Kinetic modeling of sorption–desorption cycles for phenol removal with a cyclodextrin polymer

Chitosan, xanthan and locust bean gum matrices crosslinked with β-cyclodextrin as green sorbents of aromatic compounds

Three different polysaccharides, xanthan gum, chitosan and locust bean gum, were crosslinked with or without β-cyclodextrin, using citric acid in different ratios, to create 'green' hydrogel matrices. The crosslinking of these polysaccharides was produced through an inexpensive and innocuous solvent-free synthesis process. A favorable swelling behavior of the hydrophilic matrices facilitates the sorption of the solutes tested. Interestingly, the amount of β-cyclodextrin groups is not the only factor to yield the best sorption capability for hydrophobic model molecules: polysaccharides themselves also influence the sorption depending on their characteristic functional groups, the conformation of their chains and, as mentioned above, their degrees of swelling. In order to ascertain the effect of the polysaccharides on the sorption capabilities of a model sorbate (1-naphthol), isotherms using a wide range of solute concentrations were analyzed, and the Hill equation yielded the best fitting results and provided some insight into the mechanisms of interaction.

Film-like bacterial cellulose/cyclodextrin oligomer composites with controllable structure for the removal of various persistent organic pollutants from water

The adsorptive removal of persistent organic pollutants (POPs) is reckoned as a simple, convenient, and practical technology, especially in decentralized systems and remote areas. For this purpose, it is important to design new adsorbents, with controllable structure and convenient shape, for the highly efficient removal of POPs. In this study, we describe a strategy for film-like water purifier, prepared by loading cyclodextrin (CD) oligomer onto the ultrafine nanofibers of 3D bacterial cellulose. The optimum product exhibits remarkable removal ability toward various target pollutants such as phenol, bisphenol A (BPA), glyphosate and 2,4-Dichlorophenol (2,4-DCP), with capacities higher than most adsorbents including porous carbon based materials reported previously. Moreover, our sample demonstrated stable adsorption ability over a broad pH range and under more complex water conditions, and more importantly excellent reusability. A rough cost analysis highlights the commercial potential of our sample. We reckon our study provides new insight for the design of adsorbent with high yet stable adsorption ability and controllable structure. Furthermore, the product can be used to treat actual sewage with its convenient film-like shape and excellent performance, which improves its potential in complex systems and large-scale applications.

The effective removal of phenol from aqueous solution via adsorption on CS/β-CD/CTA multicomponent adsorbent and its application for COD degradation of drilling wastewater

The 3-chloro-2 hydroxypropyltrimethyl ammonium chloride was successfully introduced into the β-cyclodextrin-modified chitosan to create the multicomponent adsorbent O-HTACC-g-CD. The structure of sorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The adsorption capacity of O-HTACC-g-CD toward phenol was investigated as a function of pH, temperature, contact time as well as adsorbent dosage. The Box-Behnken response surface methodology was employed to optimize the effects of experimental parameters including adsorbent dose, pH, and time on the adsorption of phenol at 298.15 K. The obtained optimal values for adsorbent dose, pH, and time were 0.06 g, 6, and 200 min, respectively. The obtained experimental data follows the pseudo-second-order kinetic and Langmuir model. The thermodynamic parameters such as free energy change, enthalpy change, and entropy change were calculated, revealing that adsorption of phenol on O-HTACC-g-CD is a spontaneous and exothermic process. The prepared O-HTACC-g-CD displayed high adsorption capacity (39.98 mg g-1) and excellent removal rate (96%) for phenol from the aqueous solution at 288.15 K. The gained removal rates of chemical oxygen demand (CODCr) were in the range of 60.6-61.2%. Considerable results of sorption could be attributed to the multicomponent structure of the adsorbent with more active sites including the cavities, amino, and carboxyl functional groups which provided better sites for the phenolic pollutant to adsorb on the adsorbent via Van der Waals force, hydrogen bond, and the inclusion effect. Therefore, the results obtained strongly suggest that O-HTACC-g-CD could be an effective adsorbent for the removal of phenol and CODcr from drilling wastewater.

The classification and application of cyclodextrin polymers: a review

After introducing the concept of cyclodextrin polymers, their classification and applications have been summarized.

Carbon nanotubes grafted with poly(trimesoyl, m-phenylenediamine) for enhanced removal of phenol

This work focused on the facile synthesis of carbon nanotubes grafted with a polymer of trimesoyl chloride and m-phenylenediamine (CNTs-MDP-TMC) as novel and effective adsorbent and investigation of its ability in the phenol uptake from aqueous media. The chemical and morphological characterization of the synthesized adsorbent was carried out by FT-IR, SEM, EDX, and mapping techniques. The influence of the operational parameters on the adsorption performance was inspected and optimized batch adsorption conditions by factorial design analysis. The non-linear Langmuir model was better represented the isotherm of phenol adsorption compared to the Freundlich isotherm. The CNTs-MDP-TMC had a maximum adsorption capacity as much as 261.6 mg/g. The kinetic examinations revealed that the pseudo-second-order (PSO) kinetic model depicted higher relationship with phenol adsorption than the pseudo-first-order (PFO) model. The thermodynamics findings confirmed that the phenol adsorption by the CNTs-MDP-TMC is taken place exothermically and more spontaneously with lessening temperature. The prepared adsorbent had a great adsorption/desorption performance, especially during the first four cycles. It can be drawn a conclusion form all findings that the synthesized CNTs-MDP-TMC has great prospective as a novel and influential adsorbent for phenol polluted-wastewaters.