Ecological Utilization of the CO₂ Mineralization Using Alkaline Solid Wastes: Synthesis of Porous Materials for Sandy Soil Restoration

CO2 mineralization utilizing alkaline materials synergistically mitigates CO2 emissions and aids in the management of alkaline solid wastes (ASWs). Although considerable progress has been achieved in reducing CO2 emissions through such mineralization, effective utilization of the resulting mineralization products remains challenging. This work proposed a novel strategy for the synthesis of porous materials using the reaction products of CO2 with ASWs for sandy soil restoration. The obtained materials─derived from calcium carbide slag, steel slag, and fly ash─exhibited specific surface areas of up to 158 cm3/g and a CO2 adsorption capacity of 2.43 mol. The effects of synthesis conditions on the porous structures were explored through morphology and porosity assessments. The CO2 stored by mineralization during the synthesis of porous materials is not released, and an additional part of the CO2 was fixed. Additionaly, the mixture of porous materials and sandy soil considerably reduced the saturated hydraulic conductivity (Ks = 0.005 cm/min) by 74%. Cucumber cultivation tests revealed that a porous material addition ratio of 5% improved germination rates, growth rates, leaf widths, and flowering conditions. Overall, this study presents a viable pathway for the ecological utilization of the products of CO2 mineralization with ASWs.