Sulphur K-edge XANES and acid volatile sulphide analyses of changes in chemical speciation of S and Fe during sequential extraction of trace metals in anoxic sludge from biogas reactors
2012 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 89, 470-477 p.Article in journal (Refereed) Published
The effect of sequential extraction of trace metals on sulphur (S) speciation in anoxic sludge samples from two lab-scale biogas reactors augmented with Fe was investigated. Analyses of sulphur K-edge X-ray absorption near edge structure (S XANES) spectroscopy and acid volatile sulphide (AVS) were conducted on the residues from each step of the sequential extraction. The S speciation in sludge samples after AVS analysis was also determined by S XANES. Sulphur was mainly present as FeS (~60% of total S) and reduced organic S (~30% of total S), such as organic sulphide and thiol groups, in the anoxic solid phase. Sulphur XANES and AVS analyses showed that during first step of the extraction procedure (the. removal of exchangeable cations), a part of the FeS fraction corresponding to 20% of total S was transformed to zero-valent S, whereas Fe was not released into the solution during this transformation. After the last extraction step (organic/sulphide fraction) a secondary Fe phase was formed. The change in chemical speciation of S and Fe occurring during sequential extraction procedure suggests indirect effects on trace metals associated to the FeS fraction that may lead to incorrect results. Furthermore, by S XANES it was verified that the AVS analysis effectively removed the FeS fraction. The present results identified critical limitations for the application of sequential extraction for trace metal speciation analysis outside the framework for which the methods were developed.
Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 89, 470-477 p.
Sequential extraction, Biogas, Sulphur speciation, Sulphur K-edge XANES, Acid volatile sulphide, Trace metals
IdentifiersURN: urn:nbn:se:liu:diva-73112DOI: 10.1016/j.talanta.2011.12.065ISI: 000301278000068OAI: oai:DiVA.org:liu-73112DiVA: diva2:466538
funding agencies|Swedish Energy Agency||2011-12-162011-12-162014-12-17Bibliographically approved