Nanosized vaterite production through organic-solvent-free indirect carbonation

[Display omitted] •Nanosized 100 % vaterite was produced via organic-solvent-free indirect carbonation.•Seawater, sucrose, ultrasonication, and aging exhibited a synergistic effect.•An eluent with the highest free-Ca-ion concentration was prepared by controlling the sucrose concentration.•The carbonation end pH was optimized, and the stirring speed and ultrasound intensity were adjusted to minimize interference.•After carbonation, the CaCO3-containing suspension was floated and a stable dispersion was maintained. Nanosized vaterite, which exhibits characteristics such as high specific surface area, porosity, and biocompatibility, has attracted research attention for use as a drug delivery material. However, fatal drawbacks such as high costs, difficulty in mass production, and toxicity exist in conventional nanosized vaterite production owing to the use of a large amount of organic solvents to forcibly suppress the vaterite recrystallization and particle growth. Therefore, nanosized 100 % vaterite was produced in this study via indirect carbonation without using any organic solvent, which has rarely been achieved previously. Seawater, sucrose, ultrasonication, and aging—which facilitate vaterite production and particle size reduction—exhibited a synergistic effect in producing vaterite. To realize nanosized vaterite production via indirect carbonation, seawater was used as a solvent, sucrose was added when Ca was eluted, and CO2 bubbling was performed under ultrasonication. Furthermore, the CaCO3-containing suspension obtained after the carbonation was aged. Ultrasonic waves were required to generate nanosized vaterite and reducing size at the carbonation stage. This nanosized-vaterite-production strategy involving organic-solvent-free indirect carbonation is meaningful, in that it highlights the potential of synthesizing vaterite in an economically sound, environmentally friendly manner for use as a pharmaceutical raw material.