Feedstock recycling of polyethylene over AlTUD-1 mesoporous catalyst

The catalytic degradation of high density polyethylene (HDPE) was investigated using AlTUD-1 as catalyst, a recently discovered mesoporous aluminosilicate. The catalytic activity of AlTUD-1 was evaluated by TGA measurements, using a polymer/catalyst ratio of 9:1. AlTUD-1 has a Brønsted acidic behaviour, three-dimensional (3D) connectivities and a pore diameters between 2 and 50 nm. Compared to HY zeolite, the large pore size of AlTUD-1 enhances a selective catalytic degradation of the polymer and prevents rapid deactivation. Moreover, the apparent activation energy of polymer cracking is much lower than with HY zeolite. For these reasons, AlTUD-1 is a potentially interesting catalyst for the catalytic cracking of plastic waste into liquid fuels.     

Comparison of the structure of (E)‐2‐(2‐benzylidenehydrazinylidene)quinoxaline with those of its chloro‐ and bromobenzylidene analogues

(E)‐2‐(2‐Benzylidenehydrazinylidene)quinoxaline, C₁₅H₁₂N₄, crystallized with two molecules in the asymmetric unit. The structures of six halogen derivatives of this compound were also investigated: (E)‐2‐[2‐(2‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(3‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(4‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(2‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(3‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(4‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄. The 3‐Cl and 3‐Br compounds are isomorphous, as are the 4‐Cl and 4‐Br compounds. In all of these compounds, it was found that the supramolecular structures are governed by similar predominant patterns, viz. strong intermolecular N—H...N(pyrazine) hydrogen bonds supplemented by weak C—H...N(pyrazine) hydrogen‐bond interactions in the 2‐ and 3‐halo compounds and by C—H...Cl/Br interactions in the 4‐halo compounds. In all compounds, there are π–π stacking interactions.     

Trimethoprim-selective electrodes with molecularly imprinted polymers acting as ionophores and potentiometric transduction on graphite solid-contact

This work proposes a new biomimetic sensor material for trimethoprim. It is prepared by means of radical polymerization, having trimethylolpropane trimethacrylate as cross-linker, benzoyl peroxide as radicalar iniciator, chloroform as porogenic solvent, and methacrylic acid and 2-vinyl pyridine as monomers. Different percentages of sensor in a range between 1 and 6% were studied. Their behavior was compared to that obtained with ion-exchanger quaternary ammonium salt (additive tetrakis(p-chlorophenyl)borate or tetraphenylborate). The effect of an anionic additive in the sensing membrane was also tested.Trimethoprim sensors with 1% of imprinted particles from methacrylic acid monomers showed the best response in terms of slope (59.7 mV/decade) and detection limit (4.01 × 10^− 7 mol/L). These electrodes displayed also a good selectivity towards nickel, manganese aluminium, ammonium, lead, potassium, sodium, iron, chromium, sulfadiazine, alanine, cysteine, tryptophan, valine and glycine. The sensors were not affected by pH changes from 2 to 6. They were successfully applied to the analysis of water from aquaculture.     

Ionic liquids: a pathway to environmental acceptability

Ionic liquids were initially proposed as replacements for conventional organic solvents; however, their chemistry has developed remarkably and offers unexpected opportunities in numerous fields, ranging from electrochemistry to biology. As a consequence of ionic liquids advancing towards potential and actual applications, a comprehensive determination of their environmental, health and safety impact is now required. This critical review aims to present an overview of the current understanding of the toxicity and environmental impact of the principal ionic liquid groups, and highlights some emerging concerns. Each cation type is considered separately, examining the significance of the biological data, and identifying the most critical questions, some yet unresolved. The need for more, and more detailed, studies is highlighted (176 references).     

Insight into the interactions that control the phase behaviour of new aqueous biphasic systems composed of polyethylene glycol polymers and ionic liquids

New polyethylene glycol (PEG)/ionic liquid aqueous biphasic systems (ABS) are presented. Distinct pairs of PEG polymers and ionic liquids can induce phase separation in aqueous media when dissolved at appropriate concentrations. Phase diagrams have been determined for a large array of systems at 298, 308 and 323 K. A comparison of the binodal curves allowed the analysis of the tunable structural features of the ionic liquid (i.e., anionic nature, cationic core, cationic alkyl side chain length and functionalisation, and number of alkyl substituents in the cation) and the influence of the molecular weight of the PEG polymer on the ability of these solutes to induce an ABS. It was observed that contrary to typical ABS based on ionic liquids and inorganic salts, in which the phase behaviour is dominated by the formation of the hydration complexes of the ions, the interactions between the PEG polymers and ionic liquids control the phase demixing in the polymer-type ABS studied herein. It is shown that both the ionic liquids and PEG polymers can act as the salting-out species; that is, it is an occurrence that is dependent on the structural features of the ionic liquid. For the first time, PEG/ionic liquid ABS are reported and insight into the major interactions that govern the polymer/ionic liquid phase behaviour in aqueous media are provided. The use of two different nonvolatile and tunable species (i.e., ionic liquids and PEG polymers) to form ABS allows the polarities of the phases to be tailored. Hence, the development of environmentally friendly separation processes that make use of these novel systems is envisaged.     

Inorganic salts in purely ionic liquid media: the development of High Ionicity Ionic Liquids (HIILs)

This work explores the possibility of increasing the ionicity of ionic liquids via the solubilization of inorganic salts in their midst. The resulting purely ionic media-distinct ionic liquid plus inorganic salt mixtures-are liquid in an extensive concentration range and can be aptly denominated High Ionicity Ionic Liquids (HIILs).     

Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure

A series of alkyltributylphosphonium chloride ionic liquids, prepared from tributylphosphine and the respective 1-chloroalkane, C(n)H(2n+1)Cl (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 or 14), is reported. This work is a continuation of an extended series of tetraalkylphosphonium ionic liquids, where the focus is on the variability of n and its impact on the physical properties, such as melting points/glass transitions, thermal stability, density and viscosity. Experimental density and viscosity data were interpreted using QPSR and group contribution methods and the crystal structure of propyl(tributyl)phosphonium chloride is detailed.     

Biomarkers in Catfish <Emphasis Type="Italic">Sciades herzbergii</Emphasis> (Teleostei: Ariidae) from Polluted and Non-polluted Areas (São Marcos’ Bay,Northeastern Brazil)

Biomarkers based on specific enzyme activities and histological alterations are useful tools for evaluating toxicological effects of xenobiotics in wild fish. In this work, an experimental system of biomarkers with enzyme glutathione S-transferase (GST) and branchial lesions in catfish (Sciades herzbergii) was mathematically modeled. The fish were collected along known pollution gradients (S1) and from areas regarded relatively free of anthropogenic input (S2) in São Marcos’ Bay, Brazil. GST was measured spectrophotometrically, and branchial lesions were examined by light microscope. The databases from this analysis were compiled, and non-linear models were used to analyze the dependence of the enzyme activity on the areas of sampling and on selected biological parameters of the fish. Fish weight, length, and somatic indices (gonadosomatic index) were significant in the model of GST activity only in A2. Brachial lesions were significant in the model of GST activity only in A1. The obtained model indicates that when the GST ceases to act, serious branchial lesions are observed in the fish of the contaminated regions.