LEPABE, DEMM, Faculdade de Engenharia, Universidade do Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal.
Centre for Natural Resources and the Environment (CERENA), Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal.
J Environ Manage. 2018 Oct 1;223:297-305. doi: 10.1016/j.jenvman.2018.06.019. Epub 2018 Jun 20.
The recovery of electronic waste to obtain secondary raw materials is a subject of high relevance in the context of circular economy. Accordingly, the present work relies on the evaluation of mining separation/concentration techniques (comminution, size screening, magnetic separation and gravity concentration) alone as well as combined with thermal pre-treatment to recover gold and copper from Waste Printed Circuit Boards. For that purpose, Waste Printed Circuit Boards were subjected to physical processing (comminution, size screening in 6 classes from <0.425 mm to > 6.70 mm, magnetic separation and gravity concentration) alone and combined with thermal treatment (200-500 °C), aiming the recovery of gold and copper. Mixed motherboards and graphic cards (Lot 1 and 3) and highly rich components (connectors separated from memory cards, Lot 2) were analyzed. Gold and copper concentrations were determined before and after treatment. Before treatment, concentrations from 0.01 to 0.6 % wt. and from 9 to 20 % wt. were found for gold and copper respectively. The highest concentrations were observed in the size fractions between 0.425 and 1.70 mm. The highest copper concentration was around 35 % wt. (class 0.425-0.85 mm) and when analyzing memory card connectors alone, gold concentrations reached almost 2% in the same class, reflecting the interest of separating such components. The physical treatment alone was more effective for Lot 1/3, compared to Lot 2, allowing recoveries of 67 % wt. and 87 % wt. for gold and copper respectively, mostly due to differences in particles size and shape. The thermal treatment showed unperceptive influence on gold concentration but significant effect for copper concentration, mostly attributed to the size of the copper particles. Concentrations increased in a factor of around 10 when the thermal treatment was performed at 300 °C for the larger particles (1.70-6.70 mm); the best results were obtained at 400 °C for the other sizes, when the highest rate of thermal decomposition of the material occurred.
从电子废物中回收二次原材料是循环经济背景下的一个高度相关的课题。因此，本工作依赖于评估采矿分离/浓缩技术（粉碎、粒度筛选、磁选和重力浓缩）单独使用以及与热预处理相结合，从废印刷电路板中回收金和铜。为此，废印刷电路板经过物理处理（粉碎、粒度筛选为 6 级，粒径从<0.425 毫米到>6.70 毫米、磁选和重力浓缩）单独使用和与热处理（200-500°C）结合，旨在回收金和铜。分析了混合母板和显卡（Lot 1 和 3）和高浓度组件（从存储卡中分离出的连接器，Lot 2）。处理前后测定金和铜的浓度。处理前，金和铜的浓度分别为 0.01 至 0.6%wt 和 9 至 20%wt。在 0.425 至 1.70 毫米之间的粒径范围内观察到最高浓度。最高铜浓度约为 35%wt（粒径 0.425-0.85 毫米），单独分析存储卡连接器时，金浓度在同一粒径下达到近 2%，反映了分离此类组件的兴趣。与 Lot 2 相比，单独的物理处理对 Lot 1/3 更有效，分别回收 67%wt 和 87%wt 的金和铜，主要是由于颗粒尺寸和形状的差异。热处理对金浓度的影响不大，但对铜浓度的影响显著，主要归因于铜颗粒的尺寸。当在 300°C 下对较大颗粒（1.70-6.70 毫米）进行热处理时，浓度增加了约 10 倍；当对其他尺寸在 400°C 下进行热处理时，获得了最佳效果，此时材料的热分解率最高。
