Green recovery of NaF-Na2CO3-NaCl ternary fluxing agent from aluminum dross

Abstract

The present study deliberates the recovery of sodium fluoride (NaF)-natrite (Na2CO3)-sodium chloride (NaCl) ternary fluxing agent from hazardous aluminum dross waste using three types of heating methods, including direct heating on a hotplate, heating by a drying oven, and microwave heating. Deionized water was used as a green solvent for the recovery experiments. Investigating the effects of time and temperature on recovery percentage showed that a recovery percentage of around 96.5% can be achieved under time and temperature of 90 min and 95 ℃, respectively. The recovered fluxing agent salt was characterized by XRD, FTIR spectroscopy, FESEM, and energy dispersive X-ray spectroscopy (EDS) elemental analysis. Rietveld fitting analysis of phases detected in the XRD patterns showed that the recovered fluxing agent contained 74–81 wt.% NaF, 8–11 wt.% NaCl, and 11–14.7 wt.% Na2CO3. The FESEM micrographs revealed that the retrieved salts were in nano scale. The recovered fluxing agent showed different morphologies including needle-like, round shape, and a mixture of both, corresponding to microwave, drying oven, and hotplate heating methods, respectively. The nano-needles exhibited diameter of the tip and base in the range of 39–60 nm and 50–103 nm, respectively.