A comparison between the slope of the adsorption isotherm of phosphate and that of fluoride shows that the adsorption of phosphate is stronger than that of fluoride.The adsorbed phosghate on goethite surface is made.up of two types,i.e.,the isotopically exchangeable and non-exchangeable.The proportion of non-exchangeable phosghate to total adsombed phosphate at a low level of adsorption is greater than that at a high level of adsorption.The amount of non-exchangeable phosphate is not affected by the equilibrium concentration of phosphate in suspension.The effect of fluoride on the adsorption of phosphate is very weak.On the other hand,phosphate has a strong effect on the adsorption of fluoride when a competitive adsorption of these anion species occurs.The adsorption of phosphate is not affected by fluoride when phosphate is adsorbed first,or when phosphate and fluoride are adsorbed simultaneously.However,fluoride has certain effect on the adsorption of phosphate if fluoride is adsorbed first.When phosphate is adsorbed first,the amount of adsorbed fluoride is always less than that when fluoride and phosphate are adsorbed simultaneously,and it is ereatest when fluoride is adsorbed first.