| 题名 | 废弃线路板中钯的清洁回收方法与机理研究 |
| 作者 | 张志远 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 张付申 |
| 关键词 | 废弃线路板，非酸化合成，钯回收，机械化学活化，固相反应，萃 取， Wasted printed circuit boards, Palladium Recovery, Mechanochemical activation, Solid phase reaction, Solvent extraxtion |
| 其他题名 | Clean Technology Development and Mechanism Clearification for Palladium Recovery from Waste Printed Circuit Boards |
| 学位专业 | 环境工程 |
| 中文摘要 | 废弃线路板是电子废弃物的重要组成部分，其中含有价值不菲的钯。近年来我国电子废弃物的拆解量迅速增加，但废弃线路板大多只进行简单的物理分离，回收其中的铜和树脂，关于深度回收分散稀贵金属的研究稀有报道，针对钯的研究更加少见。本研究以废弃线路板为研究对象，以环境友好的湿法冶金方法实现废弃线路板中钯的有效回收，避免强酸、强碱和强氧化剂的使用，同时解析回收过程中的反应机理，建立废弃线路板资源化的新技术和新理念，为线路板的资源化提供新的途径。具体包括三个方面：基于废弃线路板非酸化合成氯化亚铜的钯浸出方法研究，基于机械化学活化的废弃线路板中钯的浸出方法研究，废弃线路板浸出液中钯的溶剂萃取回收方法研究。研究得到的主要结论如下： 1）基于废弃线路板非酸化合成氯化亚铜的钯浸出方法研究中，采用CuSO4-NaCl体系与废弃线路板中的Cu单质反应，通过调节实验参数使铜和二价铜定向生成一价铜，进而分离得到氯化亚铜。正交实验表明，氯化亚铜合成过程中影响钯浸出的主要参数是[Cu]/[Cu2+]。实验通过在氯化亚铜合成过程中考察钯的溶出情况，确定基于非酸化合成氯化亚铜的钯浸出的最佳参数，同时达到了理想的钯回收率和氯化亚铜转化率。通过控制实验条件下，可以使 95%以上的钯转入溶液，97%以上的铜转化为氯化亚铜进行回收。方法所得氯化亚铜产品含量高达 98.7%，主要指标均符合化工行业标准中优等品的要求。对钯的浸出机理进行分析，发现 Cu2+与 Cl-是钯溶出的关键，该体系作为新的浸出体系，可以拓展用于各类含钯废料的回收。本方法全程未使用强氧化剂和强酸，在浸出钯的同时得到氯化亚铜产品，具有良好的经济效益和实际应用前景。 2）基于机械化学活化的废弃线路板中钯的浸出方法研究中，发现机械活化对于废弃线路板中钯的回收具有明显的促进作用。确立了钯的最佳机械化学活化条件：NaCl：K2S2O8为 1:1，物料比 4:1，球料比为 20:1，转速为 600 rpm，球磨时间为 3 h，该条件下钯的浸出率达到 95%以上。通过 XRD、XPS、SEM等方法研究球磨前后物料的形态变化和化学变化，并结合热力学计算分析可推知，反应产物中的钯以 PdCl2存在，球磨中的发生的反应为：K2S2O8 + 2NaCl + Pd = PdCl2+ K2SO4 + Na2SO4。在球磨过程中，K2S2O8中具有活性的氧起到氧化作用，NaCl的添加则降低了反应的 ΔG，使反应更容易进行，球磨的破碎、混合以及球与球、球与罐之间碰撞所提供的能量，使得常温下不能发生的固相反应在球磨体系中可以实现。 3）废弃线路板多金属体系中的钯通过二异戊基硫醚（S201）进行萃取回收，研究了萃取和反萃取过程中的一系列参数，并对萃取机理和 S201的重复使用性进行了研究。最佳参数条件下（10%的 S201的正十二烷溶液，A/O（水相与有机相体积比）比为 5的两级萃取，萃取时间 2分钟），钯的萃取率为 99.4%；使用S201萃取钯时，分子中的硫原子与钯直接配位，而常规金属和 S201不能和配位，从而实现钯与常规金属的有效分离。使用 0.1 mol/L的氨水对载钯的有机相进行反萃，在 A/O（水相与有机相体积比）比为 1的条件下，通过两级反萃可以实现99.5%的反萃率。萃取-反萃-再生重复 5次后，萃取剂性质稳定，萃取性能没有明显的下降，萃取率依然保持在 99%以上，实现了良好的重复利用。 |
| 英文摘要 | Waste printed circuit boards (PCBs) are important parts of the e-waste, which contain valuable palladium. In recent years，electronic waste (e-waste) dismantled in China increased rapidly. However, waste PCBs were simply disposed with mechanical separations to recovery copper and resin. But very few researchs paid attention to the recovery of rare and precious metals, especially palladium. In the present study,typical waste PCBs were utilized as experiment materials. Palladium were recovered efficiently employing novel green hydrometallurgy methods from waste PCBs. Use of corrosive acid and strong oxidant was avoided to decrease the environmental impact.New technology and new idea for waste PCBs recovery were proposed. The research includes three parts: 1) Pd leaching process based on cuprous chloride synthesis by a non-acid mehod; 2) Leaching of Pd from waste PCBs based on mechanochemical activition; 3) Selective recovery of palladium from muli-metals solution of waste printed circuit boards with solvent extraction; The main research outcomes are as follows: 1）During the Pd leaching process based on cuprous chloride synthesis, copper in waste PCBs was reacted with cupric sulfate in the presence of sodium chloride. Experimental conditions were adjusted to make sure that copper and Cu2+ were transformed into Cu+ and subsequently cuprous chloride was separated. The orthogonal experimental results showed that the most significant factor impacting the leaching rate of Pd was [Cu]/[Cu2+]. The optimum experimental parameter was determined by observation of palladium dissolution during cuprous chloride synthesis. Under the optimum condition, high Pd leaching and CuCl conversion rate were both achieved. Over 95% of Pd was dissolved and approximately 97% of Cu could be recovered from the PCBs through two synthesis circles. The CuCl product had a content of 98.7% and met the prescribed standards of premium grades. Analysis of Pd leaching mechanism indicated that Cu2+ and Cl- were key factors. The Cu2+ - Cl-system could be used for the recovery of palladium containing materials. Use of corrosive acid and strong oxidant was avoided during the whole process. High Pd leaching rate and high quality of CuCl were simultaneously achieved. Accordingly, it is believed that the process developed in the current study is economical and practical for waste PCBs recovery. 2) It was found that mechanochemical activation could significantly promote palladium recovery from waste PCBs. Optimal mechanochemical activation condition for palladium leaching was determined: K2S2O8 to NaCl mass ratio, mass ratio of comilling reagents to waste PCB particles, mass ratio of balls to milling sample, rotation speed, milling time in the ball milling process were 1:1, 4:1, 20:1, 600 rpm, 3 h, respectively. Under the above condition, the dissolution efficiency of Pd was 95%. XRD、XPS and SEM were employed to investigated the morphological and chemical changes. With the further analysis of thermodynamic calculation, mechanochemical mechanism was concluded that palladium was existed as the form of PdCl2 and the chemical reaction during ball milling was as follows: K2S2O8 + 2NaCl + Pd = PdCl2 + K2SO4 + Na2SO4. K2S2O8 reacted with metals as oxidant and the participation of NaCl significantly lowered ΔG298 of the reactions, meaning that reaction with the participation of NaCl was most likely to occur. Fracturing, mixing and energy produced by collisions either between balls or ball and inner wall of mill container brought about mechanochemical solid phase reactions during ball milling. 3) The palladium from muli-metals solution of waste PCBs was extracted by diisoamyl sulfide (S201). Various parameters during extraction and stripping were studied. The extraction mechanism and reusability of S201 were also investigated. It was found that 99.4% of Pd(II) could be extracted from the solution under the optimum conditions (10% S201, A/O ratio 5 and 2 min extraction). In the whole extraction process, the influence of base metals was negligible due to the relatively weak nucleophilic substitution of S201 with base metal irons and the strong steric hindrance of S201 molecular. Around 99.5% of the extracted Pd(II) could be stripped from S201/dodecane with 0.1 mol/L NH3 after a two-stage stripping at A/O ratio of 1. After the procedure of extraction – stripping - regeneration repeated 5 times, extraction percentage of Pd(II) with regenerated S201/dodecane was comparable with fresh S201/dodecane as more than 99% of Pd(II) could be transported to the organic phase in the 5nd cycle. Hence, S201 is a stable extractant that can be regenerated and used repeatedly for Pd(II) extraction. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34477]  |
| 专题 | 生态环境研究中心_固体废弃物处理与资源化实验室 |
| 推荐引用方式 GB/T 7714 | 张志远. 废弃线路板中钯的清洁回收方法与机理研究[D]. 北京. 中国科学院研究生院. 2015. |
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