Exploring the adsorption efficiency of a novel cellulosic material for removal of food dye from water

A cellulosic nanoadsorbent was developed from the fruit coat of a forest tree named, Kendu (Diospyros melanoxylon) to remove tartrazine dye, popularly known as the yellow dye, from the aqueous solution. The proximate and mineral content of the cellulosic nanoadsorbent were analyzed by AOAC methods, and it was further characterized by different analytical techniques. The X-ray diffraction studies established the cellulose I polymorph structure of the bionanomaterial. The appearance of the inherent peak of the cellulose in the fingerprint region of the Fourier Transform infrared spectroscopy (FTIR) and the absence of the lignin and hemicellulose peaks in the FTIR spectrum supported the formation of the cellulosic nanocrystal. The analysis of the morphology of the crystal through Transmission electron microscopy envisaged the spherical nature of the crystal with a particle size of around 36 nm. The optimal adsorption of the yellow dye was achieved when the pH and temperature of the solution, adsorbent dosage, initial dye concentration, and stirring speed were 6.0, 60 oC, 80 mg L−1, 10 mg L−1, and 200 rpm, respectively. The nanocrystals could remove more than 95% of the dye, whereas virgin Kendu fruit coat powder could remove around 75% of the dye. The adsorption was spontaneous and followed second-order kinetics. The adsorption data were assessed for the Langmuir, Freundlich, Tempkin, Elovich, Intraparticle diffusion, and Dubinin-Radushkevich adsorption isotherm models. The adsorption of the dye onto the nanocrystal occurred through both polar and nonpolar interactions. The overall study indicated that the Kendu fruit coat could be a cost-effective natural bioresource for the synthesis of an adsorbent that could remove the yellow food dye from the aqueous solution proficiently.