Leaching Br from high bromine containing circuit board smelting flue dust by sodium hydroxide solution: thermodynamics and kinetics study

Abstract

To study the debromination pretreatment and the recovery of bromide from high bromine content circuit board smelting flue dust (CBSFD) is relevant to the effective utilization of e-waste and environmental protection. In this study, the presence of cuprous bromide (CuBr) and lead bromide (PbBr2) is proved by characterizing the smelting flue dust from waste printed circuit boards (WPCBs). Chemical analysis shows that the content of bromine in the flue dust sample is as high as 24.9%. The leaching rate of bromine by NaOH and the related leaching kinetics under different operating conditions were evaluated. The results reveal the optimum leaching conditions as follows: liquid–solid ratio of 12:1, stirring speed of 600rpm, leaching temperature of 343K, NaOH concentration of 2mol/L and leaching time of 120min. The optimal bromine leaching rate is as high as 96.4%. Kinetic study results show that the bromine leaching process conforms to the ash layer diffusion control mode of the shrinking core model (SCM). The apparent activation energy calculated from the Arrhenius equation is 14.73kJ/mol.