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Liquid effluents generated during mineral processing are usually contaminated with heavy metals and oxyanions, requiring an effective technique for their simultaneous removal. This study evaluated adsorption as a method to remove ions from an artificial acid effluent containing Cu2+, Zn2+, and SO42−, using a mixture of activated carbon and barite as adsorbents. Adsorbent particles were prepared by grinding in a ring pulverizer for 120 s, using equal proportions of activated carbon and barite concentrate. The pH, contact time, and adsorbent particle mass were investigated. The results indicated that the adsorption efficiency depends on pH and adsorbent particle concentration: with increasing pH, the adsorption of Cu2+ and Zn2+ improves, while that of SO42− decreases. As the particle mass increases, the adsorption efficiency also increases. The maximum efficiency of simultaneous adsorption of ions of 55 ± 2.6% was achieved at pH 3 with an adsorbent particle concentration of 40 g·L−1. The experimental data best fit the pseudo-1st-order kinetic model, suggesting that the limiting stage is external or internal diffusion and that the predominant adsorption mechanism is physisorption. Furthermore, the results were best fitted to the Freundlich isotherm, indicating heterogeneous and multilayer adsorption. In conclusion, the mixture of activated carbon and barite is presented as a potential adsorbent for acid effluent treatment with heavy metals and oxyanions.
Santander et al. (Tue,) studied this question.