Osmium Recovery as Membrane Nanomaterials through 10–Undecenoic Acid Reduction Method

The recovery of osmium from residual osmium tetroxide (OsO4) is a necessity imposed by its high toxicity, but also by the technical-economic value of metallic osmium. An elegant and extremely useful method is the recovery of osmium as a membrane catalytic material, in the form of nanoparticles obtained on a polymeric support. The subject of the present study is the realization of a composite membrane in which the polymeric matrix is the polypropylene hollow fiber, and the active component consists of the osmium nanoparticles obtained by reducing an alcoholic solution of osmium tetroxides directly on the polymeric support. The method of reducing osmium tetroxide on the polymeric support is based on the use of 10-undecenoic acid (10–undecylenic acid) (UDA) as a reducing agent. The osmium tetroxide was solubilized in t–butanol and the reducing agent, 10–undecenoic acid (UDA), in i–propanol, t–butanol or n–decanol solution. The membranes containing osmium nanoparticles (Os–NP) were characterized morphologically by the following: scanning electron microscopy (SEM), high-resolution SEM (HR–SEM), structurally: energy-dispersive spectroscopy analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy. In terms of process performance, thermal gravimetric analysis was performed by differential scanning calorimetry (TGA, DSC) and in a redox reaction of an organic marker, p–nitrophenol (PNP) to p–aminophenol (PAP). The catalytic reduction reaction with sodium tetraborate solution of PNP to PAP yielded a constant catalytic rate between 2.04 × 10−4 mmol s–1 and 8.05 × 10−4 mmol s−1.

Polysaccharides as Support for Microbial Biomass-Based Adsorbents with Applications in Removal of Heavy Metals and Dyes

The use of biosorbents for the decontamination of industrial effluent (e.g., wastewater treatment) by retaining non-biodegradable pollutants (antibiotics, dyes, and heavy metals) has been investigated in order to develop inexpensive and effective techniques. The exacerbated water pollution crisis is a huge threat to the global economy, especially in association with the rapid development of industry; thus, the sustainable reuse of different treated water resources has become a worldwide necessity. This review investigates the use of different natural (living and non-living) microbial biomass types containing polysaccharides, proteins, and lipids (natural polymers) as biosorbents in free and immobilized forms. Microbial biomass immobilization performed by using polymeric support (i.e., polysaccharides) would ensure the production of efficient biosorbents, with good mechanical resistance and easy separation ability, utilized in different effluents’ depollution. Biomass-based biosorbents, due to their outstanding biosorption abilities and good efficiency for effluent treatment (concentrated or diluted solutions of residuals/contaminants), need to be used in industrial environmental applications, to improve environmental sustainability of the economic activities. This review presents the most recent advances related the main polymers such as polysaccharides and microbial cells used for biosorbents production; a detailed analysis of the biosorption capability of algal, bacterial and fungal biomass; as well as a series of specific applications for retaining metal ions and organic dyes. Even if biosorption offers many advantages, the complexity of operation increased by the presence of multiple pollutants in real wastewater combined with insufficient knowledge on desorption and regeneration capacity of biosorbents (mostly used in laboratory scale) requires more large-scale biosorption experiments in order to adequately choose a type of biomass but also a polymeric support for an efficient treatment process.

Contact Lenses as Ophthalmic Drug Delivery Systems: A Review

Ophthalmic drugs used for the treatment of various ocular diseases are commonly administered by eye drops. However, due to anatomical and physiological factors, there is a low bioavailability of the active principle. In order to increase the drug residence time on the cornea to adequate levels, therapeutic contact lenses have recently been proposed. The polymeric support that constitutes the contact lens is loaded with the drug; in this way, there is a direct and effective pharmacological action on the target organ, promoting a prolonged release of the active principle. The incorporation of ophthalmic drugs into contact lenses can be performed by different techniques; nowadays, the soaking method is mainly employed. To improve the therapeutic performance of drug-loaded contact lenses, innovative methods have recently been proposed, including the impregnation with supercritical carbon dioxide. This updated review of therapeutic contact lenses production and application provides useful information on the most effective preparation methodologies, recent achievements and future perspectives.

The effect of treatment with sodium carbonate and hydrogen on the activity and selectivity of polymeric Pd-containing catalysts for hydrogenation of acetylene compounds

Catalytic hydrogenation of the triple carbon-carbon bond of acetylene compounds is an important industrial process. High selectivity to the olefin compound should be provided in the process. This study considers the effect exerted by sodium carbonate treatment of the palladium catalysts containing super-cross-linked polystyrene (SPS) on their activity and selectivity in the hydrogenation of 2-methyl- 3-butin-2-ol and phenylacetylene. The effect of such treatment was shown to depend on the chosen palladium precursor and the type of polymeric support (non-functionalized SPS or that containing ternary amino groups). At atmospheric pressure of hydrogen and a temperature of 90 °C in a toluene medium, the 1%-Pd/SPS catalysts treated with Na2CO3 provided a 98 % selectivity in the hydrogenation of 2-methyl-3-butin-2-ol (at a 95 % conversion of the substrate), while selectivity in the hydrogenation of phenylacetylene reached 99.5 %.

DFO@EVOH and 3,4-HP@EVOH: Towards New Polymeric Sorbents for Iron(III)

The paper presents the synthesis and preliminary characterization of two novel solid-phase sorbents for iron(III), resulting from the functionalization of ethylene-vinyl alcohol copolymer (EVOH) with deferoxamine, DFO (DFO@EVOH), and a novel tripodal 3-hydroxy-4-pyridinone, named 3,4-HP (3,4-HP@EVOH). DFO and 3,4-HP have been covalently bonded to EVOH, using carbonyldiimidazole as a coupling agent. Before their use as Fe(III) sorbents, they were warm-pressed to obtain a thin film. Polymers have been characterized by conventional physico-chemical techniques; furthermore, the sorption properties towards Fe(III) were investigated. The physico-chemical characterization of the new solid-state devices demonstrates the effective linkage of the two receptors on the polymeric support. Despite a relatively low sorption capacity for both materials, the stoichiometry and the complexation constants of Fe(III)/DFO@EVOH and Fe(III)/3,4-HP@EVOH are in pretty good agreement with those obtained for the same ligands in aqueous solutions.

Ag nanoparticles stabilized on cubic polyhedral oligomeric silsesquioxane cross-linked poly(N-isopropyl acrylamide-co-itaconic acid): An efficient catalyst for 4-nitrophenol reduction

Ag nanoparticles were synthesized and stabilized on a polymeric support, poly([Formula: see text]-isopropyl acrylamide-co-itaconic acid)/POSS, by simply reducing Ag[Formula: see text] ions adsorbed in the interior of the polymeric network. The prepared Ag@p(NIPAM-IA)/POSS was used as an efficient and recyclable catalyst for removal of the 4-nitrophenol (4-NP) contaminant by NaBH4-induced reduction to 4-aminophenol (4-AP) in aqueous solution. Different conditions including Ag content and amount of the nanocomposite, and also temperature of the 4-NP reduction were investigated. Also, two kinetic models, zero-order and first-order kinetics, were studied for the reduction of 4-NP to 4-AP.