Oxidative Transformation of Sugarcane Bagasse by Plasma-Activated Water

This study investigates the interaction between plasma-activated water (PAW) and sugarcane bagasse (SCB), focusing on the chemical effects of reactive oxygen and nitrogen species generated during plasma–liquid interactions on lignocellulosic biomass. Initially, atmospheric cold plasma was employed as a strategy for the direct and indirect activation of SCB aiming at improving its performance in the removal of methyl orange from aqueous solutions. Direct activation was performed by exposing SCB to a helium plasma jet, while indirect activation involved treating deionized water with the plasma jet under two configurations: plasma exposure at the liquid surface and plasma treatment with gas bubbling, generating PAW with different chemical reactivities. Unexpectedly, the results indicated that PAW did not significantly enhance the dye removal capacity of the biomass. Instead, spectroscopic analyses revealed that reactive species dissolved in PAW promoted oxidation, fragmentation, and partial solubilization of lignocellulosic components, particularly lignin-derived aromatic structures. UV–Vis measurements of the liquid phase suggested the release of soluble organic compounds from the biomass, indicating chemical modification of the lignocellulosic matrix. These findings demonstrate that PAW acts not only as an oxidizing medium for pollutant degradation but also as an effective agent for the chemical pretreatment of lignocellulosic biomass. The observed oxidative transformation of SCB suggests potential applications of plasma-activated water in biomass processing and pretreatment strategies relevant to emerging biorefinery concepts. This study therefore provides new insights into plasma–biomass interactions and highlights the versatility of plasma-liquid systems for sustainable biomass valorization.