3.1 Epoxy coating removal using NaOH solution. PCB pieces as opposed to the pulverized PCB were used in this study to simplify the Cu leaching process and to reduce the cost of PCB grinding . PCB materials are coated with epoxy resins to achieve flame retardant purposes . However, in hydrometallurgical processes, these resins can prevent the efficient leaching of metals. Presently, mechanical and thermal methods are widely employed to treat waste PCBs and separate the metal and non-metal components . One important disadvantage of mechanical separation processes is the notable loss of valuable metals. The reasons for these losses include the insufficient liberation of metals due to their intimate association with plastics and the inefficiency of separation processes for metal recovery from fine fractions. Therefore, it is necessary to find a better process for removing the chemical coatings from PCBs without the loss of metals. NaOH solutions have often been employed for the efficient removal of epoxy resins from the surfaces of PCBs . In this study, PCB pieces were treated with NaOH solution. Following the NaOH treatment, most of the epoxy coatings were noticeably detached from the PCB samples. This was observed by the disappearance of the green-coloured coating on the PCB surface (Figure ). Accounts from other studies report that this change of colour is indicative of the removal of the epoxy coating . The reaction was highly exothermic due to the heat produced. The epoxy coating removal could be described by scheme 1 .