Evaluation of the efficiency of metal recovery from printed circuit boards using gravity processes

Abstract

This paper evaluates the efficiency of metal recovery from printed circuit boards (PCBs) using two gravity separation devices: a shaking table and a cyclofluid separator. The test results were compared with the results obtained from previous research, where an electrostatic separation process was used for an identically prepared feed. The feed for the separators consisted of PCBs shredded in a knife mill at cryogenic temperatures. The separation efficiency and purity of the products were evaluated based on microscopic analysis, ICP-AES, SEM-EDS, XRD, and specific density. The yield of concentrates (valuable metals) obtained from the shaking table and the cyclofluid separator amounted to 25.7% and 18.9%, respectively. However, the concentrate obtained from the cyclofluid separator was characterised by much higher purity, amounting to ~88% of valuable metals, compared to ~72% for the shaking table. In both cases, middlings formed a significant share, their yield amounting to ~25%, with the share of valuable metals of ~15%. The yield of waste obtained from the shaking table and the cyclofluid separator were 42.6% and 52.5%, respectively. In both cases, as a result of the applied process, the waste was divided into two homogeneous groups differing in grain size and shape. The recovery of metals through gravity separation is possible, in particular, by using a shaking table. These processes can also be applied to separate waste (plastics) into two groups to be selectively processed to produce new materials in line with a circular economy.

Gospodarka Surowcami Mineralnymi - Mineral Resources Management

“…plastics product (5.8% of valuable elements, mainly Cu). The products obtained using a cyclofluid separator were similar to those obtained from the shaking table (Franke et al 2021).…”

“…The same feed as the one used for flotation has been used for electrostatic separation (Suponik et al 2021) and gravity separation (Franke et al 2021). Compared to the above methods of recovering metals from PCBs, flotation is not the most efficient process due to the impurities in both products and their yields.…”

“…3. yield of separation products as a function of their density and quality parameters (Suponik et al 2021;Franke et al 2021) Due to the low values of these metals, their loss should not significantly affect the profitability of the recovery process. new goods generated from the hydrophobic product, due to its content of chromium, should be analyzed in terms of their impact on the environment.…”

“…For this purpose, the contact angle of various materials was measured and a series of flotation tests was carried out to select the reagent and its dose, the airflow rate through the flotation tank, and the concentration of the feed. The test results were then compared with the results of electrostatic separation (Suponik et al 2021) and gravity separation (Franke et al 2021) used for the same feed.…”

Exploring the comminution process of waste printed circuit boards in recycling: a review

“…Furthermore, this technique prevents or minimizes the buildup of heat, which can otherwise cause material degradation or fusion [107]. Studies by Suponik et al [108] and Franke et al [109] inferred that subjecting materials to cryogenic temperatures has a beneficial impact on the size and morphology of grains. As a result, the proposed method supports the extraction of metals from WPCBs.…”