Adsorption Of Ca Research Articles

Electrochemical and biological behaviors of porous titania (TiO 2) in simulated body fluids for implantation in human bodies

Porous titania, TiO 2, films on Ti substrates were prepared electrochemically. The adsorption of biologically compatible ions, like calcium and phosphate ions, on the formed TiO 2 films was investigated by electrochemical impedance spectroscopy, EIS, and electron diffraction X-ray, EDX, techniques. The morphology of the formed oxide films and the adsorbed layers on their surfaces was investigated by the scanning electron microscopy, SEM. The experimental impedance data were fitted to theoretical data according to proposed equivalent circuit models. The impedance data fitting enabled the explanation of the structure of the oxide film and the adsorption phenomena occurred on its surface. The film characteristics under different conditions were discussed and the adsorption of Ca 2+ and PO 4 3− was explained. The results have shown that the oxide films formed potentiostatically on Ti in H 2O 2 containing H 2SO 4 are capable to adsorb biologically compatible ions. The adsorbed layer thickness was found to increase with the increase of concentration of calcium ions present in the ambient electrolyte. The biocompatibility of these materials depends essentially on the apatite-forming ability of TiO 2 due to calcium ion incorporation in the adsorbed films. The formed oxide films with the relatively thick apatite-like adsorbed layer are good implants for bone surgeries and dental applications.

Interactions of Ca, Zn, and Cd Ions at Buried Solid/Water Interfaces Studied by Second Harmonic Generation

The adsorption of Ca, Zn, and Cd ions at the solid/water interface was studied using second harmonic generation (SHG). Specifically, we used the SHG χ(3) technique to assess and evaluate metal adsorption at a bare fused quartz/water interface, as well as at a carboxylic acid functionalized fused quartz/water interface. Adsorption isotherms were obtained for the metals at each interface and were fit with the diffuse layer and triple layer models to obtain adsorption free energies, interfacial potentials, absolute adsorbate number densities, and interfacial charge densities. The carboxylic acid functionalized interface displayed lower adsorption free energies but higher adsorbed metal number densities than the bare fused quartz/water interface. We suggest that metal binding at the bare fused quartz/water interface is driven by the initial number of deprotonated surface sites and that it proceeds through an outer-sphere mechanism. In contrast, metal binding at the carboxylic acid functionalized interface is associated with carboxylic acid deprotonation at a substantial free energy cost and proceeds directly through metal−carboxylate interactions.

“Smart Water” for Oil Recovery from Fractured Limestone: A Preliminary Study

Seawater is characterized as an enhanced oil recovery (EOR) fluid for hot, fractured chalk oil reservoirs because it is able to modify the wetting conditions and improve the displacement of oil. The chemical mechanism for the wettability alteration has been described previously, and it was verified that Ca2+, Mg2+, and SO42− played an important role because of their reactivity toward the chalk surface. Chalk, which is purely biogenic CaCO3, consists of fragmentary parts of calcite skeletons produced by plankton algae known as coccolithophorids, and it is believed to have a more reactive surface than ordinary limestone. To validate seawater as an EOR fluid also for limestone and dolomite, the affinities of these ions toward the rock surfaces must be evaluated. The present paper describes some preliminary experimental studies of the affinity of SO42−, Ca2+, and Mg2+ toward the surface of reservoir limestone cores at temperatures ranging from room temperature to 130 °C. The results confirmed that the ions interacted with the rock surface, and that the established chemical equilibrium was sensitive to the relative concentrations of the ions. It was also observed that the adsorption of Ca2+ and Mg2+ from a NaCl solution onto the limestone surface was quite similar at room temperature but that Mg2+ adsorbed more strongly at higher temperatures. At high temperatures, T = 130 °C, Mg2+ in seawater was able to substitute Ca2+ on the surface but the reactivity was less than for chalk. These findings indicate that seawater will act as an EOR fluid in limestone as well but its potential is probably smaller than for chalk. This was also confirmed by spontaneous imbibition tests performed at 120 °C.

Electrostatics of B-DNA in NaCl and CaCl2 Solutions: Ion Size, Interionic Correlation, and Solvent Dielectric Saturation Effects

The epsilon-modified Poisson-Boltzmann (-MPB) equations ( J. Phys. Chem. B, 2007, 111, 5264) have been solved on a three-dimensional grid for an all-atom geometry model of B-DNA. The approach is based on the implicit solvent model including finite sizes of hydrated ions and a dielectric approximation of the ion hydration shell. Results were obtained for the detailed geometry model of B-DNA in dilute and moderately concentrated solutions of NaCl and CaCl(2). All -MPB parameters of ions and dielectric medium were extracted from published results of all-atom molecular dynamics simulations. The study allows evaluations of the ion size, interionic correlation, and the solvent dielectric saturation effects on the ion distributions around DNA. It unambiguously suggests that the difference between the -MPB and Poisson-Boltzmann distributions of ions is low for Na(+) counterions. Such a difference in the case of divalent counterions Ca(2+) is dramatic: the dielectric saturation of the ion hydration shell leads to point-like adsorption of Ca(2+) on the phosphate groups of DNA. The -MPB equations were also applied to calculate the energy of interaction between two B-DNA molecules. Results agree with previously published simulations and experimental data. Some aspects of ion specificity of polyelectrolyte properties are discussed.

Coagulation of bitumen with kaolinite in aqueous solutions containing Ca 2+, Mg 2+ and Fe 3+: Effect of citric acid

Heterocoagulation experiments of kaolinite with solvent-diluted-bitumen were carried out to investigate the effect of hydrolyzable metal cations and citric acid on the liberation of bitumen from kaolinite. The adsorption of Ca 2+ and Mg 2+ on kaolinite, and zeta potentials of kaolinite and bitumen droplets in solutions containing 10 −3 mol / L of Ca 2+, Mg 2+ and Fe 3+ with or without citric acid were also measured. It was found that the heterocoagulation of bitumen with kaolinite was enhanced in the presence of the metal cations from pH 7 to pH 10.5, accompanied by a decrease in the magnitude of the zeta potentials and an increase in the adsorption of the metal cations on kaolinite and possibly on bitumen droplets. The addition of 5 × 10 −4 mol / L citric acid reduced the degree of coagulation from 90% to less than 40% in the presence of 10 −3 mol / L Ca 2+ and Mg 2+ cations at pH ∼ 10 , and at pH ∼ 8 for Fe 3+. It was found that hydrolyzable metal cations enhanced bitumen–kaolinite interactions through electrical double layer compression and specific adsorption of the metal hydrolysis species on the surface of kaolinite. The effect of metal cations was removed by citric acid through formation of metal–citrate complexes and/or the adsorption of citrate anions, which restored the zeta potentials of both kaolinite and bitumen. Therefore, electrostatic attraction or repulsion was responsible for the coagulation or dispersion of kaolinite particles from bitumen droplets in the tested system.

Calculations of Ca adsorption on a MgO(100) surface: Determination of the binding sites and growth mode

Density functional theory is used to calculate the adsorption of Ca adatoms on a MgO(100) surface. The Ca monomer binds preferentially to the oxygen site on the terrace with an adsorption energy of $0.84\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and diffuses by hopping to a nearest neighboring oxygen site with a barrier of $0.45\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The binding at F and ${\mathrm{F}}^{+}$ oxygen vacancy defects is weaker than on the terrace. Small Ca clusters on the surface are either unstable (dimers and trimers) or very mobile (tetramer). Therefore, a Ca adatom can diffuse around the surface until it reaches a strong-binding site such as a step $(2.1\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, kink $(3.9\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, divacancy $(5.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, or even a Mg vacancy $(10\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$. When Ca binds to MgO(100), charge is transferred from Ca to the surface. The magnitude of the charge transfer is different between different binding sites, which can help explain the different adsorption energies. The oxygen bound to a step edge can provide a stronger binding for a Ca adatom $(7.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$, but its existence on MgO(100) still remains to be verified. Based on the adsorption energetics and kinetics, further growth of the Ca particles is expected to occur at strong-binding sites and spread onto the terrace in a three-dimensional growth mode. A two-state kinetic growth model is used to compare our density functional theory calculations with measured heats of adsorption by Zhu et al. [J. Am. Chem. Soc. 130, 2314 (2008)]. This study shows that the defects on MgO(100) have different roles in the growth of alkaline earth metals, such as Ca, as compared to late transition metals, such as Pd.

Modeling Coupled Hydrologic and Chemical Processes: Long‐Term Uranium Transport following Phosphorus Fertilization

Coupling physical and geochemical processes within one integrated numerical simulator provides a process‐based tool for investigating the mobility of contaminants as affected by changing hydrologic regimes and geochemical conditions. We review interactions between physical and biogeochemical processes in the vadose zone, and then present a case study demonstrating these complex interactions. A hypothetical application is presented of the HP1 multicomponent transport simulator to predict the transport of two major elements (Ca and P) and one trace element (U) applied annually for 200 yr to a field soil in the form of an inorganic P fertilizer. Interactions of Ca, P, and U with the solid phase are described using cation exchange and surface complexation reactions. Simulations assuming steady‐state or transient flow conditions were analyzed in terms of temporal variations of the linear distribution coefficient, Kd, which depends strongly on pH and the composition of the aqueous phase. If the composition of the aqueous phase is constant, adsorption of Ca and U increases with increasing pH. Due to the annual addition of Ca, P, and U, and competition between P and U for sorption sites, the Kd of these elements decreased with time near the soil surface. Deeper in the soil, the Kd of U followed the pH increase because of a lack of competition from P. Because of the combined effects of changing hydrologic and geochemical conditions, the Ca and U distribution coefficients and solute fluxes during the transient simulation exhibited large short‐time variations of up to three orders of magnitude.

Contrasting chemical response to artificial acidification of three acid-sensitive streams in Maine, USA

We experimentally acidified three low alkalinity first-order streams in forested catchments in Maine, USA. We evaluated water samples from a reference site above the point of hydrochloric acid addition and from two or three sites located 16 to 94 m downstream. Neutralization included protonation of weak acids, adsorption of sulfate, and ion exchange of base cations and aluminum (Al) for protons (H +). Protonation of bicarbonate was significant in the relatively high pH Hadlock Brook. Protonation of weak organic acids dominated in the high dissolved organic carbon (DOC) Mud Pond Inlet. The response in low DOC, low pH East Bear Brook was dominated by stream substrate release of cations. East Bear Brook had the strongest acid neutralization response per unit catchment area. In all streams, exchangeable calcium (Ca) and magnesium (Mg) were mobilized, with Ca > Mg. Al was also mobilized. During initial stages of acidification, Ca desorbed preferentially, whereas Al mobilization dominated later. Early in the recovery, adsorption of Ca to the streambed sediments was kinetically favored over adsorption of Al. Though pH increased downstream of acid addition, the streams remained undersaturated with respect to amorphous Al(OH) 3, so Al did not precipitate. In East Bear Brook, however, Al left solution further downstream through adsorption. This process was likely kinetically controlled, because it occurred in East Bear Brook (3–4 L/s) but did not occur in Hadlock Brook (ca. 40 L/s) or Mud Pond Inlet (ca. 60 L/s). During experimental acidification, the initial Al:Ca ratio of a stream's response may indicate the acidification status of the catchment. Short-term stream acidification experiments illuminate processes characteristic of episodic stream acidification and of long-term catchment acidification. East Bear Brook and Hadlock Brook catchments are in early to intermediate stages of acidification. The Mud Pond Inlet catchment (high Al:Ca ratio) is in a later stage of acidification.

Simulated body fluid (SBF) adsorption onto a-SiC:H thin films deposited by hot wire chemical vapor deposition (HWCVD)

Hydrogen amorphous silicon carbon (a-SiC:H) film deposited by the Hot Wire Chemical Vapor Deposition (HWCVD) technique on silicon substrates were soaked in simulated body fluid (SBF). Characterization of the film with different soaking durations in SBF was carried out by Fourier Transform Infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and contact angle measurements. It was found that the relative amounts of carbon in the a-SiC:H film surface decreases with increase in soaking period. XPS results showed the adsorption of Ca and Mg on the a-SiC:H surface. This indicates the formation of negatively charged surface possibly due to formation of silanol groups or dissolution of carbon to SBF confirming the bioactivity of the material. Contact angle decreased from 74° to 65° during 30 days of soaking in the body fluid. Present study is an attempt to observe the interaction of a-SiC:H film prepared by HWCVD technique with the body environment for its future suitability as artificial heart valve and stent coating materials.

Calcium Adsorption on MgO(100): Energetics, Structure, and Role of Defects

The adsorption of Ca on the MgO(100) surface at 300 K has been studied using microcalorimetry, in combination with LEED, AES, ISS, work function, sticking probability measurements, and density functional theory (DFT) calculations. The MgO(100) thin films (approximately 4 nm thick) were grown epitaxially on a 1 microm thick Mo(100) single-crystal. The sticking probability of Ca on MgO(100) at 300 K is unity. On the basis of AES and ISS measurements, it was determined that Ca grows mainly as 3D particles on the MgO(100) surface with a density of approximately 1 x 10(12) islands/cm2. Ca adsorbs initially at defect sites with a very high heat of adsorption (approximately 410 kJ/mol). DFT calculations attribute this high initial heat to Ca binding to kink sites (376 kJ/mol), step sites (205 kJ/mol), and lower concentrations of stronger binding sites. The heat of adsorption decreases rapidly with coverage, reaching a minimum of 162 kJ/mol at approximately 0.3 ML, where Ca is mainly adding to small 3D Ca clusters. Afterward, it increases to the value of bulk Ca heat of sublimation (178 kJ/mol) at approximately 1.2 ML, attributed to the increase in stability with increasing Ca particle size. A 1.0 eV decrease of the work function with Ca coverage from 0 to 0.3 ML indicates that Ca adsorbed at defects is cationic, in agreement with calculations showing that Ca donates electron density to the MgO. Light ion sputtering of the MgO(100) surface generates point defects, but these do not change the heat of adsorption versus coverage, implying that they do not nucleate Ca particles. Oxygen vacancies are a likely candidate; DFT calculations show that F and F+ center vacancies bind Ca more weakly than terrace sites. More extensive sputtering creates extended defects (such as steps and kinks) that adsorb Ca with heats of adsorption up to approximately 400 kJ/mol, similar to that at the intrinsic defect sites.

Ｃａを含有させた木質系廃棄物由来炭化物材料の硝酸性窒素吸着特性

In this study, thermal decomposition of Hinoki chips soaked in Ca solution and adsorption properties of obtained charcoal for nitrate nitrogen were investigated to develop a novel functional charcoal. Ca(OH)2 was used as Ca source due to less environmental load and easy handling and Ca-impregnated chips were heat-treated in an electric muffle furnace at temperatures between 600 and 900°C. The Ca-loaded charcoal acid-treated with HCl exhibited adsorptive ability for nitrate nitrogen. It was revealed that adsorption of nitrate nitrogen was ion-exchange reaction and that the charcoal samples acid-treated with HCl could be regenerated repeatedly by exchanging nitrate ion for chloride ion. The measurements of adsorption properties for nitrate nitrogen revealed that the adsorptive ability and durability of these samples were higher than those of activate carbon and anion-exchange resin. It was also found the obtained charcoal exhibited selective adsorption for nitrate nitrogen and fluoride anion, but not for sulfuric acid and phosphoric acid anions. As the result, the simple method, Ca-impregnation, thermal decomposition and acid treatment of wood waste, has advantages in production of nitrate nitrogen adsorption material.

Simulation of the adsorption of CaCl2 on Mg(OH)2 planes

The adsorption behavior of Ca2+ and Cl− on Mg(OH)2 planes was simulated using Universal Force Field method. The energy, the capacity and the configuration involved in the adsorption process were estimated. The results showed that Ca2+ was easier to be adsorbed and incorporated on the (001) plane than other planes such as (100), (101) and (110) planes. The incorporation of Cl− in Mg(OH)2 was difficult since the radius for Cl− is much bigger than that of OH−. The adsorption of Ca2+ on (001) plane at elevated temperature may inhibit the growth along [001] direction, leading to occurrence of the (001) plane, the shrinkage of the (101) and (110) planes and the formation of Mg(OH)2 plates with bigger ratios of diameter to thickness.

Theoretical Study of Molecular Hydrogen Adsorption in Mg-Exchanged Chabazite

An enthalpy of adsorption of ca. −10 kJ/mol was theoretically predicted for the interaction of molecular hydrogen with Mg-exchanged low silica chabazite (Si/Al = 5/1), which is significantly higher...

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Mg-Li ALLOY WITH Ca ADDITION

Mg-9wt%Li-2wt%Zn alloy was prepared and studied in this article. The addition of Ca to the alloy from 0.1 wt% to 1wt% can refine the α-Mg and the best effect of refinement occurs when Ca content is 0.4wt%—0.5wt%. The billets can be rolled to thin sheets at room temperature, from which it is obvious that the addition of Ca improves alloys' formality, while it decreases with the excess addition of Ca. The results also show that the ultimate tensile strength (UTS) and yield strength (YS) of the alloy with 1wt% Ca may rise by 28% and 25%, respectively, however, the elongation decreases. It is clarified that the adsorption of proper Ca on the grain boundaries refines α-Mg and improves the tensile properties, but the presence of excess Ca and stable Ca 2 Mg 6 Zn 3 phase worsens the elongation.

Modeling the separation performance of nanofiltration membranes for the mixed salts solution with Mg 2+ and Ca 2+

Many investigations showed that the dependence of the separation performance of nanofiltration (NF) membrane for the single salt with Mg 2+ or Ca 2+ on the salt concentration was distinguished from that for the salt with Na + or K +. In this paper, the results of the permeation experiments of some single salt solutions with Mg 2+ or Ca 2+ through ESNA 1 membrane showed that their observed transmission decreased with the growth of the concentration. This phenomenon is explained by the counter-ion adsorption of Mg 2+ or Ca 2+ on the surface of NF membrane. In order to evaluate the separation performance of NF membranes for the mixed salts solution with Mg 2+ and Ca 2+, the regulation coefficient was added in the model proposed in our preceding paper. A simple empirical equation was built to calculate the regulation coefficient at the different mixed salts solutions with Mg 2+ and Ca 2+. The empirical parameters were obtained on the basis of the permeation experiments of two type of binary salts solutions ((1) Na +, Mg 2+ and Cl −; (2) Na +, Ca 2+ and Cl −) though three kinds of NF membranes (ESNA 1-LF, ESNA 1 and LES 90). The regulation coefficient decreased with the growth of the total concentration of mixed salts and increased with the growth of the equivalent fraction of Mg 2+ and Ca 2+. The effect of the counter-ion adsorption of Ca 2+ on the effective fixed charge density of NF membrane was more remarkable than that of Mg 2+. Finally some complex mixed salts solutions with Mg 2+ and Ca 2+ were chosen to verify the model with the regulation coefficient. The model evaluation results of the observed transmission of each ion in the mixed salts solution with Mg 2+ and Ca 2+ through ESNA 1-LF, ESNA 1 and LES 90 membranes agreed quite well with the experimental data. The deviation between the model evaluation results and the experimental data of most ions was less than 20% for the case of ESNA 1-LF and LES 90, which of ESNA 1 membrane was less than 10%.

Controlling Tailwater Sediment and Phosphorus Concentrations with Polyacrylamide in the Imperial Valley, California

External loading of phosphorus (P) from agricultural surface discharge (tailwater) is the main cause of excessive algae growth and the eutrophication of the Salton Sea, California. Continuous polyacrylamide (PAM) applications to agricultural irrigation water inflows were evaluated as a means of reducing sediment and P in tailwater. Zero (control) and 1 mg L(-1) PAM (PAM1) treatments were compared at 17 Imperial Valley field sites. Five and 10 mg L(-1) PAM treatments (PAM5, PAM10) were conducted at one site. The particulate phosphorus (Pp) fraction was determined as the difference between total phosphorus (Pt) and the soluble phosphorus (Ps) fraction. We observed 73, 82, and 98% turbidity reduction with PAM1, PAM5, and PAM10 treatments. Although eight field sites had control tailwater sediment concentrations above the New River total maximum daily loads (TMDL), all but one were made compliant during their paired PAM1 treatments. While PAM1 and PAM10 reduced tail water Pp by 31 and 78%, none of the treatments tested reduced Ps. This may have been caused by high irrigation water Na concentrations which would reduce Ca adsorption and Ca-phosphate bridging on the PAM. The PAM1 treatments resulted in <0.5 mg L(-1) drain water polyacrylamide concentrations 1.6 km downstream of PAM addition, while PAM5 and PAM10 treatments produced > 2 mg L(-1) drain water polyacrylamide concentrations. We concluded that, although PAM practically eliminates Imperial Valley tailwater sediment loads, it does not effectively reduce tailwater Ps, the P fraction most responsible for the eutrophication of the Salton Sea.

Permeability Characteristics of Lake Kojima Sediment and Their Improvement

Abstract As lake sediments are one of the causes of eutrophication, their removal and effective use has been considered. When they are used as soil in a land, proper permeability is required. However, soil permeability has not completely been understood due to diversity of clays and organic compounds. We clarified permeability characteristics of Lake Kojima sediment, nonswelling clayey soil, by measuring saturated hydraulic conductivity (K). A decrease in K during percolation of dilute electrolyte solution was small when Ca was adsorbed by the soil; K became 3.4×10−5 cm/s at pH 5, 2.9×10−5 cm/s at pH 7, 7.5×10−6 cm/s at pH 9, and 2.3×10−5 cm/s at pH 11 after pure water percolation. Although the permeability tended to decrease as pH increased, K at pH 11 became larger than that at pH 9 due to chemical reaction between soil particles and Ca. On the other hand, when Na was adsorbed, K drastically decreased with pH increase; K became 7.1×10−6 cm/s at pH 5, 3.1×10−6 cm/s at pH 7, 1.7×10−7 cm/s at pH 9, and 1.3×10−7 cm/s at pH 11 after pure water percolation. The obtained results could be explained qualitatively by the theory. Next, an improvement method of permeability of Lake Kojima sediment with hydrated lime and gypsum were investigated. Three application methods were compared in the saturated hydraulic conductivity experiment; mixing, surface distribution and solution infiltration. Hydrated lime application with mixing maintained high hydraulic conductivity. The soil structure was supposed to be stabilized by chemical reaction between soil and heterogeneously distributed hydrated lime. On the other hand, gypsum application with solution infiltration maintained the same hydraulic conductivity as that of hydrated lime application with mixing. In that case, electrostatic adsorption of Ca was considered to generate flocculation and kept high permeability.

The influence of calcium ions on the development of acidity in corrosion product deposits on SIMFUEL, UO 2

In order to clarify the influence of groundwater constituents on the formation of corrosion products and secondary phase deposits on corroding/dissolving nuclear fuel surfaces under waste disposal conditions we have investigated the influence of Ca 2+, present as CaCl 2. The influence of calcium ions on the anodic dissolution of SIMFUEL (doped uranium dioxide) has been characterized over the potential range 0–500 mV (vs. SCE). Through the use of X-ray photoelectron spectroscopy (XPS) the surface composition over this potential range has been determined. Ca 2+ was found not to influence the conversion of U IVO 2 to U 1 - 2 x IV U 2 x V O 2 + x , but to suppress the subsequent formation of a U VI surface species which lead to the formation of a hydrated deposit, UO 3 · yH 2O. The adsorption of Ca 2+ on the UO 2 surface is believed to inhibit fuel dissolution either via inhibiting the stabilization of the cation precursor (UO 2(OH) 2) ads or by blocking the O 2− anion transfer reaction from the fuel surface.

Accelerating the formation of a calcium phosphate layer on NiTi alloy by chemical treatments

Abstract A chemical treatment procedure was used to treat the acid–alkali treated NiTi samples. The accelerated formation of a dense and uniform calcium phosphate layer in simulated body fluid on the chemically treated NiTi alloy was observed within two days of immersion. The proposed chemical treatment procedure resulted in enhanced adsorption of Ca2+ and HPO 4 2 - ions onto the treated surface and consequent local Ca2+ and HPO 4 2 - ions supersaturation. The thickness of the adsorption layer, composed mainly of Ca2+ and HPO 4 2 - ions, was about 100 nm.

AMENDMENT EFFECTS ON pH AND SALT CONTENT OF BAUXITE RESIDUE

Bauxite residue, a waste product from the refining of bauxite to alumina, contains excessive Na and an elevated pH. We investigated the use of four chemical amendments to reduce bauxite residue pH and Na content and to improve soil characteristics for reclamation purposes. A control (unamended) and treatments of gypsum, acidic gypsum, sulfuric acid, or elemental sulfur were thoroughly mixed with bauxite residue at rates to reduce the exchangeable sodium percentage (ESP) to 5%, with or without an equivalent of 90 Mg ha−1 wood chips for aeration. Materials were placed in separate 32-L PVC containers, leached with water, and 8 separate pore volumes collected. All treatments were replicated three times. Pore volumes 1 through 5 and 8 were analyzed for pH, Na, Ca, Mg, and sodium adsorption ratio (SAR). The acidic gypsum and acidic gypsum + wood chips treatments significantly lowered the pH (<8.5), leached the greatest amount of Na, Ca, and Mg for all pore volumes, and lowered the SAR as compared with other treatments. On completion of the leaching experiment, we analyzed the 0- to 15-cm and 15- to 30-cm depths in the columns for Na, Ca, Mg, SAR, ESP, pH, and electrical conductivity and compared values with unamended treatment. For all treatments, the Na content and ESP were reduced by an order of magnitude, Ca and Mg content increased, pH was reduced, and SAR was reduced by several orders of magnitude as compared with pre-experiment concentrations. Overall, the acidic gypsum and the acidic gypsum + wood waste treatments showed the most promise for reducing bauxite residue pH and Na content.