THE ADSORPTION OF INOSITOL PHOSPHATES AND GLYCEROPHOSPHATE BY SOIL CLAYS, CLAY MINERALS, AND HYDRATED SESQUIOXIDES IN ACID MEDIA

Publisher Website
Google Scholar
Abstract
Summary: A study has been made of the adsorption of inositol phosphates and β‐glycerophosphate by soil clays and minerals in a wide range of acid media.Of the adsorbents tested, the most active were boehmite, a soil clay with a high sesquioxide content, ferric oxide gel, and montmorillonite.Generally, in the case of the inositol phosphates, the higher the number of phosphate groups in the molecule, the greater was the degree of adsorption. There were exceptions in the case of some of the ferric hydroxide‐inositol phosphate systems.Adsorption of inositol hexaphosphate was favoured in two distinct acid media, at pH 3 to 4, and in acid of concentration about 0·1N. Montmorillonite was reactive at pH about 4, apparently owing to its content of active aluminium; X‐ray examination gave no indication that an ordered clay‐organic complex was formed. Montrnorillonite, kaolinite, and an illitic soil clay sorbed negligible amounts of the ester in strongly acid media. Ferric oxide gel removed considerable amounts of inositol hexaphosphate from strongly acid solution, presumably partly by adsorption, and partly by precipitation of insoluble salts or complexes of the ester. At pH 3 to 4 the gel was relatively ineffective, Boehmite was very reactive over a wide range of acid concentrations, from pH 4 down to concentrations of 4N with respect to hydrochloric acid; greatest sorption occurred at pH about 1. The sesquioxide rich soil clay had a high sorption capacity for inositol hexaphosphate in a wide range of acid concentrations. Removal of active iron and aluminium destroyed its activity at pH 4, but the clay was still reactive at pH 1.Inositol mono‐, di‐, and triphosphates were adsorbed by boehmite to a greater extent in IN HCl than in 0·1N HCl. This was true also of β‐glycerophosphate which was sorbed to a greater extent at pH 2·4, and in IN HCl than in 0·1N HCl.The adsorption of phosphate esters in equivalent concentrations of hydrochloric and sulphuric acids was often markedly different.