| 摘要 |
<p>Method of recovering calcium carbonate from waste material or contamined natural calcic material. Calcium is recovered by preparing an aqueous suspension of the material containing calcium to be recovered and by lowering the pH of the suspension to pH < 6, preferably pH < 4, for providing a suspension including an acidic liquid phase containing the calcium compounds in soluble form. Thereafter the pH of the liquid phase is raised to pH > 6, preferably pH > 7, by mixing a base therein, for precipitating the main portion of aluminium therein. Thereafter the neutral or basic liquid phase is carbonized by introducing Na2CO3 or NaHCO3 therein, for precipitation of the calcium compounds as CaCO3.</p> |
