What is it about?

In this study, a ZnO/Ag/GO nanocomposite was synthesised and used as photocatalyst for effective photodegradation of naphthalene from simulated wastewater under visible light. Chemical and morphological characterisation were successfully done using XRD, PL, UV–vis, FTIR, XPS, FESEM and HRTEM analytical tools. Photocatalytic degradation experiments were first carried out under dark conditions and then under visible-light irradiation. Adsorption study of naphthalene prior to photocatalysis using synthesised material was thoroughly done by studying the kinetics and adsorption isotherm models. All as-synthesised materials (ZnO nanoparticles, binary ZnO/Ag, and ternary ZnO/Ag/GO nanocomposites) followed pseudo-second-order kinetics and the Freundlich adsorption isotherm, confirming the adsorption on hetero-structural surface. ZnO/Ag/GO could successfully adsorb 80% naphthalene in 20 min, with 500 mg.g−1 adsorption capacity. High adsorption of naphthalene molecules on ZnO/Ag/GO surfaces trigger improved photodegradation efficiency upon light irradiation. Incorporation of plasmonic Ag nanoparticles and 2D graphene oxide (GO) to ZnO semiconductor improved the photocatalytic degradation efficiency of naphthalene, achieving up to 92% degradation in 50 min. The photodegradation of naphthalene follows the Langmuir-Hinshelwood kinetics model and was found acceptable to express the photodegradation rate. Furthermore, the ZnO/Ag/GO photocatalyst could easily be recycled and reused for five cycles, maintaining up to 85% of its photodegradation efficiency.

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Why is it important?

Herein, we are reporting the synthesis of a ZnO/Ag/GO nanocomposite as photocatalyst for the removal of naphthalene from contaminated wastewater under visible light. The prime objectives of this work were: (i) synthesis of ZnO-based nanomaterials (ZnO, ZnO/Ag and ZnO/Ag/GO) with enhanced removal efficiency of naphthalene from solution, (ii) chemical and morphological characterisation of the as-synthesised nanomaterials and (iii) effective adsorption and photodegradation of naphthalene using a ZnO/Ag/GO nanocomposite under visible light.


High adsorption potential of ZnO/Ag/GO, with adsorption capacity 500 mg.g−1, eases the direct interaction of photo-generated electrons with adsorbed naphthalene molecules and hence facilitates quick photodegradation. GO nanosheets also delayed the recombination time of photo-induced electrons and holes suitable for photodegradation activities. Photocatalytic degradation of naphthalene in a solution under visible light followed pseudo-second-order kinetics. In this study, a nanocomposite was synthesised with enhanced photodegradation activity under visible light, which suggests a sustainable and cost-effective treatment system for the remediation of polluted water.

Dr Neeraj Kumar
Council for Scientific and Industrial Research

Read the Original

This page is a summary of: Removal of naphthalene from simulated wastewater through adsorption-photodegradation by ZnO/Ag/GO nanocomposite, Journal of Industrial and Engineering Chemistry, January 2020, Elsevier,
DOI: 10.1016/j.jiec.2019.09.030.
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