Strong nanostructured films and effective lead (II) removal capacity based on nitro oxidized cellulose nanofibrils prepared from banana rachis

Abstract Banana rachis is an abundant and renewable source of cellulose from agricultural wastes. The main focus of the current work is the nanostructured aspects and the potential for removing heavy metals from wastewater using banana rachis cellulose. Highly individualized cellulose nanofibrils, CNF (length = 1231 nm, diameter = 5.26 nm) with negatively charged carboxylic groups at the C6 position of different degrees of oxidations (DO) were developed through nitro oxidation (NO) followed by simple mechanical treatment. The possibility of understanding the nanostructured aspects and tailoring high purification efficiency is discussed. A film prepared through vacuum filtration of the hydrocolloid suspension was strong (tensile strength = 254 MPa, Young modulus = 10.7 GPa, tensile strain = 5.7%), with the highest strength reaching 334 MPa. The highest purification efficiency (compared to other adsorbents in the literature data) was reached at DO = 1.466 mmol/g using an initial Pb (II) concentration of 1000 ppm and followed pseudo-second-order kinetics. A good relationship between an increased Pb (II) removal to the DO (0.455–1.466 mmol/g) and the NOCNF concentration was observed whereby chemisorption is the primary adsorption mechanism. The NOCNF shows a maximum adsorption capacity of 1667 mg/g at the DO = 0.455 mmol/g based on the Langmuir equilibrium adsorption isotherm. The film formation property and high Pb (II) removal behavior were attributed to a well-individualized NOCNF, good dispersion, and high nanofibril interaction. The stiff cellulose crystal was successfully preserved even at a high DO with the crystallinity index = 72%.