Carbon nanodots as nanoadsorbents: a novel approach for dye-polluted effluent remediation

Dye pollution from industrial effluents poses a major environmental threat due to the toxicity, mutagenicity, and carcinogenicity of synthetic dyes. Conventional treatment methods-physical, chemical, and biological-often suffer from limited efficiency, high operational costs, and secondary pollution. Carbon-based nanomaterials have emerged as promising alternatives, with carbon nanodots (CNDs) gaining attention for their unique physicochemical properties. CNDs, typically 1-10 nm in size, offer high surface area (up to 600 m²/g), tunable surface functionalities, and strong visible-light-induced photoluminescence. CNDs synthesized via green routes from biomass, including food and agricultural waste, also demonstrate excellent reusability, maintaining over 90% removal efficiency across 3-5 cycles. This review discusses the synthesis methods, adsorption and photocatalytic mechanisms, and multifunctional applications of CNDs in dye removal. Comparative analysis with other carbon nanomaterials, such as CNTs and graphene oxide, highlights the superior biocompatibility and environmental performance of CNDs. Furthermore, the cytotoxicity and phytotoxicity profiles of CNDs are reviewed to ensure safe large-scale implementation. This study emphasizes the need for continued innovation in CND-based technologies to combat dye pollution effectively.