Surface Properties of Cement Kiln Dust with Water Treatment for Selective Extraction of Calcium and Potassium

Water and hydrochloric acid were employed as solvents to extract K and Ca from K- and Ca- rich cement kiln dust (CKD). It has been shown that hydrochloric acid effectively extracts Ca and K from CKD with efficiencies of more than 85 and 99%, respectively. On the other hand, water, as a solvent, selectively extracts K and Cl with an efficiency of 99%. The selectivity of Ca extracted using hydrochloric acid from treated CKD increased from 37 to 87%. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that K and Cl were dominant on the surface of fresh CKD. After extraction with water, the portion of Ca increased more than twice, and Ca species became dominant. Thus, extraction of CKD with water is capable of selectively removing KCl, leaving Ca on the surface; hence, treated Ca-rich CKD can serve as a suitable raw material for mineral carbonation.