The leaching of chromium from cement-based waste form via a predominantly biological mechanism

An evaluation of the leaching of chromium from 100% cement waste forms was carried out in this study using a refined biofilm formation method. Approximately 50% of the total chromium was leached from the experimental sample (exposed to bacterial broth of pHsimilar to2.00) within the first 24 h of evaluation. No chromium was detected in the effluent of the control sample (exposed to sterile medium chemically acidified to give pH comparable to that of bacterial broth) within the same period. An increase in the duration of the first stage of the process from 24 h to 3 days did not result in the release of chromium from the control. Comparative evaluation for the leaching of calcium gave results that contrasted sharply with those obtained for chromium. Similar levels of calcium were leached from both control and experimental samples within the first 24 It of evaluation. Evaluations carried out at elevated levels of chromium in the waste form did not result in any change in trend for both calcium and chromium. A predominant biological mechanism involving active mobilization of chromium from the matrix is suggested for the difference in leaching of chromium from control and experimental waste forms. (C) 2002 Elsevier Science Ltd. All rights reserved.