Efficient bromine removal and metal recovery from waste printed circuit boards smelting flue dust by a two-stage leaching process

A novel two-stage leaching method for Br removal and metal recovery from waste printed circuit boards (WPCBs) smelting flue dust was developed. The effects of leaching conditions on Cu, Zn, Pb and Sn extraction behavior and Br removal were studied systematically. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the phase composition and microstructure of the residues and products. Experimental results show that 63.55% Br and 96.34% Zn were extracted into the solution after water leaching, whereas most of Cu, Pb and Sn remained in the residue. The debromination can be enhanced by the introduction of alkaline agent. With Na2CO3 as leaching agent, a debromination rate of 88.65% was obtain by controlling leaching conditions at Na2CO3 addition of 53.23 wt%, liquid–solid ratio of 3:1, leaching temperature of 30 °C, and leaching time of 120 min. Remarkable debromination was achieved by a two-stage leaching process, namely, water leaching followed by Na2CO3 leaching. By subjecting the first-stage water leaching residue to Na2CO3 leaching, a favorable Br extraction yield of 96.65% was successfully obtained, where the total Na2CO3 consumption is only 47.13 wt% of the raw material. Na2Zn3(CO3)4(H2O)3 with Zn content of 35.12% was synthesized by Na2CO3 precipitation. After precipitation, NaBr salt with main phase of NaBr·2H2O and NaBr0.2019Cl0.7981 was prepared from the purified liquid. Overall results indicate that this process is an effective and promising approach for the reutilization of WPCBs smelting flue dust.