Studies on the adsorption of phosphate using lanthanide functionalized KIT- 6

The sorption of phosphorus (in the form of phosphate species) was investigated using lanthanide functionalised mesoporous KIT-6. Thirteen lanthanide functionalised KIT-6 materials were prepared and studied (La/KIT-6, Ce/KIT-6, Pr/KIT-6, Nd/KIT-6, Sm/KIT-6, Eu/KIT-6, Gd/KIT-6, Tb/KIT-6, Dy/KIT-6, Ho/KIT-6, Er/KIT-6, Tm/KIT-6, and Yb/KIT-6). The prepared materials were characterised using Small Angle X-Ray Scattering, X-Ray Diffraction, BET surface area analysis, HRTEM and electrostatic Zeta potential. Phosphate sorption tests using the prepared materials showed the La (22.76 mg/g), Pr (22.71 mg/g), Nd (22.45 mg/g), Yb (21.91 mg/g) and Sm (20.57 mg/g) functionalised KIT-6 materials achieved the highest sorption capacities under the conditions used (Temp. 25 °C, P conc. 22.80 mg/L, stirring rate 120 rpm, sorbent concentration 0.1 g/mL, in 6h). The higher capacities obtained with these materials were most likely due to a combination of the relatively higher basicity of these materials combined with their relatively low surface charge. The capacities were also most likely influenced by the differences in solubility between the lanthanide phosphates that could form due to chemisorption. Investigations on the influence of other anions (chloride, sulphate, nitrate, and bicarbonate) on phosphate removal showed that only bicarbonate had a significant negative effect on phosphate sorption for all the materials studied. The main finding from this research was that the surface zeta potential of the materials studied had a strong influence on phosphate adsorption.