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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

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2020

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Vol. 56, iss. 6

257--268

EN

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.

2

Leaching of High Arsenic Content Dust and a New Process for the Preparation of Copper Arsenate

Sheng W., Shen Y.-Y., Sheng-Quan Z.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1167--1172

EN

In this research, the high arsenic content dust of copper smelting, as a raw material, the extraction of copper and arsenic from the high arsenic content dust in the leaching system containing acidic and alkaline compounds was investigated. Meanwhile, the effects of acid/alkaline initial concentration, liquid to solid ratio, leaching temperature, leaching time on the leaching rate of copper and arsenic were studied. The optimum conditions for the leaching of high arsenic content dust and preparation of copper arsenate were determined. The results showed that acidic/alkaline leaching of high arsenic content dust was particularly effective. 93.2% of the copper, and 91.6% of the arsenic were leached in an acidic leaching process and 95% of the arsenic, while less than 3% of the copper, less than 5% of the antimony, less than 2% of the bismuth was also leached in an alkaline leaching process. A new method (the parallel flow drop precipitate method) was developed in the synthesis of copper arsenate process. The parallel flow drop method was employed to adjust the molar ratio (copper to arsenic) of the mixed solution of the acid-leaching solution and the alkali-leaching solution by taking the drop acceleration of an acidic leaching solution and an alkaline leaching solution at 10 mL/min and 12 mL/min, at a temperature of 60°C and a reaction time of 1h. Copper arsenate was prepared by mixing an acidic leaching solution and an alkaline leaching solution. The main phases of copper arsenate were CuHAsO4·1.5H2O and Cu5As4O15·9H2O. Copper arsenate contained 30.13% copper and 31.10% arsenic.

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Preliminary results of metals leaching from a spent hydrodesulphurization (HDS) catalyst

Mulak Wł., Szymczycha A., Leśniewicz A., Żyrnicki W.

Physicochemical Problems of Mineral Processing

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2006

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Vol. 40

69-76

EN

A spent industrial HDS catalyst Ni,Mo/γ-Al2O3 used for reducing sulphur in petroleum products was physically and chemically characterized by X-ray diffraction, scanning electron microscope, electron microprobe and chemical analysis. The leaching efficiency of Mo, Ni, V and Al from the spent catalyst in oxalic acid solution with hydrogen peroxide addition was investigated. The effects of oxalic acid and hydrogen peroxide concentrations and the stirring speed on the rate of metal leaching were studied. The results revealed that addition of hydrogen peroxide to oxalic acid up to 3.0M H2O2 concentration enhanced leaching of metals remarkably, and thereafter remained relatively constant. The highest extraction of metals from the spent catalyst (at 50 C in solution of 0.5M H2C2O4 with 3.0M H2O2) was found to be 90% Mo, 94% V, 65% Ni and 33% Al in 4 hour leaching.

PL

Katalizatory hydroodsiarczania HDS o składzie Ni,Mo/Al2O3 oraz Co,Mo/Al2O3 należą do najszerzej stosowanych w procesach rafineryjnych. Ich dezaktywacja następuje głównie na skutek osadzania się na powierzchni związków węgla i siarczków metali. Tego typu zużyte katalizatory zaliczane są do niebezpiecznych odpadów: są one łatwopalne, wybuchowe, toksyczne, korozyjne, a w kontakcie ze środowiskiem naturalnym wydzielają trujące gazy. Recykling tych katalizatorów jest konieczny ze względów ekologicznych i ekonomicznych. Do badań stosowano zużyty katalizator Ni,Mo/Al2O3 uprzednio odolejony toluenem. Jego charakterystykę fizykochemiczną wykonano na podstawie wyników analizy chemicznej, elementarnej, rentgenowskiej oraz skaningowym mikroskopem elektronowym z mikrosondą rentgenowską. Analiza chemiczna katalizatora wykonana metodą ICP-OES po uprzednim przeprowadzeniu próbki do roztworu wykazała następujące zawartości metali: 5,08% Mo, 5,26% Ni, 5,36% V oraz 24,57% Al. Wyniki analizy skaningowym mikroskopem elektronowym wykazały obecność wanadu, niklu, żelaza oraz siarki głównie na powierzchni katalizatora. W celu ustalenia optymalnego czynnika ługującego metale z katalizatora wykonano ługowania testujące w czasie trzech godzin w temperaturze 70oC w roztworach kwasu siarkowego (VI) oraz kwasu szczawiowego z dodatkiem takich utleniaczy jak: H2O2, NaNO3, NH4NO3 oraz (NH4)2S2O8. Wykazano, że najlepszym czynnikiem ługującym molibden i wanad jest roztwór kwasu szczawiowego z dodatkiem ditlenku diwodoru, natomiast najlepszym czynnikiem ługującym nikiel jest roztwór zawierający kwas siarkowy (VI) z dodatkiem H2O2 lub (NH4)2S2O8. Określono wpływ stężenia H2C2O4 oraz H2O2 na wydajność ługowania Mo, Ni, V oraz Al. Najwyższe wydajności wyługowania metali wynoszące 90% Mo, 94% V, 65% Ni oraz 33% Al uzyskano w roztworze zawierającym 0,5M H2C2O4 z dodatkiem 3,0M H2O2 w temperaturze 50oC po 4 godzinach ługowania.