3 research outputs found
New Chelating Ion-Exchange Resin Synthesized via the Cyclopolymerization Protocol and Its Uptake Performance for Metal Ion Removal
Azoisobutyronitrile-initiated
cycloterpolymerization of [(diallylamino)Âpropyl]Âphosphonic
acid hydrochloride (90 mol %), cross-linker 1,1,4,4-tetraallylpiperazinium
dichloride (10 mol %), and SO<sub>2</sub> (100 mol %) afforded a new
pH-responsive cross-linked polyzwitterionic acid which, upon alkaline
treatment, was transformed to a cross-linked dianionic polyelectrolyte
(CDAPE). Chelating ion-exchange resin CDAPE was tested for the uptake
of Pb<sup>2+</sup> and Cu<sup>2+</sup> ions; the adsorption process
followed pseudo-second-order kinetics with respective <i>E</i><sub>a</sub> values of 13.4 and 13.8 kJ mol<sup>–1</sup>.
The adsorption data fitted well to the Langmuir, Freundlich, and Temkin
as well as Dubinin–Radushkevich isotherm models. The maximum
uptakes of Pb<sup>2+</sup> and Cu<sup>2+</sup> were determined to
be 3.83 and 10.1 mmol g<sup>–1</sup>, respectively. The scanning
electron microscopy images and energy-dispersive X-ray spectroscopy
analysis confirmed that the CDAPE adsorbed the metal ions on the surface
as well as throughout the polymer. The negative Δ<i>G</i>° and positive Δ<i>H</i>° ensured the adsorption
process as favorable and endothermic in nature. The excellent adsorption
and desorption efficiencies demonstrated by the resin would enable
its use for the removal of toxic metal ions from wastewater. A comparison
of CDAPE with several other adsorbents in recent works ascertains
the excellent efficiency of the current resin for the removal of toxic
metal ions
Enantioselective [4 + 2]-Annulation of Oxadienes and Allenones Catalyzed by an Amino Acid Derived Phosphine: Synthesis of Functionalized Dihydropyrans
An
enantioselective [4 + 2]-annulation process between cyano-activated
oxadienes and allenones is developed. An l-valine-derived
phosphine was efficient in catalyzing the reaction, and a wide range
of highly functionalized dihydropyrans were prepared in high yields
and with excellent enantioselectivities