Influence of Na+ on vaterite formation, content and yield using steamed ammonia liquid waste as a calcium source

Abstract

In this paper, the effect of Na⁺ concentration on the crystalline phase, morphology, and content of vaterite in a system with different Ca²⁺ and CO₃²⁻ ratios using steamed ammonia liquid waste as the calcium source was investigated, and the effect of Na⁺ on the yield of vaterite was studied systematically for the first time. The obtained products were characterized by powder X-ray diffraction (XRPD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, laser particle size analysis (LPSA), and so on. The results show that the variation of Na⁺ concentration in different Ca²⁺ and CO₃²⁻ ratio systems has an effect on the particle size, morphology, content, and CaCO₃ yield of vaterite. Thermogravimetric (TG) analysis indicates that Na⁺ is involved in forming CaCO₃ but does not enter the interior of the vaterite crystals. Mechanistic analysis shows that changes in Na⁺ concentration can alter the initial pH of the reaction system and the conductivity of the solution, thus changing the processes such as early nucleation and crystal growth of vaterite as well as inhibiting the vaterite phase transition, which determines the particle size of the vaterite obtained. This study reveals to a certain extent the influence of Na⁺ on the early nucleation and crystal growth of vaterite and provides theoretical support for the realization of large-scale industrial production of vaterite.