and 90 °C for 3 h. Based on the result, bentonite activated using 0.1 M sulfuric acid at 30 °C showed a higher efficiency in removing Congo red dye from an aqueous solution and was selected for further studies. A full factorial experimental design was employed to correlate the effect of key parameters, contact time, initial dye concentration, and pH on the adsorption of Congo red dye by bentonite activated with 0.1 M sulfuric acid using batch adsorption. The removal capacity of raw bentonite was 13.8%. Modified bentonite treated at 0.05, 0.075, 0.1, 0.25, and 0.5 M concentrations of acid resulted in dye removal capacity of 85.78%, 86.4%, 88.6%, 69.27%, and 44%, respectively. The maximum adsorption capacity was determined to be 39.9 mg/g at an initial dye concentration of 900 mg/l, a pH of 5, and a contact time of 6 h. The optimum percentage of dye removal at 6 h was 95.74% for a dye concentration of 100.58 mg/l and pH of 5.03. Isotherm data for the adsorption of Congo red dye on acid-activated bentonite were evaluated by using Langmuir and Freundlich adsorption isotherms where the Freundlich isotherm model fitted better with correlation coefficient R2 = 0.997. Adsorption data was examined by pseudo-first-order and pseudo-second-order kinetics. The results indicated that the adsorption kinetics were well represented by pseudo-second-order kinetics. Activated bentonite clay can remove dye from industrial effluent by an adsorption technique.