Nowdays, one of the global distressingubiquitous environmental issue is the water pollution and contamination which released by several industrial sectors [1, 2]. Due to the numerous hazardous environmental contaminates are the discharged into aqueous environment without any adequate treatment from the different industrial sectors including petrochemical dyes, pharmaceuticals, dyes, agricultural and can pose adverse effects on human nervous system and cause so many health disorders [3, 4]. Amongst numerous environmental pollutants the synthetic organic dyes containing benzene ring in their structure containing is highly toxic and teratogenic organic compounds due its structural stabilization, difficult in degradation, bioaccumulation through food chain system and potential carcinogenic properties [5–7]. Among these dyes, Congo red (CR) is a typical cationic dye with high solubility in the aqueous media due to its physiochemical thermal and optical stability, it is difficult to biodegrade from the aqueous system [8, 9]. The paper, leather industries, textile and other pigment industries are widely applied CR dye for the processing of many products [10, 11]. Also, the small quantity of the CR dye in aqueous system causes several serious cause lot of the human health issues including eyes irritation, diarrhea, and dysfunction of headache, convulsions, behavioral disorders, kidneys, liver, tissues, central nervous system gastrointestinal and other dangerous human disease [12–14]. Therefore, it is very important to develop a cost effective method for the removal of CR dye pollutant from the aqueous system.
Currently, several analytical methods have been used for the effective removal of CR dye from aqueous system such as ultrafiltration, ion-exchange, adsorption, reverse osmosis, flocculation, coagulation and membrane separation [15–18]. But these developed methods have some serious drawbacks such as time consuming, ineffective and expensive, thus these methods are not suitable for industries operating at small level. Moreover, over these traditional developed methods the photocatalytic degradation of CR dye from wastewater is one of the most recommended methods because of its capability, simplicity, and reusability, cost-effective and quick oxidation than other methods [19–21].
Graphene oxide is a derivative of graphene, which is a two-dimensional material, composed of carbon atoms arranged in a hexagonal lattice [22]. Graphene oxide has unique properties such as high surface area, high mechanical strength, high electron mobility, good transmittance, unique optical and excellent electrical and thermal conductivity [23–25]. Due to these properties graphene oxide widely employed in different fields of advance technology such as electronics, energy storage, separation science biomedical engineering, sensors, solid oxide fuel cell, solar cell, gas sensing, supercapacitors devices, spintronic device and photocatalytic material for the remediation of various pollutants from the aqueous system [26–28]. Graphene oxide can be easily functionalized by adding different chemical groups to the surface including metal carbide, organic polymers, biomolecules carbon nanotubes, and metal and metal oxide nanoparticles which can further enhance its properties and expand its applications [29, 30]. Among them, various surface functionalizing agents the metal oxide nanoparticles have gained too much interest because of their promising electrical, mechanical, high surface area and photoelectric properties [31]. Graphene oxide is reduced to produce reduced graphene oxide (rGO) through different synthesis methods such as hydrothermal, chemical, thermal and electrochemical methods [32]. Reduce graphene oxide (rGO) have exceptional physiochemical properties due to these properties reduced graphene oxide applied in different areas of modern technology such as in batteries, supercapacitors, photocatalytic material and biosensors [33, 34]. Moreover, the various metal oxide nanoparticles are exploited with graphene oxide including ZnO, NiO, TiO2, WO3, Co2O3, NiO, V2O5, Nb2O3 and Fe2O3 for functionalization of graphene oxide [35, 36]. Amongst, different metal oxide nanoparticles copper oxide (CuO) is an important p-type semi-conductor material having high electron band gap (1.2 eV) [37]. The CuO is non-toxic, eco-friendly and low-cost semi-conductor material with unique features such as catalytic, electrical conductivity, mechanical strength, high surface area, chemical stability, high theoretical capacity and good cycling performances [38–40]. Because of these properties CuO nanoparticles are widely employed in several applications like energy storage, photocatalyst, gas sensors, solar cells and electrochemical sensors [41, 42]. Hence, the chemical immobilization or incorporation of CuO nanoparticles on the surface of graphene oxide not only provides thermal stability but also enhanced its photocatalyst properties for the removal of organic pollutant i.e. CR dye from the aqueous system.
Herein, we synthesized the rGO-CuO nanocomposite via using facile and environmentally friendly method. Then, synthesized rGO-CuO nanocomposite was used as effective photocatalyst material for the removal of the CR dye from the aqueous environment.