Experimental research on various slags as a potential adsorbent for the removal of sulfate from acid mine drainage.

Acid mine drainage (AMD) containing highly concentrated sulfate in the wastewater has caused severe impacts to human health and the environment. Implementing an economical and efficient method for sulfate reduction by utilizing low-cost adsorbents presents a significant challenge. In this study, ferrous slag (FS) and carbon steel slag (CSS) obtained from a local steel factory were utilized as adsorbents to remove sulfate from AMD. The influences of adsorbent dosage, adsorption time, adsorbent particle size, pH value and initial sulfate concentration on the adsorption capacity and regeneration properties were investigated using batch adsorption experiments. The results showed that acidic conditions were beneficial to the adsorption of sulfate. Under the optimal conditions (pH of 2, dosage of 50 g/L), the adsorption capacities of FS and CSS were 225.07 mg/g and 320.57 mg/g, respectively. The pseudo-second-order and the Langmuir isotherm models described the experimental data well. The regeneration experiment revealed that the CSS was regenerated repeatedly and to a greater extent than that of FS by using alkali (1 M NaOH) as the regeneration agent. Adsorption was determined to be the dominant processes for the removal of the sulfate by CSS, but also exhibited chemical precipitation. Overall, the CSS has a higher efficiency for the removal of sulfate over FS. The results provide a new method for the removal of sulfate from aqueous solution.