Sustainable recycling process for metals recovery from used printed circuit boards (PCBs)

Abstract

In comparison to extraction of metals from limited primary sources, the recycling of metals/materials from various alternative resources particularly from metallurgical waste and complex such as E-waste (Electronic waste) are gaining importance in view of energy, purity and environmental concern. In all E-waste, PCBs are essential components, which contain nearly 28% metallic, 23% plastic and 49% ceramic materials in a complex form. Due to tremendous increase in e-waste globally, the recycling of PCBs to recover metals are getting importance which will not only mitigate the environmental pollution but will also conserve the natural resources and energy. PCBs contain copper (Cu) in major, therefore experiments were carried out to optimize different process parameters viz. effect of acid concentration, pulp density, temperature, time, etc for maximum recovery of Cu. About 91.58% Cu was found to be leached using 3M HNO3 maintaining 75 g/L pulp density at temperature 75 °C and mixing time 120 min. The two stages leaching under the similar condition resulted in the recovery of 99.99% of Cu. To optimize the conventional hydrometallurgical process, the Response Surface Methodology (RSM) was also studied. The result obtained by using the RSM model will help the researchers to validate the data scientifically with less number of experiments. Kinetics of Cu leaching fitted well with the “Chemical reaction control dense constant size cylindrical particles model” i.e. 1−(1−X)1/2 = Kct. The leach liquor generated will be further purified by the method of solvent extraction (SX)/ion exchange (IX) to get purified metallic solution. From the pure solution obtained, the metal/salt could be produced by electro-winning/precipitation and crystallization, respectively.