Showing papers on "Dissolution published in 1986"
TL;DR: In this article, the dissolution kinetics of slightly soluble oxides and silicates are controlled by chemical processes at the surface, and the reaction controlling steps can be interpreted in terms of a surface coordination model.
635 citations
Book•
31 Mar 1986TL;DR: In this paper, Upendra Singh and Goro Uehara Chemical Modeling of Ion Adsorption in Soils, John M Zachara and John C Westall Thermodynamics of Soil Solution, Donald L Suarez Kinetics and Mechanisms of Chemical reactions at the Soil Mineral/Water Interface.
Abstract: Electrochemistry of the Double Layer: Principles and Applications to Soils, Upendra Singh and Goro Uehara Chemical Modeling of Ion Adsorption in Soils, John M Zachara and John C Westall Thermodynamics of the Soil Solution, Donald L Suarez Kinetics and Mechanisms of Chemical reactions at the Soil Mineral/Water Interface, Donald L Sparks Precipitation/Dissolution Reactions in Soils, Wayne P Robarge The Chemistry of Soil Organic Matter, Nicola Senesi and Elisabetta Loffredo Characterizing Soil Redox Behavior, Richmond J Bartlett
498 citations
TL;DR: The dissolution of goethite and other iron oxides is kinetically controlled by the detachment of an Fe center from the surface as discussed by the authors, which may occur either by direct reduction, subsequent to the adsorption of reductants, or, indirectly by electron transfer from dissolved Fe(II) ions which are generated by the same reductant in solution.
472 citations
TL;DR: The dissolution rate of albite has been measured as a function of pH and time at 25°C and 70°C in a single-pass flow-through leaching apparatus as mentioned in this paper.
328 citations
TL;DR: Pore water profiles of uranium and thorium isotopes in the muddy sediments of Buzzards Bay, MA permit an assessment of the effect of diagenetic redox reactions on the geochemical behavior of these elements as mentioned in this paper.
233 citations
TL;DR: In this paper, the authors use the IR absorption bands coming from chemical bulk groups of the solid as internal standards to characterize the influence of pH and electrolyte ions on reactions that occur a t lor near the solid-solution interface.
Abstract: droxide surface sites, characteristics of water a t the interface, and chemical structures of specifically adsorbed molecules. Also, ATR-CIR spectroscopy can qualitatively describe the influence of pH and “inert” electrolyte ions on reactions that occur a t lor near the solid-solution interface. Finally, since signal intensity is not necessarily proportional to the concentration of goethite (unless two systems have the same degree of dispersivity), this technique can be regarded as semiquantitative if and only if IR absorption bands coming from chemical bulk groups of the solid are used as internal standards. Consequently, ATR-CIR spectroscopy offers an in situ means of studying some very important reactions which occur at the solid-water interface such as photocatalysis, surface redox reactions, interfacial complexation, and ion-exchange reactions. By using such an analytical tool as ATR-CIR we should eventually be able to understand the complex nature of surface reaction stoichiometries which will in turn lead to better predictive models. Since aqueous interfacial reaction chemistry is important to a broad array of processes including mineral dissolution and flotation, corrosion, heterogeneous catalysis, and microcontaminant transport, this technique promises to be used a great deal more in the future.
219 citations
TL;DR: In this article, the role of surface chemistry and defects in the formation of etch pits in minerals is analyzed, and Elastic properties, surface free energies, and dislocation characteristics are incorporated into a theory which predicts the outcome of dislocation-controlled dissolution for a variety of free energies of reaction with aqueous solutions.
208 citations
TL;DR: The study of the relationship between the dissolution rates of organic compounds that are sparingly soluble in water and the biodegradation of these compounds by mixed cultures of bacteria suggests that spontaneous dissolution rates are only one of the factors that govern the rates of biodegrades.
Abstract: We conducted a study of the relationship between the dissolution rates of organic compounds that are sparingly soluble in water and the biodegradation of these compounds by mixed cultures of bacteria. The rates of dissolution of naphthalene and 4-chlorobiphenyl were directly related to their surface areas. The bacteria caused a decline in the concentration of the soluble substrate. The rate of bacterial growth fell abruptly when 4-chlorobiphenyl or naphthalene was no longer detectable in solution. The population continued to increase in media with different surface areas of insoluble 4-chlorobiphenyl, but the final counts were higher in media in which the surface areas of the substrate were larger. The rates of dissolution of palmitic acid, octadecane, di(2-ethylhexyl) phthalate, and 1-naphthyl N-methylcarbamate were determined in the absence of microorganisms. A mixed culture of microorganisms mineralized palmitic acid, di(2-ethylhexyl) phthalate, and Sevin (1-naphthyl N-methylcarbamate) at a logarithmic rate, but octadecane mineralization was linear. The rates of mineralization at the end of the active phase of the biodegradation were lower than the rate of dissolution of palmitic acid but higher than the rate of dissolution of octadecane in the uninoculated medium. We suggest that spontaneous dissolution rates are only one of the factors that govern the rates of biodegradation.
172 citations
TL;DR: The condensation polymerization between silicic acid and silica surfaces has been studied in the absence of nucleation, by seeding silic acid solutions with colloidal amorphous silica particles of known surface area.
161 citations
Patent•
12 Mar 1986TL;DR: In this paper, a molecular spray is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder, which is discharged in the form of long, thin fibers.
Abstract: Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a heated nozzle having a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. In another embodiment, the temperature of the solution and nozzle is elevated above the melting point of the solute, which is preferably a polymer, and the solution is maintained at a pressure such that, during expansion, the solute precipitates out of solution within the nozzle in a liquid state. Alternatively, a secondary solvent mutually soluble with the solute and primary solvent and having a higher critical temperature than that of primary solvent is used in a low concentration (<20%) to maintain the solute in a transient liquid state. The solute is discharged in the form of long, thin fibers. The fibers are collected at sufficient distance from the orifice to allow them to solidify in the low pressure/temperature region.
154 citations
Patent•
12 Mar 1986TL;DR: A molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder is vaporized and pumped away as mentioned in this paper.
Abstract: Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. The solvent is vaporized and pumped away. Solution pressure is varied to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solution temperature is varied in relation to formation of a two-phase system during expansion to control porosity of the film or powder. A wide variety of film textures and powder shapes are produced of both organic and inorganic compounds. Films are produced with regular textural feature dimensions of 1.0-2.0 μm down to a range of 0.01 to 0.1 μm. Powders are formed in very narrow size distributions, with average sizes in the range of 0.02 to 5 μm.
TL;DR: In this paper, it was shown that reliable equilibrium solubilities and solubility-derived ΔG f 0 values can neither be rigorously determined by conventional experimental procedures, nor applied in equilibriabased models of smectite-water interactions.
TL;DR: A mixing-tank model is used to simulate GI absorption of nonionized drugs and correctly predicts bioavailability as a function of particle size for both of these poorly soluble drugs.
TL;DR: In this article, Enthalpies of dissolution of nalkan-1-ols in H2O and in D2O have been determined calorimetrically at different temperatures.
TL;DR: Experimental deformation by pressure solution was performed on an aggregate of small grains subjected to deviatoric stress (50 MPa) for a long time (several weeks or months) at relatively high temperature and pressure in contact with various fluids (air, water, 0.1 to 1 N NaOH for quartz, water and 5% NH 4 Cl for calcite).
TL;DR: In this article, two solvent-mediated phase transformations, one for a dyestuff, the other for paclobutrazol, a plant growth regulator manufactured by ICI, have been studied.
TL;DR: In this paper, a surface complex formation model was used to describe the removal of fluoride by activated alumina, and the intrinsic constants, pKa1int and pKa2int, are 4.2 and 10.5, respectively, in 0.05 M NaClO4, and density of Bronsted acid sites is approximately 5.6×1013/cm2.
Abstract: Fluoride removal by activated alumina, Type F‐1, depends primarily on the pH and surface loading. The optimal pH for fluoride removal is approximately 5. However, at pH<6.0, the aluminum (III) dissolved from activated alumina reacts with fluoride ions and forms alumino‐fluoro complexes. These complexes are unstable in neutral or alkaline pH regions. Consequently, the role of pH in minimizing alumina dissolution as opposed to maximizing fluoride removal must be considered. An alkalimetric titration method was used to determine the surface acidity of the activated alumina. The intrinsic constants, pKa1int and pKa2int, are 4.2 and 10.5, respectively, in 0.05 M NaClO4, and the density of Bronsted acid sites is approximately 5.6×1013/cm2. A surface complex formation model was used to describe the removal of fluoride by activated alumina. These reaction mechanisms can be identified as a surface complex formation involving Al¯OH and Al¯OH2+. Polynuclear surface complex may be formed at high surface loading.
TL;DR: In this article, an HCl-HNO/sub 3/HF polycarbonate bomb dissolution technique using microwave heating was used for the rapid decomposition of geologic samples.
Abstract: A total of 51 geologic reference materials, including rocks, stream sediments, sulfide ores, and soils, were analyzed in evaluating a procedure for the rapid decomposition of geologic samples. The decomposition procedure consists of an HCl-HNO/sub 3/-HF polycarbonate bomb dissolution technique, using microwave heating. The resulting solutions were analyzed by inductively coupled plasma optical emission spectroscopy (ICPOES); the residues remaining were analyzed by dc arc spectrography. The dissolution technique provides recoveries greater than 95% of most elements in most of the materials studied; low recoveries of Al, Cr, Li, Pb, Si, and Zr are observed when refractory mineral phases are present. With this method, as many as 100 samples per person per day can be prepared for analysis.
TL;DR: In this article, pressure solution experiments were carried out, using a quartz knife-edge 0.26 mm wide on halite single crystals in halite saturated solutions, to observe the detailed development of pressure solution contacts and the rates of pressure solutions.
TL;DR: In this paper, a reaction model for the dissolution-passivation process of iron-chromium alloy in acidified sulfate media is proposed, where the reaction mechanism of alloy is depicted as that of iron perturbed by the chromium addition.
TL;DR: Corrosion of sintered alpha-SiC under thin films of Na2CO3/CO2, Na2SO4/O2, and Na2 SO4/SO3 was investigated at 1000 C as mentioned in this paper.
Abstract: Corrosion of sintered alpha-SiC under thin films of Na2CO3/CO2, Na2SO4/O2, and Na2SO4/SO3 was investigated at 1000 C. Chemical analysis was used to follow silicate and silica evolution as a function of time. This information coupled with morphology observations leads to a detailed corrosion mechanism. In all cases the corrosion reactions occur primarily in the first few hours. In the Na2CO3/CO2 case, rapid oxidation and dissolution lead to a thick layer of silicate melt in about 0.25 h. After this, silica forms a protective layer on the carbide. In the Na2SO4/O2 case, a similar mechanism occurs. In the Na2SO4/SO3 case, a porous nonprotective layer of SiO2 grows directly on the carbide, and a silicate melt forms above this. In addition, SiO2 and regenerated Na2SO4 form at the melt/gas interface due to reaction of silicate with SO3 and SO2 + O2. The reaction slows when the lower silica layer becomes nonporous.
TL;DR: In this article, the preparation of oxynitride glass by melting sodium metaphosphate in anhydrous ammonia is described, and models for nitrogen dissolution are used to calculate the glass composition from the measured weight loss and analyzed nitrogen content.
Abstract: The preparation of oxynitride glass by melting sodium metaphosphate in anhydrous ammonia is described. Glasses containing up to ≈ 12 wt% nitrogen were prepared with the nitrogen content depending upon the melting temperature, time, and ammonia flow rate through the furnace. Nitriding the NaPO 3 starting glass decreased the dissolution rate in water and thermal expansion coefficient while increasing the dilatometric softening temperature, glass transition temperature, refractive index, and microhardness. Oxynitride glasses were considerably more difficult to crystallize than the starting NaPO 3 glass. Models for nitrogen dissolution are used to calculate the glass composition from the measured weight loss and analyzed nitrogen content.
TL;DR: In this article, the retention of 100 eV deuterium and tritium ions in POCO AXF•5Q graphite has been measured for the temperature range 323 −1773 K.
Abstract: The retention of 100 eV deuterium and tritium ions in POCO AXF‐5Q graphite has been measured for the temperature range 323–1773 K. Both nuclear reaction analysis and dissolution counting were used. Below 1000 K, the retention is thought to be characterized by saturation of the near‐surface region and by surface diffusion on internal porosity. Above 1000 K, the retention appears to be controlled by transgranular diffusion with decoration of high energy traps.
TL;DR: In this article, phase solubility studies revealed a 12-fold increase in the Solubility of ibuprofen and the formation of an insoluble microcrystalline complex in the presence of high concentration of β-cyclodextrin (β-CD).
TL;DR: In this article, a modele mathematique decrivant les oscillations de courant observees dans le systeme fer-acide sulfurique sous des conditions potentiostatiques is presented.
Abstract: Presentation d'un modele mathematique decrivant les oscillations de courant observees dans le systeme fer-acide sulfurique sous des conditions potentiostatiques. Ce modele suppose que les oscillations sont dues a un cycle continu d'une portion d'electrode entre les etats passif et actif
TL;DR: Tole and Lasaga as mentioned in this paper showed that the dissolution rate of nepheline is determined by the ratio of the rate of input of an ion into solution by dissolution and its removal from solution by precipitation or adsorption, such that, for a first order precipitation reaction, C final = Ak + A'k − + C ieq, where A is the surface area of the precipitated phase.
TL;DR: In this paper, the depth distributions of hydroxylamine/acetic acid-extractable Co and Cd were determined in box-cores from a series of stations along the 1200 Km length of the Laurentian Trough.
TL;DR: In this paper, the authors investigated the solubility of various aromatic solutes in miscible, polar solvent/water mixtures through experiment and interpreted through chemical thermodynamic models, and they found that there was a semi-logarithmic increase in solutability with increasing solvent volume fraction.
Abstract: The solubility of various aromatic solutes in miscible, polar solvent/water mixtures was investigated through experiment and interpreted through chemical thermodynamic models. Eighteen solute/solvent/water systems were evaluated that represented different properties with respect to hydrogen bonding and functional group substitution. The presence of appreciable (i.e., percent by volume) organic solvent in the aqueous phase had a very large effect on the solubility of the more hydrophobic solutes. In general it was observed that there was a semi‐logarithmic increase in solubility with increasing solvent volume fraction. The increase in solute solubility with solvent volume fraction could be predicted by several chemical thermodynamic techniques, for which the accuracy improved with the extent of use of experimental data to account for nonideal effects. The results of this study are useful to understand solute physico‐chemical properties in heavily contaminated systems, such as in certain industrial wastewat...