Efficient Adsorption and Utilisation of Methylene Blue by NaOH-Modified Nanocellulose–Polyacrylamide Interpenetrating Network Gels

To solve the problem of dye contamination caused by methylene blue (MB), a one-step synthesised nanocellulose (CNF) and polyacrylamide (PAM) gel network was modified by using NaOH in this study, and the prepared samples were analysed for their micromorphology, chemical structure, and adsorption-release properties. The findings demonstrated that the maximum adsorption capacity of the CNF-PAM5% was 172.08 mg/g, which followed the quasi-second-order kinetic model and the Freundlich adsorption model. The adsorption of the gel increased with the increase of the NaOH-modified concentration. However, the adsorption efficiency of the CNF-PAM5% could still reach 85% after four cycles, and the CNF-PAM5% remained intact without signs of fragmentation after 4 h of stirring and water impact, which was attributed to the introduction of CNF into the PAM network to effectively improve the mechanical properties of the gel. Moreover, toxicity tests showed no significant difference in the amount of cellular activity, even when the volume of the CNF-PAM5% sample was increased up to 10-fold. This gel, which exhibits low toxicity and excellent recycling properties, serves to reduce environmental impact during the adsorption process. Furthermore, the potential exists for utilising the gel's methylene blue-releasing (MB) properties as a fungicide for fish.