An electrochemical method was used to determine the diffusion coefficient of chromium(VI) in chromium-containing slag. A slag plate was prepared from the original slag or the detoxified slag by Achromobacter sp. CH-1. The results revealed that the apparent diffusion coefficient of Cr(VI) was 4.4 x 10(-9) m(2) s(-1) in original slag and 2.62 x 10(-8) m(2) s(-1) in detoxified slag. The results implied that detoxification of chromium-containing slag by Achromobacter sp. CH-1 could enhance Cr(VI) release. Meanwhile, the results of laboratory experiment showed that the residual total Cr(VI) in slag decreased from an initial value of 6.8 mg g(-1) to 0.338 mg g(-1) at the end of the detoxification process. The Cr(VI) released from slag was also reduced by Achromobacter sp. CH-1 strain since water soluble Cr(VI) in the leachate was not detected after 4 days. Therefore, Achromobacter sp. CH-1 has potential application for the bio-detoxification of chromium-containing slag. (C) 2009 Elsevier B.V. All rights reserved.