Tea grounds inspiration for a renewable biomass-based carbon aerogel with CMC and PVA reinforcements: Dye adsorption and supercapacitor prospects

Abstract In this study, tea grounds-carbon aerogel (TG-CA) was successfully synthesized and applied effectively in organic dye adsorption and supercapacitor applications. Interestingly, the prepared material has unique properties due to the synthesis process with the combination of carboxymethyl cellulose and poly(vinyl alcohol), which can improve the mechanical properties, strengthen the three-dimensional structure, and increase the specific surface area. Besides, the fabricated carbon aerogel also demonstrated excellent adsorption capacity for rhodamine B (RhB), crystal violet (CV), and methyl orange (MO) of 158.4, 143.2, and 132.9 mg/g for 2 h, respectively. Wherein, the adsorption efficiency of RhB dye was evaluated according to the pseudo-second-order kinetic (PSO) and the Langmuir isotherm model with R 2 = 0.9947. Besides, the thermodynamic investigation of RhB adsorption using TG-CA800 reveals that the process is endothermic and the negative values of Gibb's free energy (ΔG°) demonstrate that the process was spontaneous. Regarding the electrochemical properties, the tea grounds-carbon prepared at 800 o C (TG-CA800) indicated the highest specific capacitance of 291 F/g at the current density of 10 A/g with the potential window of −1.0 to 0 V in phosphate buffer (pH 7). Additionally, the great stability of the material was also confirmed with high capacitance retention of 97.53% after 500 cycles. These results suggest that the carbon aerogel materials prepared from green precursor sources, particularly tea grounds, could be considered a potential and promising approach to tackle organic dye elimination and supercapacitor applications.