Experimental data of adsorption of Cr(III) from aqueous solution using a bentonite: Optimization by response surface methodology

Experimental data of adsorption of Cr(III) from aqueous solutions using a Colombian bentonite were acquired. The adsorbent material was characterized by XRF, XRD, and nitrogen physisorption. The effect dataset of pH, agitation speed, contact time and adsorbent amount on the removal of Cr(III) from an aqueous solution, using sodium bentonite was reported. A complete factorial design 3(2) with two replicates was used to estimate the influence of the adsorbent amount (0.50, 0.75 and 1.00 g) and pH (2.0, 3.0 and 4.0) on Cr(III) removal. Experimental dataset was evaluated with Design Expert® software using the response surface methodology (RSM) in order to obtain the interaction between the processed variables and the response. The optimal conditions for Cr(III) removal from aqueous solution of 50 mg/l were as follows: pH of 3.5, and the bentonite amount equals 0.96 g, keeping constant the contact time at 60 min and stirring speed at 250 rpm. The equilibrium isotherms at 25, 30 and 35 °C were fitted by means of the Langmuir and Freundlich models, and the respective parameters of such models were obtained. The maximum adsorption capacity of sodium bentonite to Cr(III) removal was between 6.44 ± 0.11 and 6.79 ± 0.21 mg/g in the temperature range from 25 to 35 °C. According to the experimental data acquired, sodium bentonite is an effective adsorbent for the Cr(III) removal from aqueous solutions, with the advantage of being a natural, abundant and low-cost material.