High rate pervaporation and disinfection efficacy of hypochlorous acid in vacuum-driven membrane process

This study investigated the pervaporation of hypochlorous acid (HOCl) using a vacuum-driven process with a separation module containing 6,000 silicone rubber (SR) hollow fibers. Gaseous hypochlorous acid (HOCl_(g)) discharged from the membrane module was accumulated in a 1 m³ chamber. Weakly acidic (pH 5.0) hypochlorite solutions with free available chlorine (FAC) concentrations of 100-1,000 mg/L were fed through the lumen of the SR hollow fibers. Both the HOCl permeation rate and the steady-state HOCl_(g) concentration increased with the feed FAC concentration. When a 1,000 mg/L hypochlorite solution was used, the HOCl_(g) concentration in the chamber reached 5,500 ppb within 40 min. This accumulated HOCl_(g), when applied to microorganisms on wet agar plates at a concentration of approximately 320 ppb, achieved a >3-log reduction in viable bacterial cells within 10 min and fungal spores within 20 min. These results demonstrate that high-rate pervaporation of HOCl can be achieved using an SR hollow fiber membrane in a vacuum-driven process, and the resulting HOCl_(g) is effective for rapid disinfection.