IPA purification for lens cleaning by vapor permeation using zeolite membrane

Vapor permeation (VP) properties of commercial NaA-type zeolite membranes were examined using the alcohol/ water systems, before equipments to purify isopropanol (IPA) from lens cleaning process were designed. The membranes displayed excellent water-permselective performance for water/organic solutions in the VP. With an increase in feed temperature, both the permeation flux Q and the separation factor a increased, and the membrane performance was the same for pervaporation as for VP over 0.7 relative vapor pressure p/p(s). In VP of alcohol mixtures with 5 wt.% water over p/ps = 0.7 at 120 degreesC, Q values were 2.64, 4.3 and 5.6 kg m(-2) h(-1) and a value were 4000, 5600 and 6000 for the water/methanol (MeOH), water/ethanol (EtOH) and water/IPA solutions, respectively. The repeated experiment of IPA purification by VP with a zeolite NaA membrane was carried out in waste IPA liquid. The substances (acids, particles, etc.) in the waste IPA hardly influenced membrane performance in the VP. The IPA purification plant with approximately 0.72 m(2) membrane areas was composed of 24 double tube-type modules. This plant which can purify 101 h(-1) of IPA at less than 0.5 wt.% water from 88.6 wt.% IPA at 120 C has been put into lens cleaning operation. (C) 2003 Published by Elsevier Science B.V.