Polyethyleneimine-grafted polysilsesquioxane hollow spheres for the highly efficient removal of anionic dyes and selective adsorption of Cr(VI)

Abstract

The efficient adsorption of pollutants from wastewater is of considerable importance for environmental protection. Herein, a novel polyethyleneimine (PEI)-functionalised polysilsesquioxane hollow sphere (H-PVTMS-PEI) was prepared successfully via a facile grafting approach. The product was characterised using scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption–desorption behaviour, Fourier transform infrared spectroscopy, thermogravimetric analysis, small-angle X-ray scattering, and X-ray photoelectron spectroscopy. The adsorption behaviours of H-PVTMS-PEI towards Congo red (CR) and Cr(VI) were evaluated by studying the effects of solution pH, initial pollutant concentration, coexisting metal ions, and contact time in batch adsorption experiments. The hollow adsorbent H-PVTMS-PEI-2, prepared using 2% PEI in tetrahydrofuran solution, exhibited fast adsorption kinetics and superior adsorption capacities for Cr(VI) (391.1 mg/g; < 125 min) and CR (922.4 mg/g; < 100 min), owing to its amine group-rich surface. The data for the adsorption of Cr(VI) and CR onto H-PVTMS-PEI-2 were well explained by the Langmuir adsorption isotherm and pseudo-second-order kinetic models. Furthermore, H-PVTMS-PEI-2 maintained high selectivity in the capture of Cr(VI) contaminants from the mixed aqueous solutions of Cr(VI), Zn(II), Co(II), and Cd(II). Additionally, H-PVTMS-PEI-2 exhibited excellent regeneration ability. The removal mechanism involved was investigated based on the characterisation analyses. In summary, H-PVTMS-PEI-2 has the potential to be used as an efficient adsorbent in the remediation of coexisting toxic water pollutants.