This review explores the efficiency and mechanisms of GQDs in removing contaminants from water, emphasizing their potential for environmental applications. GQDs possess unique physicochemical properties, such as a high surface area, tunable photoluminescence, and strong adsorption capacities, which enable the effective removal of diverse contaminants, including heavy metals, organic compounds, and dyes. Their electron-hole separation efficiency and functionalizability enhance their reactivity and selectivity. Notable findings include the integration of GQDs into advanced nanocomposites and supramolecular networks, significantly improving their adsorption and catalytic performance. However, challenges such as variability in synthesis methods, stability under environmental conditions, and the environmental impact of GQDs remain. Addressing these limitations and understanding the interaction mechanisms between GQDs and contaminants are critical. Future research should prioritize scalable green synthesis techniques, long-term environmental assessments, and optimized functionalization strategies to establish GQDs as a sustainable solution in water purification technologies.