Anionic collector adsorption onto bentonites and potential applications in the treatment of mining wastewater

Abstract

Mining is one of the most water-dependent industrial activities. Thus, with the goal of developing an environmental and economically viable alternative for the treatment of generated effluents originating from mining activities, the adsorbent potential of natural and modified bentonites was tested to remove fatty acid collectors used in the processing of apatite minerals. A full 23 factorial design was applied to study the effects of the process variables (initial concentration, pH and adsorbent mass). The materials were undergone to methods of characterization such as zeta potential analysis, X-ray diffraction (XRD), X-ray fluorescence (XRF), cation exchange capacity (CEC) and surface area measurements. The analysis showed the presence of negative charges on the bentonite structures, as well as high surface area (SBET = 67.99 m2 g−1), important characteristics for the adsorption process. Among the tested adsorbents, natural materials, NB1 and NB4, stood out as being highly efficient at pH values close to 8.0, and masses of 0.4 g. The kinetic data were better adjusted to the Avrami model (NB1 and NB3), Elovich (NB4) and pseudo-second order (B3CTAB). The Sips isotherm model was the most adequate for all adsorbents. The maximum adsorption capacities (Qm (mg g−1)) were 847.85, 581.67, 322.86 and 250.65 for NB1, NB4, NB3 and B3CTAB, respectively. According to the results, bentonites have a great potential to be applied as low-cost adsorbents for the treatment of mining effluents, especially for removing fatty acid-based collectors, contributing to a more sustainable process.