Sustainable Hydrothermal Synthesis of CuO Nanoparticles Using Merremia quinquefolia for Visible-Light Photocatalytic Degradation of Methylene Blue

Abstract

This growing release of artificial dyes in water bodies has led to the necessity of an efficient and sustainable method of treatment that can eliminate recalcitrant organic pollutants. This research explores the hydrothermal synthesis of copper oxide (CuO) nanoparticles using Merremia quinquefolia extract in a sustainable manner and assesses their ability to be used in visible-light photocatalytic degradation of methylene blue. The natural assisting agent used in nanoparticle synthesis involved the use of the plant extract so as to eliminate the need to use traditional chemical-intensive synthesis pathways. The preparation of CuO nanoparticles was carried out under regulated conditions of hydrothermal treatment, subsequent washing and drying, and subsequent thermal treatment. X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and UV-vis diffuse reflectance spectroscopy were used to study the crystalline and functional features, morphological and elemental properties, and optical properties of the synthesized nanoparticles. The use of methylene blue as a model dye pollutant under the influence of the visible light was used to perform the photocatalytic experiments. The influence of irradiation time, catalyst amount, initial concentration of dye, and pH of a solution on the degradation characteristic were explored systematically, photocatalytic kinetics and catalyst reusability. The results revealed the ability to construct crystalline nanoparticles of CuO possessing appropriate visual-light-sensitive properties and competent photocatalytic capability in the decomposition of methylene blue. Repeated-use experiments also suggested the possibility of the stability of the synthesized catalyst. In general, the plant-assisted hydrothermal method is a green way of synthesizing CuO photocatalysts that can have applications in dye-contaminated waste water purification.