氧化铁对磷酸根和氟离子的竞争吸附

吸附在氧化铁表面上的磷酸根包括同位素可交换性的和非交换性的二种类型.当磷酸根的吸附量低时,非交换性磷酸根与磷酸根的吸附量之比大于磷酸根的吸附量,高时二者之比非交换性磷酸根的量不受平衡悬浮液中磷酸根的浓度的影响.当磷酸根先被吸附,或磷酸根和氟离子同时吸附时,磷酸根的吸附不受氟离子的影响.当氟离子先被吸附时,它对磷酸根的吸附有一定的影响.当氟离子的吸附量低时,大部分被吸附的氟不能被磷酸根取代.随着氟的吸附量的增加,可被取代的氟离子的比例增大.

COMPETITIVE ADSORPTION OF PHOSPHATE AND FLUORIDE ON GOETHITE

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.