Efficient Mn recovery and As removal from manganese slag: A novel approach for metal recovery and decontamination

Abstract

Heavy metal contamination from mining slag poses severe environmental and health risks, especially evident with the challenges of Mn and As pollution in mining areas in China. To address this, we introduced a novel and efficient method integrating selective leaching, solvent extraction, and adsorption for Mn recovery and As decontamination. Utilizing their differential leaching behaviors, As and Mn were effectively and sequentially extracted. Under the optimal leaching conditions in our experiment, over 98% of As and 95% of Mn were leached from manganese waste slag. Mn-selective extraction was further augmented using di(2-ethylhexyl) phosphoric acid (D2EHPA), achieving a total yield of 93.1% from the HNO3 leachate solution. Concurrently, a novel nano-hydroxyapatite@cobalt ferrite, HAP@CoFe2O4, was rationally designed for As removal, achieving an As removal rate of 99.8%. HAP@CoFe2O4 exhibited a relatively large saturation magnetization value, enabling its rapid separation from the reaction system by applying an external magnetic field. The implications of this study extend beyond mere technological advancements, highlighting the need for a broad spectrum of potential users to engage with this novel methodology for Mn waste slag treatment. Overall, this approach not only facilitated Mn recovery and As decontamination but also presented a promising solution for manganese waste slag in a broader spatial context.