Precipitation of carbonate crystal on surface active glasses

Anions, such as CO32− and SO42− ions, in industrial wastewater can cause serious scale problem in drainage pipes and vessels, when combined with other metal ions in the water. In this study, it was attempted to remove CO32− ions from an aqueous solution by using surface active glasses. Glasses with various compositions of SiO2-Na2O-B2O3-RO (R = Mg, Ca, Sr, Ba) system were reacted in a CO32− ion-containing solution with various pH, then the glass surfaces were analyzed by XRD and SEM, and CO32− ions in the reacted solution were also measured. CO32− ions in the solution were combined with alkaline earth metal ions, which were leached out of the glass, and were precipitated on the glass surface as carbonate crystals. In this way, the carbonate ions could be removed from the solution. The removal capacity of CO32− ions is closely related to the surface reactivity of the glass and solubility product constants of the newly formed carbonate crystals. Glass containing either SrO or BaO showed a strong uptake capacity of CO32− ions from the solution.