Study On Recycling Method Of Metals From Bioleaching Solution Of Waste Printed Circuit Boards

A variety of metal resources are contained from bioleaching lixivium of waste printedcircuit boards (PCBs). The key step to realize metal recovery from bioleaching solution ofPCBs is the recovery of metal in high-grade form. In this study, the recovery methods wereproposed including copper recovery from bioleaching solution by electrodeposition and therecovery of other metals whose concentration were far below copper’s after ternary recyclingof leachate. Firstly, effect factors of copper recovery under condition of constant current andcopper electrodeposition kinetics in artificial bioleaching lixivium of PCBs were investigated.Then, copper recovery influencing factors in actual bioleaching solution of PCBs werediscussed. Finally, the feasibility of recycling of bioleaching solution and recovery of othermetals after ternary recycling of leachate were explored. The main conclusions are as follows.(1) The results of copper recovery artificial bioleaching lixivium of PCBs indicated thatthe maximum copper recovery efficiencies of the anode and cathode chambers were achieved96.75%and99.35%respectively under the conditions of initial Cu2+10g·L-1, graphite rod foranode materials, carbon felt for cathode material,111.11mA·cm-2of current density, initialpH2.0. Meanwhile, the minimum total and unit mass product energy consumptions were0.021kW·h and14.61kW·h·kg-1, the deposited copper on the cathode material wasdistributed fascicularly and no oxygen was detected. The electrode material, current densityand initial Cu2+concentration played an important role in copper recovery efficiency andenergy consumption, while initial pH had a greater effect on energy consumption. Kinetics ofcopper eletrodeposition in artificial bioleaching lixivium of PCBs showed that coppereletrodeposition was zero order kinetics when copper concentrations was higher than4g·L-1,and first order kinetics when copper concentration was lower than4g·L-1. Each rate constanthad a linear relationship with current density.(2) In order to implement copper recovery from actual bioleaching lixivium of PCBs,electrodeposition was also employed in chapter Ⅳ to optimize copper recovery factors. Underthe optimized conditions of initial Cu2+6.55g·L-1, graphite rod for anode materials, carbonfelt for cathode material,88.89mA·cm-2of current density, initial pH3.0,97.93%and99.23%the copper recovery efficiency were achieved in the anode and cathode chambers, and the total and unit mass product energy consumptions were0.0027kW·h,2.58kW·h·kg-1,respectively. The deposited copper on the cathode material was distributed fascicularly and nooxygen was detected. The results confirmed that copper recovery efficiency of the actualbioleaching solution had little difference with artificial bioleaching solution. However, thetotal and unit mass product energy consumptions was much lower due to other irons.(3) A series of experiments were designed to explore the medium recycling and recoveryof other metals, such as9K medium and ternary cycle bioleaching experiments, recovery ofother metals experiments, etc. The results indicated that the pre-cultured time ofAcidithiobacillus ferrooxidans Z1was extended in the process of medium recycling, butcopper leaching efficiency was slightly higher than9K medium. During three cycles, copperrecovery efficiencies were up to98%, energy consumption was relatively low, and no oxygenwas detected on the deposited copper. Recovery efficiencies of zinc, aluminum, nickel,manganese of bioleaching lixivium after three cycles were achieved99%using chemicalprecipitation.