Mechanistic Pathways of Resource Recovery from Waste PCBs: A Critical Review of Bioleaching, Hydrometallurgical, and Hydrothermal Processing Routes

Authors

  • Ousmane Lass Donzo Department of Civil Engineering, Sharda school of Engineering and Science, Sharda University, Greater Noida, INDIA.
  • Syed Musa Jeelani Department of Civil Engineering, Sharda school of Engineering and Science, Sharda University, Greater Noida, INDIA.
  • Dayanand Sharma Department of Civil Engineering, Sharda school of Engineering and Science, Sharda University, Greater Noida, INDIA.

DOI:

https://doi.org/10.55544/jrasb.icaces.21

Keywords:

Waste printed circuit boards, Electronic waste, Bioleaching, Hydrothermal processing, Subcritical water

Abstract

Waste printed circuit boards (WPCBs) constitute the most metal and hazard-intensive fraction of global electronic waste (e-waste), embedding copper, precious metals, and critical elements within a cross-linked brominated epoxy matrix that resists conventional recycling. Global e-waste generation reached 62 million tons (Mt) in 2022 and is projected to reach 82 Mt by 2030, yet only 22.3% is formally collected and recycled, squandering an estimated US$91 billion in recoverable material value annually. This review critically synthesizes the mechanistic chemistry, performance, and limitations of the principal WPCB resource-recovery technology families: pyrometallurgical and acid/cyanide hydrometallurgical processing; biohydrometallurgy (bioleaching), encompassing contact, non-contact, thiosulfate, and polysulfide mechanisms mediated by acidophilic chemolithotrophs. Hydrothermal processing (HTP) using subcritical and supercritical water (SbCW/SCW) , which exploits water's temperature-dependent dielectric constant, ionic product, and density to drive simultaneous epoxy hydrolysis, tetrabromobisphenol-A (TBBPA) debromination, and metal liberation without external reagents; and emerging green-solvent (deep eutectic solvent and ionic liquid) leaching systems. Reaction mechanisms are presented for each pathway with supporting stoichiometry, and a comparative synthesis of metal-specific leaching behavior, process variables, and recovery efficiencies is constructed from recent peer-reviewed literature spanning for the last decade. Life-cycle, circular-economy, and technology-readiness considerations are evaluated alongside future research directions including hybrid bio-HTP and machine-learning-assisted process optimization to guide the industrial deployment of sustainable WPCB recovery technologies.

 

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Published

2026-06-12

How to Cite

Donzo, O. L., Jeelani, S. M., & Sharma, D. (2026). Mechanistic Pathways of Resource Recovery from Waste PCBs: A Critical Review of Bioleaching, Hydrometallurgical, and Hydrothermal Processing Routes. Journal for Research in Applied Sciences and Biotechnology, 5(1), 171–186. https://doi.org/10.55544/jrasb.icaces.21

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Vol. 5 No. 1 (2026): Special Issue : ICACES 2025

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Copyright (c) 2026 Ousmane Lass Donzo, Syed Musa Jeelani, Dayanand Sharma

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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