Atmospheric Drying UHMWPE Membranes via Multiple Stage Extractant Exchange Drying Technique

Ultra-high molecular weight polyethylene(UHMWPE)membranes were prepared by 5 wt%UHMWPE/parafn oil gels via thermally induced phase separation method and dried in air without signifcant collapse.The UHMWPE membranes were annealed at 110℃ for increasing the pores size in order to decrease the capillary forces.Furthermore,a new multiple stage extractant exchange drying(MSEED)technique was adopted to decrease the shrinkage of the UHMWPE membranes.Specifcally,the parafn oil was extracted by dichloromethane,then dichloromethane was replaced by ethanol,next ethanol could be exchanged to other liquid which is non-afnity with UHMWPE,for example water.UHMWPE membranes(annealing for 25 min)dried by dichloromethane-ethanol-water-air process have the lowest volume shrinkage of 16.5%and the porosity is as high as 88.29%.Moreover,compared with supercritical CO_(2)(SC-CO_(2))drying,atmospheric drying UHMWPE membranes have a lower pure water permeance,but a higher carbon particles rejection.

Experimental Losses and Optimum Conditions for Phenanthrene Extraction

Polycyclic aromatic hydrocarbons （PAHs） are a class of pollutants that are widespread in the en- vironment. Their hydrophobic properties make accurate analyses very difficult. In addition, the experimental losses during extraction of PAHs are inevitable and of great concern. In this study, dichloromethane （DCM）, chloroform （CF）, and carbon disulfide （CDS） were used as solvents to extract phenanthrene （PHN）, a typical PAH, at various temperature and pressure reduction conditions. The extraction was improved using a multi- ple microtube extraction methodology. The results indicate that the CDS had the best performance followed by CF and DCM at 25~C and standard pressure. This was ascribed to the intensity of the molecular interac- tions between the solvent, the water, and the PHN due to their different molecular structures leading to dif- ferent stereo and hydrogen bonding effects. The optimum conditions for extraction of PHN by CDS were determined by correlating the experimental results. The regression shows that the experimental loss rate is linearly proportional to the pressure reduction and exponentially related to the temperature. The correlation can be used to improve extraction efficiencies.