Removal of Cresols From Water By Packed Beds of Cyclodextrin-Based Hydrogels

A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between −6.8 and −8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption-desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose-response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol.

Determination of the Competitive Ion Exchange Isotherms of Taurine and Glycine on D290 Resin by Inverse Method

With the elution curves of glycine and taurine, the ion exchange isotherm parameters of glycine and taurine on D290 anion exchange resin are determined by the inverse method. In this work, with the multi-component competitive ion exchange isotherm and the equilibrium dispersion chromatographic model, the elution curves of glycine and taurine on D290 anionic fixed bed are fitted. The parameters of competitive isotherm are determined, Ktau is 2.55, Kgly is 1.65. The result s showed good agreement between the elute curves fitted by the model and the separation data which confirmed the validity of the model selected.Keywords-taurine; glycine;competitive isotherm;inverse method;

Sirolimus-Loaded Polyurethane Graft for Hemodialysis Access in Sheep

Intimal hyperplasia is the most common final pathway for hemoaccess occlusion in dialysis patients. Drug eluting stents have been shown to decrease intimal hyperplasia in coronary arteries and possibly in peripheral arteries. We evaluated the use of a sirolimus loaded polyurethane graft as prophylaxis in hemodialysis access. Grafts were loaded with sirolimus and elution curves were determined for the polyurethane material. The arteriovenous grafts were then placed in the neck of 20 sheep. A non-loaded graft was placed in the contralateral neck. Patency rates, ultrasound evaluation, angiography and histomorphometry were determined for each graft. At 30, 60 and 90 days the drug loaded graft had improved patency rates compared to the control, with a 25% improvement noted at 3 months. Life table analysis showed the drug loaded graft consistently better patency than the control (p = .136). The control graft had greater neointimal stenosis (14.5% vs 9.17%) over the course of the study (p = .157). Although none of these findings was statistically significant in this pilot study, the sirolimus coated graft out-performed the control in every measured parameter at each time point evaluated. Further work to asses the validity of drug coated materials to prevent intimal hyperplasia in hemodialysis access is warranted.