Personal Research Database

Full Text: 1994\Soi Sci Soc Ame J58, 1829.pdf

Abstract: Recent research suggests that thiamin applied to soils or coated onto seeds may stimulate plant growth. The behavior of thiamin in soils has not been investigated. Therefore, studies were carried out to determine how thiamin hydrochloride (3-[(4-amino-2-methylpyrimidinyl)methyl]-5-(2-hydroxyethyl)-4-methylthia zolium chloride hydrochloride) is adsorbed by 17 soils and three clays. The dominate mechanism in binding of thiamin is thought to be cation exchange with clay minerals and organic matter. In soils with low to medium organic matter content, thiamin adsorption occurred primarily on clay minerals and depended particularly on the amount and composition of the clay. Adsorption is species dependent (pK(a1) [negative logarithm of the first dissociation constant] = 4.85) and takes place principally in the acidic pH range, probably with position 1’ of the pyrimidine ring. Adsorption equilibrium is attained in <30 min. Adsorption in all soils, and in kaolinite and illite clays, could be described by a one-surface Langmuir isotherm at initial concentrations ranging from 16.3 to 995 mu mol L^-1. Adsorption by smectite in the same range was log-linearly related to the equilibrium concentration. Extending the initial concentration range from 16.3 to 9890 mu mol L^-1 showed that a two-surface Langmuir equation more adequately described adsorption in hydroxy-interlayered vermiculitic and chloritic-illitic soils, whereas a one-surface Langmuir equation was found to be adequate in mixed layer-smectitic soils. Only in the case of smectite clays is thiamin allowed to lie in a monolayer configuration parallel to the basal plane.

Keywords: Clay, Organic Matter, Two-Surface Langmuir

Allen, E.R., Ming, D.W., Hossner, L.R. and Henninger, D.L. (1995), Modeling transport kinetics in clinoptilolite-phosphate rock systems. Soil Science Society of America Journal, 59, 248-255.

Full Text: 1995\Soi Sci Soc Ame J59, 248.pdf

Abstract: Nutrient release in clinoptilolite-phosphate rock (Cp-PR) systems occurs through dissolution and cation-exchange reactions. Investigating the kinetics of these reactions expands our understanding of nutrient release processes. Research was conducted to model transport kinetics of nutrient release in Cp-PR systems, The objectives were to identify empirical models that best describe NH₄, K and P release and define diffusion-controlling processes. Materials included a Texas clinoptilolite (Cp) and North Carolina phosphate rock (PR), A continuous-flow thin-disk technique was used, Models evaluated included zero order, first order, second order, parabolic diffusion, simplified Elovich, Elovich and power function, The power-function, Elovich and parabolic-diffusion models adequately described NH₄, K and P release, The power-function model was preferred because of its simplicity. Models indicated nutrient release was diffusion controlled. Primary transport processes controlling nutrient release for the time span observed were probably the result of a combination of several interacting transport mechanisms.

? Hayes, K.F., Chen, C.C. and Mcavoy, D.C. (1995), Quaternary ammonium surfactant effects on sorption of trace-metals onto quartz and aluminosilicates. Soil Science Society of America Journal, 59 (2), 380-387.

Full Text: 1995\Soi Sci Soc Ame J59, 380.pdf

Abstract: This study was conducted to investigate the potential impact of quaternary ammonium compounds (QACs) on trace metal ion desorption from soil constituents. Three soil constituents (quartz, kaolinite, and montmorillonite), two trace metal cations [Co(II) and Sr(II)], and three alkyltrimethylammoniumchloride surfactants (C₈TMAC, C₁₂TMAC, and C₁₆TMAC) were chosen for this investigation. For the quartz system, Co(II) showed no desorption while Sr(II) showed a slight pH-dependent desorption. For kaolinite or montmorillonite systems, desorption of Co(II) and Sr(II) by QACs occurred only for the fraction of the trace metal cations sorbed on permanent-charge sites. In the case of montmorillonite, Sr(II) was significantly desorbed at all pH values. This was thought to be a result of the nearly exclusive sorption of Sr(II) to the permanent-charge sites in this system. In all other clay systems studied [Sr(II), Co(II) on kaolinite, Co(II) on montmorillonite], desorption only occurred at lower pH from permanent-charge sites. No desorption occurred at higher pH values where sorption to surface hydroxyl sites was indicated. In general, QAC-induced desorption of trace metal cations was found to be significant only when QAC sorption equaled or exceeded the cation-exchange capacity. Surfactant chain length was found to have little effect on the overall pH-dependent desorption trends. As expected, higher surfactant concentration was required to cause trace metal ion desorption as the surfactant chain length decreased.

Keywords: X-Ray Absorption, Water Interface, Organic Cations, Adsorption, Complexes, Ions, Charge, Clays, Model

Olila, O.G. and Reddy, K.R. (1995), Influence of pH on phosphorus retention in oxidized lake sediments. Soil Science Society of America Journal, 59, 946-959.

Full Text: 1995\Soi Sci Soc Ame J59, 946.pdf

Abstract: Diel pH changes in lake waters resulting from high photosynthetic activity may regulate water-soluble P concentration (WSP) and P sorption by suspended sediments in shallow eutrophic lakes. Laboratory studies were conducted to determine the pH effect on P fractions and P sorption kinetics in oxidized sediment suspensions from two subtropical lakes (Lake Apopka and Lake Okeechobee, Florida). The P sorption rate was calculated for sediment suspensions adjusted to various pH levels: 6.5, 7.0, 8.5, 9.5 and 10.5 for Lake Apopka and 6.5, 7.0, 8.5, 9.5 and 10.5 for Lake Okeechobee. A decrease in pH increased the WSP concentrations in Lake Apopka sediment suspensions hut had no effect on WSP concentrations in Lake Okeechobee sediment suspensions. Lake Apopka sediment suspensions at pH 7.0 (ambient) and below did not show net P uptake. Phosphorus uptake for Lake Apopka occurred only when pH was increased to greater than or equal to 8.5 and when P treatments were increased to greater than or equal to 27 mmol P kg^-1, which resulted in supersaturation with respect to octacalcium phosphate. Phosphate solubility diagrams and mineral equilibria calculations suggest that P uptake by Lake Apopka sediment suspensions at pH greater than or equal to 8.5 was due to P coprecipitation with CaCO₃ and probable formation of nonapatitic Ca-P compounds. Phosphorus sorption on Lake Okeechobee sediment suspensions followed first-order kinetics for all pH levels studied, with rate constants (k) ranging from 0.003 to 0.75 h^-1. High P uptake by Lake Okeechobee sediment suspensions could be attributed to two reactive components: (i) amorphous or poorly crystalline Fe and Al oxyhydroxides at pH < 7.5 and (II) Ca/Mg carbonates and other minerals at pH greater than or equal to 7.5.

Schulthess, C.P. and Tokunaga, S. (1996), Metal and pH effects on adsorption of poly (vinyl alcohol) by silicon oxide. Soil Science Society of America Journal, 60 (1), 92-98.

Full Text: 1996\Soi Sci Soc Ame J60, 92.pdf

Abstract: The adsorption of pentanol onto a smectite shows an adsorption edge at pH 10. Because adsorption similarities between smectites and Si oxides have been noted in the literature, we anticipated that poly (vinyl alcohol) (PVA) would also display an adsorption edge near pH 10 on a Si oxide (SiO₂). Adsorption edges between pH 9 and 10 on Si oxide were confirmed when using two PVA polymers of 98 and 88% hydrolysis (MW = 11000 and 10000 g mol^-1, respectively). The decrease in adsorption at high pH is attributed to the interference of Na⁺ adsorption on the Si oxide. The addition of aqueous metals (Al³⁺, Pb²⁺, Cu²⁺, Mg²⁺, and Ba²⁺) significantly modified the adsorption envelope of PVA on the Si oxide in various ways. Three mechanisms are proposed: metals may modify the Si surface, interact with the PVA while in the aqueous phase, or form an additional independent surface that can adsorb the PVA polymer. New PVA adsorption envelopes were observed at high pH in the presence of Mg, Cu, and (adsorbed) Pb. The presence of metals also increased the amount of PVA (98% hydrolysis) adsorbed at low pH, but caused no change in, or decreased, the amount of PVA (88% hydrolysis) adsorbed on a mass per area basis. Because of this, we suggest that the metals can modify the effective thickness of the polymers on the surface. The adsorption of Pb and Al on the Si oxide modified the solubility of Si, suggesting a chemisorption reaction with the surface.

Salim, I.A., Miller, C.J. and Howard, J.L. (1996), Sorption isotherm-sequential extraction analysis of heavy metal retention in landfill liners. Soil Science Society of America Journal, 60 (1), 107-114.

Full Text: 1996\Soi Sci Soc Ame J60, 107.pdf

Abstract: The chemical partitioning of heavy metals in soil materials is of great importance in risk assessment, landfill bottom liner design, and remedial investigation. The sorption characteristics of clayey calcareous sediments used to construct landfill bottom liners at four sites in southeastern Michigan were studied using a new method: combined sequential extraction-sorption isotherm analysis (CSSA). After spiking to simulate high levels of contamination, the sediments sorbed large quantities of Pb (similar to 1480-145 000 mg kg^-1), Ni (similar to 750-8100 mg kg^-1), and Cd (similar to 980-5070 mg kg^-1). Sequential extraction data indicated that Pb and Ni were principally in a carbonate-occluded form, whereas Cd was mainly in an exchangeable form at high levels (>1000 mg kg^-1) of contamination. These results suggest that Pb and Ni will be immobilized by the Liner materials but Cd will probably be highly mobile. By applying sequential extraction analysis after spiking, Langmuir sorption isotherms were constructed successfully for most of the individually targeted phases. Thus, CSSA appears to be a promising method for predicting the attenuation capabilities of soils and sediments because it allows the sorption capacities of individual phases to be determined while together in a natural system.

Keywords: Roadside Soils, United-States, Sewage-Sludge, Trace Amounts, Adsorption, Lead, Cadmium, Copper, Sediments, Zinc

Notes: highly cited

? Manning, B.A. and Goldberg, S. (1996), Modeling competitive adsorption of arsenate with phosphate and molybdate on oxide minerals. Soil Science Society of America Journal, 60 (1), 121-131.

Full Text: 1996\Soi Sci Soc Ame J60, 121.pdf

Abstract: The mobility of As in soils depends on several factors including redox potential, soil mineralogy, pH, and the presence of other oxyanions that compete with As for soil retention sites. We investigated the effects of pH and competing anions on the adsorption of arsenate [As(V)] on -FeOOH (goethite) and -Al(OH)₃ (gibbsite). Batch equilibrium As(V) adsorption experiments were conducted with P and Mo as competing anions in order to produce single-anion [As(V), P, and Mo] and binary-anion [As(V)/P and As(V)/Mo] adsorption envelopes (adsorption vs. solution pH). Arsenate and P single-anion adsorption envelopes were similar with substantial adsorption occurring across a wide pH range, including pH values above the points of zero charge of the oxides. Maximum Mo adsorption occurred across a narrower pH range (pH 4-6). On both oxides, equimolar P concentrations decreased As(V) adsorption within the pH range 2 to 11, whereas Mo decreased As(V) adsorption only below pH 6. The constant capacitance model was used to predict competitive surface complexation behavior between As(V)/P and As(V)/Mo using intrinsic equilibrium constants [K-anion (int)] optimized from single-anion data. In addition, the model was applied using one-site (monodentate) and two-site (monodentate + bidentate) conceptualizations of the oxide surface. The two approaches gave comparable fits to experimental adsorption data and were consistent with competitive adsorption observed in binary adsorption envelopes.

Keywords: Adsorption, Anions, Arsenate, Competitive Adsorption, Equilibrium, Exchange, Ferrihydrite, Gibbsite, Goethite -FeOOH, Kinetics, Soils, Solution Interface, Sorption, Surface-Chemistry

? Schulthess, C.P. and Dey, D.K. (1996), Estimation of Langmuir constants using linear and nonlinear least squares regression analyses. Soil Science Society of America Journal, 60 (2), 433-442.

Full Text: 1996\Soi Sci Soc Ame J60, 433.pdf

Abstract: A nonlinear least squares (NLLS) regression analysis of the Langmuir equation is described here based on minimizing the sum of the normal distance of the data to the isotherm. This regression can yield different Langmuir constants when compared with linear regression methods and another NLLS method - one based on minimizing the sum of the squares of the vertical distance of the data to the isotherm. The two NLLS regressions can also result in two different conclusions (or suggestions) about the physicochemical characteristics of the adsorption phenomena. There is no fundamental, mathematical requirement that the nonlinear regression be based on a vertical minimum save that it is easier to evaluate. More importantly, the vertical NLLS regression is strongly biased toward fitting the low-concentration data, this is remedied by using the normal NLLS regression. None of the regressions are endorsed per se since they should all agree if the isotherm is Langmuirian. The normal NLLS regression method is not sensitive to the goodness-of-fit criteria and, therefore, is considered to be robust. The criteria for choosing a regression method should consider both its sensitivity to data error plus its sensitivity to nonideality. A deviation in the data is not necessarily due to random measurement errors only (which are often easy to identify when the data are numerous and duplicated), but may also be due to the presence of a partially non-langmuir adsorption phenomenon. In the latter case, the Langmuir constants usually remain useful, but they must be used cautiously.

Keywords: Adsorption

Buchter, B., Hinz, C., Gfeller, M. and Fluhler, H. (1996), Cadmium transport in an unsaturated stony subsoil monolith. Soil Science Society of America Journal, 60 (3), 716-721.

Full Text: 1996\Soi Sci Soc Ame J60, 716.pdf

Abstract: Heavy metal mobility in soil can adversely affect our environment. To assess Cd mobility under experimental conditions that can be found in field soils, we investigated Cd transport in an undisturbed stony monolith of a calcareous subsoil. In this context, we evaluated different batch experiments to independently predict Cd transport. Simple (monocomponent) Cd isotherms and binary Ca-Cd cation-exchange isotherms were determined. The method used for determining the ion-exchange isotherm accounted for calcite dissolution. The column experiment was carried out under unsaturated conditions by keeping the lower end at a suction of 2 kPa. A 20 mM Cd pulse was applied during 19 d and the effluent concentration monitored for 91 d. The peak concentration of the effluent exceeded the Cd concentration, as computed with thermodynamic equilibrium models, by three orders of magnitude. During elution, one-third of the Cd remained in the column, indicating sorption hysteresis. Simulations with Freundlich isotherms and selectivity coefficients were capable of describing the sorption front. We modeled the hysteresis with a two-site model that included irreversible sorption so that both sorption and desorption fronts were described equally well.

Keywords: Solute Transport, Saturated Soil, Solid-Solution, Adsorption, Sorption, Model, Calcium, Surface, Simulation, Interface.

Scheidegger, A.M., Fendorf, M. and Sparks, D.L. (1996), Mechanisms of nickel sorption on pyrophyllite: Macroscopic and microscopic approaches. Soil Science Society of America Journal, 60 (6), 1763-1772.

Full Text: 1996\Soi Sci Soc Ame J60, 1763.pdf

Abstract: Retention of heavy metal ions on soil mineral surfaces is a crucial process for maintaining environmental quality. A thorough understanding of the sorption mechanisms of heavy metals on soil mineral surfaces is therefore of fundamental importance. This study examined Ni(II) sorption mechanisms on pyrophyllite. The removal of Ni from solution was studied as a function of pH (pH = 5-8.5), initial Ni concentration (110^-4 to 110^-2 M) and ionic strength (0.01-1 M). The data suggest that Ni sorption behavior can be divided into two distinct pH regions. In the lower pH region (i.e., pH < 7), relative Ni sorption increased with decreasing ionic strength and initial Ni concentration. The adsorption maximum at pH = 6 was significantly higher than the cation-exchange capacity (CEC) at the same pH. Based on these findings, we propose that both specific and nonspecific adsorption are involved. In the higher pH region (pH > 7), nickel sorption becomes slow and does not seem to be affected by the ionic strength and the initial Ni concentration. We employed high-resolution transmission electron microscopy (HRTEM) to ascertain whether any alteration in the surface structure of pyrophyllite could be detected after reaction with Ni at pH >7. Surface deposits, not present on untreated samples, were found. At low Ni sorption densities, surface precipitation seems to occur preferentially along the edges of the particles. Based on the HRTEM findings and on results from a previous x-ray absorption fine structure spectroscopy (XAFS) study, we hypothesize that the formation of a mixed Ni-Al hydroxide phase on the pyrophyllite surface is responsible for the sorption behavior above pH 7.

Keywords: Ray-Absorption Spectroscopy, Chromium(III) Sorption, Surface Precipitation, Adsorption-Desorption, Reaction-Kinetics, Cadmium Sorption, Boron Adsorption, Oxide Surfaces, Clay-Minerals, Kaolinite

? Shen, S.Y., Tu, S.I. and Kemper, W.D. (1997), Equilibrium and kinetic study of ammonium adsorption and fixation in sodium-treated vermiculite. Soil Science Society of America Journal, 61 (6), 1611-1618.

Full Text: 1997\Soi Sci Soc Ame J61, 1611.pdf

Abstract: Ammonium fixation in vermiculite affects the movement of N in many soils. The effects of particle size, solution concentration, pH, and associated anions on NH₄⁺ fixation in vermiculite are also important information for reducing N leaching from soils. In this study, the retention of NH₄⁺ on the exchangeable and nonexchangeable sites of Montana vermiculite was determined in batch experiments. In the NH₄⁺-K⁺ exchange isotherm, the exchangeable sites of the vermiculite exhibited a preference for K⁺ to NH₄⁺, while the nonexchangeable sites preferred NH₄⁺ to K⁺. The nonexchangeable sites of the sand fraction had a higher preference for NH₄⁺ at lower solution NH₄⁺ concentration and a lower preference at higher NH₄⁺ concentration. An opposite case was observed for the NH₄⁺ concentration effect on the preference of nonexchangeable sites in the clay fraction. The retention isotherm of total NH₄⁺ in the vermiculite exhibited S-shape curves that can be described by the “two-surface” Langmuir-Freundlich equation. In the kinetic study, the clay fraction adsorbed the largest amount of exchangeable NH₄⁺, but the silt fraction fixed the most NH₄⁺ on its nonexchangeable sites. The retention of NH₄⁺ in vermiculite increased with solution NH₄⁺ concentration. Ammonium adsorption on the exchangeable sites increased at low solution pH, while NH₄⁺ fixation was unaffected by pH change. The effect of associated anions was insignificant, except they caused a pH difference in solution.

Keywords: Clay, Equation, Model, Nitrogen, Soils

? Kithome, M., Paul, J.W., Lavkulich, L.M. and Bomke, A.A. (1998), Kinetics of ammonium adsorption and desorption by the natural zeolite clinoptilolite. Soil Science Society of America Journal, 62 (3), 622-629.

Full Text: 1998\Soi Sci Soc Ame J62, 622.pdf

Abstract: The kinetics of NH₄⁺ adsorption and desorption were investigated on the natural zeolite clinoptilolite to ascertain its ability to adsorb and release the important plant nutrient N in its NH₄⁺ form at various pH values and initial NH₄⁺ concentrations. Kinetics of NH₄⁺ adsorption were evaluated on the samples using solutions containing 140.1, 280.2, 560.4, and 840.6 mg L^-1 of NH₄⁺-N at pH 4, 5, 6, and 7, equilibrated for 5, 10, 15, 20, 30, 45, 60, 75, 90, and 120 min. Samples for NH₄⁺ desorption were equilibrated with 70.1, 280.2, 560.4, and 1401 mg L^-1 NH₄⁺-N solution at pH 4, 5, 6, and 7 for 2.5 h, and adsorbed NH₄⁺ extracted with 2 M KCI for 5, 10, 20, 30, 45, 60, 90, 120, 150, 180, and 300 min. Equilibrium time for NH₄⁺ adsorption ranged from 60 min for 140.1 mg L^-1 initial NH₄⁺-N concentration at pH 4 to 120 min for 840.6 mg L^-1 initial NH₄⁺-N concentration at pH 7. Desorption was nearly complete in 150 min for low initial NH₄⁺ concentrations and 200 min for high initial NH₄⁺ concentrations. Amounts of NH₄⁺ sorbed increased with increasing pH and initial NH₄⁺ concentrations. Models evaluated included the first-order kinetics, modified Freundlich, parabolic diffusion, Elovich, and heterogeneous diffusion. All the models adequately described the NH₄⁺ adsorption process, with r² values ranging from 0.955 to 0.999. With the exception of first-order kinetics, they also described the desorption process well, with r² values ranging from 0.897 to 0.999, for all pH and initial NH₄⁺ concentrations. Reaction rate coefficients (k) were calculated from the modified Freundlich model and ranged from 0.134 to 0.193 min^-1 for the adsorption process, and 0.129 to 0.226 min^-1 for the desorption process. The models indicated that NH₄⁺ adsorption and desorption by the zeolite was diffusion controlled. Data from this study indicated the potential use of the tested natural zeolite as an NH₄⁺ adsorbent and a controlled-release NH₄⁺ fertilizer.

Keywords: Potassium-Calcium Exchange, Phosphate Release, Soil, Sorption, Equations, Systems

Reynolds, J.G., Naylor, D.V. and Fendorf, S.E. (1999), Arsenic sorption in phosphate-amended soils during flooding and subsequent aeration. Soil Science Society of America Journal, 63 (5), 1149-1156.

Full Text: 1999\Soi Sci Soc Ame J63, 1149.pdf

Abstract: Phosphate enhances the mobility of As in well-aerated soils by competing for adsorption sites. Phosphate and As may also coexist in large concentrations in hydric soils, and the influence of P on As in anaerobic systems is largely unknown. To determine the effects of P on As dynamics during a soil flooding and aeration cycle, samples of two soils were amended with Na₂HAsO₄ and Na₂HPO₄ and incubated under a N₂ atmosphere for 41 d, and then reaerated for 7 d. Subsamples were collected intermittently and dissolved As, Fe, Mn, Ca, S, P, and H₃AsO₃ concentrations were determined. Arsenic speciation in the soil solids was determined after 14 and 41 d of flooding and then after 13 h of aeration by X-ray absorption near edge structure (XANES) spectroscopy. Arsenic sorption was small under anaerobic conditions, and H₂PO₄‾ additions enhanced As(V) reduction rate in both soils and slightly suppressed As sorption in one soil. Arsenopyrite (FeAsS) was identified in the soil solids. Rapid and simultaneous As sorption and Fe precipitation occurred during the first 0.25 d of aeration, suggesting that As was retained on freshly precipitated Fe (hydr)oxides. Manganese precipitation and concomitant As sorption occurred after 1 d of aeration. Arsenopyrite was largely destroyed upon aeration but As(III) persisted. Thus, As is partitioned into the solid phase under both aerobic and anaerobic conditions, although more appreciably under the aerobic conditions of this study, and P has little influence on dissolved As during soil flooding-aeration cycles.

Sarkar, D., Essington, M.E. and Misra, K.C. (1999), Adsorption of mercury(II) by variable charge surfaces of quartz and gibbsite. Soil Science Society of America Journal,