Water Purification from Industrial Effluents Using Gas Hydrates: Process Demonstration of a Continuous Bench Scale Operation

Abstract

Industrial brines from petrochemical and allied sectors are an escalating sustainability challenge, limiting circular water use and progress toward zero-liquid-discharge and decarbonization targets. Their high salinity and refractory organics make conventional membrane and thermal processes energy and carbon-intensive. We present a continuous dual-reactor gas-hydrate crystallization platform for membrane free, nonthermal purification that enables molecularly selective water recovery under mild conditions (278 K; 0.60–0.85 MPa). Through vapor–liquid interfacial engineering, structure sII hydrates rapidly form at engineered interfaces via Capillarity-driven nucleation, while phase evolution is governed by Ostwald ripening kinetics. Using a mixed propane and HFC-134a gas pair, we achieve in a single pass >65% overall water recovery (7–10 L·h^–1) and >50% water-to-hydrate conversion. The recovered water shows 84–93% removal of total dissolved solids, chemical oxygen demand, and ammoniacal nitrogen. Mechanistically, hydrate formation and selectivity are streamlined using hydrate thermodynamics and cage occupancy. The specific energy requirement is 3.88 kWh·m^–3, with a global warming potential of 2.79 kg·CO₂-eq·m^–3 and a levelized cost of $1.65 m^–3, demonstrating superior performance relative to representative membrane and thermal baselines (4–15 kg CO₂-eq·m^–3; 30–45% recovery). These results establish clathroseparation as a new, low-exergy class of phase-selective crystallization for sustainable industrial water reuse, advancing SDGs 6, 9, and 12.