An Alkaline Glycine-Based Leach Process of Base and Precious Metals from Powdered Waste Printed Circuit Boards

  • Elsayed A. Oraby
  • Huan Li
  • Jacobus J. EksteenEmail author
Original Paper


Electronic waste (E-waste) is accumulating rapidly globally and pose a significant environmental challenge. One of the ways to cover the cost of waste processing (in addition to reducing the costs associated with landfill) is through recovery of metals. In addition, toxic and dangerous metals can and must be removed prior to repurposing, incineration or pyrolysis of the plastic substrates. E-waste is usually either transported to landfills or processed by pyrometallurgical and hydrometallurgical processes. Recently, a number of hydrometallurgical approaches have been considered in metals recovery from different electronic components. In this study, glycine (amino acetic acid) or its salts is considered as a lixiviant in an alkaline environment for base and precious metals recovery from shredded and ground printed circuit boards (PCBs). It was found that alkaline glycine solutions selectively dissolve copper, zinc, and lead over precious metals. Gold and silver were then recovered in a subsequent leaching step using glycine and small amounts of cyanide (at starvation levels, implying no free cyanide is present). The leach system remains alkaline throughout both stages of processing. In the two-stage glycine leaching system, gold, silver, zinc, lead and copper recoveries were 92.1%, 85.3%, 98.5%, 89.8%, and 99.1% respectively. The recoveries of precious and base metals by direct cyanidation, single stage glycine–cyanide leaching, and ammonia leaching were lower than the recoveries of these metals using the two-stage glycine and glycine–cyanide systems.

Graphic Abstract

Flowsheet of a two-stage glycine leaching method for metal extractions from waste PCBs proposed in this study


Glycine E-waste Printed circuit boards Leaching Metal recovery 



The authors would like to thank Dr Hatem El-Borai at Vilytics Company, Egypt for providing the PCB powder and related details and information of the PCB production. Mr. Huan Li gratefully acknowledge the financial sponsorship by Curtin University and the China Scholarship Council (CSC). Curtin University funded the working costs of this research.

Compliance with Ethical Standards

Conflict of interest

Messrs Oraby and Eksteen are listed co-inventors on patents that includes the use of glycine in alkaline environments to leach precious and chalcophile metals from materials bearing these metals.


  1. 1.
    Wang, Z., Zhang, B., Guan, D.: Take responsibility for electronic-waste disposal. Nature 536, 4 (2016)Google Scholar
  2. 2.
    Priya, A., Hait, S.: Feasibility of Bioleaching of Selected Metals from Electronic Waste by Acidiphilium acidophilum. Waste Biomass Valori 9, 871–877 (2017)CrossRefGoogle Scholar
  3. 3.
    Cui, J., Zhang, L.: Metallurgical recovery of metals from electronic waste: a review. J. Hazard. Mater. 158(2), 228–256 (2008)CrossRefGoogle Scholar
  4. 4.
    Lin, C., Chi, Y., Jin, Y.: Experimental study on treating waste printed circuit boards by molten salt oxidation. Waste Biomass Valori. 8:2523–2533 (2017).Google Scholar
  5. 5.
    Baldé, C.P., Forti, V., Gray, V., Kuehr, R., Stegmann, P.: The global e-waste monitor—2017. Accessed 10 June 2018
  6. 6.
    Khaliq, A., Rhamdhani, M.A., Brooks, G., Masood, S.: Metal extraction processes for electronic waste and existing industrial routes: a review and Australian perspective. Resources 3(1), 152–179 (2014)CrossRefGoogle Scholar
  7. 7.
    Williams, P.T.: Valorization of printed circuit boards from waste electrical and electronic equipment by pyrolysis. Waste Biomass Valori. 1(1), 107–120 (2010)CrossRefGoogle Scholar
  8. 8.
    Yildirir, E., Onwudili, J.A., Williams, P.T.: Chemical recycling of printed circuit board waste by depolymerization in sub-and supercritical solvents. Waste Biomass Valori. 6(6), 959–965 (2015)CrossRefGoogle Scholar
  9. 9.
    Shuey, S., Vildal, E., Taylor, P.: Pyrometallurgical processing of electronic waste. In: SME Annual Meeting 2006, pp. 06–037Google Scholar
  10. 10.
    Kim, B.-S., Lee, J.-C., Seo, S.-P., Park, Y.-K., Sohn, H.Y.: A process for extracting precious metals from spent printed circuit boards and automobile catalysts. JOM 56(12), 55–58 (2004)CrossRefGoogle Scholar
  11. 11.
    Sum, E.Y.L.: The recovery of metals from electronic scrap. JOM 43(4), 53–61 (1991)CrossRefGoogle Scholar
  12. 12.
    Puente-Siller, D.M., Fuentes-Aceituno, J.C., Nava-Alonso, F.: An analysis of the efficiency and sustainability of the thiosulfate-copper-ammonia-monoethanolamine system for the recovery of silver as an alternative to cyanidation. Hydrometallurgy 169, 16–25 (2017)CrossRefGoogle Scholar
  13. 13.
    Sharma, N., Chauhan, G., Kumar, A., Sharma, S.: Statistical optimization of heavy metals (Cu2+/Co2+) extraction from printed circuit board and mobile batteries using chelation technology. Ind. Eng. Chem. Res. 56, 6805–6819 (2017)CrossRefGoogle Scholar
  14. 14.
    Liu, K., Zhang, Z., Zhang, F.-S.: Direct extraction of palladium and silver from waste printed circuit boards powder by supercritical fluids oxidation-extraction process. J. Hazard. Mater. 318, 216–223 (2016)CrossRefGoogle Scholar
  15. 15.
    Yang, C., Li, J., Tan, Q., Liu, L., Dong, Q.: Green process of metal recycling: coprocessing waste printed circuit boards and spent tin stripping solution. ACS Sustain. Chem. Eng. 5(4), 3524–3534 (2017)CrossRefGoogle Scholar
  16. 16.
    Li, H., Eksteen, J., Oraby, E.: Hydrometallurgical recovery of metals from waste printed circuit boards (WPCBs): current status and perspectives—a review. Resour. Conserv. Recycl. 139, 122–139 (2018)CrossRefGoogle Scholar
  17. 17.
    Yang, H., Liu, J., Yang, J.: Leaching copper from shredded particles of waste printed circuit boards. J. Hazard. Mater. 187(1), 393–400 (2011)CrossRefGoogle Scholar
  18. 18.
    Tuncuk, A., Stazi, V., Akcil, A., Yazici, E.Y., Deveci, H.: Aqueous metal recovery techniques from e-scrap: hydrometallurgy in recycling. Miner. Eng. 25(1), 28–37 (2012)CrossRefGoogle Scholar
  19. 19.
    Koyama, K., Tanaka, M., Lee, J.-C.: Copper leaching behavior from waste printed circuit board in ammoniacal alkaline solution. Mater. Trans. 47(7), 1788–1792 (2006)CrossRefGoogle Scholar
  20. 20.
    Ficeriová, J., Baláž, P., Gock, E.: Leaching of gold, silver and accompanying metals from circuit boards (PCBs) waste. Acta Montan. Slovaca 16(2), 128 (2011)Google Scholar
  21. 21.
    Montero, R., Guevara, A., Torre, E.: Recovery of gold, silver, copper and niobium from printed circuit boards using leaching column technique. J. Earth Sci. Eng. 2(10), 590 (2012)Google Scholar
  22. 22.
    Jing-ying, L., Xiu-li, X., Wen-quan, L.: Thiourea leaching gold and silver from the printed circuit boards of waste mobile phones. Waste Manage. 32(6), 1209–1212 (2012)CrossRefGoogle Scholar
  23. 23.
    Sahin, M., Akcil, A., Erust, C., Altynbek, S., Gahan, C.S., Tuncuk, A.: A potential alternative for precious metal recovery from e-waste: iodine leaching. Sep. Sci. Technol. 50(16), 2587–2595 (2015)Google Scholar
  24. 24.
    Oraby, E., Eksteen, J.: A process for precious metals recovery. PCT Patent, PCT/AU2014/000877 (2014).Google Scholar
  25. 25.
    Oraby, E.A., Eksteen, J.J.: The selective leaching of copper from a gold–copper concentrate in glycine solutions. Hydrometallurgy 150, 14–19 (2014)CrossRefGoogle Scholar
  26. 26.
    Eksteen, J., Oraby, E.: The leaching and adsorption of gold using low concentration amino acids and hydrogen peroxide: Effect of catalytic ions, sulphide minerals and amino acid type. Miner. Eng. 70, 36–42 (2015)CrossRefGoogle Scholar
  27. 27.
    Oraby, E.A., Eksteen, J.J.: The leaching of gold, silver and their alloys in alkaline glycine–peroxide solutions and their adsorption on carbon. Hydrometallurgy 152, 199–203 (2015)CrossRefGoogle Scholar
  28. 28.
    Tanda, B.C., Eksteen, J.J., Oraby, E.A.: An investigation into the leaching behaviour of copper oxide minerals in aqueous alkaline glycine solutions. Hydrometallurgy 167, 153–162 (2017)CrossRefGoogle Scholar
  29. 29.
    Oraby, E.A., Eksteen, J.J.: Gold leaching in cyanide-starved copper solutions in the presence of glycine. Hydrometallurgy 156, 81–88 (2015)CrossRefGoogle Scholar
  30. 30.
    Oraby, E.A., Eksteen, J.J., Tanda, B.C.: Gold and copper leaching from gold-copper ores and concentrates using a synergistic lixiviant mixture of glycine and cyanide. Hydrometallurgy 169, 339–345 (2017)CrossRefGoogle Scholar
  31. 31.
    Tauetsile, P.J., Oraby, E.A., Eksteen, J.J.: Adsorption behaviour of copper and gold Glycinates in alkaline media onto activated carbon Part 2: Kinetics. Hydrometallurgy 178, 195–201 (2018)CrossRefGoogle Scholar
  32. 32.
    Aksu, S., Wang, L., Doyle, F.M.: Effect of hydrogen peroxide on oxidation of copper in CMP slurries containing glycine. J. Electrochem. Soc. 150(11), G718–G723 (2003)CrossRefGoogle Scholar
  33. 33.
    Aliyu, H.N., Na'Aliya, J.: Potentiometric studies on essential metal (II) amino acid complexes. Int. Res. J. Pharm. Pharmacol. 2(2), 76–80 (2012)Google Scholar
  34. 34.
    Eksteen, J.J., Oraby, E.A., Lombard, L., Di Prinzio, L.: Leaching of cobalt bearing nickel sulfide and furnace converter mattes with alkaline glycine, and subsequent SX and IX. Paper presented at the Proceedings of ALTA Hydrometallurgy Conference 2018, Perth, Australia, 19–26 MayGoogle Scholar
  35. 35.
    González-López, J., Rodelas, B., Pozo, C., Salmerón-López, V., Martínez-Toledo, M., Salmerón, V.: Liberation of amino acids by heterotrophic nitrogen fixing bacteria. Amino Acids 28(4), 363–367 (2005)CrossRefGoogle Scholar
  36. 36.
    Kiss, T., Sovago, I., Gergely, A.: Critical survey of stability constants of complexes of glycine. Pure Appl. Chem. 63(4), 597–638 (1991)CrossRefGoogle Scholar
  37. 37.
    Tanda, B., Oraby, E., Eksteen, J.: Recovery of copper from alkaline glycine leach solution using solvent extraction. Sep. Purif. Technol. 187, 389–396 (2017)CrossRefGoogle Scholar
  38. 38.
    Eksteen, J.J., Oraby, E.A., Tanda, B.C.: A conceptual process for copper extraction from chalcopyrite in alkaline glycinate solutions. Miner. Eng. 108, 53–66 (2017)CrossRefGoogle Scholar
  39. 39.
    Breuer, P., Dai, X., Jeffrey, M.: Leaching of gold and copper minerals in cyanide deficient copper solutions. Hydrometallurgy 78(3), 156–165 (2005)CrossRefGoogle Scholar
  40. 40.
    Lewis Sr., R.J.: Hazardous Chemicals Desk Reference. Wiley, New York (2008)CrossRefGoogle Scholar
  41. 41.
    Deng, Z., Oraby, E., Eksteen, J.: The sulfide precipitation behaviour of Cu and Au from their aqueous alkaline glycinate and cyanide complexes. Sep. Purif. Technol. 218, 181–190 (2019)CrossRefGoogle Scholar
  42. 42.
    Wang, R., Xu, Z.: Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review. Waste Manage. 34(8), 1455–1469 (2014)CrossRefGoogle Scholar
  43. 43.
    Buekens, A., Yang, J.: Recycling of WEEE plastics: a review. J Mater Cycles Waste Manage 16(3), 415–434 (2014)CrossRefGoogle Scholar
  44. 44.
    Marques, A.C., Marrero, J.-M.C., Malfatti, C.: A review of the recycling of non-metallic fractions of printed circuit boards. SpringerPlus 2(1), 521 (2013)CrossRefGoogle Scholar
  45. 45.
    Rajarao, R., Sahajwalla, V., Cayumil, R., Park, M., Khanna, R.: Novel approach for processing hazardous electronic waste. Proc. Environ. Sci. 21(Supplement C), 33–41 (2014).CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Western Australian School of Mines: Minerals, Energy and Chemical EngineeringCurtin UniversityPerthAustralia
  2. 2.Mining and Metallurgical Engineering, Faculty of EngineeringAssiut UniversityAssiutEgypt

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