Recovery and formation mechanism of high brightness calcite powders from marble waste by the alkaline hydrothermal treatment

Abstract

Abstract Large amounts of marble wastes have been generated annually from the marble processing industry, which pose serious hazards to the environment and healthcare. In this work, high brightness calcite powders were recycled from marble powder by the alkaline hydrothermal treatment. The ball milling pretreatment had a prominent effect on the brightness of calcite powders, resulting in an optimum milling time of 22 h. In the alkaline hydrothermal treatment, the brightness of calcite powders increased to constant values with increasing hydrothermal temperature and solid content, whereas it firstly increased and then decreased with the increase of soaking time and alkaline concentration. The maximum brightness of calcite powders was 95% when the milled marble powder was hydrothermally treated at 220 °C for 4 h in an alkaline solution of 0.1 mol/l. The sheet-like calcite crystallites (