Oil dispersing and adsorption by carboxymethyl cellulose–oxalate nanofibrils/nanocrystals and their kinetics

Abstract

The aim of our work is the preparation of cellulose nanofibrils or nanocrystals made from cellulose that is recovered from sugarcane bagasse agricultural waste (SC) as a dispersant instead of commercial cellulose for oil spill cleanup. In the current study, carboxymethyl cellulose was prepared by cellulose mercerization, which was then esterified by oxalic acid to create nanocellulose. Incorporation of oxalate into carboxymethyl cellulose (CMC) was verified by ¹H-NMR spectroscopy by the appearance of a new peak at 8.15 ppm for CMC–oxalate. The degree of substitution (DS) of oxalate was 0.17. The synthesized nanocellulose formed particles were roughly the same size and shape as both cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs): measuring 321–480 nm in length and 4–5 nm in width. Emulsions of paraffins made from CMC–oxalate are stable up to 10 months without undergoing precipitation. CMC–oxalate had great thermal stability and worked well as a paraffin oil dispersant. CMC–oxalate provided a barrier around the oil droplet surface, which prevented droplets from coalescing. This hypothesis is supported by the contact angle measurement for the O/W emulsion formed by CMC–oxalate being 0°, which is lower than the value for emulsions formed by underivatized CMC, 37.20°. From transmission electron microscopy observations, O/W emulsions of paraffin oil were spherical in shape, and separated from each other by a distance of 30–100 nm. This study shows that CMC–oxalate can be prepared by a low-cost method, yielding nanocellulose with characteristics that resemble CNFs and CNCs, thereby opening up new potential applications for cellulose nanomaterials.