Facile synthesis of vaterite CaCO3 microspheres from carbon capture and solid waste utilization towards microwave absorption and dye wastewater adsorption

Abstract

Mineralization of CO2 to minerals like calcium carbonate (CaCO3) has been considered as an effective approach to combat global warming. In this paper, Ca2+ ions were firstly extracted from waste carbide slag, and then facilely transformed to vaterite CaCO3 via disperse bubbling carbonization method assisted with an air stone. By optimizing the reaction conditions, highly mono-dispersed vaterite CaCO3 microspheres (VCMs) were obtained. These microspheres consisted of aggregated CaCO3 nanocrystals, bearing a mesoporous structure. As a proof-of-concept, these mesoporous microspheres were utilized for dye adsorption and electromagnetic (EM) microwave absorption. For the former, the VCMs were used to adsorb Congo red, yielding a fast adsorption time of 9 min and a high adsorption capacity of 138.77 mg/g. For the latter, EM microwave dielectric parameters were measured, and dye-adsorbed VCMs exhibited better microwave-absorption performance with a minimum reflection loss of −43.2 dB, about 3 times of pristine vaterite. To the best of our knowledge, this is the first report of solid-waste-derived VCMs as microwave absorbent and dye adsorbent. Considering the low-cost, eco-friendly and facile preparation and effective utilization of VCMs, our work provides a promising strategy for large-scale carbon capture, solid waste utilization, and treatment of microwave and wastewater pollution.