Natural rubber/poly(acrylic acid) semi‐interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures

Pervaporation membranes for the dehydration of water–ethanol mixtures were prepared from a semi‐interpenetrating polymer network (semi‐IPN) of natural rubber (NR) and crosslinked poly(acrylic acid) (PAA). The swelling studies revealed that hydrophilic PAA present in the semi‐IPN membranes caused the membranes to swell greatly in water. The swelling degree of the membranes in water was significantly affected by the amount ratio between the hydrophobic NR and the hydrophilic PAA. The sorption experiments of the NR/PAA membranes in various concentrations of water–ethanol mixtures suggested the preferential sorption to water. However, for the membrane with high PAA content, the water sorption selectivity decreased considerably at high water concentration of water–ethanol mixtures because the membrane was in the highly swollen state. Pervaporation separations of water–ethanol mixtures using NR/PAA membranes were performed and it was found that at low water concentrations of feed mixtures, increasing the PAA content of the membrane can enhance both water permeation flux and selectivity. Additionally, under low feed water concentration, increasing the feed temperature would increase the water flux with the decreasing of the ethanol flux. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

ESTIMATION OF BIOACCESSIBILITY OF HEAVY METALS IN OYSTERS USING THE PHYSIOLOGICALLY BASED EXTRACTION TEST

A physiologically based extraction test (PBET) was applied to estimate the oral bioaccessibility of cadmium, mercury, and lead from oyster tissues. The PBET measures the fraction of a metal that is solubilized from the sample under simulated gastric and intestinal conditions. Both gastric and intestinal extracted solutions as well as microwave digested residue were analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES). The bio accessibilities (relative to the total metal concentrations) of cadmium and lead in the oyster samples were 33.8–59.2% and 28.3–51.4%, respectively. The bioaccessibility of mercury was non detectable (<0.019 mg/kg wet weight) due to the relatively low levels of mercury in the oyster samples (<0.110 mg/kg wet weight).