Patent ID: 8728322

Claim:
A process for the purification of water comprising (a) obtaining a surface-treated natural calcium carbonate that was prepared by treating a natural calcium carbonate from a natural source that is not saturated with heavy metals with an acid and carbon dioxide in water to obtain surface-treated natural calcium carbonate, wherein the carbon dioxide is formed in situ and/or supplied externally, and wherein the surface-treated natural calcium carbonate has a specific surface area of from 5-200 m 2 /g as measured using nitrogen and BET method; (b) contacting the water to be purified with (i) the surface-treated natural calcium carbonate from step (a) or (ii) an aqueous suspension comprising the surface-treated natural calcium carbonate from step (a) having a pH of greater than 6.0 measured at 20° C., so that the surface-treated natural calcium carbonate absorbs impurities in the water; and (c) separating the surface-treated natural calcium carbonate with absorbed impurities from the water after step (b) has been conducted.