Download or read book Calcite Dissolution and Ca Na Ion exchange Reactions in Columns with Different Flow Rates Through High ESR Soil written by Audrey Navarre and published by . This book was released on 1999 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Miscible Displacement and Cation Exchange in Saturated and Unsaturated Soil Columns written by Ozdemir Beyce and published by . This book was released on 1964 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrodynamics of Calcium arrow Sodium Exchange in Soil Columns written by Arturo Cornejo and published by . This book was released on 1971 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applicability of Boyd s Exchange Equations to Cation Exchange in Soil Columns written by Emmet Lewis Greacen and published by . This book was released on 1949 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Calcite Dissolution Kinetics and Solubility in Na Ca Mg Cl Brines of Geologically Relevant Composition at 0 1 to 1 Bar PCO2 and 25 to 80 C written by Dwight Kuehl Gledhill and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sedimentary basins can contain close to 20% by volume pore fluids that are commonly classified as brines. These fluids can become undersaturated with respect to calcite as a result of processes such as migration, dispersive mixing, or anthropogenic injection of CO2. This study measured calcite solubility and dissolution rates in geologically relevant Na-Ca-Mg-Cl synthetic brines (35 to 200 g L−1 TDS). In brines 50 g L−1 TDS, the EQPITZER calculated calcium carbonate ion activity product (IAP) at steady-state was in reasonable agreement ("10%) with the thermodynamic solubility constant for calcite (K[subscript]c). However, the IAP systematically exceeded K[subscript]c in more concentrated brines. The deviation was strongly correlated with calcium concentration and also was observed in magnesium-free solutions. This is interpreted as an uncertainty in the carbonate ion activity coefficient, and minor adjustment in stoichiometric association constants (K*[subscript]M2+CO0[over]3) for the CaCO0[over]3 or MgCo0[over]3 ion pairs would correct for the error. The dissolution rate dependency on brine composition, pCO2 (0.1 to 1 bar), and temperature (25.0 to 82.5 °C) was modeled using the empirical rate equation R = k(1-[omega]0 [superscript]n where R is the rate, k and n are empirical fitting terms, and [omega] the degree of disequilibrium with respect to calcite. When [omega] was defined relative to an apparent kinetic solubility, n could be assumed first-order over the range of [omega] investigated ([omega] = 0.2 to 1.0). Rates increased with increasing pCO2 as did the sensitivity to brine concentration. At 0.1 bar, rates were nearly independent of concentration (k = 13.0 "2.0 x 10−3 moles m−1 hr−1). However, at higher CO2 partial pressures rates became composition dependent and the rate constant, k, was shown to be a function of temperature, pCO2, ionic strength, and calcium and magnesium activity. The rate constant (k) can be estimated from a multiple regression (MR) model of the form [unable to replicate formula]. A relatively high activation energy (E[subscript]a = 20 kJ mol−1) was measured, along with a stirring rate independence suggesting the dissolution is dominated by surface controlled processes at saturation states [omega] 0.2 in these calcium-rich brines. These findings offer important implications to reaction-transport models in carbonate-bearing saline reservoirs.

Download or read book Cation Transport in Soils and Factors Affecting Soil Carbonate Solubility written by J. J. Jurinak and published by . This book was released on 1973 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diffusion of Cations in Various Soil Systems written by Cheng-yin Cheng and published by . This book was released on 1960 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ion Exchange induced Dissolution of Calcite in Na montmorillonite CaCO3 Systems written by Jose Bruno Del Rio Durand and published by . This book was released on 1990 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ionic Exchange Reactions in Clays written by Krishnamoorthy Chivukula and published by . This book was released on 1949 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Public Roads of Tennessee written by and published by . This book was released on 1906 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Leaching Effects with High Sodium Waters on Chloride and Bicarbonate Salinized Soil Columns written by Kenneth Kazuo Tanji and published by . This book was released on 1961 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Calcite and Calcium Oxalate Sequestration of Heavy Metals written by S. Chatterjee (Sabyasachi) and published by . This book was released on 2009 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy metals like cadmium, lead and zinc pose a significant threat to human health and environment. Several factors such as pH, EH, organic matter and clay content of the soil affect the bioavailability of such heavy metals in the environment. The presence of several naturally occurring minerals such as calcite (calcium carbonate, CaCO3) and calcium oxalate (CaC2O4.) in the environment significantly influence the fate and transport of some of the heavy metal cations. Sequestration of heavy metals such as cadmium (Cd) and zinc (Zn) from solution by calcite has been clearly demonstrated in the literature. However, studies on heavy metal sequestration by calcite and calcium oxalate from a multi-metal environmental that represents real world situations are rare. In this contribution, column flow studies of Cd and Zn sequestration by calcite exposed to influent solutions saturated or non-saturated with calcite and containing either 1 mg/L of Cd, 1 mg/L of Zn or combined 1 mg/L of Zn and Cd, followed by desorption of the sequestered metals were conducted. Complementary scanning electron microscopy (SEM) coupled with electron dispersive x-ray spectroscopy (EDS) data were generated. Kinetic studies show that reaction rates of Cd and Zn with calcite are governed by a simple rate law with reaction orders of less than 1 (0.02 - 0.07) indicating at least mathematically, the occurrence of reactions that went to completion if the reaction orders did not change. When the influent solution contains a single cation, the rate of Zn removal from solution by calcite and calcium oxalate is greater than Cd removal rate. However in a multi-cation environment, cadmium removal rate was greater than zinc removal rate. MINTEQA2 a geochemical equilibrium speciation model was used to compute the equilibrium between the various species in the cation-calcite environment. Complimentary desorption studies and surface SEM/EDS analysis indicate that the removal of Cd and Zn from solution by calcite and calcium oxalate is probably due to precipitation/complexation reaction. The SEM and EDS results appear to confirm the presence of a precipitate on the mineral surface in the case of the influent solution containing Zn. The current research also examines the effect of citrate, a commonly present urinary tract species on calcium oxalate dissolution. The dissolution studies indicate that citrate solution is capable of dissolving sodium oxalate at high pH. The dissolution of calcium oxalate results in the release of heavy metals that were previously sequestered within the mineral. Results show that a greater percentage of zinc was removed than cadmium, from calcium oxalate due to its dissolution by citrate.

Download or read book The Effects Of Dilute Organic Acids On Calcite Dissolution At 22 Degrees And 10 5 PA Total Pressure written by Teresa A. DeMaio and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of dilute organic acids on calcite dissolution is important given the abundance of calcite and its importance in controlling surface and ground water geochemistry. The dissolution of calcite in the presence of three organic ligands, citrate, oxalate, and phthalate, has been investigated at 22° C and 10^5 Pa total pressure in a stirred, flow-through reactor. The input fluids were low salinity (I ranged from 0.001 to 0.02), Na-Ca-HCO3-CI solutions having an initial pH of 7.8. The dissolution rate of calcite in a ligand-free solution is essentially linear with respect to log undersaturation. In a purely inorganic solution, the dissolution rate equals 5.95 x 10·13 mol cm^-2 sec^-1 at log (IAP/K) of -1.25 and a surface area of 1890 cm^2/g. Concentrations of the ligands range from 10 to 5000 μm/1. Citrate at a concentration of 50 μm/1 appears to have no effect on calcite dissolution rates. Oxalate, at concentrations of 50 and 100 μm/l, decreases the rate of calcite dissolution. The dissolution rate of calcite in a solution containing 50 μM oxalate at log (IAP/K) -1.25 is approximately 2.60 x 10^-13 mol cm^-2 sec^-1. Phthalate decreases calcite dissolution at low concentrations, i.e., up to 50 μm/l. In some cases, the calcite dissolution rates were decreased to less than 10% of the rates found in the purely inorganic solution. For example, at a concentration of 50 μM phthalate, the calcite dissolution rate was approximately 0.49 x 10^-13 mol cm^-2 sec^-1. The decrease in calcite dissolution at low concentrations is believed due to the ligand complexing with surface dissolution sites. Higher concentrations of phthalate, 100 to 5000 μm/1, actually increase the rate of dissolution relative to changes due to simple IAP/K parameters. At a concentration of 100 μm/l phthalate, the calcite dissolution rate is 3.92 mol cm^-2 sec^-1 x 10^-13 at log (IAP/K) of -1.25. This increase in calcite dissolution is thought to be caused by the destabilization of surface sites. Calcite surfaces were examined by SEM at magnifications up to 4000x. Different organic ligands produce different etch and dissolution features.

Download or read book Ion exchange and Calcium Carbonate Solubility in Calcareous Sodic Soils written by Gonzalo Cruz Romero and published by . This book was released on 1968 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cation Exchange in Soils written by Walter Pearson Kelley and published by . This book was released on 1948 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: History of cation exchange. The cation-exchange material. Cation-exchange equations. Principles of cation exchange. Exchange capacity and kind of exchangeable cation in various soil types. The determination of exchangeable cations. Cation exchange in relation to soil properties. Identification and estimation of the clay materials.

Download or read book Calcite Reaction Kinetics in Saline Waters written by David Finneran and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of ionic strength (I), pCO2, and temperature on the reaction kinetics of calcite was investigated in magnesium-free, phosphate-free, low calcium (mCa^2+ =~ 0.01--0.02 molal) simple KCl and NaCl solutions from both undersaturated and oversaturated conditions. First order kinetics were found sufficient to describe the dissolution rate data. Dissolution rates decreased with increasing I and were faster in KCl than NaCl solutions at the same I indicating that Na^ interacts more strongly with the calcite surface than K^ or that water is less available in NaCl solutions. Rates increased with increasing pCO2 and temperature, and their influence diminished at high I. Arrhenius plots yielded a relatively high activation energy (Ea =~ 20 ± 2 kJ mol-1) which indicated that dissolution was dominated by surface controlled processes. These results are consistent with the hypothesis that the mole fraction of "free" solvent plays a significant role in the dissolution kinetics of calcite with a minimum value of ~45-50 percent required for dissolution to proceed in undersaturated solutions at 25-55 degrees C and pCO2 = 0.1--1 atm. Precipitation rates were modeled using the general and Davies and Jones rate equations yielding similar results. Reaction orders were found to typically range between 0.8 and 2.5 for both rate equations regardless of electrolyte. For both solutions, rate constants were found to range between 100.8 and 101.7 mmole m-2 hr-1 (general rate equation) and 101.5 and 102.2 mmole m-2 hr-1 (Davies and Jones rate equation). Under the experimental conditions employed and the resultant precision (~20-25 percent), I and pCO2 do not have a significant influence on the precipitation rate of calcite. Precipitation rates increased with temperature although Arrhenius plots yield a broad range of activation energies (Ea =~ 15--28 kJ mol-1, R2 = 0.72). The relatively low calculated activation energies coupled with the precision of the results suggest the possibility of surface nucleation in the present results. Overall, these findings may be useful in understanding and predicting the interaction and reactivity of the host carbonate minerals in subsurface reservoirs to the injection of CO2 although much work needs to be completed at elevated temperatures and pressures.

Download or read book Simulating the Accumulation of Calcite in Soils Using the Soil Hydraulic Model HYDRUS 1D written by Nathaniel Andrew Meyer and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The distributions of calcite rich horizons within dryland soils are commonly used as paleoclimate proxies. Comprehensive conceptual and mathematical models of calcite accumulation in soils are required to accurately interpret and calibrate these proxies. A conceptual model for calcite accumulation is already well established: As water percolates through a soil, it dissolves minerals, such as calcite, transporting the soluble minerals downward. As soil water is removed by evaporation and transpiration, the water solution becomes supersaturated resulting in precipitation of calcite at depth. The impacts of dynamic plant growth and microbial respiration have not yet been simulated in numerical models for calcite accumulation but are likely important because of their influence on variables governing calcite solubility. The soil hydraulic modeling software, HYDRUS-1D, simulates water and solute transfer through a soil column, accounting for variations in all previously studied variables (temperature, water content, soil pCO2) while additionally simulating vegetation-soil interactions. Five separate sensitivity studies were conducted to determine the importance for calcite accumulation of 1) soil texture, 2) plant growth, 3) plant phenology, 4) atmospheric CO2 concentrations, and 5) the proximal variables that control calcite dissolution and precipitation: soil CO2, soil water content, and soil temperature. In each modeling simulation, calcite was leached from the top several cm and redistributed deeper in the soil after 20 years. Soils with courser texture yield deeper (+20cm), more diffuse calcite horizons, as did simulations with bare soil compared to vegetated soil. The phenology of plant communities (late spring versus late summer growth) resulted in soil calcite accumulation at temperatures differing by at least 10°C. Changes in atmospheric CO2 concentrations do not affect the soil calcite distribution. Variations in concentration of soil CO2, rather than soil water content, have the greatest direct effect on calcite solubility. The most significant time periods of annual accumulation also corresponded with positive water fluxes resulting from high matric potential at the surface. Transpiration and evaporation moisture sinks caused solution to travel upward from higher to lower soil CO2 concentrations, causing CO2 de-gassing and calcite accumulation. This pathway describes a new qualitative mechanism for soil calcite formation and should be included in the conceptual model.