Performance and mechanisms of alkaline solid waste in CO₂ mineralization and utilization

CO₂ mineral sequestration using alkaline solid waste (ASW) is a promising strategy for synergistically reducing CO₂ emissions and reusing industrial waste. However, improvement the carbonation degree still remains challenges due to the sluggish leaching rate of Ca/Mg ion at low pH. To the issues, this study proposed an amine-mediated CO₂ absorption and mineralization process with six common ASWs, as well an ecological utilization route of CO₂-ASW productions. Experimental results indicated that calcium carbide slag (CS) had greater CO₂ mineralization capacity (86.2 g-CO₂/kg-CS) than other ASWs, while stirring rate and particle size played a more important role during CO₂ capture. Amine-mediated CO₂ capture was verified to be more excellent with steel slag (SS) as mineral medium. When the MEA concentration was increased to 2 mol/L, the extraction efficiency of Ca²⁺ was increased by 35 %, leaded to the CO₂ removal efficiency significantly promoted from 49 % to 92 %. The characterization of structural morphology referred spherical aragonite or needle-bar calcite was dominant for the porous mineralization products (30.6 m²/g). High germination index of pea seed (112.1 % at a dose of 10 g/L) inferred the negligible toxicological effects of tiny MEA residue over SS mineralization products, after centrifugally washing treatment. Pea seeds cultivated with mineralized products after centrifugal washing can achieve a growth rate of about 4 mm/d. Overall, this work provides a feasible route to apply the porous CO₂-ASWs production into water conservation in arid and sandy land.