Extracting agent-recyclable method for preparing nano calcium carbonate by carbide slag

The invention discloses an extracting agent-recyclable method for preparing nano calcium carbonate by carbide slag. The method comprises the following steps: taking citrate (such as sodium citrate, potassium, calcium or magnesium salt) as an extracting agent for extracting the carbide slag, and centrifugally separating to obtain a citrate and Ca mixed solution, and introducing CO2 into the solution for carbonizing to generate the nano calcium carbonate with particle size of 20 to 200nm; researching a method for improving the extracting efficiency of Ca and regulating a crystal form andmorphology of calcium carbonate by regulating parameters such as the concentration of the citrate, the concentration of the carbide slag, introduction rate of CO2 and a pH value of a carbonization end point (a pH value of a solution stopping carbonation reaction). The scheme provided by the invention has the characteristics of low cost of raw materials, simple operation, simple preparation process, energy saving, environ