Fast and efficient removal of lead from low concentration solutions using silicotitanate

Sodium crystalline silicotitanate (Na-CST) and niobium substituted crystalline silicotitanate (Na-Nb/CST), which were synthesized using the hydrothermal method and characterized by X-ray diffraction (XRD), BET and scanning electron microscopy (SEM), were used to separate Pb2+ from aqueous solutions. The adsorption experiments show that their maximum adsorption ability is within pH 4.00~6.50. The adsorption process reaches equilibrium within 60 min, and the maximum adsorption quantity of Na-CST and Na-Nb/CST is 70.1 and 70.7 mg·g-1, respectively. Both materials are able to remove more than 94% of Pb2+ from water when Pb2+ concentration is at 10-9kg·L-1 level. Most interestingly, the concentration of Pb2+ could be lower than 3×10-9kg·L-1 after adsorption, much lower than the standard set by of the World Health Organization for the quality of drinking water, 1×10-8kg·L-1.