Green Synthesis of Carbon Aerogel Derived from Lotus Root for the Removal of Ciprofloxacin, Oil, Organic Solvents, and Supercapacitor Applications

In this study, lotus root-carbon aerogel (LR-CA) was successfully synthesized using facile hydrothermal, freeze-drying, and pyrolysis methods. Herein, under various calcination conditions, the lotus root-carbon aerogel-nitrogen (LR-CAN) materials maintained the three-dimensional structure with a well-developed hierarchical pore structure. Besides, LR-CAN materials also showed excellent adsorption capacity for ciprofloxacin (CIP) under specific conditions: 0.4 g/L catalyst, 50 mg/L CIP concentration, and pH 7 with removal efficiency and adsorption capacity reaching 97.1% and 241.1 mg/g, respectively. Notably, the presence of interfering salts (NaCl, KCl, and Na₂SO₄) minimally affected the CIP adsorption capacity of the material and demonstrated stable performance after five reuse cycles, albeit with a slight decrease in adsorption capacity from 242.2 to 200.9 mg/g. Moreover, the LR-CAN exhibited the highest adsorption capacity with chloroform, n-hexane, and used cooking oil at 27.1, 21.0, and 14.3 g/g, respectively. In addition, the LR-CAN performed outstanding electrochemical properties with the CV curve achieving the rectangular area and specific capacitance calculated from the GCD method reaching the maximum at 292.3 F/g at the current density of 3 A/g. In addition, the ability to maintain stable capacitance after 500 cycles, retaining an efficiency of 80.1%. These findings highlight the potential of environmentally friendly CA materials in effectively treating antibiotic pollutants and their promising application in supercapacitor electrode fabrication.