Chitosan-based microparticles for immobilization of TiO2 nanoparticles and their application for photodegradation of textile dyes

The present paper deals with removal and photocatalytic degradation of the textile dyes by TiO2 nanoparticles immobilized onto chitosan-based microparticles. The microparticles composed of chitosan (Ch) and poly(methacrylic acid) (PMA) were fabricated for the first time by inverse suspension polymerization. They were utilized for colloidal TiO2 nanoparticles immobilization, synthetized by acidic hydrolysis of TiCl4. To evaluate the potential application of Ch/PMA/TiO2 microparticles for treatment of textile wastwaters, their photocatalytic activity was examined by degradation assessment of three different groups of anionic azo dyes in aqueous solutions under solar light simulating source. FTIR analysis revealed that Ch and PMA were incorporated in the polymer network. SEM and optical microscopy confirmed their spherical shape. Under illumination, Ch/PMA/TiO2 microparticles completely removed dyes C.I. Acid Orange 7, C.I. Acid Red 18, C.I. Acid Blue 113, C.I. Reactive Black 5, C.I. Direct Blue 78, while removal degree of C.I. Reactive Yellow 17 was 75%. It was found that pH had significant influence on the photocatalytic activity of Ch/PMA/TiO2 microparticles. Increase of solution pH from acidic to alkaline, lead to decrease in photodegradation rate of C.I. Acid Orange 7 during the first hours of illumination. After three illumination cycles, removal degree of C.I. Acid Orange 7 was maintained at remarkably high level (95% at pH 5.60 and 100% at pH 2.00 and 8.00), indicating that microparticles could be reused without significant loss of photocatalytic efficiency. (C) 2016 Elsevier Ltd. All rights reserved.</p

Immobilization of lipase from Candida rugosa into copolymer hydrogels of poly(N-isopropylacrylamide-co-itaconic acid) synthesized in the presence of surfactants

To overcome the problems of free enzyme application as catalysts in chemical reactions, i.e., high costs of isolation and purification processes, high sensitivity to process conditions, insufficient enzyme stability etc., different immobilization techniques need to be used. Immobilization to/within solid support improves enzyme stability decreasing its denaturation. This paper deals with hydrogels of N-isopropylacrylamide and itaconic acid with incorporated nonionic surfactants (Triton X-100, Brij 30 and Tween 80) synthesized in distilled water at room temperature by free radical polymerization. These hydrogels were used as supports for immobilization of enzyme, lipase from Candida rugosa by post-entrapment method. The aim was to investigate the effect of the non-ionic surfactants on the lipase binding capacity, as well as on its hydrolytic activity. In order to characterize the obtained hydrogels, FT-IR analysis has been performed. Further, the swelling behaviour of these samples in buffer solution of pH 6.80 has been investigated. The dynamic-mechanical properties of hydrogels have been studied, too. The immobilized lipase showed somewhat reduced hydrolytic activity, compared to the activity of free lipase as well as in comparison to the lipase immobilized to the reference sample (sample synthesized under the same polymerization conditions, but in the absence of surfactants). It was concluded that the addition of surfactants increased the hydrogel mesh size. The surfactant addition did not affect the dynamic-mechanical properties of the investigated hydrogels. The largest percentage of specific activity and yield of activity were presented by the reference sample, too. It is obvious that the absence of surfactants charged groups has no influence on the lipase binding capacity, and the obtained activity yields are to be expected.U radu je ispitana imobilizacija lipaze iz Candida rugosa u hidrogel poli(N-izopropilakrilamid-ko-itakonska kiselina) sintetisane u prisustvu nejonskih površinski aktivnih materija. Pri sintezi je varirana vrsta i sadržaj površinski aktivnih materija. Ispitana su mehanička svojstva sintetisanih hidrogelova i urađena je FT-IR analiza. Imobilizacija lipaze je izvedena bubrenjem prethodno sintetisanih hidrogelova u rastvoru lipaze, a zatim je ispitan uticaj dodatka površinski aktivnih materija pri sintezi nosača na kapacitet uklapanja lipaze u hidrogel i na aktivnost tako uklopljene lipaze. Imobilisana lipaza iz Candida rugosa je pokazala umanjenu hidrolitičku aktivnost, kako u odnosu na aktivnost slobodne lipaze, što je i očekivano, tako i u odnosu na aktivnost lipaze imobilisane u referentni hidrogel, sintetisan bez prisustva površinski aktivnih materija

The thermal stability of poly(methyl methacrylate) prepared by RAFT polymerisation

Poly(methyl methacrylate), PMMA, was prepared by reversible addition–fragmentation chain transfer, RAFT, polymerisation using 2-(2-cyanopropyl)-dithiobenzoate, CPDB, as the RAFT agent. The thermal stability of the resulting polymer approached that of anionically prepared PMMA, as determined by thermogravimetry. This was the consequence of the RAFT prepared polymer having no head-to-head links and no chain end double bonds, which are responsible for the relatively low thermal stability of radically prepared PMMA