Ji-Won Rhim

Pervaporation separation of MTBE–methanol mixtures using cross-linked PVA membranes

Poly(vinyl alcohol)(PVA)/poly(acrylic acid)(PAA) and PVA/sulfosuccinic acid (SSA) membrane performances have been studied for the pervaporation separation of methyl tert-butyl ether (MTBE)/methanol (MeOH) mixtures with varying operating temperatures, amount of cross-linking agents, and feed compositions. Typically, the separation factor, about 4000, and the permeation rate, 10.1 g/m2/h, were obtained with PVA/PAA = 85/15 membrane for MTBE/MeOH = 80/20 mixtures at 50°C. For PVA/PAA membranes, it could be considered that the flux is affected by the structural changes of the membranes due to the cross-linking and the free carboxylic acid group also took an important role in the separation characteristics through the hydrogen bonding with PVA and the feed components leading to the increase of flux. The latter membrane of the 5% SSA membrane shows the highest separation factor of 2095 with the flux of 12.79 g/m2/h for MTBE/MeOH = 80/20 mixtures at 30°C. Besides the swelling measurements were carried out for pure MTBE and MeOH, and MTBE/MeOH = 90/10, 80/20 mixtures using PVA/SSA membranes with varying SSA compositions. It has been recognized that there are two factors, the membrane network and the hydrogen bonding in the swelling measurements of PVA/SSA membranes. These two factors act interdependently on the membrane swelling.

Microencapsulation of water-soluble herbicide by interfacial reaction. I. Characterization of microencapsulation

A new microencapsulation was established in which small microcapsules with a hydrophilic polymeric wall could be fabricated, capsulizing the water-soluble content. The new microencapsulation is based on an emulsion interfacial reaction technique that combines the characteristics of an interfacial reaction and conventional emulsion processes. In this technique, hydrophilic polymers [poly(vinyl alcohol) and chitosan] were used as the wall material of the microcapsules. The microencapsulation process was composed mainly of the following steps: preparation of a water/oil (w/o) emulsion 1 containing hydrophilic polymers and a water-soluble core material and w/o emulsion 2 containing a water-soluble crosslinking agent and catalyst; the formation of microcapsules by mixing emulsion 1 and emulsion 2; and washing and drying the formed microcapsules. In the new technique an insoluble polymer film was formed easily by the fast crosslinking reaction on the surface of tiny emulsified polymer solution particles in contact with the emulsified crosslinking agent solution particles under mixing with high speed agitation. Thereby, small stable microcapsules were formed. The emphasis in this study was on the establishment of the microencapsulation process by which microcapsules were formed and controlled. The microencapsulation was characterized by analysis of the size distribution of microcapsules fabricated with process conditions. The clarification of the effect of the preparation conditions was also made on the morphology and diameter of the microcapsules.