The effect of pH and anoxia on the performance of Phoslock®, a phosphorus binding clay

This study examined the adsorption of phosphate by Phoslock, a lanthanum modified clay, by investigating the effect of solution pH and presence of algal mass on its kinetic behavior. In addition, the effect of anoxic conditions on its ability to retain the adsorbed phosphate was studied. It was found that Phoslok® was most effective at pH values between 5 and 7, and the adsorption capacity decreased above pH 9. The adsorption capacity was lower in algae-containing lake water than in prepared reverse osmosis water solutions. The phosphorus was not released from the Phoslock® under anoxic conditions.