Facile extraction and characterization of cellulose nanocrystals from agricultural waste sugarcane straw.

BACKGROUND: Sugarcane straw is an available but largely ignored lignocellulosic biomass to obtain cellulose nanocrystals (CNCs) with highly crystalline, tunable surface chemistries and a wide-ranging adaptability. Herein, we utilized sugarcane straw to obtain pure cellulose via purification processes, followed by subsequent preparation of CNCs via sulfuric acid hydrolysis. The properties of the purified fibers and obtained CNCs were assessed by their composition, morphology, chemical structure, crystallinity and thermal stability. RESULTS: After the purification process, alkali-treated fibers (ATFs) contained 886.33 ± 1.25 g kg-1 cellulose, and its morphological analysis revealed a smooth and slender fibrous structure. The CNCs obtained by treatment with 64 wt% sulfuric acid at 45 °C for 60 min were isolated in a yield of 21.8%, with a diameter and length of 6 to 10 nm and 160 to 200 nm, respectively. Moreover, crystallinity index of these CNCs reached 62.66%, and thermal stability underwent a two-step degradation. Short-term ultrasonication after hydrolysis was employed to enhance isolation of the CNC particles and improve the anionic charge with higher value -38.00 mV. CONCLUSION: Overall, isolation and characterization results indicated the potential for CNCs preparation using sugarcane straw, in addition to offering a fundamental understanding of this material and indicating potential applications. © 2021 Society of Chemical Industry.

Comparison of UV/hydrogen peroxide and UV/peroxydisulfate processes for the degradation of humic acid in the presence of halide ions.

This study compared the behaviors of two classic advanced oxidation processes (AOPs), hydroxyl radical-based AOPs ((•)OH-based AOPs) and sulfate radical-based AOPs (SO4 (•-)-based AOPs), represented by UV/ hydrogen peroxide (H2O2) and UV/peroxydisulfate (PDS) systems, respectively, to degrade humic acid (HA) in the presence of halide ions (Cl(-) and Br(-)). The effects of different operational parameters, such as oxidant dosages, halide ions concentration, and pH on HA degradation were investigated in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes. It was found that the oxidation capacity of H2O2 and PDS to HA degradation in the presence of halides was nearly in the same order. High dosage of peroxides would lead to an increase in HA removal while excess dosage would slightly inhibit the efficiency. Both Cl(-) and Br(-) would have depressing impact on the two AOPs, but the inhibiting effect of Br(-) was more obvious than that of Cl(-), even the concentration of Cl(-) was far above that of Br(-). The increasing pH would have an adverse effect on HA decomposition in UV/H2O2 system, whereas there was no significant impact of pH in UV/PDS process. Furthermore, infrared spectrometer was used to provide the information of degraded HA in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes, and halogenated byproducts were identified in using GC-MS analysis in the four processes. The present research might have significant technical implications on water treatment using advanced oxidation technologies.