【作者】 杨征宇；

【导师】 王宇新；

【作者基本信息】 天津大学 ， 化学工程， 2013， 博士

【摘要】 印刷电路板（PCB)是所有电子产品中重要的组成部分。2006年中国PCB产销量已经超过美国，欧洲及日本，成为世界第一生产大国，到2012年我国总产能已达2亿平方米。在PCB板的生产过程中产生的高含铜蚀刻废液（主要成分为氯化铜）数量巨大。据统计，我国的PCB生产厂家日平均产生废蚀刻液的总量在6000吨以上。如能妥善回收，每年可回收铜约20万吨，除减轻环境压力外可产生100亿人民币以上的效益。为了实现铜回收与蚀刻液循环再生利用，降低新鲜蚀刻液和其它化学添加剂的需求量，从而避免大量的高危险废弃物运输和异地回收，科研人员开发出多种电化学原位再生方法。但现有的电化学法由于经济和技术原因，未得到广泛应用。为实现安全、清洁、经济的PCB生产，本文提出并研究了一种新的蚀刻液再生与铜回收的电化学方法。采用碳毡作为多孔三维电极用于氧化Cu(I)，从而避免了氯气和氧气的析出。碳毡因具有更大的表面积而表现出更大的极限电流密度，并且与铂电极相比，碳毡电极对析O2反应有一定的抑制作用（析氧电位高于铂电极）。使用碳毡电极电解再生蚀刻液，阳极过电位较低，可有效的避免气体析出，从而不需要添加有害气体处理装置。依照上述提及的结构将电解池容积和电极面积同时放大11倍，并通过计算流体力学模拟结果改进了电解池流场分布器。电解实验结果与小型电解池相比，除槽电压由于集流体电阻的增加略有升高外，其它性能参数基本吻合。为了控制阳极性能的衰减，对老化电极进行了再生实验。将累积老化100小时碳毡作为阴极，在电位为-3.2V时电解NaOH溶液，除去其表面的含氧、含氯基团（电解过程中生成）。结果显示该再生方法可恢复老化过程所降低电流密度的一半。采用热处理和浸渍载铱法修饰电极。经400℃热处理后碳毡性能并未提高，但铱修饰法显著提高了碳毡电极对期望电化学反应（一价铜离子氧化）的活性。电解实验结果显示，采用铱修饰碳毡电极可使槽电压和阳极电位均降低约0.1V。使用扫描电子显微镜（SEM）、X射线光电子能谱（XPS）和X射线衍射仪（XRD）研究铱修饰碳毡电极的稳定性。结果表明铱的流失主要发生在老化的前25小时内。老化25小时和75小时铱修饰碳毡电极上铱的总载量相同，但因为老化75小时铱修饰电极载铱中金属铱所占比例较高，所以对一价铜离子氧化有更好的电化学活性。更多还原

【Abstract】 Printed circuit board (PCB) is an important component in almost any electronicproducts. In2006, China PCB production and sales had surpassed the United States,Europe and Japan, becoming the largest producer in the world. The total annualcapacity of PCB production in China reached about200,000,000m2. As a result, alarge amount of high copper-containing spent etchant was generated. According to-statistics,6,000tons or more spent etchant are generated every day in China’s PCBfactories. If they can be properly recycled, about200,000tons of copper would havebeen recovered each year, alleviating environmental pollution and gaining a benefit ofmore than10billion Yuan RMB. Different on-site electrolytic regeneration methodshave been researched and developed, in order to achieve metal recovery and etchantrecycling simultaneously so as to substantially reduce the amount of required freshetchant and other chemicals, while eliminating bulk hazardous waste shipped off-sitefor reclamation. However, electrolytic etchant regeneration has not been widelyadopted so far for technological and/or economical reasons.To realize safer, cleaner and yet economically competitive PCB production, anovel electrolytic process for simultaneous cupric chloride etchant regeneration andcopper recovery is proposed and investigated in this dissertation. A three dimensionalanode made of carbon felt is used to oxidize cuprous ions while avoiding oxygen andchlorine evolution. The limiting current of Cu(I) oxidation on carbon felt electrode ismuch higher than that on platinum electrode because of the large real surface area ofcarbon felt. The carbon felt electrode also inhibits gas evolution, as indicated by anobviously higher onset potential of gas evolution reaction in contrast to Pt electrode.The proposed electrolytic regeneration method enables effective Cu(I) oxidation atlow enough over potential that noticeable gas evolution can be avoided, thuseliminating the need of complex safety measures to deal with hazardous chlorine.Following the success of above mentioned preliminary feasibility verification,electrolytic cell scale-up has been carried out. Computational fluid dynamicssimulation is employed to study the flow patterns in the electrolytic cell and to aid thedesign of fluid distributor. A new cell as11times the volume and electrode area as theinitial small cell has been build and tested. The performance of the new cell is almost as well as the small cell, with only a little higher cell voltage caused by increasedcontact resistance.Restoration of worn carbon felt anode have also been carried out for the firsttime, in order to curb the deterioration of anode performance. The carbon feltaccumulatively worn for100h is restored under a cathodic potential of-3.2V inNaOH electrolyte to reduce the oxygen and chloride containing species formed on thefelt surface during etchant regeneration. Fortunately, roughly half of the decrease incurrent density can be regained through the simple restoration procedure.Efforts have also been made to further improve the performance of carbon felt,by thermal or Iridium modifications. While a heat treatment of the carbon felt at400C makes little difference as compared with the pristine carbon felt, Irmodification of the carbon felt significantly increases the limiting current density ofCu(I) oxidation and results in even lower cell voltage at the same Cu(I) concentration.The stability of Ir modified carbon felt is studied by using scanning electronicmicroscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-raydiffractometry (XRD). The results indicate that the loss of iridium from carbon felt ismainly during the first25hours of electrolysis process. The composition of Ir speciesremains almost invariant from the first25hours to75hours of Cu(I) oxidation.Interestingly, the75hours worn Ir modified carbon felt shows even betterelectrochemical performance, due to deepened Ir oxidation.更多还原