Preparation and neutralization of forcespun chitosan nanofibers from shrimp shell waste and study on its uranium adsorption in aqueous media

One-step synthesis of phospho-rich, silica-enhanced chitosan aerogel for the efficient adsorption of uranium(VI)

In this study, an amorphous silica reinforced, phosphoric-crosslinked chitosan foam (P-CTS@SixOy) was prepared. The introduction of amorphous silica not only increased the affinity of the adsorbent for uranium, but also improved the stability of the material. The number of active sites of P-CTS@SixOy was increased by the introduction of phosphate groups. The material exhibited excellent uranium adsorption performance with the removal capacity and efficiency of 850.5 mg g-1 and 98.1 %, respectively. After regenerations, the morphology of P-CTS@SixOy still maintained, and the uranium adsorption efficiency remained above 90 %, manifesting the excellent cycle performance of P-CTS@SixOy. In the dynamic adsorption experiment, P-CTS@SixOy successfully concentrated the volume of uranium-containing solution, and exhibited excellent uranium adsorption performance. The analysis of kinetics, isotherms, and thermodynamics manifested that the uranium adsorption behavior of P-CTS@SixOy was a spontaneous, endothermic, monolayer chemical adsorption process. X-ray photoelectron spectroscopy, Scanning Electron Microscope, and Fourier Transform Infrared Spectrometer were used to characterized the P-CTS@SixOy before and after adsorption, which demonstrated that the main interaction mechanism between uranium and P-CTS@SixOy was the complexation. These studies indicated the huge application prospect of P-CTS@SixOy in the treatment of large-scale uranium-containing wastewater.

Synthesis and characterization of chitosan-vermiculite-lignin ternary composite as an adsorbent for effective removal of uranyl ions from aqueous solution: Experimental and theoretical analyses

Chitosan (Ch), vermiculite (V) and lignin (L) were used as the components of a natural composite adsorbent (Ch-VL) for the removal of the UO₂²⁺ ions in aqueous solutions. During the study, we recorded and analyzed the initial UO₂²⁺ ion concentration, initial pH, contact time, temperature, and recovery. The recycling performance of the Ch-VL composite was assessed by three sequential adsorption/desorption experiments. Adsorption performance of the Ch-VL composite for UO₂²⁺ ions was 600 mg L^-1 at pH 4.5 and temperature of 25 °C. Thermodynamic findings, ΔH⁰:28.1 kJ mol^-1, and ΔG⁰:-14.1 kJ mol^-1 showed that adsorption behavior was endothermic and spontaneous. Its maximum adsorption capacity was 0.322 mol kg^-1, obtained from the Langmuir isotherm model. The adsorption kinetics indicated that it followed the pseudo-second-order and intraparticle diffusion rate kinetics. The adsorption thermodynamic shown indicated that the UO₂²⁺ ion adsorption was both spontaneous and endothermic. The adsorption process was enlightened by FT-IR and SEM-EDX analyses. The study suggested a simple and cost-effective approach for the removal of toxic UO₂²⁺ ions from wastewater. To highlight the adsorption mechanism, DFT calculations were performed. Theoretical results are in good agreement with experimental observations.

Indole-functionalized cross-linked chitosan for effective uptake of uranium(VI) from aqueous solution

Herein, a novel indole-modified cross-linked chitosan aerogel (IAA-CTSA) was fabricated by grafting 3-indoleacetic acid onto chitosan and adding glutaraldehyde as crosslinking agent through a facile two-step one pot method. The...

Fungal chitin-glucan nanopapers with heavy metal adsorption properties for ultrafiltration of organic solvents and water

Membranes and filters are essential devices, both in the laboratory for separation of media, solvent recovery, organic solvent and water filtration purposes, and in industrial scale applications, such as the removal of industrial pollutants, e.g. heavy metal ions, from water. Due to their solvent stability, biologically sourced and renewable membrane or filter materials, such as cellulose or chitin, provide a low-cost, sustainable alternative to synthetic materials for organic solvent filtration and water treatment. Here, we investigated the potential of fungal chitin nanopapers derived from A. bisporus (common white-button mushrooms) as ultrafiltration membranes for organic solvents and aqueous solutions and hybrid chitin-cellulose microfibril papers as high permeance adsorptive filters. Fungal chitin constitutes a renewable, easily isolated, and abundant alternative to crustacean chitin. It can be fashioned into solvent stable nanopapers with pore sizes of 10-12 nm, as determined by molecular weight cut-off and rejection of gold nanoparticles, that exhibit high organic solvent permeance, making them a valuable material for organic solvent filtration applications. Addition of cellulose fibres to produce chitin-cellulose hybrid papers extended membrane functionality to water treatment applications, with considerable static and dynamic copper ion adsorption capacities and high permeances that outperformed other biologically derived membranes, while being simpler to produce, naturally porous, and not requiring crosslinking. The simple nanopaper production process coupled with the remarkable filtration properties of the papers for both organic solvent filtration and water treatment applications designates them an environmentally benign alternative to traditional membrane and filter materials.

Amidoxime modified chitosan based ion-imprinted polymer for selective removal of uranyl ions

Ion-imprinting strategy was utilized in the development of UO₂(II) imprinted amidoxime modified chitosan sorbent (U-AOCS) that can selectively remove UO₂(II) from water. First, cyanoactic acid was linked to the chitosan -NH₂ groups and then the inserted -CN groups were converted into amidoxime moieties, which chelate the UO₂(II) ions and then the polymer chains were cross-linked by glyoxal. The UO₂(II) ions have been then eluted leaving their matching recognition sites. The prepared U-AOCS along with the control NIP displayed maximum capacities toward the UO₂(II) ions around 332 and 186 mg/g, respectively, and the isotherms were interpreted better by the Langmuir model in both adsorbents. Moreover, the selective uptake of the uranyl ions in multi-ionic aqueous solutions containing the tetravalent Th(IV) ions, trivalent Al(III), Eu(III), and Fe(III) ions, beside the divalent Pb(II), Co(II), Ni(II), Cu(II) ions confirmed the successful creation of a considerable UO₂(II) ions selectivity in the U-AOCS construction. In addition, the U-AOCS adsorbent displayed economic feasibility by maintaining around 95 % of its initial efficiency after the regeneration and reuse for 5 adsorption/desorption cycles.