Key Takeaways & Executive Findings
- •• • Carbide slag (CS) contains CaO as the primary oxide, with Ca predominantly in Ca(OH)2 and CaCO3 forms; its density ranges 2.5–3.0 g/cm³, and its high alkalinity (pH>13) necessitates treatment. • • Global CS production exceeds 40 million tonnes annually, yet utilization in China remains below 40%, primarily as cement raw material, underscoring the need for alternative valorization routes. • • Direct carbonation and indirect ammonium salt leaching-carbonation are the main pathways; process parameter regulation, amino acid modification, and multi-solid waste coordination improve reaction efficiency and product performance. • • The technology enables controlled synthesis of high-value calcium carbonate products, with derived lightweight fillers and low-carbon cementitious materials offering dual environmental and economic benefits.
Abstract
Carbide slag (CS), an alkaline industrial solid waste from acetylene production in the chlor-alkali industry, poses severe ecological risks due to long-term stockpiling. This review systematically examines CO2 mineralization pathways and applications of CS, leveraging its high reactivity dominated by Ca(OH)2. Direct gas-solid and liquid-solid carbonation mechanisms, alongside indirect ammonium salt cyclic leaching-carbonation, are elaborated. Process optimization via parameter regulation, amino acid modification, and multi-solid waste coordination significantly enhances reaction efficiency and product performance, enabling controlled synthesis of high-value calcium carbonate. Environmental and economic analyses confirm that CS mineralization achieves CO2 fixation with good economic feasibility, simultaneously addressing solid waste resource utilization and carbon emission reduction. Derived lightweight fillers and low-carbon cementitious materials exhibit both environmental and economic potential, providing theoretical and application support for a 'waste-to-waste' carbon reduction technology system.
1. Introduction
Industrial CO2 emissions, driven by fossil fuel consumption, continue to escalate, contributing to global warming and extreme weather events. Carbon capture, utilization, and storage (CCUS) technologies, particularly CO2 mineralization, offer a secure and stable sequestration route by converting CO2 into solid carbonates. Among potential feedstocks, industrial solid wastes like carbide slag (CS) exhibit higher reactivity than natural minerals due to prior thermal/chemical processing, making them ideal for mineralization.
However, CS disposal remains a critical bottleneck: its high alkalinity (pH>13) and heavy metal content pose environmental hazards, while conventional utilization as cement raw material achieves less than 40% utilization in China. This review addresses the gap by systematically analyzing CS-based CO2 mineralization pathways, process optimizations, and product applications, demonstrating a dual-benefit strategy for solid waste management and carbon emission reduction.
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LI Jing, JIA Xiaoxiao, LIU Jiaxin, GUO Hong, LU Su (2026). Research Progress of CO2 Mineralization Using Carbide Slag. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202605022
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Frequently Asked Questions
What are the key process parameters that influence the CO2 mineralization efficiency of carbide slag, and how do they affect the reaction kinetics?
The review highlights that liquid-solid ratio and gas flow rate are critical parameters. For instance, studies (GAO et al., 2025) show that optimizing these parameters can significantly enhance carbonation conversion. While specific numeric values are not detailed in the abstract, the text indicates that parameter regulation improves reaction efficiency and product performance, enabling controlled synthesis of high-value calcium carbonate.
How does the indirect ammonium salt leaching-carbonation route compare to direct carbonation in terms of product purity and process economics?
The indirect route involves cyclic leaching with ammonium salts followed by carbonation, which can yield higher-purity calcium carbonate due to selective extraction. However, it may incur additional reagent costs. The review notes that process optimization, including amino acid modification and multi-solid waste coordination, can enhance efficiency and economic feasibility, but direct comparisons of cost and purity are not quantified in the abstract.
What are the environmental and economic benefits of using carbide slag for CO2 mineralization compared to conventional disposal methods?
The technology simultaneously achieves solid waste resource utilization and carbon emission reduction. Derived products like lightweight fillers and low-carbon cementitious materials offer environmental and economic potential. The abstract states that the process exhibits good economic feasibility while fixing CO2, but specific metrics such as cost per tonne of CO2 avoided are not provided.
What is the role of amino acid modification in enhancing the mineralization process, and what mechanisms are involved?
Amino acid modification is one of the strategies used to optimize the mineralization process. It likely enhances the dissolution of Ca(OH)2 or stabilizes intermediate species, thereby improving reaction efficiency. The abstract mentions that such modifications significantly improve reaction efficiency and product performance, but detailed mechanistic insights are not elaborated in the provided text.
How does the multi-solid waste coordination strategy improve the overall process, and what synergistic effects are observed?
Multi-solid waste coordination involves combining carbide slag with other industrial wastes, such as fly ash or steel slag, to enhance reactivity or product properties. This approach can improve carbonation efficiency and yield composite materials with desirable characteristics. The abstract indicates that this strategy significantly improves reaction efficiency and product performance, but specific synergistic mechanisms are not detailed.
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