Kinetics of Cr(VI) reduction and remobilisation in an aquifer permeable reactive barrier: microcosm simulation

摘要

Chromium is found in the environment mainly as hexavalent chromium, Cr(VI), and the trivalent form, Cr(III). Cr(VI) is carcinogenic and mutagenic to living organisms including humans whereas trivalent chromium is 1,000 times less toxic than Cr(VI). Most of the anthropogenic Cr discharged to the environment is in the hexavalent. The detoxification of Cr Cr(III) produces hydroxides that tend to accumulate in underground aquifers thereby reducing the permeability of the aquifer medium. In this study, a cleanup method for an in situ underground remediation barrier system is evaluated. The process involved the remobilisation of the Cr(OH)_3 precipitate in a horizontal flow aquifer microcosm reactor using a dilute acid (0.1 % HCl) followed by recover of Cr(III) species on the negatively charged electrode (anode) of an electrokinetic field located downstream of the remediation zone. Limitation of the clean-up process was determined to be due the anode focusing effect during operation.