Experimental Studies on Coupled Treatment of Chromite Ore Processing Residue

Maria Chrysochoou, Dimitris Dermatas, Christos Christodoulatos

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

A study was performed to investigate the combined treatment of hexavalent chromium (Cr(VI)) and heaving in Chromite Ore Processing Residue (COPR). Treatment of heaving focused on the intentional exhaustion of the mineral brownmillerite, the hydration of which is considered responsible for volume expansion in COPR deposition sites in New Jersey. The addition of sufficient amounts of sulfate under different conditions of temperature, acidity, and particle size aimed in the quick transformation of brownmillerite to ettringite, a phenomenon observed during a COPR pilot scale study. Simultaneously, the reductive treatment of hexavalent chromium (Cr(VI)) in COPR was pursued using calcium polysulfide (CPS) and ferrous sulfate (FS). X-ray Absorption Near Edge Spectroscopy (XANES) analyses showed that neither reductant was able to reduce Cr(VI) below 1,000 mg/kg after three months (FS) and six months (CPS) of treatment. However, competitive sulfide oxidation by oxygen was much slower compared to ferrous iron oxidation, as evidenced by chemical analyses. Quantitative X-ray diffraction analyses showed that brownmillerite dissolved to form ettringite only in a sample treated with FS at 50°C; neither acidity or temperature alone were able to trigger brownmillerite dissolution and ettringite formation. Particle size reduction to <150 µm had also no apparent effect in the rate of brownmillerite dissolution. Thus, CPS is deemed a more appropriate reductant for Cr(VI)treatment, while the exhaustion of brownmillerite appears to be a challenging engineering task.

Original languageEnglish
Title of host publicationContaminated Sediments
Subtitle of host publicationSustainable Management and Remediation
EditorsMark Dyer, Rosa Galvez
PublisherASTM International
Pages281-295
Number of pages15
VolumeSTP 1518
ISBN (Electronic)9780803175044
DOIs
StatePublished - 2010
Event2009 Symposium on Contaminated Sediments: Sustainable Management and Remediation - Dublin, Ireland
Duration: Jun 30 2009Jul 3 2009

Conference

Conference2009 Symposium on Contaminated Sediments: Sustainable Management and Remediation
Country/TerritoryIreland
CityDublin
Period6/30/097/3/09

ASJC Scopus subject areas

  • General Engineering
  • Public Health, Environmental and Occupational Health
  • Environmental Engineering
  • General Materials Science
  • Nuclear Energy and Engineering

Keywords

  • XANES
  • chromite ore processing residue
  • hexavalent chromium
  • reduction

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