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| Boron Adsorption Data |
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| The boron adsorption data and model fits presented in this data base are described in the research paper entitled Modeling Boron Adsorption Isotherms And Envelopes Using The Constant Capacitance Model by S. Goldberg published in Vadose Zone Journal 3:676-680 (2004). The objectives of this study were to determine B adsorption isotherms and envelopes on a variety of soils having a range of soil chemical characteristics and to test the ability of the constant capacitance model to simultaneously describe B adsorption behavior as a function of both solution B concentration and solution pH. Detailed experimental and modeling methods used to obtain the adsorption data and model fits are provided in this publication. A summary will be provided below. | |
| Boron adsorption was investigated on 23 surface and subsurface soil samples from 21 soil series belonging to six different soil orders. The soils were chosen from the Salinity Laboratory soil library to provide a range of soil chemical characteristics (see Table 1). | |
| Boron adsorption isotherms (amount adsorbed as a function of equilibrium solution B concentration) and envelopes (amount adsorbed as a function of solution pH at a fixed total concentration) for the soils were determined in batch systems. Five grams of soil were equilibrated with 25 mL of a 0.1 M NaCl background electrolyte solution on a shaker for 20 h. The equilibrating solution contained 0, 0.0925, 0.185, 0.463, 0.925, 1.39, 2.31, 4.63, 9.25, 13.9, 18.5, or 23.1 mmol/L-1 B for isotherms and 0.463 mmol/L -1 B for envelopes. For the envelopes, pH was adjusted to pH 3-10 using additions of 1 M HCl or 1 M NaOH. After reaction, the samples were centrifuged, decanted, analyzed for pH, filtered, and analyzed for B concentration using inductively coupled plasma emission spectrometry. | |
| Explanation of the application of the constant capacitance model to describe B adsorption isotherms and envelopes is provided in the above publication and references cited therein. The computer program FITEQL 3.2 (Herbelin and Westall, 1996) containing the constant capacitance model of adsorption was used to fit surface complexation constants to the experimental B adsorption envelope and isotherm data simultaneously. Initial input parameter values were capacitance: C = 1.06 F/m-2 and surface site density: Ns = 2.31 sites/nm-2 as in previous modeling studies of B adsorption using the constant capacitance model (Goldberg et al., 2000). | |
| The model was fit simultaneously to the B adsorption isotherms and envelopes of all soil samples optimizing three surface complexation constants: logKB-(int) for B adsorption, logK+(int) for protonation, and logK-(int) for dissociation. Table 2 provides values of the optimized surface complexation constants. The ability of the constant capacitance model to describe B adsorption isotherms and envelopes simultaneously is indicated in the attached files. | |
REFERENCES |
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| Goldberg, S., S.M. Lesch, and D.L. Suarez. 2000. Predicting boron adsorption by soils using soil chemical parameters in the constant capacitance model. Soil Sci. Soc. Am. J. 64:1356-1363. Herbelin, A.L., and J.C. Westall. 1996. FITEQL: A computer program for determination of chemical equilibrium constants from experimental data. Rep. 96-01, Version 3.2, Dep. Of Chemistry, Oregon State Univ., Corvallis. |
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Experimental methods are described in Goldberg et al. (2000). |
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