Thermal behaviour of chromium electroplating sludge.

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Galvanic sludge is a hazardous waste requiring effective treatment.
• Incineration is a viable thermal treatment method for hazardous waste.
• Chromium is a restricted metal often present in galvanic sludge.

Purpose of the Study:

• To analyze the thermal behavior of galvanic sludge containing chromium.
• To determine the fate of chromium during high-temperature treatment.
• To characterize the resulting slag and released vapors.

Main Methods:

• Simultaneous Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TG) coupled with mass spectrometry.
• X-ray diffraction (XRD) analysis of calcined sludge.
• Energy Dispersive Spectroscopy (EDS) microprobe analysis of condensed vapor particles.

Main Results:

• A total weight loss of 34% was observed, primarily due to CO2, H2O, and SO2 release.
• Water (H2O) was liberated between 500-1,250°C, CO2 between 500-750°C, and SO2 near 1,000°C.
• Over 99.6% of chromium remained incorporated in the slag, with minimal evaporation.

Conclusions:

• Incineration effectively stabilizes chromium in galvanic sludge, immobilizing it within the slag.
• The resulting slag is primarily composed of calcium phosphate and fluoride.
• Thermal decomposition releases significant amounts of CO2, H2O, and SO2, requiring emission control.