In this study, Chromium(6+) was reduced to lower oxidation states by trace amount of organic ligands before nanoscale zero-valent iron (nZVI) treatment. The catechol, citric acid and oxalic acid were used among various organic ligands. After organic acids pretreatment, the amount of Cr(6+) species was decreased while the total amount of Cr was unchanged. The amount of organic acids were decreased but the presences of Cr(+5) ligand complex and semi-quinone radicals from catechol were confirmed by electron spin resonance spectroscopy (EPR) after reaction. In pretreatment, the redox-active ligands were oxidized reducing the Cr oxidation state and formed complex with Fe<sup>3+ </sup>so the iron oxides were less precipitated on nZVI surface and the reduced aggregation of nZVI after nZVI injection. As a result, the pretreatment using organic acids enhanced Cr reduction and adsorption by nZVI.

Organic ligands pretreatment enhancing chromium removal by nano-scale zero-valent iron

251st National Meeting (2016)

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