Ferrate(VI): A green chemical for the oxidation of cyanide in aqueous/waste solutions

Abstract

The higher oxidation state of iron, i.e. Fe(VI), was employed for the oxidation of the important toxic ion cyanide in aqueous/waste waters. Cyanide was oxidized to cyanate, which is 1,000 times less toxic than cyanide, and can often be accepted for its ultimate disposal. It was noted that Fe(VI) is a very powerful oxidizing agent, and can oxidize most of the cyanide within a few minutes, ca 5 minutes, of contact. The extent of the reduction of Fe(VI) was obtained using the UV-Visible measurements. Further, the UV-Visible data was used to explain the reaction kinetics involved in the redox reaction between ferrate(VI) and cyanide. The pseudo–first-order rate constant was calculated by maintaining the cyanide concentration in excess, with the overall second order rate constant values obtained for initial Fe(VI) concentrations of 1.0 and 0.1 mmol/L. The oxidation of cyanide was again confirmed using a cyanide probe. Fe(VI) was further employed for its possible application in the treatment of industrial wastewaters containing cyanide, along with some heavy metals, such as those obtained from electroplating industries.

Keywords:

• Ferrate(VI)
• cyanide
• wastewater
• oxidation
• Cu(II)
• Ni(II).

Acknowledgements

This work was partly supported by a grant (No. R01-2006-000-10284-0) obtained from the Basic Research Program of the Korea Science and Engineering Foundation, and partly supported by a grant (No. RTI05-01-02) from the Regional Technology Innovation Program of the Ministry of Commerce, Industry and Energy (MOCIE), Korea.

Notes

* Analyzed by cyanide probe;

**Analyzed by AAS;

^# Reported by the supplier;

^$ Analyzed by the TOC Analyzer.

*The final concentration achieved within only 50 secs of contact, and the cyanide concentration was below the probe detection limit (8 × 10^{− 6} mol/L).