Currently, great interest is focused on developing auto-tandem catalytic reactions; a substrate is catalytically transferred through mechanistically distinct reactions without altering any reaction conditions. Here by incorporating a pyrrolidine moiety as a chiral organocatalyst and a polyoxometalate as an oxidation catalyst, a powerful approach is devised to achieve a tandem catalyst for the efficient conversion of CO2 into value-added enantiomerically pure cyclic carbonates. The multi-catalytic sites are orderly distributed and spatially matched in the framework. The captured CO2 molecules are synergistically fixed and activated by well-positioned pyrrolidine and amine groups, providing further compatibility with the terminal W=O activated epoxidation intermediate and driving the tandem catalytic process in a single workup stage and an asymmetric fashion. The structural simplicity of the building blocks and the use of inexpensive and readily available chemical reagents render this approach highly promising for the development of practical homochiral materials for CO2 conversion.
A novel adsorbent based on cellulose (CGD) was prepared via modifying with glycidyl methacrylate (GMA) and diethylenetriamine pentaacetic acid (DTPA), characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential thermogravimetry (DTA/TGA). Malachite green (MG) and basic fuchsine (BF) were used to resemble cationic dyes in wastewaters. The influences of several parameters (contact time, pH, temperature, initial concentration) were evaluated to determine the best adsorption conditions. Langmuir adsorption isotherm items explained MG adsorption well, while BF was fitted well with the Freundlich model. The maximum adsorption capacities were greater than some other reports, 1155.76 mg•g −1 for a BF internal concentration of 2000 mg•L −1 and 458.72 mg•g −1 for MG in theory. Kinetics and thermodynamics were adopted to explain in-depth information associated with the adsorption process. The adsorption processes of dyes were both feasible spontaneous and well-described by the pseudosecond-order model. The dynamic adsorption/desorption experiments, with saturated sodium bicarbonate solution as the eluent, show that the adsorbent could be reused for five cycles or four cycles, keeping the adsorption rate above 85 % and 90 % for BF and MG, respectively.
A novel
cellulose-based adsorbent (CGS) was synthesized by a facile,
two-step modification route. It was characterized by the FTIR, XRD,
and SEM technique. The adsorption characteristics of CGS were compared
with those of native cellulose using crystal violet (CV) as an adsorbate
in this work. The effects of contact time, temperature, pH, and initial
concentration on the sorption were all investigated. The adsorption
kinetics for both CGS and cellulose were found to follow a pseudo-second-order
(P-S-O) kinetic model. The equilibrium data of CGS fitted well with
the Langmuir isothermal model, and the maximum theoretical adsorption
capacity of CGS for CV was 218.82 mg g–1 at 50 °C;
the adsorption increased by 70.8% compared to that of native cellulose.
A thermodynamics study was also performed. The comparative study confirmed
that the structure of CGS is more conducive for the adsorption of
CV than cellulose. Furthermore, adsorption/desorption experiments
showed that CGS could be reused for at least eight cycles with stable
sorption ability after being regenerated with 50% ethanol solution
(pH 3.0).
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