Abstract
Water scarcity and contamination are critical global concerns, with organic pollutants such as dyes, phenolic compounds, pharmaceuticals, and pesticides increasingly entering aquatic systems and posing serious risks to ecosystems and human health. Among various treatment technologies, photocatalysis has emerged as a sustainable and effective strategy for wastewater purification, particularly for degrading persistent organic contaminants. However, conventional metal-semiconductor photocatalysts suffer from inherent drawbacks, including limited visible-light absorption, sluggish surface kinetics, and rapid electron–hole recombination, which restrict their large-scale applicability. These challenges can be addressed by incorporating graphene and its derivatives graphene oxide (GO) and reduced graphene oxide (rGO) which provide high surface area, excellent electron mobility, and tunable chemical functionality, making them ideal co-catalyst supports. Unlike numerous reviews that broadly summarize graphene-based photocatalysts, the present work adopts a pollutant-specific comparative framework. It systematically evaluates the performance of graphene, GO, and rGO-based composites in degrading four major categories of contaminants: dyes, phenolic compounds, pharmaceuticals, and pesticides. Special emphasis is placed on understanding the role of operational parameters such as pH, oxidizing agents, light wavelength, photocatalyst dosage, and pollutant concentration in influencing degradation outcomes. Mechanistic insights, recyclability, and efficiency trends are critically examined through case studies, highlighting both synergies and limitations across pollutant classes. By adopting this targeted approach, the review not only underscores key advancements but also identifies existing knowledge gaps, offering valuable perspectives for designing next-generation graphene-based photocatalysts tailored to specific water pollutants.