Photocatalytic Degradation of Organic Micropollutants in Water by Zr-MOF/GO Composites

Rina Heu,Chihiro Yoshimura,Mohamed Ateia,Patiparn Punyapalakul,Dion Awfa

doi:10.3390/jcs4020054

Abstract

Nanocomposites of UiO-66 and graphene oxide (UiO-66_GO) were prepared with different GO contents by a one-step hydrothermal method, and their photocatalytic activities for the degradation of carbamazepine (CBZ) were investigated under ranges of GO loading, catalyst dose, initial pollutant concentration, and solution pH. The UiO-66_GO nanocomposites showed photocatalytic rate constant up to 0.0136 min−1 for CBZ degradation and its high overall removal efficiency (>90%) in 2 h. The photocatalytic rate constant over the UiO-66_GO nanocomposite was about 2.8 and 1.7 times higher than those over pristine GO and UiO-66, respectively. The enhancement of photocatalytic activity by GO was attributed to increased surface area and porosity, improved light absorption, and narrowed band gap. The composite also showed substantial recyclability and stability over five consecutive cycles of photocatalytic degradation. The experimental results indicated that O2●− and OH● are the responsible radicals for photocatalytic degradation, which helped us propose a photocatalytic mechanism for the enhanced CBZ photodegradation. This work provides a reference for the development of GO-based composite photocatalysts and expands the application of UiO-66 as a photocatalyst for the degradation of persistent micropollutants in water.

Highlights

Heterogeneous photocatalysis is one of the so-called advanced oxidation processes (AOPs) and has attracted a great deal of attention over the past few decades for water purification and disinfection due to its advantages of being non-selective, chemical-free, cost-effective, and simple to operate [1,2,3,4]
We present a facile hydrothermal method for preparing UiO-66_GO nanocomposites, and report, for the first time, its application for the photodegradation of an organic micropollutant (OMP)
The increase in interlayer spacing after oxidation was due to the presence of oxygen functional groups on each carbon layer, as could be confirmed by Fourier-transform infrared (FTIR), indicating that graphite was oxidized to graphene oxide (GO)

Summary

Introduction

Heterogeneous photocatalysis is one of the so-called advanced oxidation processes (AOPs) and has attracted a great deal of attention over the past few decades for water purification and disinfection due to its advantages of being non-selective, chemical-free, cost-effective, and simple to operate [1,2,3,4]. New semiconductor photocatalysts have been developed with the aim of achieving improved photocatalytic performance [5,6] In this regard, metal–organic frameworks (MOFs), as crystalline porous materials, have attracted extensive interest as emerging metal complex photocatalysts and semiconductor photocatalysts in recent years [7,8]. MOFs are composed of inorganic metal ions as connecting centers and organic moieties as linkers and offer two significant advantages in photocatalysis. Their high surface areas (up to 3000 m2/g), high porosity (up to 1 cm3/g), and abundance of functional groups increase the number of active sorption sites, while providing additional pathways for photo-induced electron migration, facilitating charge carrier separation [9,10]. Low chemical, thermal and hydrothermal stabilities are one of the main weaknesses of MOF materials [4], limiting their application for photocatalytic processes in actual treatment plants

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