Electronic wastes containing precious metals have great potential as a sustainable source of such metals. Separation and refining, however, remain complicated, and none of the existing technologies have yet experienced commercialization. A novel porphyrin-based porous polymer, named COP-180, was recently introduced as a powerful adsorbent option, especially for gold, and in this study, aspects of desorption and recovery of adsorbed gold and regeneration of the polymer were investigated.According to ionic states of adsorbed gold, two approaches were introduced: physical and electrochemical processes. The elemental gold was separated via gravitational sedimentation using glycerol as a separation media. Recovery efficiency and purity of the collected gold were improved by adding a dispersing agent, sodium hexametaphosphate. The remaining gold on the adsorbent was then retrieved by desorption and plating. A hydrometallurgical approach on the basis of non-cyanide leaching agents was developed, and an acid thiourea-based solution was found to be suited for COP-180. The unaffected structure and desorption efficiency of COP-180 after its repeated use were proved the potential of its regeneration. Gold in the thiourea solution was then recovered as a film through electroless plating. Also, the application of the gold-thiourea solution to electroless nickel/immersion gold process was verified; corrosion resistance of the gold layer was comparable to the existing technology and deposition rate faster. All this clearly showed the use of gold-thiourea solution can indeed offer a workable option as a commercialized process. Electroplating was also made possible with lower energy consumption than the previous reports. The regeneration of thiourea was confirmed with the electroplating and leaching efficiency drop was marginal.The whole suggested processes appear to be a potential route especially as a closed-loop system for the purpose of gold recovery in electronic industry, and in so doing valuable resources are recovered with wastes treated in a simultaneous manner.
전자산업의 급격한 발전에 따라 전자산업폐기물 역시 급증하고 있으며, 이러한 폐자원으로부터 귀금속을 회수하는 기술들이 주목받고 있다. 최근 금을 선택적으로 흡착가능한 포피린 구조 흡착제가 개발됨에 따라, 본 연구에서는 이러한 흡착제로부터 효과적으로 금을 탈착·회수하고, 흡착제 재사용이 가능한 공정을 개발하였다. 흡착된 금은 이온 상태에 따라 물리적, 전기화학적 방법으로 회수되었다. 흡착된 고체 금 입자는 글리세롤을 분리 매개로 한 중력침강으로 회수하였으며, 분산제를 통해 회수 효율 및 순도를 개선시켰다. 본 과정 이후 남은 금은 침출 및 전기도금으로 회수되었다. 침출액으로 티오요소를 이용하여 금을 탈착시켰으며, 흡착제 재사용 가능성 역시 보였다. 티오요소에 녹은 금은 전기도금을 통해 필름형태로 회수되었다. 무전해 도금법으로 금을 기판에 침적시켰으며, 금 필름의 높은 내식성을 확인함으로써, 상업적으로 활용되는 무전해니켈/금도금 공정으로의 적용 가능성을 확인하였다. 적은 에너지를 소비하는 전기도금법 역시 활용되었으며, 티오요소 소모가 억제되는 것을 확인되었다. 따라서 본 박사학위 논문연구에서 제안된 새로운 방법들은 전자산업 내에서의 고부가가치 자원 순환 및 폐기물 처리를 동시에 수행할 수 있는 지속가능형 신공정으로 활용 가능하다.
