Evaluating the optimal digestion method and value distribution of precious metals from different waste printed circuit boards

Abstract

Knowing the metal content of electronic waste is essential to evaluate metal recovery. Lack of a standard method for digestion of precious metals from electronic waste has resulted in difficulty in comparison to the efficiency of recovery. In this study, different precious metal digestion methods and economic value of precious metals from different types of waste printed circuit boards in different fraction sizes, including computer printed circuit boards, mobile phone printed circuit boards, television printed circuit boards, fax machine printed circuit boards, copy machine printed circuit boards, and central processing unit were examined. The optimal digestion method using aqua regia, hydrogen peroxide, hydrofluoric acid, and boric acid was adopted. The precious metal content was analyzed to answer what precious metals and types of printed circuit boards is preference. The results presented the following order of total value of precious metals ( $$\sum {W_{ti} \Pr_{ti} }$$ ): central processing unit > Mobile phone > Copy > Fax > Computer > Television. Among the precious metals, gold and palladium were, respectively, attributed to the highest value distribution. The average values of the precious (gold and palladium) and all of the metals of electronic waste are about 19 and 21 times higher than the average cost of the world’s top ten mines.