Acid-functionalized magnetic nanocatalysts mediated pretreatment of sugarcane straw: an eco-friendly and cost-effective approach

The ubiquitous nature of lignocellulosic biomass on planet earth and its economic viability attracted a great deal of attention from researchers and becomes foremost feedstock for biofuel production particularly bioethanol. However, due to complexity in structure, its pretreatment is essentially required prior to actual use. In the present study, a promising approach has been proposed through the development of acid-functionalized magnetic nanocatalysts. Two different acid-functionalized magnetic nanocatalysts i.e. alkylsulfonic acid functionalized magnetic nanoparticles (Fe₃O₄-MNPs-Si-AS) and butylcarboxylic acid functionalized magnetic nanoparticles (Fe₃O₄-MNPs-Si-BCOOH) were developed and their efficacy was studied in the pretreatment of sugarcane straw at varying concentrations (100, 200, 300, 400, 500 mg/g of straw). The enhanced concentration dependent production of sugar (xylose) was reported in case of both the nanocatalysts. The maximum 17.06 g/L for Fe₃O₄-MNPs-Si-AS and 15.40 g/L for Fe₃O₄-MNPs-Si-BCOOH sugar was reported at 500 mg which is comparatively higher than normal acid (H₂SO₄) (14.63 g/L) and non-treated (0.24 g/L) sugarcane straw. Further, both the nanocatalysts were recovered by applying an external magnetic field and reused for the next two subsequent cycles of pretreatment. It was observed that with every reuse of nanocatalysts the concentration of sugar production was reduced. Moreover, generation of very less amount of toxic inhibitors was reported in the hemicellulosic hydrolyzate obtained in the present study. Considering these facts, it is believed that such nanocatalysts can be used as an effective, eco-friendly and economically viable alternative to the conventional pretreatment agents like mineral acids.