Method of fixing carbon dioxide comprising a step of recycling the used extraction solvent

Abstract

A method of fixing carbon dioxide is provided. After metal ion components are extracted from natural mineral or steel slag through acid treatment, carbon dioxide is injected to fix carbon dioxide by carbonating the same. Since the procedure of pH adjustment is unnecessary, the reaction is carried out effectively, and a continuous process is enabled. Further, since the used extraction solvent is recycled, the cost of fixing carbon dioxide is reduced. The disclosed method of fixing carbon dioxide enables effective removal of carbon dioxide produced from the steelmaking industry, thereby significantly reducing greenhouse gas emission and allowing recycling of the conventionally discarded steel slag.

1 . A method of fixing carbon dioxide comprising the steps of:
 (a) treating natural mineral or steel slag with an acid to extract metal ion components, thereby providing an extraction solution containing the metal ion components;   (b) injecting carbon dioxide into the extraction solution containing the resulting metal ion components to carbonate the same, thereby providing a solution in which resulting carbonates are dissolved;   (c) transferring the solution in which the resulting carbonates are dissolved to a dissolved carbonate storage tank;   (d) transferring the solution from the dissolved carbonate storage tank to a carbonate separation/purification tank, and adjusting pH to 7 or above to separate the carbonates;   (e) treating the solution from which the carbonates have been separated with an acid; and   (f) recycling the treated solution to step (a) as an extraction acid.   
     
     
         2 . The method of fixing carbon dioxide according to  claim 1 , wherein said treating with the acid in step (e) is performed at about pH 3-5. 
     
     
         3 . The method of fixing carbon dioxide according to  claim 1 , wherein said carbonating is performed at normal temperature under normal pressure. 
     
     
         4 . The method of fixing carbon dioxide according to  claim 1 , wherein step (e) comprises adjusting pH to about 3-5 using one or more acid(s) selected from a group consisting of formic acid, acetic acid, propionic acid, phosphoric acid, phosphorous acid, citric acid and oxalic acid.