Sorption properties of indium oxohydroxides

Abstract

The influence of the pH of precipitation and of the ionic medium on the sorption properties (the surface charge and the kinetic characteristics of sorption) of indium oxohydroxides obtained by alkaline hydrolysis of indium nitrate was investigated. It was found by the method of zero charge point, by the indicator reactions of heterogeneous hydrolysis, by drop titration, and by thermography that In(OH)3 -0.5 H20 9 (0.2--0.3) NaOH with a very small degree of erystallinity is formed at pH > 6. The basic properties of the oxohydroxide increase with increasing pH of precipitation up to 9--10 and then remain constant. The rates of the indicator reactions depend slightly on the pH of precipitation. The sorption properties of indium oxohydroxides differ markedly from those of ferrogels obtained trader similar conditions. The results obtained can be explained by the tbrmation of quasistable microstructures during the precipitation of indium oxohydroxide.Key words: sorption properties; zero charge point; indium oxohydroxide; indicator reaction rate.Oxohydroxide-based sorbents are of great interest for both chemical and environmental technologies. 1,z It has been shown previously 3 that as-prepared gelatinous oxohydroxide sorbents have significant advantages as compared to dry granulated oxide sorbents. Nevertheless, the sorption properties of gelatinous oxohydroxides are poorly studied. Previuosly, a comparative study of the sorption properties of gels of metal oxohydroxides in various ionic media has been carried out in order to create a theoretical model for prediction of the conditions of extracting complex-forming metals from complex-forming media by inorganic oxohydroxide sorbents. 4-g The behavior of as-prepared oxohydroxides at the initial period was of special interest.In this work, indium oxohydroxides that were not subjected to drying and known as indiogels were studied.It was of interest to compare the behavior of indium0a) oxohydroxides with that of iron0,) 4-6 and chromium(111) oxohydroxides, since they have the equally charged central atoms but different ionic radii and electronic structures. The sorption properties of indium oxohydroxides are practically unknown except work 9 in which the effects of the pH of precipitation and the temperatures of drying and calcination on the specific surface area and pore structure of In(OH) 3 were studied by the adsorption method (sorption of benzene vapor). The samples obtained at pH 8 and 10 and dried at temperatures not higher than 120~ have Ssp = 169 and 124 m z g-l, respectively. Calcination results in a decrease in Ssp to 25--30 m 2 g-l.In this work, a series of samples of indium oxohydroxide was obtained and their sorption properties were studied by the method of zero charge point (ZCP)t~ and by the indicator reactions of heterogeneous hydrolysis of complex anions (IrCl62-and PtCI42-). 1'4-s The sorption properties mean the capability of an oxohydroxide (a dispersed phase) to extract a sorbate from the bulk of a solution (a dispersion medium) rapidly and to a high d...

The use of the pH at the point of zero charge for characterizing the properties of oxide hydroxides

“…[14][15][16][17][18][19][20][21][22] In this review, we describe a simple and efficient method for the determination of this value and consider the relationship between this parameter and the surface properties of oxide hydroxides and the scope of its application. [14][15][16][17][18][19][20][21][22] In this review, we describe a simple and efficient method for the determination of this value and consider the relationship between this parameter and the surface properties of oxide hydroxides and the scope of its application.…”