Graphitic Quantum Dots from Wheat Straw as Efficient Adsorbents for Removal of U(VI) from Water

ABSTRACT A new sustainable method for in‐situ preparation of graphene quantum dots (GQDs) from waste wheat straw at an optimal temperature (∼60°C) using a deep eutectic solvent (DES) composed of ZnCl 2 and lactic acid is established. The Lewis acidic nature of ZnCl 2 , along with Cl − ions, facilitated the breakdown and dissolution of wheat straw in DES. Various techniques confirm the formation of GQDs appended with different functional groups. The resulting GQDs showed excellent adsorption performance toward U(VI) ions, removing over 95% of U(VI) from groundwater samples (50–360 µg L −1 ) collected from the northwestern Punjab region, India, using batch and column methods. Adsorption studies indicated that the process is endothermic and spontaneous, and follows the Langmuir isotherm with a maximum adsorption capacity of 301 mg g −1 under optimum adsorption parameters: pH = 6, contact time = 30 min, and adsorbent dose = 0.4 g L −1 . The DES has been restored for reuse. This is the foremost report on dissolution and processing of wheat straw in a deep eutectic solvent (DES) under mild, low‐temperature conditions, enabling in‐situ formation of graphene quantum dots (GQDs) in a single step. This work is expected to enhance renewable biomass into sustainable materials using DESs.