EFFECT OF MONTMORILLONITE ON PHOSPHATE SORPTION BY HYDROUS AL-OXIDES

Phosphate sorption by two hydrous oxides of aluminium was studied, as a function of pH and phosphate concentration, in the presence and absence of different amounts of montmorillonite. The clay had no effect on P sorption when the sorption values were independent of the amount of sorbent. When P sorption was dependent on the mass of sorbent, the clay was effective in eliminating such dependence. The results are explained in terms of the adsorption capacity of the clay in reducing the amounts of Al-hydrolysis species that are normally present in hydrous oxide suspensions, and are known to possess high affinities for phosphate in solution.