Separation and recovery of heavy metals zinc and lead from phosphorus flue dust by vacuum metallurgy

Yellow phosphorous flue dust (YPFD) is a solid waste produced by the yellow phosphorus industry that contains heavy metals such as zinc (Zn) and lead (Pb), causing environmental damage. In this work, a vacuum metallurgy method is proposed to separate and recover Zn and Pb from solid waste YPFD. Under optimized conditions of 1173 K, 30 wt% reductant dosage, 60 min, and 5-10 Pa, the pre-separation of Zn and Pb was realized and the recovery rates of Zn and Pb reached 92.47% and 99.78%, respectively. In addition, gallium (Ga) remained in the residue with little loss, and then recovered by raising the reaction temperature to 1323 K. The recovery rates of Ga reached 87.57%. The principle of metal volatilization under vacuum at different temperatures was also clarified. The thermodynamic calculations of the carbothermal reduction reaction of metal oxides under vacuum were carried out. The analysis of the product obtained at 1173 K showed that Zn and Pb mainly existed in the form of elemental or simple compounds. At 1323 K, Ga in the residue was highly enriched in the condensation zone, which is conducive for the subsequent purification. The whole process is short, there is no waste water, low levels of pollution of emitted, and the technology provides a clean and sustainable way to reuse YPFD.

Automated summary

The vacuum metallurgy method proposed in this study successfully achieved the pre-separation and efficient recovery of Zn and Pb from YPFD, with recovery rates reaching 92.47% and 99.78%, respectively, under optimized conditions. Ga in the residue was also recovered with little loss by raising the reaction temperature to 1323 K. The entire process is short, with no waste water discharge, low pollution emission levels, providing a clean and sustainable way to reuse YPFD.