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Comparative smelting of thermally pretreated electronic waste

Szczepaniak Włodzimierz, Zabłocka-Malicka Monika, Gurgul Agnieszka, Leśniewicz Anna, Ochromowicz Katarzyna

Physicochemical Problems of Mineral Processing

2021

Vol. 57, iss. 6

55--70

Used electronic inverters were processed thermally to eliminate organic matrix components through oxidative incineration (IN), oxidative steam gasification (SG), and pyrolysis (PY). Such prepared material was melted at 1250°C with sodium/calcium silicate waste glass under reductive and oxidative atmospheres. The highest Cu recovery in the form of a gravitationally separated metallic phase was found for oxidative smelting of the PY sample and reductive smelting of the IN sample. Recovery of precious metals was analyzed, taking Cu recovery as the reference. It was found that the recovery of Pd was better than copper recovery in each experiment, and the recovery of Au was only in the oxidative smelting of the SG sample and reductive smelting of the IN sample. Recovery of Ag and Cu was similar but only for the reductive smelting of the PY and SG samples. It was demonstrated that Cu, as well as Au, Ag, and Pd recovery, substantially depends on the transport of metals through the metal/slag interface.

Acidic leaching of steam gasified, pyrolyzed and incinerated PCB waste from LCD screen

Szczepaniak Włodzimierz, Zabłocka-Malicka Monika, Gurgul Agnieszka, Ochromowicz Katarzyna

Physicochemical Problems of Mineral Processing

2020

Vol. 56, iss. 6

257--268

In the recycling of WEEE, two approaches are common: a pyrometallurgical or hydrometallurgical treatment, preceded by a mechanical and/or physical separation. In this study, twostep processing of unmodified waste samples of LCD screen inverters was investigated: hightemperature processing followed by acidic leaching under fixed conditions (1M H2SO4, 90 ℃, 1 bar). The analysis carried out concerned a correlation between the type of HT treatment (pyrolysis, incineration, or gasification) and the dynamics of metals’ leaching from samples pretreated this way. It was found that HT method can act as “thermal disintegration”, since it affects, to a varying degree, the structure of the samples and cause elimination of organics and carbonaceous residue (incineration/gasification). The greatest mass loss (~18%) and the most loosened structure was observed for the gasified sample. Varying oxygen potential in HT-processes correlates well with the leachability of thermally treated inverters. The incineration was found to be the most favorable for copper extraction (>95%) by acidic leaching due to oxidized form of Cu, whereas Cu leaching from pyrolyzed and gasified samples needed oxygen and was controlled by the oxygen supply achieving only 36/43% after 6 h. The course of Pd leaching was similar to copper, although with lower efficiencies; 47% of palladium was extracted from the incinerated sample, and only 4 or 7% from gasified and pyrolyzed samples, respectively. Au was leached immediately but only to a slight extent. Contrary to Pb, leaching of Zn, Sn, Sb, and Ni was gradual, probably due to the formation of alloys with copper.