Feasibility Study on the Utilization of Serpentine Residues for Mg(OH)2 Production

Serpentinite tailings from La Nationale chrysotile mine in Thetford Mines (Quebec, Canada) were studied to extract the Mg contained therein. The study began with an initial chemical characterization of the residue to determine the Mg concentration in the different grain size fractions. The resulting Mg-containing fractions were leached under a variety of parameters such as type of acid, acid concentration, treatment time, and temperature, and the obtained solution was neutralized with NaOH for the selective recovery of the metals. The results of this study were used to design a process to obtain Mg as a marketable chemical. The tested process consists of a leaching step using an H2SO4 solution followed by the purification of the leachates using NaOH at pH 8 and Mg recovery with NaOH at pH 10. A final product composed of mirabilite (Na2SO4) and brucite (Mg(OH)2) was obtained. The procedure was tested, and its economic viability was discussed. The approach proved to be technically feasible, promoting clean production.