Macro-/nanoporous Al-doped ZnO via self-sustained decomposition of metal-organic complexes for application in degradation of Congo red

Abstract

Pure and Al-doped macro-/nanoporous ZnO were synthesized via solution combustion method by using zincacetate dihydrate (Zn(CH3COO)2·2H2O), zinc nitrate hexahydrate (Zn(NO3)26H2O), aluminum nitrate nonahydrate (Al(NO3)3·9H2O), hydrazine hydrate (N2H4·H2O) and glycine (C2H5NO2) as precursors. The morphology, structure and catalytic properties of the as-synthesized macro-/nanoporous products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption and Fourier transform infrared spectroscopy (FTIR), respectively. Pure and Al-doped ZnO have coral-like shape with the pores size ranging from several nanometers to ten micrometers. The walls of the macropores contain smaller nanopores, exhibiting the hierarchically porous morphology. The catalytic activities of the as-synthesized samples were tested by measuring the degradation efficiency of azo dye Congo red (CR) under visible light, UV light and dark light, respectively. The results show excellent removal capacity for organic pollutants CR in wastewater. Macro-/nanoporous Al-ZnO with different contents of Al have better catalytic degradation efficiency than pure ZnO. The experimental results indicate the potential use of macro-/nanoporous Al-ZnO for catalytic degradation of Congo red dye in different environments, which provides a potentially low-cost alternative for the remediation of azo-dye effluents.