Pretreatment of coal gasification wastewater by acidification demulsion

Wenqi Zhang*, Jun Ma, Shidong Yang, Tao Zhang, Yongfeng Li

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


General pretreatment processes of ammonia stripping and phenols solvent extraction can reduce the concentration of toxic compounds of the coal gasification wastewater for the following biological treatment. However, some emulsified coal tar still exists in the influent and many substances in coal tar are refractory and toxic to microorganisms. This study is mainly on the removal of emulsified coal tar by acidification demulsion. The experimental results show that the acidification process of the wastewater by pure hydrochloric acid can reduce the chemical oxygen demand (COD), total organic carbon (TOC), total phenolics and oil about 3.1%-11.3%, 6%-10.8%, 5.3%-8.6% and 25.2%-57.4% respectively with pH value in the range of 4 to 7. The analysis of molecular weight distribution indicates that compounds removed from the wastewater by this process are large molecular substances. The experiment also shows that the efficiency of COD removal in the demulsion process by different acids is different and the phosphoric acid is prominent. The preserved time of the wastewater also affects the efficiency of demulsion. Small amount low-cost solid additives including kaolin and diatomite can improve the rate of coal tar sedimentation and enhance the removal efficiency of organics in the phosphoric acidification process.

Original languageEnglish (US)
Pages (from-to)398-401
Number of pages4
JournalChinese Journal of Chemical Engineering
Issue number3
StatePublished - Jun 2006
Externally publishedYes


  • Acidification
  • Coal gasification wastewater
  • Coal tar
  • Demulsion
  • Pretreatment

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Biochemistry
  • Environmental Engineering


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