Printed circuit boards (PCBs) are difficult to recycle because of the layered structure of non-metal (i.e., epoxy resin, glass fiber) and copper. In this work, we conducted a systematic investigation to effectively recover copper from PCB. A thermal treatment was employed for improving the crushing performance of PCB and conducted by varying the temperature and the gas. Then, the mechanical strength, degree of liberation (DL), and copper separation efficiency of the heat-treated and untreated PCBs were investigated. After heat treatment under a 300 °C air atmosphere, the mechanical strength of PCB decreased from 386.36 to 24.26 MPa, and copper liberation improved from 9.3% to 100% in the size range of a coarser size fraction (>1400 μm). Accordingly, when electrostatic separations were performed under these conditions, a high-Cu-grade concentrate and high recovery could be obtained. The results show that the change in the physical properties of the PCBs leads to an improvement in the DL following thermal decomposition at 300 °C in air. Our study elucidates the physical properties of PCBs and the DL under various heat treatment conditions. Furthermore, it shows that the heat treatment condition of 300 °C in air is ideal for recovering copper from the PCB.

In this study, the effect of NaOH on the synthesis of mesoporous silica (MS) by using municipal solid-waste incinerator (MSWI) ash slag was investigated. Moreover, the prepared MS was used as a support to evaluate its potential for the recovery of gold ions (Au(III)) from aqueous solution. The extraction process for the MSWI ash slag activated through mechanical grinding entailed alkali treatment, using varying concentrations of NaOH. The content of Si extracted from MSWI ash slag increased with the increasing grinding time and NaOH concentration. As the NaOH concentration increased, the pore structure (e.g., Brunauer–Emmett–Teller (BET) surface area and pore volume) of the synthesized MS improved. In addition, the amount of adsorbed Au(III) increased with increasing sulfur content immobilized on the support, and the sulfur content was in turn governed by the silanol content of the MS support. The adsorbent prepared by using the MS-3M support exhibited the highest Au(III) adsorption capacity (110.3 mg/g), and its adsorption–desorption efficiency was not significantly affected even after five adsorption–desorption cycles.

The aim of this study is to diagnose and optimize a closed multistage gold ore flotation circuit in an operational industrial plant. Linear circuit analysis (LCA), a partition-based model, and a mass balance model using flotation first-order kinetics are employed to diagnose the current process. The result shows that the current circuit operates with high recovery but the gold grade of the final concentrate is low owing to the low buoyancy ratio. Hence, several alternative circuits with different streamlines and cell arrangements are proposed and simulated using LCA and a mass balance model. The result suggests that if the current process is changed to an alternative circuit in which the floated product stream of the rougher bank is changed, then the gold grade of the concentrate can be improved by 128%. Finally, the current circuit is optimized by changing it to an alternative circuit. This study provides a methodology for adapting the simulation of optimization for the flotation circuit of an industrial plant via LCA and mass balance simulation.