Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi, 221005, India.
CSIR-National Metallurgical Laboratory, Jamshedpur, 831007, India.
Environ Sci Pollut Res Int. 2024 Aug;31(39):51401-51414. doi: 10.1007/s11356-024-34616-9. Epub 2024 Aug 7.
Waste printed circuit boards (WPCBs) encompass abundant metals (gold, silver, and copper), along with other harmful materials including brominated epoxy resins, plastics, and heavy metals (lead, mercury, and cadmium). Direct burning and landfilling of WPCBs may cause severe health issues and impair the environment. Therefore, sustainable treatment of WPCBs is necessary to recover valuable metals and remove hazardous materials before disposal. The present work investigates the separation of copper-rich metallic fractions from the WPCBs by the combination of hammer milling and ultrasonic irradiation. Initially, discarded mobile phone PCBs are pre-processed and shortened into 1 × 1 cm. Downscaled WPCBs are fed into the hammer mill to obtain the fine ground powder. The Powdered WPCBs are further processed through ultrasonic treatment to acquire metal-rich fraction. XRD, SEM-EDS, and ICP/AAS analysis revealed that the current technique can efficiently separate the metal-rich fraction without using toxic solvents. Results show the enhancement of copper fraction from 42.73 to 87 wt. % after ultrasonic treatment of WPCBs ground powder. Further, nitric acid leaching has been implemented to metal-rich fractions, and the parameters have been optimized for copper leaching with the assistance of response surface methodology (RSM) of the design of experiments (DOE). Quantitative dissolution (98.96%) of copper occurred using 3.5 M nitric acid within 3 h at 30 °C with 50 GPL pulp density and 500 rpm agitation speed. Finally, the kinetics of the leaching process were studied to conform the kinetics model. Moreover, the activation energy for diffusion (19.075 kJ/mole) and reaction kinetics model (13.29 kJ/mole) has also been calculated. The low energy consumption due to room temperature pre-treatment and effective leaching ensures the industrial feasibility of the proposed process.
废弃印刷电路板（WPCBs）中含有丰富的金属（金、银和铜），以及其他有害物质，包括溴化环氧树脂、塑料和重金属（铅、汞和镉）。直接燃烧和填埋 WPCBs 可能会导致严重的健康问题，并损害环境。因此，有必要对 WPCBs 进行可持续处理，以在处置前回收有价值的金属并去除有害物质。本工作研究了通过锤磨和超声辐射相结合从 WPCBs 中分离富铜金属部分。首先，对废弃手机 PCB 进行预处理，切成 1×1cm 的小块。将小块 WPCBs 送入锤磨机，获得细磨粉末。然后对粉末 WPCBs 进行超声处理，获得富金属部分。XRD、SEM-EDS 和 ICP/AAS 分析表明，该技术无需使用有毒溶剂即可有效地分离富金属部分。结果表明，超声处理 WPCBs 磨碎粉末后，铜的含量从 42.73%提高到 87wt.%。进一步对富金属部分进行硝酸浸出，在实验设计（DoE）的响应面法（RSM）的辅助下优化了铜浸出的参数。在 30°C、50GPL 浆体密度和 500rpm 搅拌速度下，用 3.5M 硝酸在 3 小时内定量溶解（98.96%）铜。最后，研究了浸出过程的动力学，以验证动力学模型。此外，还计算了扩散的活化能（19.075kJ/mol）和反应动力学模型（13.29kJ/mol）。由于室温预处理和有效浸出所需的能耗较低，保证了所提出工艺的工业可行性。
