A novel recovery method of copper from waste printed circuit boards by supercritical methanol process: Preparation of ultrafine copper materials. (February 2017) - Xiu, Fu-Rong
Graphical abstract: Highlights: We report a SCM process for preparing ultrafine Cu materials from waste PCBs. Non-uniform mixture of Cu and Cu2 O was formed due to the effect of Fe 3+ . Uniform spherical and monodispersed nano-Cu was prepared after Fe removal. Up to 96.8 wt.% of the Cu in waste PCBs was recovered as nano-Cu in this study. Effect of SCM conditions on the prepared ultrafine Cu materials was studied. Abstract: In this study, supercritical methanol (SCM) process was successfully used for the preparation of ultrafine copper materials from waste printed circuit boards (PCBs) after nitric acid pretreatment. Waste PCBs were pretreated twice in nitric acid. Sn and Pb were recovered by the first nitric acid pretreatment. The leach liquor with a high concentration of copper ions after the second nitric acid leaching was subjected to SCM process. The mixture of Cu and Cu2 O with poor uniformity of particle size was formed due to the effect of ferric iron contained in the leach liquor of waste PCBs, while more uniform and spherical Cu particles with high monodispersity and smaller size could be prepared after the removal of Fe. The size of Cu particles increased obviously with the decline of SCM temperature, and particles became highly aggregated when the reaction temperature decreased to 300 °C. The size of Cu particles decreased markedly with the decrease of initial concentration of copper ion in the leach liquor of waste PCBs. It is believed that the process developed in this study is simple and practical for the preparation of ultrafine copper materials from waste PCBs with the aim of recycling these waste resources as a high value-added product.