title: Morphology characteristics and mode of CaO encapsulation during treatment of electrolytic manganese solid waste.
abstract: Electrolytic manganese solid waste (EMSW) is composed of manganese, calcium, and other sulfates. Common practice in China is to treat EMSW with quicklime (CaO); however, the per unit mass treatment efficiency of CaO is low. Studies of the interface between the CaO and EMSW particle and their microstructural characteristics are limited; these interactions may explain the low treatment efficiency. We conducted leaching experiments and measurements of the secondary heat generated by hydration of CaO to assess the extent of excess CaO in EMSW. The microstructure of CaO was also analyzed. It was determined that excess CaO particles in the EMSW were encapsulated, which influenced CaO hydration and morphology. The outer layer of the encapsulated CaO contained high levels of calcium and sulfur, which postulated to be caused by CaSO4precipitates formed from the reaction of CaO hydration products with soluble sulfate. Three types of CaO encapsulation were identified: fully encapsulated CaO (55 % of the total CaO), partly encapsulated CaO (32 %), and self-encapsulated CaO (13 %). High concentrations of soluble sulfates in EMSW cause CaO encapsulation. These react to form CaSO4, which could negatively influence mass transfer and result in low treatment efficiency of EMSW by CaO.
authors.affiliation: 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.|Institute of Resources and Environmental Engineering, Shanxi University, Taiyuan, People's Republic of China.
authors.forename: Bing
authors.initials: B
authors.lastname: Du
authors.affiliation: Technology Center for Heavy Metal Cleaner Production Engineerings, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China. danzg@craes.org.cn.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Dan
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment & Cleaner Production Centre, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.
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: Tingzheng
authors.initials: T
authors.lastname: Guo
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: Haiyan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Technology Center for Heavy Metal Cleaner Production Engineerings, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Shi
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: D017610:Calcium Compounds / Q000737:chemistry*; D002681:China; D004572:Electrolysis; D004785:Environmental Pollutants / Q000737:chemistry; D008345:Manganese / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D013431:Sulfates; D013455:Sulfur
chemical_list: D017610:Calcium Compounds; D004785:Environmental Pollutants; D010087:Oxides; D013431:Sulfates; D008345:Manganese; D013455:Sulfur; C016538:lime
keywords: Calcium oxide; Electrolytic manganese solid waste; Encapsulation; Microstructure; Secondary hydration heat