Effects of NH+4 concentration on the vaterite formation via direct carbonation use waste carbide slag under the different ammonium systems

Abstract

The effect of NH+4 concentration on the formation process of vaterite under three special systems containing NH+4 was investigated via direct carbonation of waste carbide slag. The synergistic effects of NH+4 with organic (CH3COO-) and inorganic (S2O2–8) systems on vaterite formation were systematically studied. The obtained particles were characterized by X-ray powder diffraction (XRD), scanning electron spectroscopy (SEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA) analytical techniques. The results show that the content of vaterite significantly increases when the presence of NH+4, and the maximum content of vaterite is 93.37%, 95.78% and 95.39% in NH4Cl, CH3COONH4 and (NH4)2S2O8 systems. The different systems affect the vaterite particle content, morphology, particle size and distribution at the same NH+4 concentration was studied. Mechanistic analysis shows that NH+4 can change the leaching rate of Ca2+, CH3COO- can adsorb on the vaterite surface, and S2O2–8 can make the CaSO4 intermediate appear in the reaction system. Apparent synergistic interactions between NH+4 and CH3COO-, S2O2–8 affect the nucleation and growth process of vaterite. This study can provide theoretical support for the preparation of vaterite, the functional utilization of waste carbide slag, and the mineralization of CO2.