Separation of aqueous phenol through polyurethane membranes by pervaporation. II. Influence of diisocyanate and diol compounds and crosslinker

Abstract

ABSTRACT:The influence of diisocyanate and diol compounds of polyurethane and crosslinking agent on the separation of phenol aqueous solution by pervaporation was investigated. Polyurethanes were prepared by polyaddition of diisocyanate and diol compounds and trimethylolpropane (TMP) using dibutyltindilaulate as a catalyst. The polyurethane membrane was prepared by a casting method and was sandwiched with a porous polypropylene membrane (Celgard 2500). Pervaporation measurement was carried out under vacuum on the permeate side, and the permeant was collected with a liquid nitrogen trap. Little influence of diisocyanate compounds on the phenol permselectivity through diisocyanate-polytetramethyleneglycol [PTMG(1000)] membranes was observed since the influence on the solubility and the diffusivity was small. The phenol permselectivity was increased with an increase in the molecular weight of PTMG and polycaprolactone diol (PCL) for the 1,6-diisocyanato hexane (HMDI)-PTMG and HMDI-PCL membranes. It was considered that the increase in phenol diffusivity can be attributed to an increase in phenol selectivity. The permeability and selectivity of HMDI-[PTMG(2900)-TMP] membrane was relatively constant below the 2% TMP content.

Separation of aqueous phenol through polyurethane membranes by pervaporation. III. Effect of the methylene group length in poly(alkylene glycols)

“…Pervaporation measurements were carried out with an apparatus that was reported in a previous work. 25 A permeation cell was assembled from two half-cells of stainless steel and fastened together by bolted clamps. A Viton O-ring was used between the pervaporation cell's upper compartment and the membrane.…”

“…The concentration of the absorbate was measured with an apparatus that was previously reported. 25 After weighing the swollen membrane for the degree of swelling measurement, the membrane piece was frozen in a glass vessel with liquid nitrogen. The glass vessel and a cold trap were under vacuum, and the glass vessel was then heated after removing the liquid nitrogen.…”

“…For the polyurethanes of HMDI-PTMG, the degree of swelling in 1 wt % phenol aqueous solution increased with increasing the molecular weight of the PTMG. 25 The distance of urethane groups in the polymer chain becomes long, and a physical crosslinking density by a hydrogen bond of urethane groups decreased in the polyurethane consisting of the high molecular weight of the PTMG. The molecular weight of poly(alkylene glycols) was nearly equal (ca.…”

“…In previous work, we have reported polyurethane membranes for the separation of phenol from dilute aqueous solutions. 24,25 The polyurethane, which was made from polytetramethyleneglycol (PTMG), showed a good phenol permselectivity. The phenol concentration in the permeate solution increased from 0 to 65 wt %, and the total flux also increased up to 930 g ⅐ m Ϫ2 ⅐ h Ϫ1 with increasing the feed concentration of phenol from 0 to 7 wt % for the polyurethane of 1,6hexamethylenediisocyanate (HMDI)-PTMG.…”

A novel solid–liquid two‐phase partitioning bioreactor for the enhanced bioproduction of 3‐methylcatechol

“…Organic solvents possessing ester functionality, and thus hydrogen bonding potential, have been shown to absorb 3MC from solution (Prpich and Daugulis, 2006b). In addition to molecular structure, physical characteristics, such as polymeric chain mobility have also been shown to affect uptake of small organic molecules (Hoshi et al, 1999). It was predicted that HYTREL TM , a polyether-ester thermoplastic, would demonstrate superior uptake of 3MC as it possessed the appropriate molecular functionality (ester groups) and desired chain mobility (low glass transition temperature).…”