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Abstract

The paper presents an assessment of flotation efficiency in the separation of plastics from metals derived from printed circuit boards (PCBs). The PCBs were ground in a knife mill prior to flotation. The contact angles of various materials corresponding to the grains from ground PCBs were measured, and a series of flotation tests was carried out to obtain the best product. The impact of the following parameters were investigated: the reagent and its dose, the airflow rate through the flotation tank and the feed concentration. The highest efficiency of metal recovery from PCBs was achieved for Dimethoxy dipropyleneglycol at a concentration of 157 mg/dm3 and with an airflow of 200 dm3/h and a feed concentration of <50 g/dm3. In the hydrophilic product (concentrate), it was mainly Cu (40%) and Sn (7.8%) that were identified by means of XRF, but there were also trace amounts of precious metals such as Au (0.024%), Ag (0.5797%) and Pd (149 ppm). Impurities in the form of Si (5%), Ca (3.2) and Br (2.1) were also identified in this product. Small amounts of metals in their metallic form were identified in the hydrophobic product (waste), mainly Cu (2.3), Al (1.7) and Sn (1.1). As a result of the research, high recovery ratios were obtained for Cu (93%), Sn (84), Ag (83) and Au (69). The purity of obtained metal concentrate with this method was lower in comparison with the other methods of the recovery of metals from ground PCBs for the same feed, i.e. electrostatic or gravity separation. Also considering other factors such as the environmental impact of the flotation process, the number of facilities and their energy consumption, this process should not be used in the developed metal recovery technology. Using electrostatic separation for the same feed obtained much better results.
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Authors and Affiliations

Dawid M. Franke
1
ORCID: ORCID
Umut Kar
2
ORCID: ORCID
Tomasz Suponik
1
ORCID: ORCID
Tomasz Siudyga
3
ORCID: ORCID

  1. Silesian University of Technology, Gliwice, Poland
  2. Eskisehir Osmangazi University, Turkey
  3. University of Silesia, Katowice, Poland
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Abstract

The possibility of removing organic compounds from wastewater originating from the photochemical production of printed circuit boards by use of waste acidification and disposal of precipitated photopolymer in the first stage and the UV-Fenton method in a second stage has been presented. To optimize the process of advanced oxidation, the RSM (Response Surface Methodology) for three independent factors was applied, i.e. pH, the concentration of Fe(II) and H2O2 concentration. The use of optimized values of individual parameters in the process of wastewater treatment caused a decrease in the concentration of the organic compounds denoted as COD by approx. 87% in the first stage and approx. 98% after application of both processes. Precipitation and the decomposition of organic compounds was associated with a decrease of wastewater COD to below 100 mg O2/L whereas the initial value was 5550 mg O2/L. Decomposition of organic compounds and verification of the developed model of photopolymers removal was also carried out with use of alternative H2O2 sources i.e. CaO2, MgO2, and Na2CO3·1,5H2O2.

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Authors and Affiliations

Barbara Białecka
Maciej Thomas
Dariusz Zdebik

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