【作者】 张潇尹；

【导师】 陈亮；

【作者基本信息】 东华大学 ， 环境工程， 2008， 硕士

【摘要】 随着电子工业的迅猛发展,废印刷线路板的数量急剧增加。除了含有卤素阻燃剂、汞、硒、镍、铅、铬等污染物,废印刷线路板还含有多种贵金属,如金、银、铂等,回收这些金属尤其是贵金属如金是废印刷线路板资源化的主要推动力。本文以某种废弃印刷线路板为例,总结了废印刷线路板的特点及国内外废印刷线路板资源化的技术如机械处理、火法、热解、湿法处理、超临界水氧化等,重点介绍了回收金的湿法工艺,并详细阐述了开发一种无毒或低毒、浸金效率高、生产成本低的非氰浸金方法的合理性和迫切性。在研究和比较了多种非氰试剂之后,选择了硫氰酸盐作为浸取废印刷线路板中金的试剂。为硫氰酸盐法从废印刷线路板中浸金的工业化打下基础,促进废印刷线路板资源化的研究。本论文工作主要涉及三个部分:（1）分析废印刷线路板颗粒中的金属元素;（2）去除废印刷线路板颗粒中的铜;（3）硫氰酸盐法浸取去铜后的废印刷线路板颗粒中的金。第一部分:采用火焰原子吸收分光光度法（AAS法）测定出PCB中主要金属元素的含量,同时配以电感耦合等离子体发射光谱法（ICP—AES法）验证测定结果。其中铜的含量为883.5mg/g,金为0.324mg/g。第二部分:采用H₂SO₄—H₂O₂体系溶解废印刷线路板颗粒中的铜,对废印刷线路板进行预处理。该工艺的最佳运行条件为:30℃,每2克废印刷线路板颗粒与40mL 2.4mol/L的硫酸和10mL双氧水混合,机械搅拌反应2.5h小时。铜的浸出率可高达98%以上。第三部分:采用硫氰酸盐法浸取预处理过的废印刷线路板颗粒中的金。首先从浸金体系,浸金体系氧化剂选择判据的推导,浸金体系络合剂和氧化剂的关系等三个方面对浸金过程进行理论分析。浸金体系均由氧化剂和络合剂构成。金氧化电势的降低,取决于金络合物的稳定性和特定的浸出条件。在标准条件下,浸金体系选择氧化剂的依据是:氧化电势E₁>（1.68-0.05921gK₁）V或E₁>（1.50-0.0592/3×1gK₂）V。浸金体系氧化剂的选择标准和金（Ⅰ/Ⅲ）络合物的稳定常数相关,稳定常数越大,所需氧化剂的最小氧化电势越小。浸金体系选择络合剂的原则是其与金能生成稳定的络合物,络合物越稳定,越有利于金的浸出。然后在浸金理论的指导下,采用硫氰酸盐作为络合剂,二氧化锰和铁（Ⅲ）作为氧化剂分别组成硫氰酸盐——二氧化锰和硫氰酸盐——铁（Ⅲ）两个浸金体系。本实验考察了反应时间、反应温度、pH值、固液比、氧化剂浓度和用量等因素对浸金率的影响,分别确定了两个浸金体系的最佳运行条件:①硫氰酸盐——二氧化锰体系:MnO₂与待浸金颗粒质量比为1:O.7,0.4mol/LNaSCN溶液,固液比（g/ml）为1/22,pH=l～2,恒温（～20℃）振荡3h,浸金率超过96%;②硫氰酸盐——铁（Ⅲ）体系:0.1mol/L Fe³⁺,0.4mol/L SCN^-,pH=2,固液比为1/22,恒温（～20℃）振荡3h,浸金率达到96%。最后,分别对实验结果建立动力学模型,分析得出:两种浸金体系都符合一级反应动力学,硫氰酸盐——二氧化锰体系的活化能E_a为5.3kJ/mol,硫氰酸盐——铁（Ⅲ）体系的活化能E_a为5.1kJ/mol,都属于扩散控制的反应。总的来说,在酸性溶液中硫氰酸盐可作为络合剂与作为氧化剂的MnO₂和铁（Ⅲ）形成高速且高效的浸金体系。用硫氰酸盐法浸取废印刷线路板中的金具有浸金效率高,浸金速率快,可回收,毒性低微,对环境污染极小等优点,是一种新的有发展前途的提金方法。更多还原

【Abstract】 The rapid development of the electronic industry leads to a significant increase of waste printed circuit board（PCB）. PCB is composed of plastic, refractory oxides and metals such as Au Ag Cu Hg Se Ni Pb Cr. The main economic driving force for the recycling of PCB is the recovery of metals, particularly precious metals like gold.In this paper, some kinds of PCB have been taken as examples to summarize the characteristics of PCB and the methods of recycling metals from PCB at home and abroad. The methods can be broadly divided into physical processes, pyrometallurgical processes, hydrometallurgical processes, pyrolysis, supercritical water oxidation, and so on. The objective of this research is to offer basic data for industrial application of gold recovery from waste PCB by thiocyanate process and to promote a sustainable development of recycling of waste PCB through proposing the non-cyanide process for gold recovery.The work described in this thesis mainly deals with three parts, i.e., Analysis of the component and content of metals in PCB; Dissolving the copper from PCB; Gold leaching from PCB by thiocyanate process.Part one: The element component and content of metals in PCB were determined by AAS and ICP-AES methods respectively. Result indicated that the circuit board was mostly composed of copper（883.5mg/g）; the content of gold was 0.324mg/g.Part two: Dissolving copper from PCB by H₂SO₄—H₂O₂ system was the pretreatment for gold leaching. Experimental results obtained were listed as follows: 30℃, 40mL 2.4mol/L H₂SO₄ and 10ml H₂O₂ mixed with every 2g powder of PCB, 2.5h, which resulted in recovery of 98 % of copper.Part three: Leaching gold from pretreated powder of PCB by thiocyanate process.First, the composition characteristic for gold leaching systems, the relationship between oxidants and ligands and the thermodynamic criterion of oxidants selected for gold leaching systems t were analyzed in details. The gold leaching systems are composed of ligand and suitable oxidant. The oxidation potential of gold is controlled by the stability constant of gold-complex species and special leaching conditions. The larger stability constants, the smaller the standard electrode potential of oxidants needed for gold leaching systems. The leaching in the form of gold（III）-complex species could be performed spontaneously provided that the standard electrode potential of oxidants is larger than （1.50—0.0197lgK₂） V, and when the standard electrode potential of oxidants is larger than （1.68—0.0591lgK₁） V, the leaching in the form of gold（I）-complex species could be carried out according to thermodynamic prediction.Second, under these theoretic analyses, the effect of time, temperature, pH value, solid/liquid ratio, concentration of oxidants on the leaching of gold was discussed in detail. Experimental results obtained were listed as follows:①Thiocyanate-MnO₂ system: powder of PCB : MnO₂（weight）=1: 0.7, 0.4mol/L NaSCN, solid/liquid ratio: 1/22, pH=1～2,～20℃, 3h. The recovery of gold was over 96%.②Thiocyanate-iron（III） system: 0.1mol/L Fe³⁺, 0.4mol/L NaSCN, solid/liquid ratio: 1/22, pH=2,～20℃, 3h. The recovery of gold was about 96%.Third, kinetics models have been established for the processes of gold leaching by these two systems respectively. The results indicated that the rates of the reactions were both first order; the activation energy of the thiocyanate-MnO₂ was found to be 5.3 kJ/mol; the activation energy of the thiocyanate-iron（III） system was found to be 5.1 kJ/mol and both of these two processes were considered to be diffusion-controlled.Generally speaking, the recovery of gold from waste PCB by thiocyanate process is feasible in technique and beneficial in both economy and environment.更多还原