ADSORPTION OF PHOSPHATE BY GIBBSITE

Abstract

Summary The effects of the salts were studied using I per cent suspensions of gibbsite at pH 5.5 and 26°C. At 480μM phosphate and I mM calcium, the kinetic pattern was an initial rapid adsorption reaction, which approached equilibrium in 24 h, revealing a slower reaction. Adsorption isotherms determined at 24 h, with a range of final phosphate concentrations from 0.1 to 1000 μ in solution, were not affected by 20 mM sodium or potassium chloride or 10 mM magnesium chloride. Increasing calcium chloride from o to 20 TIM increased the adsorption of phosphate over the range from 1 to 100 μM final phosphate concentration. At lower (0.1 μM) and higher (1000 μM) phosphate, the effect of calcium was smaller. These results help to explain several effects of the various cations on the adsorption of phosphate by clays and soils, when effects of neutral salts on pH are also considered.