Extraction of metal cations by polyterephthalamide microcapsules containing a poly(acrylic acid) gel

Preparation of capsules containing 1-nonanol for rapidly removing high concentration phenol from aqueous solution

This study investigated the potential of capsules containing 1-nonanol for the adsorption of phenol at high initial concentrations. The polysulfone capsules containing 1-nonanol (PSF@1-nonanol capsules) were successfully prepared with a phase inversion method, and the results showed that 1-nonanol was encapsulated with polysulfone as an encapsulation capacity of 67.99% was achieved. Systematic studies on phenol adsorption equilibrium, kinetics and isotherms by PSF@1-nonanol capsules were carried out. The results showed that the rate of adsorption of phenol is initially quite rapid and equilibrium is reached in about 90 min. Phenol adsorption uptake was found to increase with increase in initial concentration and adsorption time, whereas adsorption of phenol was more favourable at acidic pH and low temperature. The adsorption kinetics of phenol followed pseudo-second-order model, and the best fits of adsorption isotherms were achieved with the Freundlich equation. These results demonstrate that the use of PSF@1-nonanol capsules enhanced the mass transfer rate and the uptakes to phenol at high initial concentrations. Furthermore, after seven times of repeated extraction and stripping, the microcapsules kept almost the same adsorption ability, which indicated that the PSF@1-nonanol capsules have very good stability in the adsorption process. Therefore, PSF@1-nonanol capsules can be taken as an ideal adsorbent for rapid removal of high concentration phenol from aqueous solution.

Adsorption and recovery of Cu (II) with polysulphone microcapsules containing chitosan gel

Polysulphone (PSF) microcapsules (PSF-CTS) containing chitosan gel with higher mechanical stability and anti-biodegradability were prepared using a novel surface coating method. The thickness and microstructures of the polysulphone coating layer were analysed by SEM. The experiments to examine the mechanical improvement of the encapsulated gel beads were carried out. The adsorption for Cu2+ and regeneration properties of unencapsulated and encapsulated gel beads were also tested. The results showed that the mechanical strength of the encapsulated gel beads was significantly enhanced. However, this improvement led to a decrease of the adsorption kinetics due to the increase of the mass transfer resistance. The potentially available methods are suggested to reduce mass transport resistance through the PSF coating layer.

Biological properties of photocrosslinked alginate microcapsules

An alternative form of gene therapy using recombinant cell lines delivering therapeutic products encapsulated in alginate hydrogel has proven effective in treating many murine models. The lack of long-term capsule stability has led to a new strategy to reinforce the microcapsules with a photopolymerized interpenetrating covalent network of N-vinylpyrrolidone (NVP) and sodium acrylate. Here the properties for potential application in gene therapy are reported. In assessing potential toxicity of the unpolymerized residues, HPLC showed that even after 1 week of washing, no toxic monomers could be detected. Their ability to sustain cell growth was monitored with growth of the encapsulated cells in vitro and in vivo. Although the initial photopolymerization caused significant cell damage, the cells were able to recover normal growth rates thereafter. After implanting into mice, the NVP-modified capsules showed a high level of biocompatibility as measured by hematological and biochemical functional tests. There was also no difference in the amount and type of plasma proteins adsorbing to the NVP-modified and the classical alginate capsules, thus indicating their similar biological compatibility. Both in vitro and in vivo tests confirmed that the NVP-modified capsules were more resistant to osmotic stress than the alginate microcapsules. Furthermore, when applied to the treatment of a murine model of human cancer by delivering encapsulated cells secreting angiostatin, the NVP-modified microcapsules suppressed tumor growth as successfully as the regular alginate microcapsules. In conclusion, the covalently modified microcapsules have shown a high level of biocompatibility, safety, increase in stability, and clinical efficacy for use as immunoisolation devices in gene therapy.

Complexing capsules--metal extraction and modeling of ion transfer

Polyamide complexing capsules containing a poly(acrylic acid) gel are synthesized by a two steps polymerization process with various diameters (10 microm for microcaps or 200 microm for mcaps). A cationic exchange between gel carboxylic functions and metal ions is realized. Extraction and stripping measurements show that the composition of the capsule membrane doesn't hinder the mass transfer. A model, taking account only of the diffusion in the gel phase, is studied.