International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 01 | Jan -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 830 Influence of Oxidizing Agent on Recovery of Metals Including Gold and Silver from Printed Circuit Boards Sneh Patel 1 , Rushabh Patel 1 , Alok Gautam 1 , Shina Gautam 1* 1 Department of Chemical Engineering, Shroff S. R. Rotary Institute of Chemical Technology, Ta-Vataria 393 135, Gujarat 1* Associate Professor, Department of Chemical Engineering, Shroff S. R. Rotary Institute of Chemical Technology, Ta-Vataria 393 135, Gujarat ------------------------------------------------------------------***----------------------------------------------------------------- Abstract: Due to rapidly depleting natural resources of metals, it becomes essential to find secondary resources for metals. E-waste can be a potential secondary source for that. It contains a number of metals which can be recycled after successful separation. Owing to the fact that e-waste contains precious metals like silver and gold, the present work is focused on extracting silver and gold along with other metals like Cu, Zn, Ni etc. from e-waste. Dismantling of the e-waste was done manually and after pretreatment of the e-waste, metals were extracted with a mixture of nitric acid and hydrochloric acid. Nitric acid in this experimental study was used as an oxidant and the effect of oxidant was observed on the extraction behavior. It was observed that as the concentration of nitric acid was increased in the mixture of acids the extraction of all metals like Au, Ag, Mn, Cr, Ni, Fe, Cu, Pb, Zn, Cd were extracted upto 95-98%. Nevertheless the recovery of all metals was dropped to 10 % if 100 % nitric acid was used as a solvent. Similarly 100 % hydrochloric acid was resulted in a lower extraction for all metals. The extraction of metals was observed dependent on nitric acid concentration which is used as an oxidant. Other than concentration of acids in the acids mixture, time of extraction and temperature were also observed for the extraction of different metals. Keyword: e waste, aquaregia, oxidant effect, metal recovery, pcb extraction 1. Introduction Waste from electric and electronic equipment is a fastest growing solid waste in the world [1]. Infromally it is known as e-waste Due to high metal content and thermosetting plastic it is difficult to recycle or biodegrade it as it is. This is one of the reasons, this waste is catching attention. The metals from the e-waste can be removed by several ways like pyro metallurgical process, hydrometallurgical process, electro-winning process and bio-metallurgical. Due to high energy requirement in pyrometallurgical process the process is not favorable economically. Microbiological leaching uses a natural ability of microorganisms to transform metals present in the waste in a solid form (in the solid matrix) to a dissolved form. Apart from the possibility of bioleaching of metals in alkaline environment (involving cyanegenic bacteria), acidophilus microorganisms and conducting biological process of leaching in an acidic environment play a crucial role in the bio-hydrometallurgical techniques [2]. Biohydrometallurgical processing of solid waste is similar to natural biogeochemical metal cycles and reduces the demand of resources, such as ores, energy and landfill space. This technology is environmentally friendly (in comparison to chemical method) and it is considered a green technology (generates less amount of waste) [3, 4]. The paper presents the experimental investigation recently carried out for the extraction of different metals from pcb with hydrometallurgical route. Commonly aqua- regia is used for extraction of different metals from e- waste where 30% HNO3 and 70% HCl by volume is used to prepare aqua-regia. The solvent works best to extract almost all the metals due to presence of nitric acid as an oxidant. Metal extraction with nitric acid have been investigated by Cerna (1992), Zongcheng (1989) [5, 6]. More than 95 % copper and lead extractions were achieved by Mecucci and Scott (2002) using nitric acid [7]. In the present work the amount of oxidant (nitric acid) for the extraction of different metals have been varied from 0-20%. This specific study has not been found in literature. The experiments were carried for different time and