Adsorption isotherms of lanthanum to soil constituents and effects of pH,EDTA and fulvic acid on adsorption of lanthanum onto goethite and humic acid

Abstract

La³⁺ adsorption isotherms to five soil constituents (quartz, feldspar, kaolinite, goethite and humic acid) are studied. EDTA, fulvic acid and pH effects are also investigated on the adsorption of lanthanum by goethite and humic acid because of their relative importance in affecting metal environmental behavior. Adsorption isotherms of La³⁺ to five constituents show differences in adsorption capacity and in shape in the studied range of La³⁺. These constituents can be classified according to their adsorption capacity: humic acid > goethite ≈ kaolinite > feldspar ≈ quartz. pH increase could promote humic acid and goethite adsorption of La³⁺ while EDTA could reduce the adsorption by these two adsorbents. Fulvic acid can reduce humic acid adsorption but has less effect on adsorption by goethite.