Recovering Metals From The Leaching Liquid Of The Printed Boards By Cyclone Electrowinning

Printed circuit boards(PCBs)are so important parts of the electronic products that the amounts of these boards account most in the waste electronic wastes.Mainly the chemical and biological methods were used to recover the metals from the PCBs.These methods can leach the metals into the liquid.It is necessary to use the electrowinning to get the metals from the leaching liquid.Traditional electrowinning must ensure the purity of liquid and high concentration of the target ions.Cyclone electrowinning can reduce the concentration polarization during the electrolytic deposition.The waste gas can also treat well to avoid the harm to body.In this paper,cyclone electrowinning was used to recover the metals:copper,nickel,lead,zinc and tin step by step.Using the mechanical stirring to stimulate the flow condition of the liquid in cyclone electrowinning.In the alkaline system,zinc,lead and tin can be extracted from the liquid step by step.Firstly,the amount of additive,temperature,the concentration of zinc,the concentration of alkaline and the stirring speed were studied to know the best condition for the deposition of zinc as pieces.The results show that in the condition that the zinc concentration was 20g/L,the alkaline concentration was 5mol/L,temperature was 30?,the current density was 300A/m~2,stirring speed was 50r/min and the 0.3g/L gelatin,0.4g/LEDTA,0.3g/L DPE,0.14g/L yellow lead oxide were added,the zinc deposition efficiency can reach to 98%.The zinc product is slick and smooth.In the alkaline system,lead is deposited first as showing in the cyclic voltammetry curve.When the lead concentration decreases to 0.14g/L,the zinc deposits.Tin can not deposit in the high alkaline concentration liquid(5mol/L),so the zinc deposits first.When the zinc concentration decreases to 0.1g/L,it can decrease the alkaline concentration to 2mol/L,the tin can deposit.This paper studied on the effect of different stirring speed,the concentration of target irons,temperature and the current density on the deposition efficiency of the copper.The structure and components were tested by the SEM and XRD.The results show that the deposition efficiency of copper increase with the increasing stirring speed at the certain range(50-150r/min),the highest efficiency was 99%.Once it out of the range,the efficiency decreased.The stirring speed can make the liquid form the liquid flow to deposit the copper as pieces.In the acid system,the main metals are irons,nickel and copper.The influence of irons and nickel on the deposition efficiency of copper were studied.The results show that irons have great influence on the copper deposition and certain stirring speed(no more than 100r/min)can benefit the copper deposition under the situation that the concentration of irons0.3 times of the copper.So it can reduce the process to pure the liquid with lots of iron ions.The nickel has no effect on the deposition of copper when the concentration of the acid was1.25mol/L.When the concentration of the copper decreases to 0.2g/L,it only needs to change the pH of the liquid to 2~3 and sustain the pH during the deposition of nickel.By this way,copper and nickel can be recovered from the liquid step by step.In the last part of the paper,using the cyclone electrowinning equipment to test the conclusions.The results show that adding certain amount of the addition(0.3g/L gelatin,0.4g/L EDTA,0.3g/L DPE,0.14g/L yellow lead oxide)can deposit smooth zinc as pieces under the condition that current was 120A/m~2.To get the best efficiency and the product quantity,the flow speed should be 400L/h.When the concentration of the copper is 1g/L,it can deposit copper as pieces under the flow speed of 700L/h.The deposition efficiency can be more than 70%under the condition that current was 3.8A,flow speed was 700L/h and the concentration of the iron was 0.6 times of the copper.