Purification of calcium leachates derived from alkaline wastes for the production of precipitated calcium carbonate

The goal of this work is the production of commercial quality precipitated calcium carbonate (PCC) for use in papermaking as filler or coating pigment. The calcium source explored is not traditionally pure calcium (hydr)oxides or salts, but rather leachates extracted from steelmaking slags. Utilizing a waste-derived source for PCC production enables the possibility to valorize two thermal residues of steelmaking, namely the slag and carbon dioxide. Additionally, after the calcium extraction, the residual solids, rich in silica and aluminum oxide, can be valorized as a raw material for zeolite synthesis. The main challenge addressed in this work is the prevention of impurity contamination of the formed PCC’s, especially Al, Fe, Mg, Mn, Si and Ti. Three approaches are investigated: (i) the selective leaching of calcium, (ii) the purification of the calcium-rich leachates using physico-chemical separation methods, and (iii) the preferential crystallization of pure PCC by controlling precipitation conditions. The produced PCC’s are characterized for chemical, mineralogical, morphological and optical properties to assess their applicability for use in papermaking. The next stage of this research will be the utilization of the produced PCC’s in papermaking applications.status: publishe