Chlorella vulgaris nanocellulose in hydrogel beads for dye removal

Water pollution requires sustainable materials to develop green treatment solutions. Nanocellulose with outstanding properties is a sustainable building block of adsorbent for wastewater treatment. However, nanocellulose extraction from plants remains an energy and chemical-intensive process. This study aims to produce nanocellulose from microalgae via facile extraction for the synthesis of hydrogel adsorbents. Without TEMPOmediated oxidation, nanocellulose was successfully extracted from Chlorella vulgaris through alkaline treatment, bleaching, and hydrolysis only in a high-speed blender in this study. The effects of acid concentration on nanocellulose properties were studied. The maximum yield (58.5%) was achieved using sulphuric acid with a concentration of 60%(v/v). Scanning electron microscopy and transmission electron microscopy images showed the fibrillated structure at the nanoscale. Fourier-transform infrared spectroscopy results confirmed the elimination of lignin and hemicellulose through alkaline treatment, while X-ray diffraction patterns proved that microalgae nanocellulose were typical cellulose I. The microalgae nanocellulose was further incorporated into carboxymethyl cellulose/sodium alginate beads. Methylene blue adsorption capacity raised from 28.46 mg/g to 109.03 mg/g. Dye removal percentage as high as 93.7% could be achieved due to the hydrogen bonding and electrostatic interaction with carboxylate groups.