Coconut Coir derived Nanocellulose as an Efficient Adsorbent for Removal of Cationic Dye Safranine -O: A detailed Mechanistic Adsorption Study

Abstract

Coconut (cocos mucifera) coir is an abundant agricultural waste prevalent worldwide. Utilization of this waste has been carried out in this study by obtaining nanocellulose (NC) fibres for waste water remediation purposes. Nanocellulose was obtained from coconut coir using bleaching, acid-alkali treatments followed by ultrasonication and lyophilization. The structural, compositional, surface and thermal properties of the synthesized material were identified using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption/desorption, differential thermal (DT) and derivative thermogravimetric (DTG) analyses. These analyses confirmed the synthesized NC with enhanced thermal stability and porosity which was further used for adsorption process. After synthesis, NC was used for the removal of cationic dye Safranin-O from water under ambient conditions through batch adsorption studies. The batch adsorption studies revealed that at 10 ppm of dye concentration, above 99% removal was achieved by 100 mg dosage of NC within 4.5 h at room temperature with qe value of around 83 mg. g-1. The corresponding adsorption process fitted well fitted with Langmuir isotherm and pseudo-second order kinetics. The modes of adsorption from the thermodynamic studies were found to be chemisorption. Optimization of The adsorption process was achieved through response surface methodology (RSM) study which revealed that at optimized conditions of temperature 35°C with a dose of 137.50 mg and contact time of 180 mins, above 99% of dye (conc. 0.01mg/mL) was removed. The present comprehensive study revealed that a greener eco-friendly synthesis of nanocellulose from waste material coconut coir was an effective nanoadsorbent for dye removal having high efficacy. This surely opens up opportunities to develop sustainable protocols for efficient environmental remediation.