Biomedical subjects

T Zuyi

Publications and source records attributed to T Zuyi.

7 recordsLinked to original sources

PubMed2001

Comparative study on sorption/desorption of radioeuropium on alumina, bentonite and red earth: effects of pH, ionic strength, fulvic acid, and iron oxides in red earth.

The sorption and desorption of Eu(III) as a representative of trivalent lanthanides and actinides on bentonite, alumina, red earth and red earth treated to remove free iron oxides were comparatively investigated by using batch technique and radiotracer 152 + 154Eu. The effects of pH, ionic strength, fulvic acid, iron oxides in red earth and the sorption mechanism were also discussed. As compared to alumina and red earth, Eu(III) presents a considerable distribution coefficient (Kd) onto bentonite. It was found that the pH and the presence of clay minerals are the main factors dominating the sorption/desorption characteristic of Eu3+ in the soil, and that a sorption-desorption hysteresis on bentonite and red earth actually occurs. Furthermore, the main sorption mechanism of lanthanides onto bentonite, alumina and red earth is the formation of bridged hydroxo complexes with the surface, and there are negative effects of fulvic acid and free iron oxides in red earth on the sorption of Eu(III). The results of this paper indicate that the additivity rule on the sorption characteristic of a soil from the individual component's characteristics is not general.

Journal Article↗

PubMed2001

Sorption characteristics of zinc(II) by calcareous soil-radiotracer study.

65Zn was used as a radiotracer to study the sorption characteristics of zinc by two calcareous soils from Gansu Province (China). The sorption and desorption isotherms of Zn on two untreated calcareous soils and on two soils treated to remove CaCO3 were determined at 20 +/- 2 degrees C, pH 7.8 +/- 0.2 in the presence of 0.001 mol/l CaCl2. The contribution of CaCO3 to the Zn sorption by the two calcareous soils was approximately 70% of the total amount sorbed and the sorption-desorption hysteresis was definitely demonstrated, thus the CaCO3 in calcareous soil is undoubtedly the most significant sink for zinc at high pH range.

Journal Article↗

PubMed2000

On the Application of Surface Complexation Models to Ionic Adsorption.

Surface complexation models (SCMs) have been used extensively to describe the acid-base properties and adsorption behaviors of inorganic and organic cations and anions on many single-phase adsorbents. The success of SCMs results from the conformation of adsorption to mass-action and material-balance laws and the flexibility in adjustable parameters. However, the assumptions made in the derivation of the SCMs are really not justified and the SCMs are not so thoroughly grounded in fundamental chemistry. The SCMs are really the data-fitting model, rather than the chemical model. The premises of application of SCMs are the accurate identification of surface species and the low surface coverage. Though the application of the SCMs comes into vogue, the SCMs should be applied with caution. Copyright 2000 Academic Press.

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PubMed2000

On the Applicability of the Langmuir Equation to Estimation of Adsorption Equilibrium Constants on a Powdered Solid from Aqueous Solution.

The Langmuir adsorption equation has become popular for summarizing solution-solid adsorption data and estimating adsorption equilibrium constants. The applicability of the Langmuir equation to estimation of adsorption equilibrium constants at solid-aqueous solution interfaces was theoretically examined in terms of (1) comparisons of solid-solution adsorption with solid-gas adsorption, (2) deductions of the Langmuir mathematical expression for the nonelectrolyte/solvent exchange, the phase exchange, the ion exchange, and the simple association reactions, and (3) the fitting procedure. The restrictive assumptions underlying the Langmuir equation for solid-gas adsorption may not be valid for adsorption of solute of small molecules or ions by a powdered solid surface from the aqueous solution phase. The fit of adsorption data to the Langmuir mathematical expression cannot be ascertained solely by the linearity of the commonly used equilibrium concentration/amount adsorbed versus the equilibrium concentration plot and does not provide the actual mechanism of the loss of small molecules or ions from aqueous solution. Therefore, the parameters of fitting to the Langmuir mathematical expression may not provide an unambiguous chemical meaning. In addition, we attempt to bring attention to the importance of the standard states of surface phase and solution phase. Copyright 2000 Academic Press.

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PubMed2000

Sorption and desorption of radiocesium on red earth and its solid components: relative contribution and hysteresis.

The relative contributions of organic matter and iron oxides to the Cs+ sorption on red earth were investigated by using the batch technique and selective extraction methods. The sorption and desorption isotherms and the distribution coefficients of Cs+ on the untreated red earth and the three treated soils to remove organic matter, iron oxides and organic matter plus iron oxides were determined at 20 degrees C, pH 6.3+/-0.2, in the presence of 0.01 mol/l CaCl2. It was found that all the isotherms are linear in the Cs+ concentration range used here, that the sorption desorption hysteresis on the red earth actually occurs, and besides the clay minerals, the organic matter present in the red earth is a significant trap of Cs+ and is responsible for the hysteresis instead of the iron oxides.

Adsorption↗

PubMed2000

Adsorption characteristics of 47 elements on a calcareous soil, a red earth and an alumina: a multitracer study.

The distribution coefficients, Kd of 47 elements from Na to Bi on a calcareous soil, a red earth and an alumina were, respectively, determined using a multitracer technique. The multitracer solution was prepared by irradiation of UO2(NO3)2 with 40Ar ion beam. It was found that there is a common general trend of variation in Kd for both soils and the alumina, i.e. all the shapes of plots of log Kd versus electron binding energy (Iz) are an 'inverted V', hence the important role of chemical interaction in the adsorption of trace inorganic cations, anions and neutral complexes on the soils and the oxides was demonstrated. For the alkali and alkaline earth elements, the common sequences of Kd values on the three adsorbents were Na+ < K+ < Rb+ < Cs+ (except for Rb+ on the alumina) and Mg2+ < Sr2+ < Ba2+ and accord with the sequences of effective ionic radii or single ion hydration enthalpies.

Adsorption↗

PubMed1998

Comparison between the One pK and Two pK Models of the Metal Oxide-Water Interface.

The one pK and two pK models of the metal oxide-water interface were examined by using chemical thermodynamics. The concentration units, the standard states, and the reference states in both models were compared. It was shown that the chemical thermodynamics can give a unified description of protonation and deprotonation of surface of hydrous oxides and that a proper understanding of the choices of different standard states is at the heart of the comparison between one pK and two pK models. The inner meaning of intrinsic acidity constants in the two pK model was discussed. Copyright 1998 Academic Press.

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