title: Aging of solidified/stabilized electrolytic manganese solid waste with accelerated carbonation and aging inhibition.
abstract: High concentrations of soluble Mn in electrolytic manganese solid waste (EMSW) in soil cause the severe contamination in China. Calcium oxide and magnesium oxide-dominated stabilizers are suitable for the solidification/stabilization (s/s) of EMSW. However, the long-term performance of s/s using those two types of stabilizer is problematic. The aim of this study was to develop an accelerated aging method to simulate the long-term natural carbonation of solidified/stabilized EMSW. The joint use of accelerated carbonation, leaching test, mineralogical analysis, and microstructural observation was applied to assess the long-term performance of the s/s EMSW system. On an accelerated carbonation test for solidified/stabilized EMSW, an increase in Mn leaching from 13.6 to 408 mg/kg and a 1.5-2.3 decrease in pH was achieved by using CaO-dominated stabilizers, while an increase in manganese (Mn) from 30 to 266 mg/kg and a decrease in pH of 0.17-0.68 was seen using MgO-dominated stabilizers. CaO+Na3PO4and CaO+CaCO3were exceptions in that the leaching value of soluble Mn was lower after carbonation. Mineralogical analysis showed that rhodochrosite in the carbonated s/s system was generated not only from the reduction of hausmannite but also from the reversible reaction between Mn(OH)2and MnCO3. Carbonation destroyed the tight particle structure resulting in a porous and loose structure. As for s/s EMSW treated by MgO-dominated stabilizers, carbonation affected the agglomerating structure and mineralogical composition by increasing magnesium (Mg) migration, thereby forming hydromagnesite that had weak binding ability and a nested porous shape. Therefore, carbonation by itself does not cause deterioration to s/s products of the soluble Mn but does have significant effects on the microstructure and mineralogical composition. It is recommended to add Na3PO4or CaCO3into a single CaO stabilized EMSW system to prevent aging of the system, allow formation of Mn phosphate precipitates, and improve the absorption and oxidation of soluble Mn(II).
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.|Technology Center for Heavy Metal Cleaner Production Engineerings, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.|Key Laboratory for Solid Waste Management and Environment Safety, School of Environment, Tsinghua University, Beijing, People's Republic of China.
authors.forename: Bing
authors.initials: B
authors.lastname: Du
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China. zhoucb@craes.org.cn.
authors.forename: Changbo
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Technology Center for Heavy Metal Cleaner Production Engineerings, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Dan
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: Xianjia
authors.initials: X
authors.lastname: Peng
authors.affiliation: Key Laboratory for Solid Waste Management and Environment Safety, School of Environment, Tsinghua University, Beijing, People's Republic of China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Liu
authors.affiliation: Technology Center for Heavy Metal Cleaner Production Engineerings, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.
authors.forename: Ning
authors.initials: N
authors.lastname: Duan
mesh_terms: D002254:Carbonates / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods*; D004785:Environmental Pollutants / Q000032:analysis / Q000737:chemistry; D008345:Manganese / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D062611:Solid Waste / Q000032:analysis*; D013997:Time Factors
chemical_list: D002254:Carbonates; D004785:Environmental Pollutants; D062611:Solid Waste; D008345:Manganese
keywords: Accelerated carbonation; Aging; Calcium oxide; Electrolytic manganese solid waste; Magnesium oxide