Free radical copolymerization of functional water-soluble poly(N-maleoylglycine-co-crotonic acid): polymer metal ion retention capacity, electrochemical, and thermal behavior

In this study, the water-soluble polymers of N-maleoyl glycine (MG) with crotonic acid (CA) were copolymerized by free radical polymerization to obtain hydrophilic polymers, in order to study the effect of the functional groups in the copolymers on the metal ion retention capacity, electrochemical and thermal behavior, since that important requirements for their use in technological applications are: high solubility in water, chemical stability, a high affinity for one or more metal ions, and selectivity for the metal ion of interest. The metal complexation properties of poly(MG-co-CA) for the metal ions were investigated at pH 3, 5, and 7 in aqueous solution. The metal ion investigated were: Cu(II), Co(II), Cr(III), Ni(II), Cd(II), Zn(II), and Fe(III). The polymeric systems showed high metal ion retention for Zn (II) and Fe(III) at different pH. At different pHs, the MRC of the poly(MG-co-CA) for Fe(III) ions varied from 122.1 to 146.2 mg/g and from 120.5 to 133.5 mg/g, (samples 1 and 2 at pH 3 and 7, respectively). The MRC had the highest retention values for both copolymer systems at pH 7. The copolymers presented higher thermal decomposition temperature (TDT) in comparison with copolymer–metal complexes at pH 3 and 5. The cyclic voltammetry (CV) for poly(MG-co-CA) (20 mM) was compared with the CV of the [poly(MG-co-CA)–Fe(III)] copolymer complex. Moreover, [poly(MG-co-CA)–Fe(III)] showed a redox wave difference between +0.25 and +0.50 V possibly due to the presence of metal complexed with the polymer. The electrochemical characterization of the copolymer poly(MG-co-AC) shown the reduction of carboxylic acid groups of the N-maleoylglycine and crotonic acid moiety to hydroxyl group. The results support the assumption that the copolymer presents convenient electroactivity.     

Continuous combined Fenton's oxidation and biodegradation for the treatment of pentachlorophenol-contaminated water

Pentachlorophenol (PCP) was studied as a model recalcitrant compound for a sequential chemical oxidation and biodegradation treatment, in a continuous laboratory-scale system that combined a Fenton’s chemical reactor and a packed-bed bioreactor.PCP degradation and dechlorination were observed in the Fenton’s reactor at a residence time of 1.5 h, although no reduction of total organic carbon (TOC) was observed. Both PCP degradation and dechlorination were strongly dependent on the H₂O₂ dose to the chemical reactor. The PCP degradation intermediates tetrachlorohydroquinone and dichloromaleic acid were identified in this reactor. Further treatment of the Fenton’s reactor effluent with a packed-bed bioreactor (operating at a residence time of 5.5 h) resulted in partial biodegradation of PCP degradation intermediates and reduction in TOC, although no further reduction of PCP or dechlorination was achieved in the bioreactor. Increased residence time in the bioreactor had no significant impact on degradation of TOC. Recycle of the effluent from the bioreactor to the chemical reactor increased the TOC degradation, but not the extent of the PCP degradation or dechlorination.A mathematical model of the combined Fenton’s oxidation and biodegradation system supported the experimental results. While the model over-predicted the PCP and TOC degradation in the combined system, it adequately predicted the sensitivity of these parameters to different H₂O₂ doses and recycle rates. The model indicated that high recycle rates would improve TOC degradation.     

Chelating water-soluble polymers associated with ultrafiltration membranes for metal ion removal

This article describes the retention properties of commercial chelating water-soluble polymers, for different metal ions in aqueous solution using a liquid-phase polymer-based retention (LPR) technique. The polymers studied were poly(ethyleneimine) or P(EI) (water-free and a 50?% aqueous solution) and poly(ethyleneimine epichlorohydrin) or P(EIE) (a 17?% aqueous solution). These commercial polymers were fractionated by ultrafiltration membranes and then characterized by Fourier-transformed infrared spectroscopy. The extraction process was performed using the following metal ions: Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺, Pb²⁺ and Cr³⁺. In the washing studies, we varied the pH (3, 5 and 7) and retention time. The results showed that P(EI) showed high retention for all the metal ions at pH 7 and for selective retention of Cu²⁺ at pH 5, while P(EIE) showed selective retention of Cu²⁺ ions at pH 7. Using the enrichment method, the maximum retention capacity of Cu²⁺ and Cd²⁺ was achieved using a 50?% aqueous solution of P(EI) at pH 5 and 7, respectively. Finally, charge–discharge experiments for Cu²⁺ were analysed by changing the pH from basic to acidic over three cycles. These results showed that it is possible to remove metal ions and regenerate the removal capacity of the polychelatogens using the LPR technique.     

Structural effects of WO3 incorporation on USY zeolite and application to free fatty acids esterification

Zeolites have occupied a distinguished position due to their unique properties as solid acids and catalytic results achieved in several industrial reactions. This work studied the influence of supported WO₃ on USY zeolite structure, acidity and activity towards an esterification reaction. High dispersion of WO₃ species on USY was achieved, but at higher loading (?11.4%), microcrystalites of WO₃ were detected below the theoretical monolayer coverage (∼32%). Tungsten species were deposited preferentially inside the zeolite structure and interacted with the Brønsted sites of USY as well as on silanol surface groups with the formation of small aggregates. In addition, dealumination took place, especially in the samples with high WO₃ loading. USY had the most and the strongest acidic sites (Brønsted type), but the incorporation of WO₃ decreased the amount and the strength of the new sites. However, all WO₃/USY catalysts were more active than USY in the esterification of oleic acid with ethanol (conversion above 74%, 2 h at 200 °C). The calculation of the TOF for a 1 h reaction demonstrated that 11.4% WO₃/USY was the most active catalyst. Furthermore, it had the lowest rate of deactivation of acid sites after the reaction (∼13% after four cycles). The better performance of the 11.4% WO₃/USY sample was also attributed to a better distribution of strength of the acidic sites and a more hydrophobic character of the synthesized material.     

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.     

Boundaryless finite-difference method for three-dimensional beam propagation

A two-dimensional optical field paraxial propagation scheme, in Cartesian and cylindrical coordinate systems, is proposed. This is achieved by extending the method originally proposed by Ladouceur [Opt. Lett. 21, 4 (1996)] for boundaryless beam propagation to two-dimensional optical wave fields. With this formulation the arbitrary choice of physical window size is avoided by mapping the infinite transverse dimensions into a finite-size domain with an appropriate change of variables, thus avoiding the energy loss through the artificial physical boundary that is usually required for the absorbing or the transparent boundary approach.     

Modification of cellulose acetate films using nanofillers based on organoclays

The present work has been oriented on the development of cellulose acetate films with nanofillers of montmorillonite/alkylammonium (hexa- and tetra-decyltrimethylammonium) and montmorillonite/chitosan which have been synthesized using a cationic exchange process. All synthesized organoclays have been characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). These analyses confirmed the modification of clay structures which proved to be dependent on the chemical structure of chosen organic precursor. On the other hand, the different organoclays have been used to produce cellulose acetate nanocomposites by solvent-casting technique. The nanocomposite films have been characterized by XRD, TGA, Differential scanning calorimetry (DSC), oxygen and water vapor permeability and scanning electronic microscopy (SEM). All nanocomposites obtained showed the intercalation of polymer inside the clay structure and an important reduction of oxygen transmission rate (OTR) compared to cellulose acetate films without nanofillers.     

Use of needle track detection to quantify the displacement of stranded seeds following prostate brachytherapy

We aim to compute the movement of permanent stranded implant brachytherapy radioactive sources (seeds) in the prostate from the planned seed distribution to the intraoperative fluoroscopic distribution, and then to the postimplant computed tomography (CT) distribution. We present a novel approach to matching the seeds in these distributions to the plan by grouping the seeds into needle tracks. First, we identify the implantation axis using a sample consensus algorithm. Then, we use a network flow algorithm to group seeds into their needle tracks. Finally, we match the needles from the three stages using both their transverse plane location and the number of seeds per needle. We validated our approach on eight clinical prostate brachytherapy cases, having a total of 871 brachytherapy seeds distributed in 193 needles. For the intraoperative and postimplant data, 99.31% and 99.41% of the seeds were correctly assigned, respectively. For both the preplan to fluoroscopic and fluoroscopic to CT registrations, 100% of the needles were correctly matched. We show that there is an average intraoperative seed displacement of 4.94±2.42 mm and a further 2.97±1.81 mm of postimplant movement. This information reveals several directional trends and can be used for quality control, treatment planning, and intraoperative dosimetry that fuses ultrasound and fluoroscopy.     

Modified paramagnetic beads in a microfluidic system for the determination of zearalenone in feedstuffs samples

In this work, we have developed and characterised a novel microfluidic immunoassay methodology for rapid and sensitive quantification of ZEA in feedstuffs samples. The detection of ZEA was carried out using a competitive direct immunoassay method based on the use of anti-ZEA monoclonal antibodies immobilized on magnetic microspheres 3-aminopropyl-modified manipulated for an external remobilize magnets. The ZEA in feedstuffs sample is allowed to compete with ZEA-horseradish peroxidase (HPR) conjugated for the immobilized anti-ZEA antibody. The HPR, in the presence of hydrogen peroxide (H₂O₂) catalyses the oxidation of 4-tert-butylcatechol (4-TBC) whose back electrochemical reduction was detected on gold electrode at 0.0 V. The calculated detection limits for electrochemical detection and ELISA procedure were 0.41 and 2.56 μg kg⁻¹ respectively, the intra and inter-assay coefficients of variation were below 6.5% and the total assay time was 30 min. The microfluidic immunosensor showed higher sensitivity and lower detection limits than the standard ELISA method, which shows potential for detecting ZEA in foods and feeds diagnosis.