电积铜用聚苯胺/四氧化三钴复合阳极的研究

【作者】 李发闯；

【导师】 郭忠诚；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2011， 硕士

【摘要】 目前,工业铜电积过程中广泛采用Pb-Ca-Sn阳极,由于其价格相对低廉,而且在电积过程中可以形成PbO2保护层,基本上可以满足工业生产需要。然而从能耗和环保方面考虑,Pb合金阳极在电积过程中具有高的析氧过电位(600mV),占电解槽能耗的30%左右,而且Pb合金阳极的溶解会影响阴极铜的品质,为了解决这些问题,人们正致力于研发更优性能的阳极材料。聚苯胺(PAN[)基复合材料具有高导电性和催化活性,并且对环境友好,应用前景十分广泛。本文采用PANI基节能阳极作为替换阳极,通过原位聚合法制备出高导电和催化活性的PANI/Co304复合材料,研究了合成条件对复合材料导电性的影响,并通过傅里叶红外光谱(FT-IR)、X射线衍射(XRD)、热分析(TGA-DTG).扫描电镜(SEM)等对复合材料的结构和表面形貌进行了表征；通过模压成型工艺制备出所需阳极,系统的研究了PANI/Co304复合阳极在硫酸铜电解液体系和盐酸溶液中的电化学性能,并研究PANI/Co304阳极在铜电积应用中的恒电流极化、槽电压、阳极寿命、电能消耗等,分析了PANI基阳极失效的原因；在此基础上,与纯PANI和Pb-Ag(1％)阳极进行了对比,研究结果如下：(1)确定出PANI/Co304复合材料的最佳制备工艺条件：CAn=0.5 mol·L-1, C氧化剂=0.5mol·L-1, C酸=1 mol·L-1,其中SSA与H28O4的配比为2.5：10,在5℃条件下反应10h；C0304的加入使得PANI链的电荷离域化作用增强,体系致密性提高,从而提高了复合材料的导电性,当mCo304:mAn=5％时,电导率最高为4.56 S/cm；(2)研究表明PANI/Co304复合材料中两种粒子之间存在着相互作用,热稳定性较PANI有所提高,PANI和PANI/Co304复合材料在200℃以下都保持稳定；PANI/Co304复合材料粒径分布较为均匀,C0304基本上被PANI所包裹形成一种有序的核壳结构组织；(3)PANI基阳极在硫酸体系中的耐腐蚀性好于盐酸体系,在同一种体系中,阳极材料的耐腐蚀性依次为：PANI<PANI/Co304(3％)<PANI/Co304(10％)< PANI/Co304(5％),适量C0304的加入可以提高复合材料耐腐蚀性,其中PANI/Co304(5％)阳极具有较好的电荷传递和传质扩散性能；(4)PANI/Co304阳极的表观活化能仅为15.71kJ·mol-1,表现出最好的催化活性,并能够显著降低阳极的极化电位,从而可以达到较好的节能效果,而且复合阳极具有较好的电化学稳定性；(5)在电流密度为200A/m2的条件下,PANI基阳极电位明显小于Pb-Ag(1%)阳极电位,槽电压降低0.26-0.36V,可以节约能耗13.92-19.27%,其中PANI-Co3O4阳极节能效果最为明显,电解铜单位能耗为1364.21 kWh/t-Cu;(6)电解后PANI仍然为本征态结构,并没有被完全氧化而失去催化活性,证明了PANI基阳极的失效主要与阳极的开裂有关。更多还原

【Abstract】 At present, the Pb-Ca-Sn anodes are widely used in industrial copper electrowinning, which can basically meet the needs of industrical production, because of its relatively inexpensive and forming PbO2 protective layer during the electrowinning process. However, from the energy consumption and environmental considerations, the Pb alloy anodes have a high oxygen over potential(600mV) in electrolysis process, that consume 30 percent of cell energy, and the Pb alloy anodic dissolution affects the quality of cathode copper, in order to solve these problems, people are committed to the development of better performance anode materials.PANI composites have very prospect of application with high conductivity, catal-ytic activity and environment-friendly. PANI base energy saving anodes were used as replaced anode in this article, the PANI/Co3O4 composites with high conductivity and catalytic activity were prepared by in situ polymerization, the effect of synthesis conditions on the conductivity of composite was researched, the structure and surface morphology of the composite were characterized by means of FT-IR, XRD,TGA-DTG, and SEM. The required anodes were preparation by molded forming technology. The electrochemical performance of PANI/Co3O4 composite anodes in copper sulfate electrolysis liquid system and hydrochloride solution were systemic researched, and the constant current polarization, cell voltage, anodes life and power consumption were also researched during copper electrowinning process, the failure of PANI based anodes was analysised at last. Based on that, and pure PANI and Pb-Ag (1%) anodes were used for comparison, research results following:(1) The optimum technological conditions for preparation of PANI/Co3O4 composites were determined:CAn=0.5mol-L"1, Coxidant=0.5mol·L-1, Cacid=1mol-L-1, the ratio of SSA and H2SO4 is 2.5:10. The joined Co3O4 can enhance the charge delocalization of PANI chain and improve the compactness of system, thereby improving the conductivity of composite materials, when mCo304:An=5%, the conductivity of up to 4.56S/cm.(2) Chemical bonds interaction is existed between two particles in composites, the composites are more thermally stable, and the stability of both PANI and PANI/Co3O4 composites can be able to remain below 200℃. The particle size distribution of PANI/Co3O4 composites is more uniform, Co3O4 is basically packaged by PANI through a organized core-shell structure.(3) PANI based anodes have good corrosion resistance in sulfuric acid system than in hydrochloric acid, in the same system, the corrosion resistance of anodes is following as:PANI<PANI/Co3O4(3%)<PANI/Co3O4(10%)<PANI/Co3O4(5%), the corrosion resistance of PANI with defined amount of Co3O4 could be improved, PANI/Co3O4(5%) anode has better properties of charge-transfer and mass transfer diffusion.(4) The apparent activation energy of PANI/Co3O4 anode is only 15.71kJ·mol-1 showing the best of catalytic activity, and PANI/Co3O4 anode can significantly reduce anode polarization potential, so that composite anodes achieve better energy saving effect and electrochemical stability.(5) Under the conditions of current density of 200A/m2, the anodic potential of PANI based anodes is significantly smaller than the Pb-Ag (1%), cell voltage reducing 0.26～0.36V, that can save energy 13.92～19.27%, of which PANI/Co3O4(5%) anodes show the most obvious effect energy saving that the unit energy consumption electrolytic copper was 1364.21 kwh/t-Cu.(6) The structure of PANI is still eigenstate after electrolysis, so catalytic activity was not completely lost, that prove the failure of PANI based anodes related primarily to cracking of the anodes.更多还原