Laboratory Amplification For Metals Recovering From WPCBs By Slurry Electrolysis

Waste printed circuit boards?WPCBs?is an important part of almost all e-waste.Slurry electrolysis can directly separate and recover secondary metals from the extremely complex WPCBs in one-step,showing a promise prospect for industriail application.In order to promote its industrial application,its amplification experiments?from 100 mL to 5000 mL,enlarging for 50 times?were conducted with the aim to confirm the feasibility of laboratorial amplification,meanwhile to provide data and theoretical support for possible industrial application by discussing the effect of each environmental factor,such as the way of suspension?airflow and mechanical stirring?,liberation degree??4 mm,?1 mm;0.6 mm completely separated?and so on,after WPCBs crushing.The main research conclusions are as followings:1.Laboratory amplification with air suspension and coarse particles:because air can not suspend WPCBs partitles,which basically sink at the bottom of the electrolytic cell.Therefore,within the discussed range of electrolysis time and H₂SO₄ concentration,copper can not be separated and recovered by slurry electrolysis.The total metal recovery rates remain 42%as the extension of time;while the recovery rate of total metal increases with the increase of H₂SO₄ concentration,up to 43.05%.2.Laboratory amplification with mechanical stirring and coarse particles:in order to completely leach copper from WPCBs,mechanical stirring was employed.Without oxidant,the recovery rate of copper and total metal increase with the increase of current density,up to3.39%and 45.82%,respectively.Obviousely,copper current efficiency decreases with the increase of current density.By adding H₂O₂,the recovery rate of copper increases significantly,from 9.87%to 29.51%;meanwhile,the recovery rate of total metals also increases to 59.06%.The recovery rate of copper and total metal,content of copper in the electrodeposited metal and electrolyte increase with the increase of current density.This indicates that,the addition of oxidation agent can promote the leching of copper and also effect copper depositing in the cathode.3.Laboratory amplification with mechanical stirring and fine particles:introducing mechanical stirring,adding oxidant could greatly enhance the separation and recovery of metals from WPCBs.However,the results is not ideal due to particle size of WPCBs is?4mm,incomple dissociation of metal and nonmetal.After curshing these WPCBs to?1 mm,the effect of NaCl concentration,CuSO₄·5H₂O concentration and WPCBs dosage is investigated.The recovery rate of copper and total metal increase dramatically,from 29.51%and 59.06%to 94.51%and 78.98%,respectively.The recovery rate and current efficiency of copper first increase and then decrease with the increase of NaCl concentration,the recovery rate of total metal increases with the increase of NaCl concentration.With the increase of NaCl concentration,the content of copper in the electrodeposited metal frist increases and then decreases.The content of copper decreases in the electrolysis residue and increases in electrolyte as the increase of NaCl concentration.The recovery rate of copper and total metal first increases and then decreases with the increase of CuSO₄·5H₂O concentration.With the increase of CuSO₄·5H₂O concentration,the content of copper in the electrodeposited metal first increases and then decreases,in the electrolyte and electrolysis residue it first decrease and then increase.The recovery rate of copper and total metal frist increase and then decrease with the increase of WPCBs dosage;copper current efficiency increases with the increases of WPCBs dosage.With the increase of WPCBs dosage,the content of copper in the electrodeposited metal first increases and then decreases,it increases in the electrolysis residue,while it decreases in the electrolyte.4.The optimal elargment experiment:the optimal parameters obtained from the previous experiments are 30 g/L WPCBs,10 g/L CuSO₄·5H₂O,30 g/L NaCl,190 g/L H₂SO₄,300 A/m²and 8 h.In order to better understanding this process,the enlargement experiment was reconducted and the results shows that:under these conditions,the output and cell voltage first increase and then decrease with the increase of electrolysis time.Copper concentration in the cathode and anode zone frist increases and then decreases with the increase of electrolysis time.The concentration of Zn,Fe,Al,Ca,Ni increase with the increase of electrolysis time.The recovery rate of copper and total metal are up to 94.51%and 69.76%,respectively.Current efficiency of copper is 33.51%.The main component of recovered metal is copper,which is92.91%,and other metals are all less than 3%.Copper in the recovered metle powders is Cu and CuO,which is dendritic.The dominant metals in the electrolysis residue are Ca,Fe and Zn,which content are 7.57%,5.19%and 5.10%,respectively.While copper in the electrolysis residue is only 2.25%,and other metals are all less than 3%.This indicates that it is feasible to recover metals from WPCBs by slurry electrolysis though its industrial application still needs to optimize parameters and carry industrial experiments.