Oxidation of Ni(II)-cyano and Co(III)-cyano complexes by Ferrate(VI): Effect of pH

Khemarath Osathaphan, Wasinee Kittisarn, Prapaporn Chatchaitanawat, Ria A. Yngard, Hyunook Kim, Virender K. Sharma

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Free cyanide (CN-) and metal-cyanide complexes (tetracyanonickelate(II)), Ni(CN)42- and hexacyanocobaltate(III)), Co(CN)63- are common constituents of effluents of mining, coal gasification, and petroleum refining. This article presents the degradation of Ni(CN)42- and Co(CN)63- by ferrate(VI) (FeVIO 42-, Fe(VI)) in alkaline media. The effect of pH (9.0-11.0) and reactant molar ratios on the degradation of the cyanide complexes was investigated. The removal of Ni(CN)42- ion in 200 min was found to be > 90% at pH 9.0; forming cyanate (NCO-) ions as the stoichiometric products ([Fe(VI)]:[Total CN-] = [Fe(VI)]:[NCO-] ≈ 1.0). The degradation efficiency decreased with an increase in pH from 9.0 to 11.0. Comparatively, the Co(CN)6 3- ion could be degraded only up to 10% in 200 min at pH 9.0 and the final oxidized products were nitrite and nitrate ions. The oxidation efficiency of removing Co(CN)63- did not vary significantly with pH. Fe(VI) consumptions as a result of the oxidation of free cyanide and metal-cyanides and their products are compared and discussed.

Original languageEnglish
Pages (from-to)1380-1384
Number of pages5
JournalJournal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering
Issue number12
StatePublished - 15 Oct 2014


  • Complexed cyanide
  • cyanate
  • cyanide
  • ferrate
  • nitrate
  • nitrite
  • removal


Dive into the research topics of 'Oxidation of Ni(II)-cyano and Co(III)-cyano complexes by Ferrate(VI): Effect of pH'. Together they form a unique fingerprint.

Cite this