Table of Contents
ISRN Inorganic Chemistry
Volume 2013, Article ID 969746, 10 pages
http://dx.doi.org/10.1155/2013/969746
Research Article

Near-Stoichiometric Adsorption of Phosphate by Silica Gel Supported Nanosized Hematite

1Institute for Sorption and Problems of Endoecology, 13 General Naumov Street, 03164 Kyiv, Ukraine
2Institute of Geochemistry, Mineralogy and Ore Formation, 34 Palladin Prospect, 03142 Kyiv, Ukraine
3Joint Department of Electrochemical Energy Systems, 38A Vernadsky Avenue, 03142 Kyiv, Ukraine

Received 3 June 2013; Accepted 20 June 2013

Academic Editors: A. M. Fonseca and Y. Wei

Copyright © 2013 L. I. Gromadskaya et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Decreasing the size of oxide particles to nanoscale enables one to ensure maximal reaction rates and depths in the solid due to the enhancement of the specific surface area and the increase of the diffusion rate caused by shortening diffusion paths. For that reason, one may suggest that in the case of adsorption onto nanoparticles, the complete conversion of sorbents to stoichiometric compounds would become possible. Adsorption of phosphate ions onto nanosized hematite supported on silica gel surface has been studied. Modification of silica gel surface by hematite in the quantity of 0.62 and 1.25 mass% has been carried out by means of a citric acid aided method. The morphology of the samples obtained has been characterized using DTA, XRD, SEM, and low temperature desorption of nitrogen. It has been found in batch experiments that unlike natural and synthetic hematites, for which the limiting adsorption values do not exceed 14 mg/g, silica gel supported nanosized hematite adsorbs 400–2000 mg of the phosphate ions per gram, thus forming near-stoichiometric iron phosphates on the surface of the support. The degree of conversion of hematite to iron phosphates is greater in acidic media and at a lower surface coverage, when hematite crystallites are small and better accessible by adsorbate.