The discarded electronic wastes have attracted great attention from researchers because of their large potential values as a future secondary source of precious metals. In spite of persistent efforts, technologies of separation and refining of these metals are not yet matured to be commercialized. Recently, a novel adsorbent, porphyrin-based porous polymer, called COP-180, has been developed for selective adsorption of gold. Although investigations on characteristics and adsorption abilities of COP-180 has been deeply conducted, desorption and recovery of adsorbed gold and reusability of the polymer are still remained to be solved. Herein, processes for efficient gold desorption and recovery from COP-180 was suggested by methods of leaching and plating. Leaching solution was explored for efficient desorption of gold from COP-180. Chloride, thiosulfate and thiourea, which are typical non-cyanide gold leaching solutions, were examined and thiourea showed the best desorption efficiency. FTIR analysis supported that result as the adsorbent structure maintained after being treated with thiourea. More than 98% of the adsorbed gold on the polymer was recovered in thiourea solution. The dissolved gold in thiourea was then collected as a thin-layer film by means of electroless and electro- plating. As an electroless plating method, immersion gold process with nickel substrate was applied to gold-thiourea solution. Gold was deposited over 99.8% with porous layer under varying conditions of temperature and reaction area. The electroplating of gold was also proceeded resulting more than 96% of deposition on the cathode. Calculated energy during the plating was 0.13 kWh/kg, which value was the smallest compared to previous reports. The regeneration of COP-180 and thiourea solution were also verified by cyclic operations. Hence, this work certainly implied that the proposed leaching-deposition system showed possible abilities not only to recover gold but also to regenerate the adsorbent which take a large portion in industrial application.

Processes for gold recovery from electronic waste using porous porphyrin polymer and adsorbent regeneration

2019 Fall National Meeting

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