Synthesis and Characterization of Mesoporous Silica Modified with Purpald and Its Application in the Preconcentration of Cu2+ and Cd2+ from Aqueous Samples through Solid-Phase Extraction

The synthesis of an organofunctionalized mesoporous silica was accomplished by a two-step process involving (1) the co-condensation of a silylant agent at the surface of silica, followed by (2) the immobilization of Purpald (ligand) at the organic termination of the silytant agent. The characterization of the organofunctionalized material indicated the presence of NH2 groups, and the immobilization of the ligand was confirmed by Si-29- and C-13-nuclear magnetic resonance. The material's surface area was determined as 370 m(2) g(-1). Batch adsorption experiments enabled the determination of optimum pH conditions for the adsorption of Cu(II) and Cd(II). Under optimal pH, the pseudo-second-order kinetic model and Langmuir model provided the best correlations to describe the materials adsorption behavior, suggesting a chemisorption mechanism. When tested in continuous-flow preconcentration experiments, the flow rate and eluent concentration demonstrated to affect the removal of Cu(II) and Cd(II), while the buffer concentration had an effect only over the adsorption of Cu(II). Under optimized preconcentration conditions, it was possible both to determine the concentrations of Cu(II) and Cd(II) in samples such as mineral water, ground water, tap water and river water. Ions commonly found in drinking and natural waters (Na+, K+, Ca2+, Mg2+, Fe3+, Ba2+, Cl-, SO42-, HCO3-, and H2PO(4)(-)) did not affect the preconcentration of any of the studied analytes. Reutilization experiments indicated that the adsorbent material can withstand at least 40 adsorption/desorption preconcentration cycles with no efficiency loss.

Automated summary

A two-step process was used to synthesize an organofunctionalized mesoporous silica, involving the co-condensation of a silylant agent on the surface of silica and the subsequent immobilization of Purpald at the organic termination of the silytant agent. The material was characterized to have NH2 groups, and the immobilization of the ligand was confirmed through Si-29 and C-13 nuclear magnetic resonance. The material exhibited a surface area of 370 m(2) g(-1). Batch adsorption experiments revealed the optimum pH conditions for Cu(II) and Cd(II) adsorption, and the adsorption behavior was described by the pseudo-second-order kinetic model and Langmuir model. Continuous-flow preconcentration experiments showed that the flow rate and eluent concentration affected the removal of Cu(II) and Cd(II), while the buffer concentration only affected the adsorption of Cu(II). Under optimized preconcentration conditions, the concentrations of Cu(II) and Cd(II) in various water samples could be determined. The adsorbent material exhibited reusability for at least 40 adsorption/desorption preconcentration cycles without efficiency loss.