An Integrated Resource Recovery and Co-Treatment System of Desalination Brine and Flue Gas via Waste Brine Electrolysis and Sustainable CO2 Mineralisation (From Brine to NEWSeawater)
1 October 2026
Affiliation
NTU
Focus topic
CO2 Capture
Turning desalination waste and flue gas into hydrogen, carbon, and clean water
Summary
Integrated co-treatment of Seawater Reverse Osmosis (SWRO) desalination brine and industrial flue gas, coupling brine softening, CO₂ mineralisation and modified chlor-alkali electrolysis in a closed loop. NaOH dosing precipitates Mg(OH)₂; flue gas (~20% CO₂) is bubbled through the alkaline brine to mineralise CO₂ as CaCO₃ (R2); the softened brine is acidified to pH 2 (R3) and electrolysed against a softened-seawater catholyte, yielding Cl₂, H₂ and caustic. The caustic is recycled to R1/R2, eliminating external alkali.
Results on real Tuas plant brine: Purities: Mg(OH)₂ ≥85%, CaCO₃ ≥95%, H₂ >99%, Cl₂ >95%; CER Faradaic efficiency ~99% at pH 2 versus 80% at pH 7 (70.9% over 7–8 h); HER FE >97%; Mg/Ca cut to 0.1–0.6 ppm; TDS from 70.9 to 44.3 g/L and chloride 35 to 18 g/L in 8 h; ~70% thermodynamic efficiency at 3–3.5 V, 3–5 kA/m²; Alkali self-sufficiency at 350 mol/m².
Carbon abatement: CO₂ is fixed as stable CaCO₃ and NaHCO₃, needing no solvent regeneration, compression or geological storage; capture capacity scales with electrolysis, offsetting the process's own power footprint. Life Cycle Assessment (LCA) GWP100 per tonne Cl₂ beats conventional and brine-to-chlor-alkali routes; discharge ecotoxicity 16.3 versus 28.9 PAF·m³·day.
What makes this novel compared to best-in-class technology?
Removes the energy-dominant evaporation/pre-concentration step of prior brine-to-chlor-alkali schemes by electrolysing softened brine directly at seawater-level catholyte (pH 13). Balancing osmotic pressure so thin, cheap membranes work, while recycling its own caustic for carbon capture and discharging only near-seawater rather than large nanofiltration rejects.
TRL Level
1-3
Relevant for
Coastal SWRO desalination plants co-located with stationary CO₂ point sources, natural gas and biomass power plants, waste-to-energy plants, anaerobic digesters, chlor-alkali producers seeking low-carbon brine feedstock, construction-materials/Mg(OH)₂ off-takers
About
Inventors: Tu Wei Han, Chan Wei Ping, Grzegorz Lisak
Affiliation: Nanyang Technological University, Singapore (NTU), Nanyang Environment and Water Research Institute (NEWRI)
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