The use of microemulsions to remove chromium from industrial sludge

In this work microemulsion systems were used to remove chromium from leather tannery sediments. The sludge was treated by a solid-liquid extraction process (acid digestion). The effects of particle size, digestion temperature and digestion time with regards to the efficiency of chromium removal were considered. The raw sludge (3 Mesh) was dried, grounded and sieved. Particles with 3, 14, 65, 100, 200, and 325 Mesh were evaluated. Sludge digestion solutions were prepared using each studied granule size at 25 degrees C, 70 degrees C, and 95 degrees C. Microemulsion extraction experiments to remove chromium III from the acid digestion solution were made according to a Scheffe Net experimental design methodology, using microemulsion systems inside the Winsor II region (System I) and inside the microemulsion region (Winsor IV - System II). A statistical treatment was used to obtain the isoresponse plots. Chromium extraction percentages were up to 73.3% for System I and up to 93.4% for System II. (C) 2008 Elsevier Ltd. All rights reserved.