Eco-Friendly Preparation of Nanofibrillated Cellulose from Water Hyacinth Using NaOH/Urea Pretreatment

Abstract

In this work, we described an effective approach to prepare nanofibrillated cellulose (NFC) with cellulose II structure under mild condition. Firstly, the water hyacinth (WH) was subjected to a series of a two-step chemical treatment, NaOH/urea pretreatment, and mechanical defibrillation at different defibrillation times. After that, raw water hyacinth fiber (RWF), bleached water hyacinth fiber (BWF), NaOH/urea pretreated water hyacinth fiber (PWF), and the resulting NFC were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) as well as rheological measurements. It was found that RWF and BWF exhibited cellulose I crystal structure, whereas PWF and the obtained NFC possessed cellulose II crystal structure. FTIR analysis confirmed the evidence that no other chemical reactions preferentially occurred during both NaOH/urea pretreatment and mechanical defibrillation. As evidenced by rheological properties analysis, the NFC aqueous suspension with a gel-like structure demonstrated a shear-thinning behavior. The obtained NFC could potentially be utilized as a reinforcement for polymeric composites.