Industrial wastewaters, particularly those associated with mining and mineral processing, can contain high con-centrations of sulphate. There are various methods of sulphate removal e.g. reverse osmosis, ion exchange, precipitation by lime, cements, and salts of barium and the biological removal process. The soluble salts of barium are most commonly used for precipitation of sulphate from aquatic acidic solutions to the insoluble product barium sulphate BaSO4. Benefits of precip-itation are high sulphate removal efficiency but limitations are toxicity of barium compounds and high economical costs. For this reason the recycling of BaSO4 to barium sulphide BaS (the precipitating reagent) is very important.
The paper deals with study of BaSO4 reduction by activated carbon to BaS by thermal analysis and infrared spectrometry. DCS analysis indicated that conversion of BaSO4 to BaS in the range of temperature 800–1,000 °C was performed. Thermal analysis and infrared spectra of the products confirmed the change in its composition, but process of reduction by carbon was incomplete and in sample was still present a part of BaSO4. Presence of BaS was confirmed by colorimetric method.