Thiol groups controls on arsenite binding by organic matter: new experimental and modeling evidence.

摘要: Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, thiol functional group humic acid (HA) was shown be an important potential site for As(III). Isotherm experiments on sorption HAs, have either grafted with or not, were thus conducted investigate preferential sites. There a low level HA, which strongly dependent abundance thiols. Experimental datasets used develop new model (the modified PHREEQC-Model VI), defines HA as discrete carboxylic, phenolic and Protonation/deprotonation constants determined each sites (pKA=4.28±0.03; ΔpKA=2.13±0.10; pKB=7.11±0.26; ΔpKB=3.52±0.49; pKS=5.82±0.052; ΔpKS=6.12±0.12 thiols sites, respectively) from HAs not. The pKS value corresponds single thiol-containing ligands. Two models tested: Mono model, considered is bound monodentate complexes, Tri tridentate complexes. A simulation available literature validate logKMS=2.91±0.04, i.e. hypothesis. This study highlighted importance groups in OM reactivity and, notably, concentration (considering Fe lacking at least negligible) able determine concentrations OM.