Synthesis and characterization of ZnZr composites for the photocatalytic degradation of phenolic molecules: addition effect of ZrO2 over hydrozincite Zn5(OH)6(CO3)2

BACKGROUND The composite materials ZrO2/Zn-5(OH)(6)(CO3)(2) were prepared in only one step by chemical co-precipitation and thermal hydrolysis of urea. ZrO2 was added at 5, 8 and 10 mol%. The samples were dried at 80 degrees C and characterized by adsorption-desorption of N-2 isotherms, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, and diffuse reflectance (DRS), UV-visible, Fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies. The materials were assessed in the photodegradation of phenol and polychlorinated phenolic molecules under UV-light irradiation. The possible mechanism was discussed from studies that corroborated or discarded the formation of the species center dot OH, center dot O-2(-) and h(+). RESULTS The addition of ZrO2 to Zn-5(OH)(6)(CO3)(2) resulted in a composite material with high photoactivity. The material containing 8 mol% of ZrO2 (ZnZr-8.0%) was the sample with the best percentages of photodegradation and mineralization. The photodegradation enhancement was achieved partly by an increment in the specific surface area and principally due to localized states originating in the composite interphase which improved charge transfer. XPS study revealed that the ZrO2 addition increases the oxygen vacancies which enhanced the organic molecule photodegradation via direct hole attack. CONCLUSION The ZnZr composite system constitutes an excellent alternative for the photodegradation of persistent organic pollutants due to the low cost, high stability and null toxicity of the support Zn-5(OH)(6)(CO3)(2). (c) 2019 Society of Chemical Industry