Immobilization of simulated evaporator concentrate waste in low density polyethylene

Simulated evaporator concentrate was prepared by pre-treating sodium borate with calcium hydroxide to produce an insoluble, ulexite-like borate salt. The resultant solid waste was blended by extrusion with virgin and recycled low density polyethylene (LDPE) at 30 and 50 wt% load. Samples were evaluate to homogeneity by density determinations (ASTM D792-91), compressive strength (ASTM D695-91) and leaching behavior by accelerated leaching tests (ASTM C1308-95). Coefficient of variation of density was lower than 5% for all evaluated waste forms, indicating a satisfactory homogeneity. Compressive strengths have complied to U.S.NRC standard and were above CNEN standard limit for cement waste products if 5% strain could be considered a reasonable limit to assure the structural integrity of the material. Cumulated fraction leached after 11 days of accelerated leach test was found to be lower than 10%, and diffusion coefficients of boron have varied between 3.86 × 10^?10 and 9.06 × 10^?10 cm²/s. Boron concentrations for all materials have shown a tendency to reach an asymptotic value at the end of the test (around 0.25 and 0.7 mg/L for 30 and 50% waste load, respectively). Measured cumulated fraction leached (CFL) data with time have shown a tendency of becoming asymptotic sooner than it was predicted by the diffusion model.     

Cationic hybrids from poly(N,N‐dimethylaminoethyl methacrylate) covalently crosslinked with chloroalkyl silicone derivatives effective in binding anionic dyes

The synthesis and characterization of some novel ionic organic/inorganic hybrids containing quaternary ammonium salt groups in the side chain, built on the basis of poly(N,N‐dimethylaminoethyl methacrylate), as an organic component and cation provider, and chloroalkyl‐functionalized silicone derivatives as crosslinkers and anion generators, are reported in this work. The resulted structures were investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and energy dispersive X‐ray spectroscopy. The swelling behavior of the ionic hybrids in water as a function of pH as well as the water vapor sorption capacity in dynamic regime was also studied. The cationic hybrids have a higher swelling capacity at pH 2 compared with deionized water (pH 6) due to the presence of tertiary amine groups belonging to the organic compound. The ionic organic/inorganic hybrids were tested as potential sorbents for anionic species such as dyes [e.g., methyl orange (MO)]. The equilibrium sorption capacity increased with the increase of the organic component up to around 32 mg MO/g hybrid. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43942.     

Role of rare earth oxide coatings on oxidation resistance of chromia-forming alloys

Rare earths (RE) have been used to increase high temperature oxidation resistance of chromia and alumina forming alloys. The RE can be added as elements (or oxides) to the alloys or applied as oxide coatings to the alloy surface. This paper presents the effect of different RE oxide coatings and lanthanum chromite coatings on the high temperature oxidation behavior of Fe20Cr and Fe20Cr4Al alloys. The oxidation resistance of the Fe20Cr alloy increased with increase in ionic radius of the RE element in the coating. The RE oxides decreased chromia growth rate more than alumina growth rate. In extended cyclic oxidation tests that were carried out from peak temperatures of 900 °C, 1,000 °C and 1,100 °C to room temperature at cooling rates of 300 °C/s and 1,000 °C/s, the La₂O₃ coating increased cyclic oxidation resistance of the Fe20Cr alloy significantly more than the Pr₂O₃ coating. The role of RE in increasing overall oxidation resistance of chromia forming alloys is discussed.     

Sorption of aromatic compounds on macroporous anion exchangers based on polyacrylamide: Relation between structure and sorption behavior

The sorption of phenol, p-toluenesulfonic acid (p-TSA), Na-p-toluenesulfonate (Na-p-TS), 1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt (Tiron), and 3-hydroxy-4(sulfonaphthyazo)-5,7-naphthalenedisulfonic acid trisodium salt (Poceau 4R) on the macroporus anion exchangers with acrylamide structural units (weak and strong basic anion exchangers) and on the ion exchangers with amidoxime groups were studied. The maximum specific sorption of p-TSA was almost identical with the total exchange capacity for both the weak and strong basic anion exchangers. The sorption of Na-p-TS is strongly related to the functional group structure of the anion exchangers, being significant on the strong basic anion excahngers. The maximum specific sorption of Tiron was higher tan the total exchange capacity of the strong basic anion exchangers because it is mainly dependent on the ionic exchange properties. The morphological characteristics influenced only the establishement rate of the sorption equilibrium. The sorption of Ponceau 4R, which has the highest molecular weight, is important on the strong basic anion exchangers with high permanent porosity. The sorption of the organic anions is also dependent on the number of the sulfonic groups. © 1995 John Wiley & Sons, Inc.     

Separation of selected bioactive compounds from orange peel using the sequence of supercritical CO2 extraction and ultrasound solvent extraction: optimization of limonene and hesperidin content

ABSTRACT

The orange peel (Citrus sinensis L.) from the variety Washington Navel was extracted by supercritical CO₂ (SC-CO₂) at different parameters. The extracts were analyzed by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). Limonene predominance was found (up to 89%). The principal oxygenated monoterpenes were linalool, α-terpineol, decanal, and (E)-citral. Ultrasound-assisted extraction was performed on the remaining solid residue (after SC-CO₂extraction) to obtain the extracts rich in hesperidin. The influence of different extraction parameters on hesperidin content (3.3–23.0 µg/mL) was determined. The prediction performance in optimizing the extraction yield of dominant compounds was studied by response surface methodology and artificial neural network.     

Anionic polymerization of cyclosiloxanes in heterogeneous medium

Anionic polymerization of various cyclosiloxanes [octamethylcyclotetrasiloxane (D₄), 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (V₄), and hexamethylcyclotrisiloxane (D₃)] was performed. As catalysts, IRA-900 and PB-100 type anionites with benzyltrimethylam-monium and 3-acrylamidopropylbenzyldimethylammonium groups, respectively, were used. The anionite with higher strongly basic exchange capacity (IRA-900) is more efficient in dimethylcyclosiloxane polymerization. PB-100 anionite with less strongly basic capacity is more active for polymerization of the V₄ monomer with bulky and electronegative sub-stituent. © 1996 John Wiley & Sons, Inc.     

Solubility and kinetics of soybean oil and fatty acids in supercritical CO2

Supercritical CO₂ extraction of soybean oil was investigated. The fatty acid composition was determined using GC. The solubility and kinetic experiments were performed in the pressure range of 100–300 bar and in the temperature range of 313–323 K. The solubility data were correlated using empirical equation proposed by Gordillo et al. Mass transfer model described by Martinez et al. was used to describe the kinetic curves of soybean oil. The main fatty acids of soybean oil were linoleic, oleic, palmitic, stearic and linolenic acid. The improved Gordillo et al. equation was proposed to correct the effect of temperature on the solubility. The new equation was successfully applied for calculating the solubility of fatty acids and soybean oil in supercritical CO₂.     

Impedimetric Measurements for Monitoring Avidin-Biotin Interaction on Self-Assembled Monolayer

Avidin-biotin has been controllable immobilized on the surface of gold electrodes using mercaptopropionic acid as self-assembled monolayer. Electrochemical impedance spectroscopy (EIS) was employed to investigate the changes that appear at the electrode surface in the presence of a redox mediator, K₃[Fe(CN)₆]. An electrical model more complex than that in other studies was used to interpret the EIS measurements (Randles circuit). This model is very useful because it takes into consideration both the transfer of electrons at the electrode/electrolyte interface and the diffusion of redox species through the double layer. The model allowed us to determine some important parameters like solution resistance R_sol, charge-transfer resistance R_ct, double-layer capacitance C_dl, Warburg resistance R_W, and the diffusion time constant τ. The EIS results proved that immobilization of avidin-biotin increased the charge-transfer resistance R_ct, due to the insulating character of these molecules.     

Electrochemical polymerisation of thiophene derivative induced by Lewis acid: Electrosynthesis of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate]

Films of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate] were deposited on ITO electrodes by potentiodynamic, potentiostatic and galvanostatic methods using a (C₄H₉)₄NBF₄/CH₃CN electrolyte system containing 20% boron trifluoride diethyl etherate. Polymerisation occurred as a charge dependent process at a potential of 1.4 V vs. Ag/Ag⁺(CH₃CN). The surface morphologies of the films so-formed were examined using atomic force microscopy. The film deposited by the galvanostatic method displayed more homogeneous grain geometry and a larger superficial area than those formed by the other methods. Cyclic voltammetry revealed a well defined redox couple at the anodic region, attributable to polymer p-doping, and a poorly defined redox pair at the cathodic region, attributable to the reduction of the nitro group. The polymeric films obtained were yellow in colour (λ_max 425 nm) in the reduced state and light blue (λ_max 745 nm) in the oxidised state.