A zero-emission collaborative treatment method for brown corundum fly ash and carbide slag: Producing silicon fertilizer while recovering gallium and potassium

Abstract

Brown corundum fly ash (BCFA) is a fine dust generated during the smelting process of brown corundum. It is rich in gallium and potassium, and improper handling can cause severe environmental damage. This study proposes a cyclic process of calcification leaching, carbonation precipitation, and lye regeneration for the collaborative treatment of BCFA and carbide slag. The leaching efficiencies of gallium and potassium were determined to be 94.02 % and 85.32 %, respectively, under the optimized conditions (120 min, 180 °C, Ca/Si molar ratio 0.9, KOH 10 g/L) of calcification leaching. The contents of effective SiO2 and CaO in the silicon fertilizer were measured at 34.71 wt% and 33.02 wt%, respectively. During the carbonation precipitation process, gallium and aluminum were extracted from the filtrate and achieved respective contents of 2.1429 wt% and 32.99 wt% in the resulting coprecipitate. The carbonated lye was regenerated through a causticization reaction, and after four cycles, the regenerated lye maintained a consistently high leaching efficiency for gallium and potassium. This method achieves the comprehensive utilization of BCFA and carbide slag without generating any waste residue or wastewater. Additionally, it provides a novel approach for the collaborative treatment of similar solid wastes.