Sequential separation of lanthanides, thorium and uranium using novel solid phase extraction method from high acidic nuclear wastes

A novel grafted polymer for selective extraction and sequential separation of lanthanides, thorium and uranium from high acidic wastes has been developed by grafting Merrifield chloromethylated (MCM) resin with octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) (MCM-CMPO). The grafting process is well characterized using FT-IR spectroscopy, (31)P and (13)C CPMAS (cross-polarized magic angle spin) NMR spectroscopy and CHNPS elemental analysis. The influence of various physico-chemical parameters during metal ion extraction by the resin phase are studied and optimized by both static and dynamic methods. The resin shows very high sorption capacity values of 0.960mmolg(-1) for U(VI), 0.984mmolg(-1) for Th(IV), 0.488mmolg(-1) for La(III) and 0.502mmolg(-1) for Nd(III) under optimum HNO(3) medium, respectively. The grafted polymer shows faster rate exchange kinetics (<5min is sufficient for 50% extraction) and greater preconcentration ability, with reusability exceeding 20 cycles. During desorption process, sequential separation of the analytes is possible with varying eluting agents. The developed grafted resin has been successfully applied in extracting Th(IV) from high matrix monazite sand, U(VI) and Th(IV) from simulated nuclear spent fuel mixtures. All the analytical data is based on triplicate analysis and measurements are within 3.5% rsd reflecting the reproducibility and reliability of the developed method.     

Coexistence of folded and extended conformations of a tripeptide containing alpha, alpha -di-n-propylglycine in crystals

The crystal structure of the tripeptide Boc-Leu-Dpg-Val-OMe (Dpg, alpha, alpha -di-n-propylglycine) reveals the coexistence of two distinct backbone conformations. In molecule A the Dpg residue adopts a fully extended conformation (phi = 76.0 degrees, psi = 180.0 degrees) while in molecule B a left handed helical conformation (phi = 62.8 degrees, psi = 39.6 degrees) is observed. Molecule B adopts a folded structure corresponding to a highly distorted Type II beta-turn conformation, which lacks an intramolecular 4 -> 1 hydrogen bond. In contrast, molecule A has an open, extended conformation. The results demonstrate that both fully extended and helical conformations are energetically accessible to the Dpg residue.     

Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process

The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant. The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III) concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction. The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction in the MEO process.     

Diversity among various forms of catechins and its synthesizing enzyme (phenylalanine ammonia lyase) in relation to quality of black tea (Camellia spp.)

BACKGROUND: Quality of tea depends on the cultivar and climatic conditions. Biochemical pathways within the plant and climatic factors can result in noticeable changes in chemical composition, which determine the quality of tea. Black tea quality attributes are influenced by various forms of catechins, namely gallated, non‐gallated, dihydroxylated and trihydroxylated catechins and their ratios. Hence the variations in grouped catechins and their synthesizing enzyme in relation to quality of south Indian black tea grown in different seasons and different cultivars were studied. RESULTS: Gallated, non‐gallated, dihydroxylated, trihydroxylated catechins and catechin index were significantly higher in crop shoots harvested during summer. A significant and wide diversity in various forms of catechins was noticed among the cultivars tested. Among the cultivars, UPASI‐3 registered the higher amount of various forms of catechins and activity of phenylalanine ammonia lyase (PAL), followed by UPASI‐9 and UPASI‐17 respectively, while the lowest amount was exhibited by ‘Assam’ seedlings and TRI‐2043. CONCLUSION: Overall quality as evaluated by tea tasters was positively correlated to the cultivars and seasons tested. This positive correlation can be attributed to higher levels of grouped catechins and PAL activity. Thus the contents of various forms of catechins could be the most important quality parameter of the south Indian black teas. Copyright © 2010 Society of Chemical Industry     

Production of okara and soy protein concentrates using membrane technology

Microfiltration (MF) membranes with pore sizes of 200 and 450 nm and ultrafiltration (UF) membranes with molecular weight cut off of 50, 100, and 500 kDa were assessed for their ability to eliminate nonprotein substances from okara protein extract in a laboratory cross-flow membrane system. Both MF and UF improved the protein content of okara extract to a similar extent from approximately 68% to approximately 81% owing to the presence of protein in the feed leading to the formation of dynamic layer controlling the performance rather than the actual pore size of membranes. Although normalized flux in MF-450 (117 LMH/MPa) was close to UF-500 (118 LMH/MPa), the latter was selected based on higher average flux (47 LMH) offering the advantage of reduced processing time. Membrane processing of soy extract improved the protein content from 62% to 85% much closer to the target value. However, the final protein content in okara (approximately 80%) did not reach the target value (90%) owing to the greater presence of soluble fibers that were retained by the membrane. Solubility curve of membrane okara protein concentrate (MOPC) showed lower solubility than soy protein concentrate and a commercial isolate in the entire pH range. However, water absorption and fat-binding capacities of MOPC were either superior or comparable while emulsifying properties were in accordance with its solubility. The results of this study showed that okara protein concentrate (80%) could be produced using membrane technology without loss of any true proteins, thus offering value addition to okara, hitherto underutilized. Practical Application: Okara, a byproduct obtained during processing soybean for soymilk, is either underutilized or unutilized in spite of the fact that its protein quality is as good as that of soy milk and tofu. Membrane-processed protein products have been shown to possess superior functional properties compared to conventionally produced protein products. However, the potential of membrane technology has not been exploited for the recovery of okara protein. Our study showed that protein content of okara extract could be improved from approximately 68% to approximately 81% without losing any true proteins in the process.     

Synthesis and evaluation of trimethylolpropane triacrylate crosslinked superabsorbent polymers for conserving water and fertilizers

A series of superabsorbent polymers (SAP) were synthesized by free radical thermal copolymerization of acrylic acid and N‐isopropyl acrylamide monomers using trimethylolpropane triacrylate as crosslinker. They were characterized by FT‐IR and thermal stability (TGA/DTG), and evaluated for their water and fertilizer uptake and release characteristics under different crosslinker levels, temperature, pressure, and pH. The observed maximum absorption of water by the SAP was 1130 g/g of polymer. The release was modeled which showed a non‐Fickian mechanism. The water uptake of SAP was correlated with the average molecular weight between the crosslinks and crosslink density. Analysis of the weight loss data from TG in air revealed a zero order kinetics for the initial degradation step with an activation energy (AE) of 70.8 kJ/mol. The AEs for water uptake and release for thermal degradation were also determined through Arrhenius plots. The results inferred that the synthesized SAP can be exploited for commercial agricultural applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface Modification of Wood Using Nitric Acid

Surface modification of wood flakes by oxidation with nitric acid has been investigated at three different moisture contents of wood, and two different concentrations of the oxidant. It is shown that a significant number of the acid groups generated are chemically linked to wood. Increasing moisture content in wood has the effect of local dilution of the nitric acid oxidant while reduction in moisture content of wood during drying makes potential oxidation sites less accessible. Thus, two different regimes of oxidation, one of more accessible, and another, of less accessible, sites are observed. The nature of the generated acid is established as carboxylic, which is capable of undergoing a coupling reaction with 2-(l-aziridinyl)ethyl methacrylate. The catalysis of in situ polymerization of furfuryl alcohol by bound acid has also been shown to occur.     

Local and Regional Secondary Organic Aerosol: Insights from a Year of Semi-Continuous Carbon Measurements at Pittsburgh

We present Scanning Mobility CCN Analysis (SMCA) as a novel method for obtaining rapid measurements of size-resolved cloud condensation nuclei (CCN) distributions and activation kinetics. SMCA involves sampling the monodisperse outlet stream of a Differential Mobility Analyzer (DMA) operated in scanning voltage mode concurrently with CCN and condensation particle counters. By applying the same inversion algorithm as used for obtaining size distributions with a scanning mobility particle sizer (SMPS), CCN concentration and activated droplet size are obtained as a function of mobility size over the timescale of an SMPS scan (typically 60–120 s). Methods to account for multiple charging, particle non-sphericity, and limited counting statistics are presented. SMCA is demonstrated using commercial SMPS and CFSTGC instruments with the manufacturer-provided control software. The method is evaluated for activation of both laboratory aerosol and ambient aerosol obtained during the 2004 NEAQS-ITCT2k4 field campaign. It is shown that SMCA reproduces the results obtained with a DMA operating in voltage “stepping” mode.     

Yellow Beads and Missing Particles: Trouble Ahead for Filter-Based Absorption Measurements

Particulate emissions from low-temperature biomass burning are dominated by organic matter. Here, we show that such emissions have a liquid, bead-like appearance when collected on fibrous filters, and the number of these beads are far less than expected for solid spherical particles. These shapes are in line with published drop-on-fiber theories for liquids entrained on filaments. A smoldering pine sample is yellowish, with organic carbon over 99% of the total carbon, and chars substantially in thermal-optical analysis (TOA), indicating that such liquid organic particles could affect both absorption measurements and TOA of such samples. Similar colored samples collected in the field from rice-straw burning and cook stove emissions also show a similar liquid appearance.     

In situ Diamond Anvil Cell–Raman Spectroscopy and Nanoindentation Study of the Pressure‐Induced Phase Transformation in Pure and Zinc‐Doped β‐Eucryptite

β‐eucryptite (LiAlSiO₄), a member of the family of lithium aluminum silicates, is known to undergo a reversible pressure‐induced phase transformation at ~0.8 GPa to ε‐eucryptite. This study correlates the results between two techniques, in situ diamond anvil cell–Raman spectroscopy and nanoindentation experiments, to explore how doping (substituting Zn for Li) influences this pressure‐induced phase transformation. Diamond anvil cell tests carried up to 3 GPa hydrostatic stress under Raman spectroscopy were compared with nanoindentation results, which provide a more localized, multiaxial stress state. The results indicate that the magnitude of hysteresis observed (difference between the pressures required for the forward and reverse transformation) is lower for Zn‐doped β‐eucryptite; however, the onset of the phase transformation is unchanged by doping with Zn. Furthermore, calculations of activation volume from nanoindentation experiments yield similar values (~0.1 nm³) for pure and Zn‐doped β‐eucryptite, suggesting that the nucleation event that establishes the onset of the phase transformation is the same for both materials.