Selective adsorption and efficient removal of phosphate using lanthanum-modified mesoporous silica from aqueous solutions

Lanthanum-modified mesoporous silica (MS-La) with a specific surface area of 386 m(2)/g was prepared using mesoporous silica and lanthanum(III) as raw materials by co-precipitation method. The composite adsorbent is ideal for the removal of solutions contaminated with phosphate, due to their chemical stability and a strong affinity with phosphate. MS-La could effectively removal of phosphate within the pH range of 3-6. The coexisting anions result manifested that MS-La with excellent selectivity to phosphate was determined by the hydrogen bonding mechanism in competitive anion solutions. The adsorption kinetics was well fitted with the pseudo-second-order kinetic equation, suggesting chemical adsorption. The Langmuir isothermal model could better describe the adsorption isotherm data and the maximum adsorption capacity of 27.98 mg/g. Furthermore, the main mechanism of phosphate adsorption was electrostatic attraction and ligand exchange. Its efficient adsorption capacity ensures a bright prospect for low-concentration phosphate removal.