To investigate secondary pollution issued during the preparation of sintered brick from waterquenched yellow phosphorus slag, the composition of slag was experimentally measured in this study. The thermal conversion process and gas phase products associated with S-, P-, F-, and As-containing species present in the heating system were theoretically calculated by means of thermochemical software FactSage 7.0 and databases. The results showed that F and As were released at 700ºC and the gaseous products contained AsF3. Also, large amounts of F remained in solid CaF2 and Ca10(PO4)6F2. At a calcination temperature of 900ºC, all As was transferred into gaseous AsF3 and S started to convert into gaseous SO2 and SO3. Other data suggested that the released amounts of SO2 and SO3 increased as calcination temperature rose. At calcination temperatures ranging from 100-1000ºC, all P existed as solid Ca10(PO4)6F2. These findings indicated that low calcination temperatures were beneficial for reducing released harmful gases during the production of sintered brick.

When preparing lightweight ceramsite using carbide slag, trace amounts of toxic elements are released into the atmosphere due to high-temperature calcination, posing a significant risk to the environment. The real-time monitoring of the released gases is challenging under laboratory conditions while preparing large quantities of ceramsite. Therefore, heating was simulated using experimental data and the FactSage 7.0 thermochemical database to study the release of harmful Al-, C-, H-, S-, and F-containing elements when using carbide slag to prepare lightweight ceramsite. The results indicated that no Al, C, H, S, or F elements were evident in the high-temperature liquid products obtained in a 50 °C to 1150 °C calcination temperature range. Al was present in a solid state with no gaseous products. When the temperature reached 450 °C, CO gas was released and its level increased as the temperature rose. H and S mainly combined into H₂S gas, starting at 250 °C and reaching a peak at 1050 °C. H and F primarily combined into HF, starting at 400 °C. Other F-containing gases mainly included SiF₄ and TiF₃, which began to release at 800 °C and 900 °C, respectively. The release trends of HF, SiF₄, and TiF₃ were consistent with those of CO. This study aimed to conduct an environmental impact and management assessment for the preparation of lightweight ceramsite using carbide slag. The use of raw material carbide slag for the low-cost treatment of tail gas was proposed, which provides theoretical and up-to-date support for greening the application of the process.