SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2019, Vol. 27 ›› Issue (12): 2917-2924.DOI: 10.1016/j.cjche.2019.07.002

• Separation Science and Engineering • Previous Articles     Next Articles

Acid precipitation coupled electrodialysis to improve separation of chloride and organics in pulping crystallization mother liquor

Zhaoyang Li, Rongzong Li, Zhaoxiang Zhong, Ming Zhou, Min Chen, Weihong Xing   

  1. State Key Laboratory of Materials-Oriented Chemical Engineering, National Engineering Research Center for Special Separation Membrane, Nanjing Tech University, Nanjing 211816, China
  • Received:2019-05-27 Revised:2019-06-25 Online:2020-03-17 Published:2019-12-28
  • Contact: Ming Zhou, Weihong Xing
  • Supported by:
    Supported by the Prosepective Joint Research Project of Jiangsu Province (BY2014005-06).

Acid precipitation coupled electrodialysis to improve separation of chloride and organics in pulping crystallization mother liquor

Zhaoyang Li, Rongzong Li, Zhaoxiang Zhong, Ming Zhou, Min Chen, Weihong Xing   

  1. State Key Laboratory of Materials-Oriented Chemical Engineering, National Engineering Research Center for Special Separation Membrane, Nanjing Tech University, Nanjing 211816, China
  • 通讯作者: Ming Zhou, Weihong Xing
  • 基金资助:
    Supported by the Prosepective Joint Research Project of Jiangsu Province (BY2014005-06).

Abstract: Inefficient separation of inorganic salts and organic matters in crystallization mother liquor is still a problem to industrial wastewater treatment since the high salinity significantly impedes organic pollutant degradation by oxidation or incineration. In the study, acidification combined electrodialysis (ED) was attempted to effectively separate Cl- ions from organics in concentrate pulping wastewater. Membrane's rejection rate to total organic carbon (TOC) was 85% at wastewater intrinsic pH=9.8 and enhanced to 93% by acidifying it to pH=2 in ED process. Negative-charged alkaline organic compounds (mainly lignin) could be liberated from their sodium salt forms and coagulated in acidification pretreatment. Neutralization of the organic substances also made their electro-migration less effective under electric driving force and in particular improved separation efficiency of chloride and organics. After acid-ED coupled treatment (pH=2 and J=40 mA·cm-2)[TOC] remarkably reduced from 1.315 g·L-1 to 0.048 g·L-1 and[Cl-] accumulated to 130 g·L-1 in concentrate solution. Recovery rate of NaCl was 89% and the power consumption was 0.38 kW·h·kg-1 NaCl. Irreversible fouling was not caused as electric resistance of membrane pile maintained stably. In conclusion, acidic-ED is a practical option to treat salinity organic wastewater when current techniques including thermal evaporation and pressure-driven membrane separation present limitations.

Key words: Crystallization mother liquor, Acid precipitation, Electrodialysis, Chloride recovery

摘要: Inefficient separation of inorganic salts and organic matters in crystallization mother liquor is still a problem to industrial wastewater treatment since the high salinity significantly impedes organic pollutant degradation by oxidation or incineration. In the study, acidification combined electrodialysis (ED) was attempted to effectively separate Cl- ions from organics in concentrate pulping wastewater. Membrane's rejection rate to total organic carbon (TOC) was 85% at wastewater intrinsic pH=9.8 and enhanced to 93% by acidifying it to pH=2 in ED process. Negative-charged alkaline organic compounds (mainly lignin) could be liberated from their sodium salt forms and coagulated in acidification pretreatment. Neutralization of the organic substances also made their electro-migration less effective under electric driving force and in particular improved separation efficiency of chloride and organics. After acid-ED coupled treatment (pH=2 and J=40 mA·cm-2)[TOC] remarkably reduced from 1.315 g·L-1 to 0.048 g·L-1 and[Cl-] accumulated to 130 g·L-1 in concentrate solution. Recovery rate of NaCl was 89% and the power consumption was 0.38 kW·h·kg-1 NaCl. Irreversible fouling was not caused as electric resistance of membrane pile maintained stably. In conclusion, acidic-ED is a practical option to treat salinity organic wastewater when current techniques including thermal evaporation and pressure-driven membrane separation present limitations.

关键词: Crystallization mother liquor, Acid precipitation, Electrodialysis, Chloride recovery