Thermal behavior of chromium electroplating sludge

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride, and minor concentrations of metals. A total weight loss of 34% was observed. The greatest port of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1250 degreesC. CO2 in the range of 500 750 degreesC and SO2 near 1000 degreesC. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag. (C) 2001 Elsevier Science Ltd. All rights reserved.