CITRIC ACID CROSSLINKED NANOFIBRILLATED CELLULOSE FROM BANANA (MUSA ACUMINATA X BALBISIANA) PSEUDOSTEM FOR ADSORPTION OF Pb2+ AND Cu2+ IN AQUEOUS SOLUTIONS

Nanofibrillated cellulose was isolated from banana pseudostem, a common agricultural waste, using acid hydrolysis and ultrasound irradiation and was thermochemically crosslinked with citric acid and used for the adsorption of Pb2+ and Cu2+ ions in an aqueous solution. The synthesized nanofibrillated cellulose was characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and the analysis of the point of zero charges (PZC). The SEM data showed that nanofibrillated cellulose has a width of around 69 nm and the EDX spectra depicted the successful removal of inorganic constituents. The linkage of citric acid to cellulose was confirmed by FTIR and the analysis of the PZC revealed that citric acid modification imparted negatively charged carboxyl groups to the cellulose surface. The optimization of the solution pH and adsorbent dosage showed that 99% of Pb2+ and Cu2+ ions were removed under optimum conditions of pH 5 and 2.5 g/L of adsorbent, with high recyclability and following the Freundlich isotherm model. In addition, it was found that the adsorption process is exothermic, reversible, and driven by physisorption. The maximum adsorption capacity was found to be 205.42 mg/g for Pb2+ and 56.04 mg/g for Cu2+, which makes CA-NFC comparable to existing citric acid modified agricultural wastes.