Cyanide Speciation as the Determinant of Treatment Performance: A Critical Review of Removal, Destruction and Recovery Routes for Cyanide-Bearing Wastewater
More details
Hide details
1
Institute of Metallurgy and Ore Beneficiation, Satbayev University, Shevchenko str., 29/133, 050010, Almaty, Kazakhstan.
2
Department of Mechanical Engineering, Centre for Corrosion Research (CCR), Institute of Contaminant Management for Oil and Gas (ICM), Universiti Teknologi PETRONAS, Seri Iskandar 32610, Perak, Malaysia
Corresponding author
Nazerke Tolegenova
Institute of Metallurgy and Ore Beneficiation, Satbayev University, Shevchenko str., 29/133, 050010, Almaty, Kazakhstan.
KEYWORDS
TOPICS
ABSTRACT
Cyanide-containing wastewater is a multicomponent system: cyanide occurs as free cyanide, within weak acid dissociable (WAD) cyanide and stable metal-cyanide complexes, and alongside thiocyanate, metals and other impurities. The chemical form of cyanide and the composition of the aqueous matrix govern treatment performance, which makes direct comparison between technologies difficult. This review covers physical and physicochemical, chemical, electrochemical, photochemical and biological methods; for each group it examines the process mechanism, the target cyanide species, the treatment conditions, the secondary streams generated, the scope for recovery and the level of technological maturity. Removal, destruction and recovery of cyanide are treated as distinct outcomes, because an identical removal efficiency may conceal a fundamentally different final fate of the pollutant. No universal treatment technology exists, and data obtained on model solutions cannot always be transferred to real multicomponent effluents. For concentrated process streams, the feasibility of cyanide extraction and reuse should be assessed first; where recovery is not viable, destructive processes followed by deep polishing are applied. Further work requires testing on real wastewater, lower energy and reagent consumption, smaller volumes of secondary waste, scale-up of promising processes, and integrated schemes in which recovery, destruction and polishing are matched to the characteristics of the specific stream.