Acidic treatment of sodium sulfide by-product sediment to recover sodium oxide and preparation porous ceramics for building applications

The manufacture of sodium sulfide through a carbon reduction process, using sodium sulfate as raw material, generates sodium sulfide by-product sediment, which has potential health and environmental impacts. Herein, a novel strategy is proposed to recover sodium oxide from the sediment by using acidic treatment and the influence of solution pH on sodium oxide content is systematically studied. The results reveal that the sodium oxide content decreases with decreasing pH value of the solution. At pH = 4, the as-treated sediment results in Na2O content of 3.10 wt. %, which recovery rate is about 90%. Furthermore, the influences of sintering temperature and time on compressive strength and bulk density are studied. In general, the compressive strength and bulk density increase with increasing sintering temperature and time. After sintering at 1,300 degrees C for 120 min, the compressive strength and bulk density of the sintered porous ceramic are 26.66 MPa and 1.31 g/cm(3), respectively. The porous ceramic, sintered at 1,300 degrees C, mainly consists of hauyne, gehlenite and hematite phases. In summary, the few flaws in cell-walls result in high compressive strength of the as-prepared porous ceramics.