Materials recovery from waste printed circuit boards by supercritical methanol

Abstract

a b s t r a c tThe recovery of valuable materials from waste printed circuit boards (PCBs) is quite difficult due to the heterogeneous mix of polymer materials, multiple kinds of metals and glass fiber. A feasibility study was conducted using supercritical methanol (SCM) to simultaneously recover polymers and metals from waste PCBs. The study focused on the characteristics of both oils and solid products obtained from the SCMtreated waste PCBs. The operation conditions were temperature range of 300-420• C, treatment time between 30 and 120 min and solid-to-liquid ratio (S/L) of 1:10-1:30 (g/mL) so as to understand the products and depolymerization mechanisms of waste PCBs in SCM. GC-MS results revealed that the oils mainly contained phenol and its methylated derivatives, and the methylated derivatives increased with the increase of reaction temperature. The methylated reaction occurred mainly above 400• C. The liquid products also contained a significant number of phosphated fire retardant additives such as triphenyl phosphate, which decreased significantly with the increase of reaction temperature. The solid product mainly consisted of Cu, Fe, Sn, Pb and Zn, as well as lower concentrations of precious metals such as Ag and Au.

Comparative study on copper leaching from waste printed circuit boards by typical ionic liquid acids

“…Therefore, both traditional and advanced methods, such as mechanical-physical approaches, especially corona electrostatic separation which has obtained great success in China (Li and Xu, 2010), hydrometallurgy (Kim et al, 2011), pyrometallurgy (Zhan and Xu, 2008), bioleaching (Yang et al, 2014) and sub/supercritical fluid (Xiu and Zhang, 2010), are widely discussed for the recovery of metals form WPCBs. Among these processes, hydrometallurgic processes offer high metal selectivity and recovery with a flexible mode of operation and suitability for small scale applications, making it an attractive alternative for the treatment of WPCBs.…”

Recovery of metals from waste printed circuit boards by supercritical water pre-treatment combined with acid leaching process

“…In addition, according to our previous studies (Zhang and Itoh, 2006;Bo et al, 2009;Xiu and Zhang, 2010), supercritical fluid such as water and methanol is strong enough to destroy the solid particles such as fly ash or waste PCBs particles. An increasing number of porous structures can be produced in the solid waste particle as the reaction temperature rise during the SCWD process.…”

“…According to previous studies (Xiu and Zhang, 2010;Bo et al, 2009), supercritical fluid such as methanol or water is strong enough to destroy the solid particles and produce some porous structure in the solid waste particle due to the high pressure environment in SCW process. As a result, the porous structure are supposed to be positive for the diffusing of gas and liquid offspring produced inside the waste PCBs during the SCW process and accelerating the reaction of oxidation or depolymerization.…”

A novel recovery method of copper from waste printed circuit boards by supercritical methanol process: Preparation of ultrafine copper materials

“…The SCM preparation process is a more reliable, simpler, and less chemical-intensive technique that can produce ultrafine copper materials with high quality and no addition of other reducing agents, surfactants, and nanoparticles stabilizer. In our previous work (Xiu and Zhang, 2010), SCM was used to simultaneously decompose polymers and concentrate metals in waste PCBs. The study was focused on the decomposition behavior of polymers contained in waste PCBs, and it was found that the decomposition product mainly contained phenol and its methylated derivatives, which could be recovered as resource.…”