Adsorption of Cu(II)-EDTA chelates on tri-ammonium-functionalized mesoporous silica from aqueous solution

The preparation and application of tri-ammonium-functionalized mesoporous silica SBA-15 (NNN-SBA-15) for sequestering Cu(II)-EDTA chelates from aqueous solution with low concentration of 0.1 mmol/L were explored. The adsorption properties of copper in the presence of equimolar EDTA were examined as a function of initial pH, ionic strength, initial concentration and temperature. Results revealed that the adsorption of Cu(II)-EDTA chelates on NNN-SBA-15 achieved equilibrium within 2 min and fitted well with the Langmuir model. The maximum copper adsorption capacity was estimated to be 26.3 mg/g. High ionic strength (0.1 mol/L of NaNO3) influenced the removal of Cu(II)-EDTA chelates, while temperature (from 15 to 35 °C) had slight effect on the adsorption capacity. Compared with the copper sorption system without EDTA species, the capture ability of copper increased significantly with coexistence of EDTA species in acidic condition. XPS spectrum studies indicated that Cu(II)-EDTA was removed from aqueous solution by the electrostatic interaction and hydrogen bond interaction between the protonated amine groups of NNN-SBA-15 and Cu(II)-EDTA chelates.