extraction behavior comparison of hydrophilic ionic liquids for chromium on humic acid–microporous system

In soil, humic acids (has) are found on the external surface of micropores. has supply a sorption site for metals. in the present work, the fate of hexavalent cr (cr(vi)) without effect of other metals in microporous system was observed. by component-fitted x-ray absorption near the edge structure (xanes) spectra, approximately 84% of hexavalent cr (cr(vi)) was adsorbed on ha–zeolite y (simulated ha on external surface of microporous system in soil). the reduction of cr(vi)–ha (cr(vi) adsorbed on ha) occurred to form cr(iii)–ha (cr(iii) adsorbed on ha) in ha–zeolite y. the hydrophilic ionic liquids (ils) (1-butyl-3-methylimidazolium chloride ([c4mim][cl]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([c4mim][bf4])) were used to extract the chromium compounds in ha–zeolite y. by xanes, cr(vi)–ha desorbed from the external surface of zeolite y and was substantially reduced to cr(iii)–ha in [c4mim][cl] and [c4mim][bf4]. the extraction and reduction efficiencies of chromium species were less in [c4mim][bf4] than in [c4mim][cl] due to high hydrogen bond basicity of [c4mim][cl]. the 1h nmr and ftir spectra also show that the interaction between extracted chromium species and cations of [c4mim][cl] is associated with the feasibilities of extraction and reduction. the extracted and non-extractable cr(vi)/cr(iii) mole ratios in ils and ha–zeolite y were decreased, respectively, which diminished the toxicity of the chromium compounds in ha–zeolite y. appropriate ils, e.g., [c4mim][cl], used as extracting solutions, can enhance extraction and reduce toxicity for cr(vi) compounds.