Chlorine production from brine using a novel superhydrophobic PTFE-PI-TiO₂ photocatalytic membrane contactor

This study presents a photocatalytic membrane contactor for the simultaneous generation and separation of chlorine gas from acidified brine. This system uses a novel superhydrophobic polyimide-reinforced polytetrafluoroethylene composite membrane containing TiO₂ nanoparticles (PTFE–PI–TiO₂) fabricated via solution blow spinning. Incorporation of polyimide binder with optimal TiO₂ loading yielded hierarchical micro- and nanoscale porous membranes with high porosity (78 to 84 %). Surface wettability analysis demonstrated stable Cassie-Baxter superhydrophobicity up to 15 wt% TiO₂ loading, enabling stable gas-phase transport through membrane pores. Under UV illumination, the PTFE–PI–TiO₂-15 membrane achieved a peak steady-state chlorine generation rate of 19.50 mmol·m⁻²·h⁻¹ from 35 g L⁻¹ NaCl solution at pH 1. Radical scavenger and EPR studies indicated that chlorine evolution proceeded via direct hole oxidation of chloride ions without radical intermediates. Mass transfer modeling suggests that chlorine flux was governed by surface-exposed photocatalytic activity rather than membrane transport limitations. This work establishes a scalable and energy-efficient approach for chlorine recovery from desalination brine, offering a sustainable solution for brine management and decentralized chemical production.