Efficient recycling of waste printed circuit boards by flotation has become a research focus. In this study, waste printed circuit boards were treated by alkaline immersion to enhance the flotation efficiency. Firstly, the SEM-EDS analysis of the crushed products shown that metal and nonmetal were completely liberated in the −0.25 mm fraction. When the printed circuit boards were modified by alkaline immersion, the recovery of metal increased from 64.34% to 72.35%. Further, the mixture of metal and nonmetal at the edge of nonmetal was discovered by EPMA. This was the cause of metal loss during the flotation process. Secondly, by adjusting the alkaline immersion time and pH value, a good flotation effect was achieved at 40 min alkaline immersion time and the pH = 11. Meanwhile, the XPS analysis of nonmetal found that the intensity of the OH peak was significantly enhanced, while the intensity of the O peak was evidently decreased. The change of the resin molecular structure indicated that the O linked to the benzene ring was broken under the action of alkaline immersion, resulting a free bond was generated on the benzene ring. This made the free OH adsorb to the free bond. This conduct promoted the dispersion of nonmetal in the slurry due to the increased nonmetal surface energy and metal hydrophilicity. Thus, this study provides a new route to improve the flotation efficiency of waste printed circuit boards.

通过浮选有效地回收废印刷电路板已成为研究重点。在这项研究中，对废印刷电路板进行了碱浸处理，以提高浮选效率。首先，对粉碎产品的SEM-EDS分析表明，金属和非金属在-0.25 mm的分数中完全释放出来。当通过碱浸对印刷电路板进行改性时，金属的回收率从64.34％增加到72.35％。此外，EPMA发现了在非金属边缘的金属和非金属混合物。这是浮选过程中金属损失的原因。其次，通过调整碱浸时间和pH值，在碱浸40分钟和pH = 11时可获得良好的浮选效果。同时，对非金属的XPS分析发现OH峰显着增强，而O峰的强度明显下降。树脂分子结构的变化表明，在碱浸的作用下，与苯环相连的O被破坏了，从而在苯环上产生了一个自由键。这使得游离OH吸附到游离键上。由于增加了非金属表面能和金属亲水性，这种行为促进了非金属在浆料中的分散。因此，本研究提供了提高废印刷电路板浮选效率的新途径。