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.

Abstract

A silica gel material modified with nitrilotriacetic acid (NTA-silica gel) was sensibly designed and prepared via a simple method for the super rapid removal of Cu ²⁺, Cd ²⁺ and Pb ²⁺ from water.