Solidification of heavy metal elements in waste phosphate acid activated metakaolin geopolymer with environmental and economic benefits

This paper investigates the feasibility of using industrial waste acid to prepare geopolymer with significant environmental and economic benefits. Two types of waste acid were examined to discuss the effect of waste acid content on the microstructure, mechanical performance, thermal stability and heavy metal solidification efficiency. The core issue solved in this investigation is the harmless treatment of industrial waste acid and solidification efficiency of heavy metals, so as to reduce the pollution of heavy metals on the environment and the urgent demand for low carbon emissions in the construction and ceramic industries. The results showed that the metal elements (Ag, Fe, Mo, Cu and Ni) can be successfully solidified with over 95% solidification efficiency, indicating that the geopolymers are appropriate for hazardous material stabilisation, and the leaching of the heavy metals to the environment can be well controlled. The environmental and economic analysis indicates that the carbon and energy consumption intensity were reduced by 92.7% and 77.9%, respectively, compared to cement. What is more important is that the cost intensity is negative due to the income of waste acid treatment, meaning that additional value benefit was added to the product. This paves a promising way for the low-carbon transformation of ceramic enterprises and industrial waste treatment enterprises, drives further breakthroughs in high-tech industries, and promotes the sustainable development of the local national economy.