Review: adsorption of dyes from wastewater by graphene oxide and its composites

Recent studies have demonstrated the efficacy of graphene oxide (GO) as an adsorbent for removing various dyes from water, owing to its large surface area, high porosity, and abundance of oxygen-containing functional groups. The primary goal of this review article is to collect the dispersed information of a diverse range of efficient GO composite adsorbents to remove dyes from water, providing a comprehensive overview of their synthesis, characterization, and functionalization methods. Various modification approaches of GO that increase its adsorption capacity are discussed in detail, as well as influencing factors on its performance, which include adsorbent dosage, initial dye concentration, nature of functional groups, contact time, pH, and temperature. Additionally, this review explores the adsorption mechanisms of dyes onto various GO-based materials and the extent to which different adsorption kinetics and isotherm models are applied. Such models include Langmuir and Freundlich that can further improve the understanding of dye–adsorbent interactions and help to design more efficient adsorption systems. It also covers a summary of the dye adsorption capacities of different GO composites and the parameters that control performance. On the basis of the extensive literature studied, critical insights were drawn, and several recommendations for future research were proposed, including the exploration of more sustainable synthesis routes and the development of novel functionalized GO composites.