A novel method for the stabilization of soluble contaminants in electrolytic manganese residue: Using low-cost phosphogypsum leachate and magnesia/ calcium oxide

摘要

Electrolytic manganese residue (EMR) contains a large amount of NH4+-N and Mn2+ and can negatively impact the environment. A stabilization treatment of soluble contaminants in the EMR is necessary for its reuse and safe stacking. This study presents experimental results for the stabilization of NH4+-N and Mn2+ in the EMR using phosphogypsum leachate as a low-cost phosphate source and MgO/CaO (PLMC) process. The results demonstrated that the stabilization efficiency of NH4+-N and Mn2+ was 93.65% and 99.99%, respectively, under the following conditions: a phosphogypsum leachate dose of 1.5 mL g(-1), an added MgO dose of 0.036 g g(-1), an added CaO dose of 0.1 g g(-1) and a reaction time of 2 h. The stabilization effect of the PLMC process was higher and more cost effective than that of using Na3PO4 center dot 12H(2)O and MgO/CaO. The concentration of NH4+-N and Mn2+ in the leaching liquor decreased to 80 mg L-1 and 0.5 mg L-1, respectively, after the stabilization under the optimum conditions. The stabilization characteristics indicated that NH4+-N was stabilized to form NH4MgPO4 center dot 6H(2)O (struvite) and that Mn2+ was stabilized to form Mn-5(PO4)(2)(OH)(4), Mn-3(PO4)(2)center dot 3H(2)O and Mn (OH)(2). PO43--P, F-, and heavy metal ions of the phosphogypsum leachate were removed from the leaching liquor and stabilized in the treated EMR.