New insight on gold and copper leaching from waste printed circuit boards by chromobacterium violaceum : three steps process

Printed circuit boards (PCBs), have a high metal content including copper, silver and gold, making them interesting to recycle, both to reduce pollution and, from an economic perspective, by reusing the precious metals. We implemented a three-phase process leading to a) the bio production of hydrogen cyanide (HCN) in a commercial medium in a continuous flow stirred-tank reactor (CSTR), b) gold and copper leaching from PCBs, and c) HCN degradation by Chromobacterium violaceum. This process was more efficient at leaching gold than it was at leaching copper. HCN production by C. violaceum in CSTR was 94.1 g/m3 every 3 days in A5MNF medium, and was recovered by an absorption column. The addition of Iron (III) chloride had an effect on the expression of hcnA, while adding potassium nitrate improved the increase in biomass. The maximum expression of hcnA in A5MFN was obtained by a flow of 0.27 cm3 /s, guaranteeing the best production of HCN in CSTR. The addition of H2O2 every 4 hours to the leaching medium and a pH of 12.5 potentiated a higher recovery rate of gold over copper. The third step of this process is shown to be able to reduce the HCN concentrations from 12.8 g/m3 a 0.021 g/m3 in 4 days. The degradation of the remaining HCN from the leaching process responds to the formulation of new environmentally responsible technologies.

• Autores: Giraldo Gómez, Iván Alejandro
• Fecha de publicación: 2016
• Institución: Universidad de los Andes
• Repositorio: Séneca: repositorio Uniandes
• Idioma: spa
• OAI Identifier: oai:repositorio.uniandes.edu.co:1992/13232
• Acceso en línea: http://hdl.handle.net/1992/13232
• Palabra clave: Lixiviación - Investigaciones; Cianuración; Metalurgia del oro - Investigaciones; Metalurgia del cobre - Investigaciones; Biología
• Rights: openAccess
• License: http://creativecommons.org/licenses/by-nc-sa/4.0/