Adsorption of sulfate from acid mine drainage in Northwestern China using Malan loess

Malan loess is a gray-yellow/brown-yellow, highly porous substance that has carbonate and calcium nodule late quaternary sediment formed by the accumulation of windblown dust. In this paper, the adsorption performances and mechanisms of sulfate adsorbed on Malan loess (Q3) were evaluated using batch adsorption experiments. The effects of the solid-to-liquid ratio, contact time, initial concentration, temperature, and pH on sulfate adsorption in acid mine drainage (AMD) were studied. The results indicated that sulfate adsorption capacity in loess increased with increasing contact time, initial concentration, and temperature, but decreased with an increased solid-to-liquid ratio. The acid condition was beneficial to the adsorption of sulfate. The optimal solid-to-liquid ratio was 100 g/L within the 50 to 800 g/L range, whilst the adsorption capacity and removal rate were 123.86 mg/g and 61.38%, respectively. XRD and FTIR analysis with or without sulfate adsorption demonstrated that calcite of loess played a key role during adsorption. Based on the results of batch experiments and physiochemical analysis, chemical adsorption was the dominant contributor. These results suggest that Malan loess is an applicable adsorbent for sulfate pollution.