Decontamination of industrial effluents for environment protection and recycling of metals

• Published in: Resources, conservation and recycling Vol. 10; no. 1; pp. 97 - 106
• Main Authors: Gaballah, I., Goy, D., Kilbertus, G., Thauront, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1994
• ISSN: 0921-3449; 1879-0658
• DOI: 10.1016/0921-3449(94)90042-6

The electroplating industries generate large volumes of industrial effluent containing hexavalent chromium ions. The classical treatment of these effluents is via the reduction of Cr 6+ to Cr 3+ before precipitation. This produces a significant amount of calcium sulfate and chromium hydroxide. Due to environmental regulations, high waste disposal costs and the necessity to recycle these heavy cations, research on a new approach has been initiated. This paper describes the preliminary results of a low cost process dedicated to the decontamination of these industrial effluents by chemically treated barks. Decontamination of solutions containing hexavalent chromium by this organic support has been studied on the laboratory scale. Experiments conducted with the main European tree species have shown that the metal removal percentage, from synthetic solutions, depends upon pH, initial concentrations and the tree species. More than 95% of Cr 6+, contained in a 10, 100 or 1000 ppm solution, can be recovered at pH 3.80. The ashes obtained by the incineration of the saturated bark contain up to 50% of chromium metal, which could be recycled by the traditional metallurgical processes. Spectroscopic analysis of the saturated bark is used to investigate the type of ligand between the treated bark and the chromium. Pilot plant trials were successful in eliminating about 90% of Cr 6+ from industrial effluents containing 5000 ppm.