Feasibility and environmental safety investigation of making fired bricks by using heavy metals-contained soil

Soil heavy metal pollution in China is still relatively serious, and inappropriate disposal of heavy metal contaminated soil can lead to a serious damage to both the ecological environment and human health. However, soil normally contains a significant amount of SiO₂, Al₂O₃ and Fe₂O₃, which makes it applicable to prepare sintered bricks. In order to ascertain the feasibility and environmental safety of making sintered bricks by using heavy metal contained soil, an industrialization experiment was carried out in a brick kiln, with a blending ratio of 70% soil to replace shale, to investigate the heavy metal emission in flue gas, and the leaching and distribution properties in fired brick. The results revealed that soil had a similar content of SiO₂, Al₂O₃ and Fe₂O₃ compared to shale, and therefore, it could be used as a substitute for shale raw materials. The mechanical properties of the fired bricks met the product quality standards. During the sintering process with heavy metal soil as raw material, the emission of conventional flue gas pollutants and heavy metal pollutants met the relevant standards, and the environmental risk was controllable. The concentration of leachable heavy metals in sintered bricks was significantly lower than the leaching limit of Technical Specification for Cooperative Disposal of Solid Waste in Cement Kilns （GB 30760-2014 ）, and therefore, the leaching risk was low during using bricks. As, Cd, Cr, Mn, Ni, Pb and Cu basically stayed in fired bricks under sintering, and the contents of heavy metals remained in the desulfurization filter cake after flue gas volatilization and wet desulfurization filter pressing were extremely low. The research showed that using heavy metal-contained soil to make sintered brick could meet the existing standards from both mechanical and environmental safety aspects and had certain resource benefits.