Revealing the role of calcium alginate-biochar composite for simultaneous removing SO and Fe in AMD: Adsorption mechanisms and application effects.

The remediation of acid mine drainage (AMD) is particularly challenging because it contains a large amount of Fe and a high concentration of SO. To reduce the pollution caused by SO and Fe in AMD and realize the recycling of solid waste, this study used distillers grains as raw materials to prepare biochar at different pyrolysis temperatures. Calcium alginate-biochar composite (CA-MB) was further synthesized via the entrapment method and used to simultaneously remove SO and Fe from AMD. The effects of different influencing factors on the sorption process of SO and Fe were studied through batch adsorption experiments. The adsorption behaviors and mechanisms of SO and Fe were investigated with different adsorption models and characterizations. The results showed that the adsorption process of CA-MDB600 on SO and Fe could be well described by Elovich and Langmuir-Freundlich models. It was further proved by the site energy analysis that the adsorption mechanisms of SO onto CA-MDB600 were mainly surface precipitation and electrostatic attraction, while that of Fe removal was attributed to ion exchange, precipitation, and complexation. The applications of CA-MDB600 in actual AMD proved its good application potential. This study indicates that CA-MDB600 could be applied as a promising eco-friendly adsorbent for the remediation of AMD.