| Printed circuit board?PCB?is a indispensible component in various electronic products,and its present production process produces a large amount of spent etchant.The spent etchant contains a large amount of copper chloride,hydrochloric acid,and sodium chloride.In order to protect the environment and conserve resources,it is necessary to reuse the spent etchant reasonably.Ideally,electrolysis can realize the regeneration of copper chloride etchant and the recovery of metal copper simultaneously,meeting the requirements of green production and environmental protection.However,methods of electrolytic etchant regeneration and copper recovery have been rarely adopted so far for technological and economic reasons.We have proposed a new electrolytic process for on-site etchant regeneration and copper recovery from spent etchant,which is compatible with the PCB etching production line.The electrolyzers,metering pumps,electric heating pipes and liquid storage tanks were designed and manufactured.A pilot scale electrolytic plant was designed and set up,and the experiment of etching solution regeneration and copper recovery was carried out.Through the adjustment and improvement of the experimental scheme,the problems such as high cell voltage,chlorine gas evolution on the anode and poor copper deposition on the cathode were solved effectively.Simultaneous etchant regeneration and copper recovery were finally achieved.The copper deposited was in the form of plate and its purity exceeds 99%.The voltage of the working electrolytic cell was as low as 1.141.17 V.Therefore,the newly proposed electrolytic process and the corresponding design of pilot plant show obvious advantages over previously known methods and are thus promising to find practical applications.In order to increase the electrochemical activity of the graphite felt anode and to improve the contact of the anode with current collector,the graphite felt was modified and a method to adhere the anode to the current collector was develpoed.The hydrophilicity of the modified graphite felt was greatly improved and the electrochemical reactivity with copper ions was improved.A facile and reliable adhesion between a graphite felt electrode and a current collector of flexible graphite paper was realized,using an in-house made conductive adhesive made up of highly conductive carbon black as the filler and polyvinylidene fluoride as the binder.The influences of the adhesive composition,the amount of the adhesive used and the curing pressure on the contact resistance and adhesion strength between the graphite felt and the flexible graphite paper were investigated.In contrast to the case without using adhesive,the interface adhered under suitable conditions shows a marked drop of contact resistance by 50%in a wet environment.Meanwhile the tensile shear strength of the adhered samples reaches 25.3×10-3 MPa,which is at the same magnitude as the strength of the felt.When applied to the electrolytic regeneration of acidic copper chloride etchant in printed circuit board production,the adhering method results in a drop of single cell voltage by 0.08 V.This would translate into a reduction of power consumption by 80 KW·h for every ton of metal copper recovered. |
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