Selective heavy metal removal and water purification by microfluidically-generated chitosan microspheres: Characteristics, modeling and application

Many industrial wastewater streams contain heavy metals, posing serious and irreversible damage to humans and living organisms, even at low concentrations due to their high toxicity and persistence in the environment. In this study, high-performance monodispersed chitosan (CS) microspheres were prepared using a simple microfluidic method and evaluated for metal removal from contaminated water. Batch experiments were carried out to evaluate the adsorption characteristics for the removal of copper ions, one representative heavy metal, from aqueous solutions. The inherent advantages of microfluidics enabled a precise control of particle size (CV = 2.3%), while exhibiting outstanding selectivity towards target ions (adsorption capacity 75.52 mg g−1) and fair regeneration (re-adsorption efficiency 74% after 5 cycles). An integrated adsorption mechanism analytic system was developed based on different adsorption kinetics and isotherms models, providing an excellent adsorption prediction model with pseudo-second order kinetics (R2 = 0.999), while the isotherm was fitted best to the Langmuir model (R2 = 0.998). The multi-step adsorption process was revealed via quantitative measurements and schematically described. Selective adsorption performance of CS microspheres in the present of other competitive metal ions with different valence states has been demonstrated and studied by both experimental and density functional theory (DFT) analysis

Catalytic Versatility of Novel Sulfonamide Functionalized Magnetic Composites

The present work describes two novel magnetic composite catalysts, synthesized by functionalizing the silica/iron oxide composite surface with sulfaguanidine and sulfadiazine. The sulfaguanidine functionalized catalyst was found to be very efficient for multicomponent coupling reactions of phenylacetylene with various aldehydes and amines. The sulfadiazine functionalized catalyst was successfully applied in the synthesis of various 1,8-dioxo-octahydroxanthenes in water. Both the sulfaguanidine and sulfadiazine functionalized catalysts were very active and selective in the alkylation of toluene with benzyl chloride

Continuous Flow Alcoholysis of Furfuryl Alcohol to Alkyl Levulinates Using Zeolites

The present work explores the catalytic activity of various zeolites for the production of methyl levulinates from hemicellulose derived furfuryl alcohol and explores the performance of H-ZSM-5-50 zeolite in continuous flow alcoholysis. Methyl levulinate yields up to 80% were achieved at 170 °C (50 bar) using a high load (1.6 M furfuryl alcohol) feed at 0.2 mL min^–1 flow rate. Angelica lactones were produced in significant amounts as one of the side products, albeit in lower amounts in continuous flow mode. Catalyst deactivation occurred at high furfuryl alcohol load through formation of pore blocking polyfurfuryl alcohols. The zeolites showed good reusability after regeneration at 500 °C. The levulinate yields in ethanol and <i>n</i>-propanol were 20% lower

Structural Characterization of Wheat Straw Lignin as Revealed by Analytical Pyrolysis, 2D-NMR, and Reductive Cleavage Methods

The structure of the lignin in wheat straw has been investigated by a combination of analytical pyrolysis, 2D-NMR, and derivatization followed by reductive cleavage (DFRC). It is a <i>p</i>-hydroxyphenyl-guaiacyl-syringyl lignin (with an H:G:S ratio of 6:64:30) associated with <i>p</i>-coumarates and ferulates. 2D-NMR indicated that the main substructures present are β-<i>O</i>-4′-ethers (∼75%), followed by phenylcoumarans (∼11%), with lower amounts of other typical units. A major new finding is that the flavone tricin is apparently incorporated into the lignins. NMR and DFRC indicated that the lignin is partially acylated (∼10%) at the γ-carbon, predominantly with acetates that preferentially acylate guaiacyl (12%) rather than syringyl (1%) units; in dicots, acetylation is predominantly on syringyl units. <i>p</i>-Coumarate esters were barely detectable (<1%) on monomer conjugates released by selectively cleaving β-ethers in DFRC, indicating that they might be preferentially involved in condensed or terminal structures

Modification of the Lignin Structure during Alkaline Delignification of Eucalyptus Wood by Kraft, Soda-AQ, and Soda‑O₂ Cooking

The modification of the lignin structure of an eucalyptus feedstock during alkaline delignification by kraft, soda-AQ, and soda-O₂ cooking processes has been investigated by different analytical techniques (size exclusion chromatography (SEC), pyrolysis gas chromatography–mass spectroscopy (Py-GC/MS), ¹H–¹³C two-dimensional nuclear magnetic resonance (2D-NMR), and ³¹P NMR). The characteristics of the lignins were compared at different pulp kappa levels, and with the native lignin isolated from the wood. The structural differences between the kraft, soda-AQ, and soda-O₂ residual lignins were more significant at earlier pulping stages. At the final stages, all the lignin characteristics were similar, with the exception of their phenolic content. Strong differences between lignins from pulps and cooking liquors were observed, including enrichment in guaiacyl units in pulp residual lignin and enrichment in syringyl units in black liquor lignin. A comparison of the alkaline cookings indicate that soda-O₂ process produced higher lignin degradation and provided promising results as pretreatment for the deconstruction of eucalyptus feedstocks for subsequent use in lignocellulose biorefineries