Quaternized salicylaldehyde Schiff base modified mesoporous silica for efficiently sensing Cu(II) ions and their removal from aqueous solution

In this study, quaternized salicylaldehyde Schiff base modified SBA-15 mesoporous silica (SBA-AP) was developed. The characterization of SBA-AP shows that the Schiff base ligand has been successfully introduced and ordered mesoporous structure of SBA-15 has been well-preserved after the post-grafting procedure. The quaternized linkage made the as-prepared nanohybrid very dispersible in water, and the salicylaldehyde Schiff base acted as a multifunctional ligand for complexing Cu(II). By adding Cu(II) into the SBA-AP suspension, the absorbance UV intensity at ∼ 420 nm gradually increased. In addition, the adding Cu(II) caused dramatic fluorescence quenching that was very selective for Cu(II) ions. The linear detection range for the Cu(II) chemosensor was 0.05–4 mg/L, and the detection limit was 3.7 × 10−7 M. The SBA-AP could also be used as an adsorbent for removing Cu((II) from water. The adsorption kinetics were fast and followed the pseudo-second-order kinetics model. The adsorption isotherms were fitted well by Langmuir isotherm mode and theoretical maximum Langmuir adsorption capacity of the SBA-AP toward Cu(II) was 34.73 mg/g. Thus, the SBA-AP offers promise for detecting, adsorbing, and recovering Cu(II) ions from water.