Immobilization of Mn and NH4 +-N from electrolytic manganese residue waste
2016
Chen, Hongliang | Liu, Renlong | Liu, Zuohua | Shu, Jiancheng | Tao, Changyuan
The objective of this work was the immobilization of soluble manganese (Mn) and ammonium nitrogen (NH₄ ⁺-N) leached from electrolytic manganese residue (EMR). Immobilization of Mn was investigated via carbonation using carbon dioxide (CO₂) and alkaline additives. NH₄ ⁺-N immobilization was evaluated via struvite precipitation using magnesium and phosphate sources. Results indicated that the immobilization efficiency of Mn using CO₂ and quicklime (CaO) was higher than using CO₂ and sodium hydroxide (NaOH). This higher efficiency was likely due to the slower release of OH⁻ during CaO hydrolysis. The immobilization efficiency of Mn was >99.99 % at the CaO:EMR mass ratio of 0.05:1 for 20-min reaction time. The struvite precipitation of NH₄ ⁺-N was conducted in the carbonated EMR slurry and the immobilization efficiency was 89 % using MgCl₂ · 6H₂O + Na₃PO₄ · 12H₂O at the Mg:P:N molar ratio of 1.5:1.5:1 for 90-min reaction time. A leaching test showed that the concentrations of Mn and NH₄ ⁺-N in the filtrate of the treated EMR were 0.2 and 9 mg/L, respectively. The combined immobilization of Mn and NH₄ ⁺-N was an effective pretreatment method in the harmless treatment of the EMR.
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