Phosphorus Removal from Model Wastewater Using Lanthanum Hydroxide Microcapsules with Poly(Vinyl Chloride) Shells

Abstract In this study, lanthanum hydroxide microcapsules with 20 wt% of poly(vinyl chloride) shells were prepared by encapsulation as a means of removing phosphorus from wastewater. Scanning electron microscopy observations showed that the microcapsules were highly porous and lanthanum hydroxide particles were densely located on the pore walls. The phosphorus adsorption and desorption properties of microcapsules were investigated using model wastewater with a phosphorus concentration of 1 mg-P/dm3. The maximum phosphorus uptake of the microcapsules with arithmetic mean size of 0.38 mm was 92 mg-P/g in a batch experiment, corresponding to the phosphorus uptake of 115 mg-P per gram of lanthanum hydroxide in the microcapsule, which was almost the same as the maximum phosphorus adsorption capacity (118 mg-P/g) of lanthanum hydroxide powder used for the encapsulation. The phosphorus in phosphorus-loaded microcapsules can be effectively desorbed using 3 mol/dm3 sodium hydroxide and the regenerated microcapsules can be repeatedly used without degrading the phosphorus adsorptivity. A fixed-bed column study showed that the microcapsules can effectively remove phosphorus from model wastewater to less than 0.1 mg-P/dm3 until 11000 times the bed volume, even in the third adsorption–desorption cycle.