Methylthiazole Schiff base functionalized SBA-15 for high-performance Pb(Ⅱ) capture and separation

Selective recovery of Pb(II) from effluent reduces its toxic impact on environment and benefits for saving non-renewable lead resources. To capture and separate Pb(II), a kind of methylthiazole Schiff base modified mesoporous silica, denoted as MTCI-SBA-15, was fabricated via grafting amino groups onto SBA-15 which was followed by Schiff condensation with 4-methylthiazole-5-carboxaldehyde. A variety of characteristic methods monitored the evolution of the modified adsorbent. Pb(II) uptake to MTCI-SBA-15 was studied in batch mode concerning pH, contact time, initial concentration, temperature, coexisting metallic ions, etc. Kinetic analyses revealed that the pseudo-second-order model was suitable for describing adsorption process. The adsorption isotherms were well represented by the Langmuir model. The thermodynamic study confirmed that the sorption was spontaneous and endothermic. The maximal load ability of MTCI-SBA-15 (283 mg g−1) for Pb(II) outperformed that of most modified mesoporous silica adsorbents. Moreover, Pb(II) removal efficiency higher than 99% can be reached with a low initial concentration (<50 mg L−1). Testing on the effects of competing ions suggested that MTCI-SBA-15 exhibited a desirable selectivity for Pb(II). Further, MTCI-SBA-15 was recyclable, retaining 93.1% of the adsorption capacity after five successive cycles. Mechanisms investigation indicated that the imine N atom on the Schiff base and the S atom on the 4-methylthiazole ring played a synergistic role during the adsorption process for Pb(II). The MTCI-SBA-15 showed excellent application potential for Pb(II) capture and separation.