Fractal Growth During WPCBs Reutilization By Slurry Electrolysis

As a typical e-waste,waste printed circuit boards(WPCBs)contain great economic value.Slurry electrolysis could efficiently recycle metals from WPCBs.However,during the recovery process,dendrite growth was observed in the metal deposited around the cathode plate.Dendrite growth is a typical non-linear process,which has a great influence on the resource recovery by slurry electrolysis.Therefore,the non-equilibrium and non-linear behaviors in the process of WPCBs recycling slurry electrolysis is discussed deeply in this research.In this paper,the mechanisms of metal fractal grow during the electrodeposition process was discussed by point,line and surface anode;second,this three processes were simulated by the improved DLA model;finally,these two parts were combined and applied in the research of metal recycle from WPCBs by slurry electrolysis.Main conclusions are as follows: 1.Point electrode electrodeposition: The initial value of current increases from 0.0047 A to 0.0235 A with the increase of electrolytic voltage,and from 0.0051 A to 0.0224 A with the increase of copper sulfate concentration.Increasing voltage,morphology of the deposited products changed from compact to open,and the fractal dimension increased from 1.129 to 1.529.With the increase of copper sulfate concentration,morphology of the products changes from open to dense,and the fractal dimension decreased from 1.348 to 1.083.Adding SDS,gelatin and hydrochloric acid,the morphology and crystal of the products changed obviously,and all of them were dendrite crystals.The simulation results are consistent with the actual electrodeposition results,thus the modified model is available.2.Wire electrode electrodeposition: The initial value of current increases from 0.1364 A to 0.5463 A with the increase of electrolytic voltage,and from 0.1658 A to 0.6509 A with the increase of copper sulfate concentration.SDS,gelatin and hydrochloric acid all could inhibit the growth of dendrite structure.3.Surface electrode electrodeposition: The increase of current at the end of electrolysis increases from 0.9168 A to 5.9845 A with the increase of electrolysis voltage,and from 0.4557 A to 3.3256 A with the increase of copper sulfate concentration.With the increase of voltage and copper sulfate concentration,the morphology of the products shows obvious dendrite structure.Gelatin has the most obvious effect on the product morphology.It could be seen from XRD and XPS that additives changed the phase composition and chemical state of the products.The simulation results are consistent with the actual electrodeposition results,thus the modified model is available.4.WPCBs recycling by slurry electrolysis: the phases of the metal deposition products are mainly single copper crystal and copper oxide crystal.Copper on the surface of the products mainly exists as copper oxide.The addition of SDS could loose the metal crystal structure and the dendritic crystal form would reduce;the addition of gelatin and hydrochloric acid would denser the metal crystal structure.The difference is that the former promotes the formation of fine dendrites,while the latter is dominated by small particle agglomerates.