Adsorption behavior of phosphate on Lanthanum(III) doped mesoporous silicates material

A series of lanthanum doped meosoporous MCM-41 (La(x)M41, x is Si/La molar ratio) was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N-2 adsorption/desorption technique. The content of La in the materials was determined by ICP. It was found that the La content of La(25)M41, La(50)M41 and La(100)M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, La(x)M41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of La(x)M41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.