Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

Abstract

Modified uncrosslinked and crosslinked chitosan derivatives were investigated as green sorbents for the removal of copper (Cu 2+ ) and lead (Pb 2+ ) cations from simulated solutions. In this regard, N, O carboxymethyl chitosan (N, O CMC), chitosan beads (Cs-g-GA), chitosan crosslinked with glutaraldehyde/methylene bisacrylamide (Cs/GA/MBA), and chitosan crosslinked with GA/epichlorohydrin (Cs/GA/ECH) were prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analyses. Atomic force microscopy investigation was carried out to compare the surface topography of the prepared samples before and after the metal uptake. The kinetics of the removal process were investigated by pseudo-first-order and -second-order models. Moreover, the adsorption isotherms were carefully studied by applying Langmuir and Freundlich models. The data reveal that upon adsorption of copper(II) metal ions, all chitosan-modified products followed the Langmuir isotherm except for Cs/GA/ECH which followed the Freundlich isotherms, and the highest adsorption capacity ( q e ) was obtained for Cs/GA/MBA due to the formation of stable chelate structures between the metal cation and the functional groups present on the modified chitosan product. The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCh (Cu: 30.2 mg/g, Pb: 44.8 mg/g). The AFM data confirmed the metal uptake process by comparing the roughness and height measurements of the free sorbents and the metal-loaded sorbents.

Optimization, Kinetics, and Isotherm Studies of Methyl Thioninium Chloride Removal from Simulated Solutions Using Chitosan Derivatives

“…This in turn had an impact on the modified chitosan's surface area, which was discovered to be 22.4, 31.6, 51.6, and 68.9 m 2 /g for N,O CMCs, Cs/GA, Cs/GA/ECH, and Cs/GA/MBA, respectively. 34 On the other hand, it can be noticed that the maximum swelling capacity was attained at pH = 9 due to the attraction between the −OH groups and the protons of the amine groups existing within the molecule.…”

“…Moreover, AFM can be effectively used in monitoring the adsorption process by comparing the surface features and the height of the surface before and after adsorption. , Figure illustrates AFM images of dry and MB-loaded sorbents. Moreover, Gwyddion software was used to analyze the phase differentiation of the AFM images to show the different phases comprising the matrix.…”

“…Uncross-linked Chitosan Adsorbent Preparation. 34 Shortly, 5 g of chitosan (Cs) was well dissolved in 100 mL of 1% acetic acid solution. The pH was then adjusted to roughly 5.0 with NaOH solution while rapidly stirring for 4 h at room temperature with the gradual addition of 8 g of ketoglutaric acid.…”

“…Chitosan Adsorbents. 34 Freshly prepared wet Cs/GA beads were heated to 45 °C and then mixed in a cross-linker solution (pH = 10) comprising 0.2 M equal molar ratio of GA/ECH or GA/MBA and then stirred for 2 h. The cross-linked beads were filtered and thoroughly rinsed with distilled water to eliminate any unreacted cross-linkers, before being filtered and air-dried. Before usage, the newly produced products (Cs/GA/ECH and Cs/GA/ MBA) were crushed and sieved to a consistent size (<250 μm).…”

“…On the other hand, in the presence of certain agents such as glutaraldehyde (GA) and epichlorohydrin (ECH), chitosan chains can be chemically cross-linked to create triple network architectures with enhanced mechanical and adsorption capabilities. 34 This research article focuses on the functionalization of chitosan modified from shrimp shell chitin using carboxymethylation, grafting with GA, cross-linking with ECH, and with methylene bis(acrylamide) (MBA) (as per our previous work 34 ) to create reasonably priced sorbents for the removal of MB from aqueous environments. The kinetics of the removal process and the adsorption isotherms were carefully examined, and the produced derivatives were fully described by using a variety of techniques.…”