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Elimination of the interference of sulfides by zinc ions on the determination of hexavalent chromium in soil by Method 3060a & Method 7196a

Year: 2025
Type: article
Abstract: The sulfides are recognized as the most promising reducing agents for remediation of chromium-contaminated soils due to their strong reducing ability and low cost. However, the residual sulfides and elemental sulfur (S 0 ) from the oxidation of sulfides significantly interfere with the determination of hexavalent chromium (Cr(Ⅵ)) in soil, seriously hindering the engineering application and experimental researches. The effectiveness of the Cu 2+ -EDTA method in removing S 0 interference is unsatisfactory due to the inability to maintain sufficient Cu 2+ concentrations during alkaline digestion. The toluene-mercury method, utilizing hot toxic toluene for pre-extraction of S 0 , makes the operation complex and require higher personal safety protection. This paper proposes a simple method for eliminating sulfides and S 0 interference using Zn 2+ , only involving the addition of Zn 2+ before alkaline digestion without extra operation. Experimental results indicate that at pH > 12.5, S 0 begins to produce a large amount polysulfides (S n 2- ) during the alkaline digestion, which in turn reduces Cr(Ⅵ). At the same pH, Zn 2+ predominantly exists as aqueous Zn(OH) 4 2- and instantly eliminates the S 0 -generated S n 2- by the formation of ZnS precipitates. Experiments also indicate that the addition of Zn 2+ exerts no significant influence on the method detection limits of the USEPA Method 3060a & Method 7196a.
DOI: 10.1016/j.jhazmat.2025.137801
Language: English
Open Access status: hybrid
Estimated APC paid: $4,340
OpenAlex ID: W4408059386
FWCI:
Cites: 35
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Related to: 10