Resources Recycling (자원리싸이클링)

The Korean Institute of Resources Recycling (한국자원리싸이클링학회)
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Study on Recovery of Precious Metal (Ag, Au) from Anode Slime Produced by Electro-refining Process of Anode Copper

양극동의 전해정련시 발생된 양극슬라임으로부터 귀금속(Ag, Au) 회수에 대한 연구

  • Received : 2018.08.07
  • Accepted : 2018.10.16
  • Published : 2018.12.28
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Abstract

Recently rapid economic growth and technological development have led to an increase in the generation of waste electrical and electronic equipment (WEEE). As the amount of electric and electronic waste generated increases, the importance of processing waste printed circuit boards (PCB) is also increasing. Various studies have been conducted to recycle various valuable metals contained in a waste PCB in an environmentally friendly and economical manner. To get anode slime containing Ag and Au, Anode copper prepared from PCB scraps was used by means of electro-refining. Ag and Au recovery was conducted by leaching, direct reduction, and ion exchange method. In the case of silver, the anode slime was leached at 3 M $HNO_3$, 100 g/L, $70^{\circ}C$, and Ag was recovered by precipitation, alkali dissolution, and reduction method. In the case of gold, the nitrate leaching residues of the anode slime was leached at 25% aqua regia, 200 g/L, $70^{\circ}C$, and Au was recovered by pH adjustment, ion exchange resin adsorption, desorption and reduction method. The purity of the obtained Au and Ag were confirmed to be 99.99%.

최근 급속한 경제성장과 기술발달로 전기전자폐기물(WEEE)의 발생량이 꾸준히 증가하고 있으며, 이에 따라, 전기전자폐기물의 처리에 대한 중요성 또한 높아지고 있다. 이중, 인쇄회로기판(PCB)의 경우, 유가금속을 다량 함유하고 있기 때문에 친환경적이고 경제적인 재활용 방법에 관한 다양한 연구가 활발히 이루어지고 있다. 본 연구에서는 PCB스크랩으로부터 제조된 양극동의 전해정련 과정에서 발생한 양극슬라임을 활용하여 Ag 및 Au 회수를 위한 실험을 수행하였다. Ag의 경우, 3 M $HNO_3$, 100 g/L, $70^{\circ}C$로 침출하였고, 침전, 알칼리 용해, 환원 방법에 의하여 Ag를 회수하였다. Au의 경우, 양극슬라임의 질산 침출 잔사를 25% Aqua regia (왕수), 200 g/L, $70^{\circ}C$로 침출하였고, pH조정, 이온교환수지 흡착 및 탈착, 환원 방법에 의하여 Au를 회수하였다. 최종적으로 얻어진 Au, Ag의 순도는 99.99%로 확인되었다.

Keywords

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Fig. 1. Anode slime & anode copper.

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Fig. 2. Diagram of experimental process.

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Fig. 3. Leaching efficiency (%) as a function of the HNO3 concentration.

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Fig. 4. Leaching efficiency (%) as a function of the reaction time.

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Fig. 5. Photos of the Ag powders manufacturing. (a) AgCl precipitate, (b) Ag powder.

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Fig. 6. Leaching efficiency (%) as a function of the aqua regia concentration.

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Fig. 7. Adsorption efficiency of Au as a function of pH.

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Fig. 8. Results of maximum absorption capacity experiments of ion exchange resin.

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Fig. 9. Au desorption efficiency as a function of the ratio (Au loaded resin: desorption solution).

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Fig. 10. Au recovery efficiency as a function of the amount of reducing agent.

Table 1. Average chemical composition of the prepared anode copper and slime

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Table 2. Results of the Ag reduction experiments

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Table 3. Chemical composition of produced Ag metal

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Table 4. Desorption efficiency according to the types of desorption solutions

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Table 5. Chemical composition of produced Au metal

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