The demand for rare and precious metals (RPMs), e.g. gold, is increasing, as these are used in the ever-increasing amount of electronics needed for technological development and digitalization. Due to their rarity, virgin mining of RPMs is becoming more difficult and expensive. At the same time, over 62Mt of e-waste is created globally each year. The high concentration of gold and other RPMs in e-waste makes it an excellent source for recycling. Unfortunately, current recycling methods need to separate the different metals and the current pyrometallurgical and hydrometallurgical processes also create toxic pollutants, large amounts of wastewater and require highly corrosive substances. Here we present a new method for gold removal for the purpose of recycling, using only water and high-intensity focused ultrasound to induce material erosion through cavitation. An 11.8MHz ultrasonic transducer is used to first image the sample to locate gold-coated pads on discarded printed circuit boards (PCBs) and subsequently to remove only the gold layer. We demonstrate that the gold removal can be controlled by the number of transmitted ultrasonic bursts and that the energy efficiency is optimal when only minute amounts of the nickel layer beneath are also removed. Removing solely the gold layer also decreases the need for further processing steps. This greener gold removal method for e-waste is therefore well aligned with, and contributing to, the United Nations Sustainable Development Goal 12: Ensure sustainable consumption and production patterns.

中文翻译：

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使用高强度聚焦超声从电子垃圾中去除金


对稀有金属和贵金属 （RPM），例如黄金，的需求正在增加，因为这些金属被用于技术开发和数字化所需的不断增长的电子产品中。由于它们的稀有性，RPM 的原始开采变得越来越困难和昂贵。与此同时，全球每年产生超过 62 公吨的电子垃圾。电子垃圾中高浓度的黄金和其他 RPM 使其成为极好的回收来源。不幸的是，目前的回收方法需要分离不同的金属，而目前的火法冶金和湿法冶金工艺也会产生有毒污染物、大量废水，并需要高腐蚀性物质。在这里，我们提出了一种以回收为目的的去除金的新方法，仅使用水和高强度聚焦超声通过空化诱导材料腐蚀。首先使用 11.8MHz 超声波换能器对样品进行成像，以定位废弃印刷电路板 （PCB） 上的镀金焊盘，然后仅去除金层。我们证明，金的去除可以通过传输的超声波爆发的数量来控制，并且当仅去除下面的微量镍层时，能源效率是最佳的。仅去除金层也减少了对进一步加工步骤的需求。因此，这种更环保的电子垃圾除金方法与联合国可持续发展目标 12：确保可持续的消费和生产模式完全一致，并有助于实现。