Industrial solid waste contains various metal elements that react with CO2. Its utilization for CO2 mineralization, an important part of CCUS technology, enables permanent CO2 storage and solid waste resource recovery, while delivering significant environmental and economic benefits. As a key CO2 mineralization method, indirect mineralization uses leaching agents to selectively extract Ca2+ from solid waste and convert it into high-value light calcium carbonate with both leaching and mineralization reactions occurring in the leaching medium. Leaching agents are central to this technology, directly affecting Ca2+ leaching efficiency/selectivity, CO2 mineralization rate, reagent recovery, and regulating CaCO3 particle size, crystal type, and morphology, critical for industrial implementation. Leaching agents are categorized into three types-acid–base, ammonium salt, and multifunctional organic-based on their properties and functions. This paper systematically reviews the research progress of indirect mineralization, focusing on the mechanism, advantages, and limitations of each type of leaching agent. Acid–base agents exhibit high efficiency in leaching calcium from alkaline solid wastes, but they suffer from strong equipment corrosion, low selectivity, and poor recyclability, which increase process costs. Ammonium salt agents are low-corrosive, high-selective, and recyclable; however, they react with alkaline components in solid waste to emit ammonia, leading to reagent loss and higher industrial application costs. Multifunctional organic leaching agents exhibit advantages in Ca2+ leaching, CO2 mineralization, cyclic stability, equipment corrosivity, and crystal form regulation. Among them, amino acids and protonated amines enhance Ca2+ dissolution and mineralization reactions through proton transfer. The –NH2 functional group provides an additional reaction pathway by interacting with CO2, forming carbamate intermediates to accelerate the CO2 mass transfer. Chelating agents, such as sodium citrate and sodium gluconate, facilitate Ca2+ dissolution through the formation of soluble complexes with Ca2+. They further enable in situ regeneration of the leaching agents via pH self-regulation throughout the leaching and mineralization processes. However, organic agents are limited by high synthesis costs and insufficient environmental safety evaluation, and high exogenous reagent costs generally hinder indirect mineralization industrialization. Future research should optimize organic agent molecular structures to reduce costs while retaining functions and strengthen environmental safety assessments to support industrial applications. This review provides a comprehensive reference for improving the leaching agent performance, cutting costs, and advancing the industrial implementation of indirect CO2 mineralization.
Liu et al. (Mon,) studied this question.