Studies of the Solubility of BaSO₄ Nanoparticles in Water: Kinetic Size Effect, Solubility Product, and Influence of Microporosity

Abstract

Dissolution experiments are carried out with nanoparticles of barium sulfate in water. An unusual concentration-time behavior is observed. A concentration maximum is measured at the very beginning of the dissolution process. This maximum considerably exceeds the saturation concentration of bulk material. The maximum concentration is followed in time by a decrease of the concentration until the saturation concentration of the bulk material is obtained. This behavior is called kinetic size effect and it is a characteristic of nanoscale particles in general. The colloidal system can be modeled theoretically by thermodynamic and kinetic considerations that cover all processes which may occur in the system: nucleation, particle growth, Ostwald ripening, and dissolution of particles. It has been shown that only the outer surface of the particles is responsible for the dissolution kinetics; it is suggested that the surface of micropores yields no contribution. The dissolution curves observed experimentally follow from the model considerations. It is possible by comparison of experiment and theory to estimate the saturation concentration influenced by the ionic strength in the solution. This effect can be well described by the extended Debye-H€ uckel law. The measured numerical values of the saturation concentrations are found to be in the range of 4-14 μmol L -1 and therefore in the vicinity of the solubility product of BaSO 4 . The saturation activity at infinite dilution (I f 0) is a Ba ¥ = 2.43 ( 0.12 μmol L -1 and the thermodynamic solubility product is K L ¥ = 10 -11.23 . Furthermore, the model calculations provide the possibility to estimate the interfacial tension of the system nanoparticle-solution. The numerical value of 1.1 N m -1 is obtained. The error of the estimated interfacial tension is approximately as large as about 15%. This seems to be acceptable in view of a lack of reliable data in the literature. It is possible furthermore to calculate a kinetic rate constant for any changes that may occur in the colloidal system. The error of this rate constant, however, may be as large as a factor of 10.

Accurate Rates of the Complex Mechanisms for Growth and Dissolution of Minerals Using a Combination of Rare-Event Theories

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Barite crystallization in presence of novel fluorescent-tagged antiscalants

“…A common strategy to reduce barite scale formation is the addition of phosphonates [4][5][6] or of polyacrylates [1,7] to the seawater injected in the reservoir to inhibit BaSO 4 nucleation or growth. However, irrespective of numerous studies over past five decades [8][9][10][11][12][13][14][15][16][17], the mechanisms of barite formation from aqueous solutions, and of the influence of additives still remain unclear [1,2,5,15,16].…”

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials

“…For nanoparticles there is usually a kinetic size effect, a phenomenon in which an initial high concentration of the dissolved species is observed followed by a decrease in concentration until the saturation is reached [ 77 ]. It has been shown that the kinetic size effect increases with decreasing particle size [ 76 , 77 ].…”