β-Cyclodextrin conjugated bifunctional isocyanate linker polymer for enhanced removal of 2,4-dinitrophenol from environmental waters

Abstract

In this work, we reported the synthesis, characterization and adsorption study of two β-cyclodextrin (βCD) cross-linked polymers using aromatic linker 2,4-toluene diisocyanate (2,4-TDI) and aliphatic linker 1,6-hexamethylene diisocyanate (1,6-HDI) to form insoluble βCD-TDI and βCD-HDI. The adsorption of 2,4-dinitrophenol (DNP) on both polymers as an adsorbent was studied in batch adsorption experiments. Both polymers were well characterized using various tools that include Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller analysis and scanning electron microscopy, and the results obtained were compared with the native βCD. The adsorption isotherm of 2,4-DNP onto polymers was studied. It showed that the Freundlich isotherm is a better fit for βCD-TDI, while the Langmuir isotherm is a better fit for βCD-HMDI. The pseudo-second-order kinetic model represented the adsorption process for both of the polymers. The thermodynamic study showed that βCD-TDI polymer was more favourable towards 2,4-DNP when compared with βCD-HDI polymer. Under optimized conditions, both βCD polymers were successfully applied on various environmental water samples for the removal of 2,4-DNP. βCD-TDI polymer showed enhanced sorption capacity and higher removal efficiency (greater than 80%) than βCD-HDI (greater than 70%) towards 2,4-DNP. The mechanism involved was discussed, and the effects of cross-linkers on βCD open up new perspectives for the removal of toxic contaminants from a body of water.

Poly(β-cyclodextrin)-Activated Carbon Gel Composites for Removal of Pesticides from Water

“…All poly(β-CD)-based materials revealed a further thermal degradation at around 452 °C. That can be justified by the cleavage of the ester bond between β -CD and 1,6-HDI [ 64 ]. It should be stressed that the latter can also be indicative of a successful synthesis of PCD.…”

“…The two bands at 2935 cm −1 and 2862 cm −1 are associated to the methylene groups stretching vibrations of the 1,6-HDI crosslinker. The absence of a peak at 2270 cm −1 , corresponding to the isocyanate group, indicates a complete polymerization reaction [ 64 ]. A characteristic band appears at 1710 cm −1 , which is due to the stretching vibration of the carbonyl group of the ester bond between the -OH at C-6 position of the β -CD and the terminal carbonyl of the isocyanate group of 1,6-HDI.…”

Cyclodextrin-Based Nanosponges: Overview and Opportunities

“…A higher removal efficiency (ca. 74%), at acidic pH and low analyte concentration, was observed; the RE remained constant along five sorption/desorption cycles ( Anne et al, 2018 ). In the same study, the performance of βCD:TDI for the removal of 2,4NP has been compared with that obtained by using βCD:HDI.…”

“…85%) than the non-porous βCD:HDI. However, results can also be justified by considering the presence of the phenyl groups of the linkers, which can form π ‒ π interactions with 2,4-dichlorophenoxy acid (2,4D) ( Anne et al, 2018 ).…”

Evaluation of Polyethylene Glycol Crosslinked β-CD Polymers for the Removal of Methylene Blue

“…It should be noticed that the BET analysis of PEGCD2 was not recorded due to its gel form. According to Anne [66], β-CD presented a micropore structure with a surface area of 2.45 m 2 .g −1 . PEGCD1 exhibited a higher surface compared to EGCD.…”