Search

In this study, polyvinylidene fluoride (PVDF) hollow-fiber hemodialysis membranes were prepared by non-solvent-induced phase separation. The PVDF hollow-fiber hemodialyzers were prepared by centrifugal casting. The results showed that the PVDF membrane had better mechanical and separation properties when the membrane wall thickness was 40 μm and the N,N-dimethylacetamide in the core was 70 Vol%. Compared with commercial polysulfone hemodialysis membrane (Fresenius F60S membrane), the PVDF membrane had better mechanical property and ultrafiltration (UF) flux of pure water. The PVDF dialyzer's removal efficiency for middle molecules was proven to be much higher than that of the F60S dialyzer. The UF coefficient of a high-flux PVDF dialyzer is 62.6 ml/h/mm Hg, whereas F60S is 42.5 ml/h/mm Hg, which can promote clearance for middle molecules.

Polyethersulfone (PES) hollow fibers were fabricated by dry-wet spinning method for hemodialysis application. The effects of additives polyethylene glycols (PEG) in the dope solution and of fiber thickness and inner diameter fiber on the membrane mechanical characters were investigated. The dialysis tests were conducted by using a simulated solution prepared by dissolving bovine serum albumin (BSA), lysozyme and urea in de-ionized water to test the effects of membrane characters and operating conditions on dialysis efficiency. The results indicated that the reduction of PEG concentration from 27.6 wt% to 24.1 wt% in the dope solution improved the clearance of toxins, but slightly decreased the mechanical characters. The reduction of fiber thickness or fiber inner diameter was found to improve the clearance of toxins by removing 64.2% of lysozyme and 89.4% of urea (membrane area 0.2 m2), whilst BSA retention was found being maintained above 98%. The dialysis efficiency was also noted to increase with the increase in the flow rate of either the simulated or the dialysate solution, or increasing the membrane area. Moreover, The result of a comparison on the clearance of toxins between commercial F60S and PES dialyzers indicated higher dialysis efficiency per area of the fabricated PES membrane.

In order to investigate the uptake of lead by rice plant and the distribution of lead in different parts of rice, pot experiment was conducted with 20 rice cultivars of different genotypes by adding lead to soil. The results showed that there existed significant differences among the cultivars in the lead uptake and distribution by rice plants, but the differences had no obvious relationship with rice genotypes. The lead concentrations decreased rapidly from roots to grains along rice plants, so the concentrations of lead were very low in grains compared with other parts of rice plants. The regression analysis showed that there were significant negative correlations between adjacent organs of rice plant, but positive correlations, mostly significant, between disconnected organs, for the lead concentrations in them. Lead concentration in the leaf of heading stage showed a significant positive correlation with that in the grain of ripening stage. Lead was not distributed uniformly in different parts of grain structure, and the lead accumulation in polished rice was only 32.88% of the total lead accumulation in grain.