SCI和EI收录∣中国化工学会会刊

Chin.J.Chem.Eng. ›› 2013, Vol. 21 ›› Issue (11): 1303-1312.DOI: 10.1016/S1004-9541(13)60626-6

• ENERGY, RESOURCES AND ENVIRONMENTAL TECHNOLOGY • Previous Articles     Next Articles

Reactive Crystallization of Calcium Sulfate Dihydrate from Acidic Wastewater and Lime

DENG Licong1,2, ZHANG Yifei1, CHEN Fangfang1, CAO Shaotao1, YOU Shaowei1,2, LIU Yan1,2, ZHANG Yi1   

  1. 1 Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
    2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2012-07-30 Revised:2012-12-17 Online:2013-11-26 Published:2013-11-28
  • Contact: ZHANG Yifei, CHEN Fangfang
  • Supported by:

    Supported by the National High Technology Research and Development Program of China (2011AA060701) and the National Water Pollution Control and Management Science Program of China (2009ZX07529-005).

Reactive Crystallization of Calcium Sulfate Dihydrate from Acidic Wastewater and Lime

邓立聪1,2, 张亦飞1, 陈芳芳1, 曹绍涛1, 游韶玮1,2, 刘艳1,2, 张懿1   

  1. 1 Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
    2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • 通讯作者: ZHANG Yifei, CHEN Fangfang
  • 基金资助:

    Supported by the National High Technology Research and Development Program of China (2011AA060701) and the National Water Pollution Control and Management Science Program of China (2009ZX07529-005).

Abstract: The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from platelet-like and needle-like shape to rod-like shape when the temperature was increased from 25 to 70 ℃. An increase in the agglomeration of calcium sulfate was found with increasing lime concentration. Metal ions markedly retard the rate of crystallization of calcium sulfate dihydrate. The crystallization of gypsum was slowed with the existence of Mg2+ in the solution, and the morphology of gypsum was transformed from platelet-like shape to rod-like shape when Mg2+ concentration reached 0.08 mol·L-1. The amorphous ferric hydroxide was coated on the calcium sulfate after the co-precipitation process while Zn2+ and Al3+ ions in the solution enhanced the agglomeration of the calcium sulfate by absorbing on the surface of the crystals. Comprehensive acidic wastewater containing heavy metals was efficiently purified by the two stage lime neutralization technology, and highly agglomerated gypsum precipitates with needle-like shape were obtained. The precipitates could be purified by sulfuric acid washing, and the metal ions were effectively separated from the calcium sulfate by-products.

Key words: reactive crystallization, acidic wastewater, lime milk, calcium sulfate dihydrate

摘要: The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from platelet-like and needle-like shape to rod-like shape when the temperature was increased from 25 to 70 ℃. An increase in the agglomeration of calcium sulfate was found with increasing lime concentration. Metal ions markedly retard the rate of crystallization of calcium sulfate dihydrate. The crystallization of gypsum was slowed with the existence of Mg2+ in the solution, and the morphology of gypsum was transformed from platelet-like shape to rod-like shape when Mg2+ concentration reached 0.08 mol·L-1. The amorphous ferric hydroxide was coated on the calcium sulfate after the co-precipitation process while Zn2+ and Al3+ ions in the solution enhanced the agglomeration of the calcium sulfate by absorbing on the surface of the crystals. Comprehensive acidic wastewater containing heavy metals was efficiently purified by the two stage lime neutralization technology, and highly agglomerated gypsum precipitates with needle-like shape were obtained. The precipitates could be purified by sulfuric acid washing, and the metal ions were effectively separated from the calcium sulfate by-products.

关键词: reactive crystallization, acidic wastewater, lime milk, calcium sulfate dihydrate