Enhanced degradation of Acid Red 73 by using cellulose-based hydrogel coated Fe3O4 nanocomposite as a Fenton-like catalyst.

Carboxymethyl cellulose-based hydrogel coated Fe3O4 magnetic nanoparticles were prepared using a coprecipitation combining graft copolymerization method, and characterized by various techniques to study their structure-property relationships. The nanocomposite was used as a heterogeneous Fenton-like catalyst for Acid Red 73 degradation. The effects of several key parameters, solution pH, H2O2 concentration, catalyst dosage, and temperature of the reaction medium on the pseudo-first-order kinetics of dye degradation was evaluated. The results showed that the nanocomposite catalyst were highly effective in activating H2O2 to produce reactive radicals for dye degradation, achieving complete decomposition under optimal conditions of 300 min at 25 °C and pH 3.5 with 100 mM H2O2 and 200 mg·L-1 catalyst. The complexing hydrogel-Fe2+/Fe3+ were the key factors that speed up the redox cycling between Fe2+ and Fe3+ species, thus accelerate the fast degradation rate of target pollutants. Scavenging experiments and electron paramagnetic resonance analyses revealed that Acid Red 73 was decomposed mainly by the attack of •OH radicals. Besides, reusability of the prepared nanocatalyst was also tested.

Rapid method for the determination of 5-hydroxymethylfurfural and levulinic acid using a double-wavelength UV spectroscopy.

This study reports on a rapid method for the determination of levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) in acid hydrolyze system of glucose based on UV spectroscopy. It was found that HMF and LA have a maximum absorption at the wavelengths of 284 nm and 266 nm, respectively, in a water medium, and the absorptions of HMF and LA at 284 nm and 266 nm follow Beer's law very well. However, it was found that a major spectral interference species will arise in the quantification of HMF and LA; nonetheless, this interference can be eliminated through the absorption treatment of charcoal. Therefore, both HMF and LA can be quantified with a double-wavelength technique. The repeatability of the method had a relative standard deviation of less than 4.47% for HMF and 2.25% for LA; the limit of quantification (LOQ) was 0.017 mmol/L for HMF and 4.68 mmol/L for LA, and the recovery ranged from 88% to 116% for HMF and from 94% to 105% for LA. The present method is simple, rapid, and accurate. It is suitable to use in the research of the preparation of HMF and LA in biorefinery area.