Helal, A, Patil, J, Bregante, D, Counihan, M, Letwat, N, Kim, HYC, Weiss, V, Nguyen, T, Gagne, K, Desai, A, Burns, S, Agahi, A, Melvin, S, Grossman, J, Gurieff, NB & Smith, B 2025, 'Chemical-free remediation and valorisation of raw acid mine drainage 
via silicon-based filtration and electro-extraction', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-12, https://doi.org/10.36487/ACG_repo/2515_91
(https://papers.acg.uwa.edu.au/p/2515_91_Smith/)
Abstract: This paper reports on a proprietary technology that utilises silicon electro-extraction (SEE) and silicon nanofiltration (SNF) to valorise and remediate acid mine drainage (AMD). Waste streams such as AMD present significant challenges during mine operations and closure due to their complexity, low-pH, dynamic composition, and perpetual high-volume flow. The proprietary technologies are designed to efficiently address these challenges. 
SEE utilises silicon-based electrodes to selectively electro-extract metallic products in a single stage, enabling the recovery of high-purity copper through a chemical-free approach. SNF utilises a nanoporous silicon membrane to selectively reject multivalent ionic species, leveraging the intrinsic durability of the membrane’s monolithic silicon architecture. The SEE and SNF stages can be deployed in series to valorise and remediate raw AMD containing high dissolved and suspended solids with pH <3. 
Onsite and remote testing at 1–100 L/day system throughputs has demonstrated single-stage copper recovery from AMD containing up to 700 mg Cu/L, achieving yields as high as 97%. The recovered copper consistently exceeds 99.9% purity, with some cases approaching 99.99%, with energy efficiencies ranging from 2–5 kWh/kg copper. Pairing SEE with SNF in a chemical-free two-step process, the approach demonstrates multivalent ion rejection reducing total dissolved solids (TDS) and sulphates by 60% regardless of input composition or pH. Further optimisation of the technology and process is expected to increase yield, purity, and efficiency of copper recovery to bolster primary copper supply, while substantially improving final effluent quality.

Keywords: acid mine drainage, copper recovery, silicon nanofiltration, silicon electro-extraction, waste remediation, recovery