Super rapid removal of copper, cadmium and lead ions from water by NTA-silica gel

Abstract

Copper (Cu 2+ ), cadmium (Cd 2+ ) and lead ions (Pb 2+ ) are toxic to human beings and other organisms. In this study, a silica gel material modified with nitrilotriacetic acid (NTA-silica gel) was sensibly designed and prepared via a simple amidation procedure for the removal of Cu 2+ , Cd 2+ and Pb 2+ from water. The NTA-silica gels showed rapid removal performances for the three metal ions (Pb 2+ (<2 min), Cu 2+ and Cd 2+ (<20 min)) with relatively high adsorption capacities (63.5, 53.14 and 76.22 mg g −1 for Cu 2+ , Cd 2+ and Pb 2+ , respectively). At the same concentration of 20 mg L −1 , the removal efficiencies of the three metals by the adsorbent ranged from 96% to 99%. The Freundlich and Langmuir models were utilized to fit the adsorption isotherms. The adsorption kinetics for the three metal ions was pseudo-second-order kinetics. The removal performance of the NTA-silica gels increased in a wide pH range (2-9) and maintained in the presence of competitive metal ions (Na + , Mg 2+ , Ca 2+ and Al 3+ ) with different concentrations. In addition, the NTA-silica gels were easily regenerated (washed with 1% HNO 3 ) and reused for 5 cycles with high adsorption capacity. This study indicates that the NTA-silica gel is a reusable adsorbent for the rapid, convenient, and efficient removal of Cu 2+ , Cd 2+ , and Pb 2+ from contaminated aquatic environments.