Energy-storage materials with stable structure through carbide slag modification by acid impregnation and manganese doping†

Herein, calcium-based energy-storage materials that directly absorb solar energy were prepared through wet modification of carbide slag (solid waste). It was found that at a carbonization temperature of 700 °C and calcination temperature of 800 °C, the carbonation conversion rate of 50%FA-100 : 10 Mn remains 66.7% after 10 cycles, which is only 6.4% lower than the initial rate. Through ultraviolet spectrophotometry, it was found that after the addition of a small amount of manganese nitrate, the average absorbance of the energy-storage material was 44.14% higher than that of carbide slag. The use of formic acid as a solvent to acidify modified calcium carbide slag for the preparation of energy-storage materials improves the internal structure of the energy-storage materials, which facilitates the entrance of carbon dioxide into the energy-storage material during the diffusion reaction stage to initiate carbonation reaction. The kinetic calculation shows that the activation energy of the modified energy-storage material decreases by 11.3 kJ mol⁻¹ in the carbonation reaction stage and 9.25 kJ mol⁻¹ in the calcination reaction stage. After the activation energy decreases, the carbonation/calcination reaction is easier to carry out; thus, the reaction time is reduced.