Facile fabrication of Cu(II) coordinated chitosan-based magnetic material for effective adsorption of reactive brilliant red from aqueous solution.

In order to effectively remove reactive brilliant red (RBR) in aqueous solution, a novel Cu(II) coordinated chitosan-based magnetic composite (CTS-Cu@SiO2@Fe3O4) was prepared. The physicochemical properties of the resultant adsorbent were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) thermogravimetric (TG) analysis, scanning electron microscopy (SEM) and N2 adsorption-desorption. The adsorption capacity toward RBR was systematically investigated as a function of contact time, solution pH, initial concentration, ionic strength and temperature. Compared with CTS@SiO2@Fe3O4, CTS-Cu@SiO2@Fe3O4 showed better adsorption performance in removing RBR, reaching a maximum of 880.84 mg/g at pH 4, which confirmed that the coordination of Cu(II) can improve the adsorption capability. The adsorption kinetics of CTS-Cu@SiO2@Fe3O4 was found to follow the pseudo-second-order kinetic model, and the equilibrium adsorption data were well described by the Freundlich isotherm model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. XPS analysis confirmed that the adsorption was mainly controlled by electrostatic interaction between copper/amino cation and RBR anion. Furthermore, regeneration experiments demonstrated that CTS-Cu@SiO2@Fe3O4 can be used repeatedly. In a word, CTS-Cu@SiO2@Fe3O4 can be served as a promising adsorbent for dye wastewater scavenging.

Facile fabrication of chitosan-based adsorbents for effective removal of cationic and anionic dyes from aqueous solutions.

To develop chitosan-based adsorbents for the treatment of dye wastewater, poly acrylic acid (PAA) and poly acrylamide (PAM) were simultaneously grafted onto the chitosan (CTS) chain to obtain a grafted-crosslinked material g-CCTS, and then, Fe-g-CCTS was prepared via coordination of Fe(III) onto the prepared g-CCTS. Two adsorbents g-CCTS and Fe-g-CCTS were fully characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Nitrogen adsorption and desorption, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis. In adsorption experiment, g-CCTS exhibited effective adsorption towards cationic dye methylene blue (MB), and Fe-g-CCTS showed effective adsorption towards anionic dye reactive brilliant red (RBR). The effects of solution pH, salt concentration and temperature on the adsorption process were investigated. The maximum adsorption capacity of g-CCTS for MB was up to 79.09 mg/g at pH 12, and that of Fe-g-CCTS for RBR reached 918.53 mg/g at pH 2. It was observed that both adsorption processes were monolayer adsorption, and conformed to the pseudo-second-order model and the Langmuir isotherm model. This research provided a facile and accurate method for effective dyes removal from wastewater.

Green Process without Thinning Agents for Preparing Sebacic Acid via Solid-Phase Cleavage.

A green and environmentally friendly route of no thinning agent was designed to prepare sebacic acid. Sodium ricinoleate was selected as the raw material to carry out solid-phase cleavage in a tubular furnace. The reaction parameters including catalyst, ratio of sodium ricinoleate/KOH, reaction time, reaction temperature, and absolute pressure were optimized to obtain a high yield of sebacic acid. A satisfactory yield (70.2%) of sebacic acid was received in the presence of 1% catalyst (Fe2O3) by weight (w/w), with 5:4 (w/w) ratio of sodium ricinoleate/KOH at 543 K under the absolute pressure of 0.09 MPa in 60 min. Sebacic acid was identified by gas chromatography analysis, and the purity (98.1%) of the product was further assessed by its melting point (306.3 K). Alkaline enhancement generates a better cracking effect. The yield of sebacic acid can be improved by a certain absolute pressure as a result of avoiding oxidation of sodium ricinoleate as well as reducing the residence time of hydrogen.

Preparation of aminated chitosan microspheres by one-pot method and their adsorption properties for dye wastewater.

Polyamine chelating adsorbents have a good removal effect on dye wastewater. In this study, small molecule triethylenetetramine and macromolecular poly(ethylene imine) were selected as aminated reagent, and two kinds of aminated chitosan microspheres, TETA-CTSms and PEI-CTSms, were obtained by emulsion cross-linking method. The microspheres were fully characterized by FTIR, SEM, XRD, EDS and TGA. EDS results showed that the N content of the PEI-CTSms and TETA-CTSms microspheres increased significantly after the cross-linking reaction and can reach 5.7 wt% and 7.3 wt%, respectively. Adsorption experiments confirmed that TETA-CTSms and PEI-CTSms showed greater adsorption characteristics for anionic dye reactive yellow (RY) in aqueous solutions compared with CTSms, and the adsorption capacity per unit area was increased by 39.11% and 88.56%, respectively. The adsorption capacity of aminated microspheres for RY decreased with the increase of pH. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption process was in accordance with the Langmuir isotherm model. The negative value of ΔG confirmed that the adsorption process was spontaneous, and the dye adsorption was a multiple process dominated by chemical chelating and physical adsorption.

Facile fabrication of functional chitosan microspheres and study on their effective cationic/anionic dyes removal from aqueous solution.

This study provided a simple one-step chemical process for the preparation of aminated magnetic chitosan microspheres (TETA-MCTSms), which were applied for adsorbing anionic dye reactive brilliant red (RBR). Meanwhile, magnetic grafted microspheres (MCTSms-PMAA) were prepared based on magnetic chitosan microspheres via a surface-initiating system NH2/S2O82-, for adsorbing cationic dye methylene blue (MB). The physical properties and structure of the obtained microspheres were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA), and their adsorption performance for removal of cationic dye MB and anionic dye RBR was also investigated. MCTSms-PMAA performed excellent performance for cationic dye MB, represented by the adsorption capacities reaching a maximum of 211.22 mg·g-1 at pH 12; TETA-MCTSms performed remarkable adsorption properties for anionic dye RBR, represented by the adsorption capacities reaching a maximum of 637.41 mg·g-1 at pH 2. The kinetic analyses and equilibrium adsorption behaviors of dye wastewater onto chitosan microspheres were investigated using various models. The adsorption mechanism was further analyzed by X-ray photoelectron spectroscopy (XPS), and it was found that the adsorption was mainly driven by hydrogen bonding and electrostatic interaction.