Removal of chromium(VI) from wastewater by combined electrocoagulation- electroflotation without a filter

Ping Gao, Xueming Chen, Feng Shen, Guohua Chen

Research output: Journal article publicationJournal articleAcademic researchpeer-review

215 Citations (Scopus)

Abstract

A combined electrocoagulation and electroflotation process was designed to reduce Cr6+to Cr3+first and then to remove the total Cr from wastewater to a value below 0.5 mg/L. Acidic condition was employed in the reduction of Cr6+and neutral conditions were found to be beneficial for the coagulation of the precipitates of Cr(OH)3and Fe(OH)3. The formation of Fe(OH)3was ensured by sparging compressed air in the coagulation unit through a draft tube. The air not only oxidizes Fe2+produced electrically, but also helps to mix the water for a better coagulation of the particles. The two-stage electroflotation arrangement can separate the solids from the wastewater to a value of less than 3 mg/L with total Cr less than 0.5 mg/L. The residence time required is about 1.2 h. The optimal conditions for the treatment are: charge loading about 2.5 Faradays/m3water, pH value in the coagulation unit is 5-8. The power consumption is less than 1 kW h/m3water at the conductivity of 1.5 mS/cm. When aluminum ions are either added or produced in situ in the coagulation unit, the treated wastewater can be discharged without any filtration.
Original languageEnglish
Pages (from-to)117-123
Number of pages7
JournalSeparation and Purification Technology
Volume43
Issue number2
DOIs
Publication statusPublished - 1 May 2005
Externally publishedYes

Keywords

  • Electroplating
  • Filtration
  • Flotation
  • Precipitation
  • Reduction
  • Wastewater

ASJC Scopus subject areas

  • Analytical Chemistry
  • Filtration and Separation

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