Representative coal gangue in China: Physical and chemical properties, heavy metal coupling mechanism and risk assessment

Abstract

Based on the source and distribution of coal gangue (CG) in China, this study introduces the current situation of CG storage in China and the problems existing in the process of CG utilization. For the benefit of solve the difficulty of CG utilization and the risk control of heavy metals (HMs), representative CG samples were selected, and the chemical composition of CG was analyzed according to the microscopic test results. The main reasons for the difficulty of mineral composition and resource utilization were revealed, and the specific environmental protection utilization regulation model of CG samples was constructed, the carbon emission value of CG products was studied by life cycle method, and the broad prospects of CG products under the background of the times were revealed. The heavy metal leaching amount of CG samples in representative areas was detected. Three kinds of HM soil safety evaluation methods and human health risk assessment (HHRS) methods were used to evaluate soil environmental safety, carcinogenic and non-carcinogenic human health risks. The results showed that the characteristic HMs in CG were As, Pb and Cr. The valence states of As, Pb and Cr in CG were As3+, As5+, Pb2+, Pb4+, Cr3+ and Cr6+, respectively. The valence states of As, Pb and Cr in CG were mainly carbonate-bound state and metal oxide-bound state, which exist in the layered silicate minerals of a triclinic system dominated by kaolinite. Considering that the HMs in CG are finally ingested into the human body through the soil, while constructing a complete HM environmental safety control system, based on the relevant environmental quality standards and the HHRS of HMs, the risk control system and control limits of characteristic HMs in CG resource utilization were established, in order to provide theoretical guidance for the high-value environmental protection utilization of CG.