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Structures and charging of alpha-alumina (0001)/water interfaces studies by sum-frequency vibrational spectroscopy

Description: Sum-frequency vibrational spectroscopy in the OH stretch region was employed to study structures of water/{alpha}-Al{sub 2}O{sub 3} (0001) interfaces at different pH values. Observed spectra indicate that protonation and deprotonation of the alumina surface dominate at low and high pH, respectively, with the interface positively and negatively charged accordingly. The point of zero charge (p.z.c.) appears at pH {approx}6.3, which is close to the values obtained from streaming potential and second harmonic generation studies. It is significantly lower than the p.z.c. of alumina powder. The result can be understood from the pK values of protonation and deprotonation at the water/{alpha}-Al{sub 2}O{sub 3} (0001) interface. The p.z.c. of amorphous alumina was found to be similar to that of powder alumina.
Date: November 10, 2008
Creator: Zhang, L.; Tian, C.; Waychunas, G.A. & Shen, Y.R.
Partner: UNT Libraries Government Documents Department

Reduction of sample volume and waste generation in acid/base titrations using microelectrodes

Description: The Analytical Development Section (ADS) has developed microelectrode methods for use with pH titrations and pH determinations. These microelectrode methods offer increased sensitivity and enable analyses to be done with smaller sample and buffer volumes than are used with standard size electrodes. This report establishes the technical validity of the methods and describes the application of these methods to decreased detection limits, decreased waste generation, and decreased radiation exposure.
Date: March 22, 1996
Creator: Ekechukwu, A.A.
Partner: UNT Libraries Government Documents Department

Transformation of Pb(II) from Cerrusite to Chloropyromorphite in the Presence of Hydroxyapatite under Varying Conditions of pH

Description: Cerrusite (PbC03) is soluble under acidic conditions and considered to be a highly bioavailable soil Pb species. In this study, synthetic cerrusite and hydroxyapatite [Ca5(P04)30H] were reacted under constant and dynamic pH conditions with various P/Pb molar ratios in an attempt to evaluate the effect of reaction kinetics on the formation of chloropyromorphite (Pb5(P04)3Cl) and solubilization of Pb. Under constant pH conditions, dissolution rates of both cerrusite and apatite were rapid when pH was low. Complete conversion of Pb from cerrusite to chloropyromorphite occurred within 60 tin at pH 4 and below when the amount of phosphate in the added apatite was stoichoimetrically equal to that needed to transform all added Pb into chloropyromorphite. The concentration of soluble Pb depended upon the volubility of chloropyromorphite. The dissolution rates of apatite and cerrusite decreased with increasing pH, and the transformation was incomplete at pH 5 and above in the 60 rnin reaction period. The soluble Pb level, therefore, was determined by the volubility of cerrusite. In the dynamic pH system which simulated the gastrointestinal tract (GI tract) system, a complete transformation of Pb from cerrusite to chloropyromorphite was achieved due to the complete dissolution of apatite and cerrusite at the initial low pHs. Chloropyromorphite was the exclusive reaction product in both constant and dynamic pH systems as indicated by XRD analysis. The differences in transformation rate and the control of Pb volubility between the reactions occurring in constant and dynamic pH systems indicate the significance of kinetics in controlling the bioavailability of Pb and the potential for the reaction to occur during ingestion.
Date: October 14, 1998
Creator: Ryan, J.A. & Zhang, P.
Partner: UNT Libraries Government Documents Department

Batch Microreactor Studies of Base Catalyzed Ligin Depolymerization in Alcohol Solvents

Description: The depolymerization of organosolv-derived lignins by bases in methanol or ethanol solvent was studied in rapidly heated batch microreactors. The conversion of lignin to ether solubles by KOH in methanol or ethanol was rapid at 290 "C, reaching the maximum value within 10-15 minutes. An excess of base relative to Lignin monomer units was required for maximum conversion. Strong bases (KOH, NaOH, CSOH) convert more of the lignin to ether soluble material than do weaker bases LiOH, Ca(OH)2, and NacCO2). Ethanol and methanol are converted to acetic and formic acid respectively under the reaction conditions with an activation energy of approximately 50 kcal/mol. This results in a loss of solvent, but more importantly neutralizes the base catalyst, halting forward progress of the reaction.
Date: February 3, 1999
Creator: Evans, L.; Littlewolf, A.; Lopez, M. & Miller, J.E.
Partner: UNT Libraries Government Documents Department

High Precision Measurement of Isotope Effects on Noncovalent Host-Guest Interactions

Description: Isotope effects (IEs) are a powerful tool for examining the reactivity of, and interactions between, molecules. Recently, secondary IEs have been used to probe the nature of noncovalent interactions between guest and host molecules in supramolecular systems. While these studies can provide valuable insight into the specific interactions governing guest recognition and binding properties, IEs on noncovalent interactions are often very small and difficult to measure precisely. The Perrin group has developed an NMR titration method capable of determining ratios of equilibrium constants with remarkable precision. They have used this technique to study small, secondary equilibrium isotope effects (EIEs) on the acidity of carboxylic acids and phenols and on the basicity of amines, measuring differences down to thousandths of a pK{sub a} unit. It occurred to us that this titration method can in principle measure relative equilibrium constants for any process which is fast on the NMR timescale and for which the species under comparison are distinguishable by NMR. Here we report the application of this method to measure very small EIEs on noncovalent host-guest interactions in a supramolecular system.
Date: June 23, 2009
Creator: Mugridge, Jeffrey S.; Bergman, Robert G. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

Controlled Assembly of Heterobinuclear Sites on Mesoporous Silica: Visible Light Charge-Transfer Units with Selectable Redox Properties

Description: Mild synthetic methods are demonstrated for the selective assembly of oxo-bridged heterobinuclear units of the type TiOCrIII, TiOCoII, and TiOCeIII on mesoporous silica support MCM-41. One method takes advantage of the higher acidity and, hence, higher reactivity of titanol compared to silanol OH groups towards CeIII or CoII precursor. The procedure avoids the customary use of strong base. The controlled assembly of the TiOCr system exploits the selective redox reactivity of one metal towards another (TiIII precursor reacting with anchored CrVI centers). The observed selectivity for linking a metal precursor to an already anchored partner versus formation of isolated centers ranges from a factor of six (TiOCe) to complete (TiOCr, TiOCo). Evidence for oxo bridges and determination of the coordination environment of each metal centers is based on K-edge EXAFS (TiOCr), L-edge absorption spectroscopy (Ce), and XANES measurements (Co, Cr). EPR, optical, FT-Raman and FT-IR spectroscopy furnish additional details on oxidation state and coordination environment of donor and acceptor metal centers. In the case of TiOCr, the integrity of the anchored group upon calcination (350 oC) and cycling of the Cr oxidation state is demonstrated. The binuclear units possess metal-to-metal charge-transfer transitions that absorb deep in the visible region. The flexible synthetic method for assembling the units opens up the use of visible light charge transfer pumps featuring donor or acceptor metals with selectable redox potential.
Date: June 4, 2008
Creator: Frei, Heinz; Han, Hongxian & Frei, Heinz
Partner: UNT Libraries Government Documents Department

Feasibility of Large-Scale Ocean CO2 Sequestration

Description: The project accomplishments in 2005 have been exceptional, and have seen radical new techniques successfully devised and implemented. At the outset the goal set was to create a system dubbed FOCE--Free Ocean CO{sub 2} Enrichment--for investigating the impact of rapidly growing ocean CO{sub 2} levels from passive absorption by the surface ocean. A paper describing progress in this area is included with this report. On June 29, 2005 the P.I. presented a seminar on this work at NETL, and after discussion with Program Officers it was suggested that a return to the original project focus of investigating direct disposal techniques, rather than passive disposal effects, should be undertaken. This suggestion was rapidly acted upon, and in November 2005 a major field breakthrough was accomplished in collaboration with colleagues from NETL, MIT, and AIST (Japan). In this effort the real time three-dimensional acoustic detection of a freely released small-scale CO{sub 2} plume was accomplished. In addition we have successfully field tested the theoretical model of Zeebe and Wolf-Gladrow for CO{sub 2} system kinetics at depth, thus leading to more accurate prediction of the local pH perturbations of a CO{sub 2} plume.
Date: December 1, 2005
Creator: Brewer, Peter G. & Barry, James
Partner: UNT Libraries Government Documents Department

Improved Processes to Remove Naphthenic Acids

Description: In the past three years, we followed the work plan as we suggested in the proposal and made every efforts to fulfill the project objectives. Based on our large amount of creative and productive work, including both of experimental and theoretic aspects, we received important technical breakthrough on naphthenic acid removal process and obtained deep insight on catalytic decarboxylation chemistry. In detail, we established an integrated methodology to serve for all of the experimental and theoretical work. Our experimental investigation results in discovery of four type effective catalysts to the reaction of decarboxylation of model carboxylic acid compounds. The adsorption experiment revealed the effectiveness of several solid materials to naphthenic acid adsorption and acidity reduction of crude oil, which can be either natural minerals or synthesized materials. The test with crude oil also received promising results, which can be potentially developed into a practical process for oil industry. The theoretical work predicted several possible catalytic decarboxylation mechanisms that would govern the decarboxylation pathways depending on the type of catalysts being used. The calculation for reaction activation energy was in good agreement with our experimental measurements.
Date: December 9, 2005
Creator: Zhang, Aihua; Ma, Qisheng; Wang, Kangshi; Tang, Yongchun & Goddard, William A.
Partner: UNT Libraries Government Documents Department

Ming Parameter Input: Emma Model Redox Half Reaction Equation Deltag G Corrections for pH

Description: The purpose of this calculation is to provide appropriate input parameters for use in MING V 1.0 (CSCI 300 18 V 1.0). This calculation corrects the Grogan and McKinley (1990) values for {Delta}G so that the data will function in the MING model. The Grogan and McKinley (1990) {Delta}G data are presented for a pH of 12 whereas the MING model requires that the {Delta}G be reported at standard conditions (i.e. pH of 0).
Date: July 23, 1998
Creator: Jolley, D.M.
Partner: UNT Libraries Government Documents Department

"Smart" Multifunctional Polymers for Enhanced Oil Recovery

Description: Herein we report the synthesis and solution characterization of a novel series of AB diblock copolymers with neutral, water-soluble A blocks comprised of N,N-dimethylacrylamide (DMA) and pH-responsive B blocks of N,N-dimethylvinylbenzylamine (DMVBA). To our knowledge, this represents the first example of an acrylamido-styrenic block copolymer prepared directly in homogeneous aqueous solution. The best blocking order (using polyDMA as a macro-CTA) was shown to yield well-defined block copolymers with minimal homopolymer impurity. Reversible aggregation of these block copolymers in aqueous media was studied by {sup 1}H NMR spectroscopy and dynamic light scattering. Finally, an example of core-crosslinked micelles was demonstrated by the addition of a difunctional crosslinking agent to a micellar solution of the parent block copolymer. Our ability to form micelles directly in water that are responsive to pH represents an important milestone in developing ''smart'' multifunctional polymers that have potential for oil mobilization in Enhanced Oil Recovery Processes.
Date: October 15, 2005
Creator: McCormick, Charles & Lowe, Andrew
Partner: UNT Libraries Government Documents Department

Anodonta imbecillis QA Test 1, Clinch River - Environmental Restoration Program (CR-ERP)

Description: Toxicity testing of split whole sediment samples using juvenile freshwater mussels (Anodonta imbecillis) was conducted by TVA and CR-ERP personnel as part of the CR-ERP biomonitoring study of Clinch River sediments to provide a quality assurance mechanism for test organism quality and overall performance of the test. In addition, testing included procedures comparing daily renewal versus non-renewal of test sediments. Testing of sediment samples collected July 15 from Poplar Creek Miles 6.0 and 5.1 was conducted from July 21-30, 1993. Results from this test showed no toxicity (survival effects) to fresh-water mussels during a 9-day exposure to the sediments. Side by side testing of sediments with daily sediment renewal and no sediment renewal showed no differences between methods. This may be due to the absence of toxicity in both samples and may not reflect true differences between the two methods for toxic sediment.
Date: June 1, 1997
Creator: Simbeck, D.J.
Partner: UNT Libraries Government Documents Department

Development of the indicator-photopolymer chemistries for multianalyte sensor arrays

Description: Remediation of ground and waste water facilities requires the analysis of the pollutants. Multianalyte fiber-optic chemical sensors based on indicators have been developed, with multiple indicators immobilized at the distal end of a single imaging fiber. By coupling the imaging fibers to a charge coupled device detector, one can spatially and spectrally discriminate the multiple sensing sites and hence monitor multiple analyte concentrations simultaneously. This report describes the development of the indicator chemistry and immobilization procedures developed for pH, Al{sup 3+}, and hydrocarbons. A polymer matrix is used to mass transfer the analyte to the indictor.
Date: January 1, 1995
Creator: Healey, B.G.; Chadha, S.; Walt, D.R.; Richards, J.B.; Brown, S.B. & Milanovich, F.P.
Partner: UNT Libraries Government Documents Department

Consequence analysis of a NaOH solution spray release during addition to waste tank. Revision 2

Description: Toxicological consequences are presented for three postulated accidents involving caustic soda (sodium hydroxide) addition to a waste tank to adjust the tank waste pH. These are spray from the skid mounted delivery system, spray from a cargo tank truck, and rupture of a cargo tank truck. Consequences for the onsite and offsite receptor are calculated.
Date: July 8, 1997
Creator: Van Vleet, R.J. & Lancing, L.C.
Partner: UNT Libraries Government Documents Department

Effect of pH on the growth of KDP

Description: The acidity of KDP salt solution is one of the important parameters. This parameter determines a lot of properties of solution, crystallization processes in solution, properties of grown crystals. An alteration of the KDP salt solution acidity changes it`s properties such as KDP salt volubility, stability of the KDP solution, solution density, solution viscosity, solution heat capacity, etc. It also changes state of impurities in the solution and characteristics of interaction between growing faces of the crystal and solution impurities. As a result kinetics of crystallization changes, habit and physical properties of the grown crystal change too. It should be mentioned that investigations in were done for low rate processes of crystal growth. Here we report the results of our investigations which have been done for high rate crystal growth processes (R{sub Z} {approx} 20 mm/day).
Date: March 20, 1998
Creator: Rashkovich, L. N.
Partner: UNT Libraries Government Documents Department

Production and preliminary testing of multianalyte imaging sensor arrays

Description: This report covers the production and preliminary testing of fiber optic sensors that contain a discrete array of analyte specific sensors on their distal ends. The development of the chemistries associated with this technology is covered elsewhere.
Date: November 1, 1994
Creator: Richards, J.B.; Brown, S.B.; Milanovich, F.P.; Healey, B.G.; Chadha, S. & Walt, D.R.
Partner: UNT Libraries Government Documents Department

Electrodissolution of electrodeposited iron oxides

Description: Galvanostatic reduction of ferric oxide was studied in phosphate solutions over a range of pH values. The oxides were prepared on gold by anodic electrodeposition from dilute ferrous borate solution. With increased pH, the potential of the reduction arrests decreased and the charge associated with the arrest increased. A dependence of -60 mV/pH was observed except between pH 7.5 and 8.5 where the slope approximated -180 mV/pH. Above pH 7.5 the slope was consistent with the thermodynamic predicted slope of -180 mV/pH expected from reductive dissolution of ferric oxide forming soluble ferrous ions. At higher pH values, a slope of -60 mV/pH has been accounted for by oxide reduction to form a solid lower valent oxide.
Date: December 31, 1996
Creator: Isaacs, H.S.; Ryan, M.P.; Kalonousky, D.N. & Virtanen, S.
Partner: UNT Libraries Government Documents Department

Consequence analysis of a NaOH solution spray release during addition to waste tank

Description: Toxicological consequences were calculated for a postulated maximum caustic soda (NaOH) solution spray leak during addition to a waste tank to adjust tank pH. Although onsite risk guidelines were exceeded for the unmitigated release, site boundary consequences were below the level of concern. Means of mitigating the release so as to greatly reduce the onsite consequences were recommended. Consequences for the mitigated release were estimated and both onsite and offsite consequences were found to negligible.
Date: October 9, 1996
Creator: Himes, D.A., Westinghouse Hanford Co.
Partner: UNT Libraries Government Documents Department

Exploring the conformational energy landscape of proteins

Description: Proteins possess a complex energy landscape with a large number of local minima called conformational substates that are arranged in a hierarchical fashion. Here we discuss experiments aimed at the elucidation of the energy landscape in carbonmonoxy myoglobin (MbCO). In the highest tier of the hierarchy, a few taxonomic substates exist. Because of their small number, these substates are accessible to detailed structural investigations. Spectroscopic experiments are discussed that elucidate the role of protonations of amino acid side chains in creating the substates. The lower tiers of the hierarchy contain a large number of statistical substates. Substate interconversions are observed in the entire temperature range from below 1 K up to the denaturation temperature, indicating a wide spectrum of energy barriers that separate the substates.
Date: April 1, 1997
Creator: Nienhaus, G.U.; Mueller, J.D. & McMahon, B.H.
Partner: UNT Libraries Government Documents Department

Chemical and isotopic variations of precipitation in the Los Alamos Region, New Mexico

Description: Precipitation collectors were installed at 14 locations on the Pajarito Plateau and surrounding areas to study variations in chemistry, stable isotopes and tritium for the years 1990 to 1993. The volume of precipitation was measured and samples were collected and analyzed every three to four months. All precipitation samples contain <2.50 mg/kg Cl and have pH values ranging from 5.4 to 6.7. The stable isotope ({delta}D/{delta}{sup 18}O) results record seasonal variations in precipitation as the weather patterns shift from sources in the Pacific Ocean to sources in the Gulf of Mexico. The stable isotope results also show isotopic variations due to elevation differences among the collection points. The tritium contents ({sup 3}H) in rain samples vary from 6.54 T.U. to 141 T.U. Contouring of high tritium values (e.g. >20 T.U.) from each collection period clearly shows that Laboratory activities release some tritium to the atmosphere. The effect of these releases are well below the limits set by the Environmental Protection Agency for drinking water (about 6200 T.U.). The magnitude of the releases is apparently greatest during the summer months. However, anomalous tritium values are detected as far north as Espahola, New Mexico for many collection periods. Tritium releases by the Laboratory are not constant; thus, the actual amount of tritium in each release has been diluted in the composite samples of our three to four month collection periods.
Date: February 1, 1995
Creator: Adams, A.I.; Goff, F. & Counce, D.
Partner: UNT Libraries Government Documents Department

Patterned functional arrays by selective de-wetting

Description: Using a micro-Contact Printing ({mu}-CP) technique, substrates are prepared with patterns of hydrophilic, hydroxyl-terminated SAMS and hydrophobic methyl-terminated SAMS. Beginning with a homogeneous solution of silica, surfactant, ethanol, water, and functional silane, preferential ethanol evaporation during dip-coating, causes water enrichment and selective de-wetting of the hydrophobic SAMS. Correspondingly, film deposition occurs exclusively on the patterned hydrophilic SAMS. In addition, by co-condensation of tetrafunctional silanes (Si(OR){sub 4}) with tri-functional organosilanes ((RO){sub 3}Si(CH{sub 2}){sub 3}NH{sub 2}), the authors have selectively derived the silica framework with functional amine NH{sub 2} groups. A pH sensitive, micro-fluidic system was formed by further conjugation reactions with pH sensitive dye molecules.
Date: May 11, 2000
Partner: UNT Libraries Government Documents Department

Dissolution of Oxide Films on Aluminum in Near Neutral Solutions

Description: Simple linear potentiodynamic cycling measurements have been made on abraded pure Al in borate, chromate, phosphate, sulfate and nitrate solutions. In borate and chromate solutions the currents continued to decrease with each subsequent cycle. In phosphate dissolution of the oxide takes place producing repetitive repeat curves. The current variations in borate and chromate were simulated using a high field conduction oxide growth model. Including oxide dissolution in the model simulated the phosphate behavior. Results in sulfate and nitrate solutions were more complex. The behavior in the sulfate solution was attributed to effects of sulfate the oxide/solution interface.
Date: October 17, 1999
Creator: Isaacs, Hugh S.; Xu, Feng & Jeffcoate, Carrol S.
Partner: UNT Libraries Government Documents Department