Influence of a soil enzyme on iron-cyanide complex speciation and mineral adsorption

• Published in: Chemosphere (Oxford) Vol. 70; no. 6; pp. 1044 - 1051
• Main Authors: Zimmerman, Andrew R., Kang, Dong-Hee, Ahn, Mi-Youn, Hyun, Seunghun, Banks, M. Katherine
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2008; Elsevier
• Subjects: Absorption; adsorption; Aluminum hydroxide; Aluminum Hydroxide - chemistry; Applied sciences; Bentonite - chemistry; Biological and physicochemical properties of pollutants. Interaction in the soil; bioremediation; chemical speciation; Coriolus versicolor; Cyanide; cyanides; Cyanides - chemistry; Cyanides - metabolism; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; enzyme activity; Exact sciences and technology; ferricyanide; Ferricyanides - chemistry; Ferricyanides - metabolism; Ferrocyanide; Ferrocyanides - chemistry; Ferrocyanides - metabolism; Fungal Proteins - metabolism; iron; Laccase; Laccase - metabolism; Metal adsorption; montmorillonite; oxidation; Oxidation-Reduction; Pollution; Pollution, environment geology; Protons; Soil and sediments pollution; Trametes versicolor; Cyanide; Metal adsorption; Ferrocyanide; Aluminum hydroxide; Laccase; Coriolus versicolor; Mobility; Environmental factor; Cyanides; Soil pollution; Basidiomycota; Fungi; Enzymatic activity; Soil interaction; Speciation; Aluminium Hydroxides; Montmorillonite; Enzyme; Pollutant behavior; Sediments; Edaphic factor; Adsorption; Hexacyanoferrates III; Oxidoreductases; Hexacyanoferrates II
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2007.07.075

Cyanide is commonly found as ferrocyanide [Fe II(CN) 6] −4 and in the more mobile form, ferricyanide [Fe III(CN) 6] −3 in contaminated soils and sediments. Although soil minerals may influence ferrocyanide speciation, and thus mobility, the possible influence of soil enzymes has not been examined. In a series of experiments conducted under a range of soil-like conditions, laccase, a phenoloxidase enzyme derived from the fungi Trametes versicolor, was found to exert a large influence on iron-cyanide speciation and mobility. In the presence of laccase, up to 93% of ferrocyanide (36–362 ppm) was oxidized to ferricyanide within 4 h. No significant effect of pH (3.6 and 6.2) or initial ferrocyanide concentration on the extent or rate of oxidation was found and ferrocyanide oxidation did not occur in the absence of laccase. Relative to iron-cyanide–mineral systems without laccase, ferrocyanide adsorption to aluminum hydroxide and montmorillonite decreased in the presence of laccase and was similar to or somewhat greater than that of ferricyanide without laccase. Laccase-catalyzed conversion of ferrocyanide to ferricyanide was extensive though up to 33% of the enzyme was mineral-bound. These results demonstrate that soil enzymes can play a major role in ferrocyanide speciation and mobility. Biotic soil components must be considered as highly effective oxidation catalysts that may alter the mobility of metals and metal complexes in soil. Immobilized enzymes should also be considered for use in soil metal remediation efforts.