Magnetic chitosan microspheres: An efficient and recyclable adsorbent for the removal of iodide from simulated nuclear wastewater

Fluorescent cellulose nanofibrils-based hydrogel incorporating MIL-125-NH2 for effective adsorption and detection of iodide ion

To remove iodine ion (I-) from wastewater, a novel hydrogel, the fluorescent cellulose nanofibrils-based hydrogel (FCNH), was synthesized to enable both detection and adsorption of I-. The FCNH comprised cellulose nanofibrils (CNs), silver nanoclusters (AgNCs), and MIL-125-NH2. It exhibited an excellent adsorption capacity for I-, with a maximum adsorption capacity of 373.7 mg/g, fitting both the Langmuir and pseudo-second-order models. Additionally, FCNH displayed excellent regeneration properties, retaining 88.0 % of its initial adsorption capacity after six adsorption-desorption cycles. Functioning as a fluorescent sensor, the synthesized FCNH enabled the detection of I- through dynamic quenching, with linear ranges of 5 to 200 mg/L and 0.2 to 1.0 μg/L, and a determination limit of 0.11 μg/L. Analysis of the adsorption and detection mechanisms revealed that FCNH's outstanding performance arose from its 3D porous structure comprising CNs, AgNCs, and MIL-125-NH2. Economic analysis indicated that FCNH was inexpensive compared to commercially available activated carbon. Thus, FCNH demonstrated significant potential as an economical and reusable adsorbent for iodine ion removal.

Supramolecular Structure of the β-Cyclodextrin Metal-Organic Framework Optimizes Iodine Stability and Its Co-delivery with l-Menthol for Antibacterial Applications

The spread of upper respiratory tract (URT) infections harms people's health and causes social burdens. Developing targeted treatment strategies for URT infections that exhibit good biocompatibility, stability, and strong antimicrobial effects remains challenging. The dual antimicrobial and antiviral effects of iodine (I2) in combination with the cooling sensation of l-menthol in the respiratory tract can simultaneously alleviate URT inflammation symptoms. However, as both I2 and l-menthol are volatile, addressing stability issues is crucial. In this study, a potassium iodide β-cyclodextrin metal-organic framework [β-CD-POF(I)] with appropriate particle size was used to coload and deliver I2 and l-menthol. Primarily, β-CD-POF(I) was employed as the most efficient carrier to significantly enhance the stability of I2, surpassing any other known protection strategies in the pharmaceutical field (CD complexations, PVP conjugations, and cadexomer iodine). The mechanism underlying the improvement in stability of I2 by β-CD-POF(I) was investigated through scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular docking. The results revealed that the key processes involved in improving stability were the inclusion of I2 by β-CD cavities in β-CD-POF(I) and the formation of polyiodide anion between iodine ions and I2. Furthermore, the potential of β-CD-POF(I) to load and deliver drugs was validated, and coloading of l-menthol and I2 demonstrated reliable stability. β-CD-POF(I) achieved a rate of URT deposition ≥95% in vitro, and the combined antibacterial effects of coloaded I2 and l-menthol was better than I2 or PVP-I alone, with no irritation noted following URT administration in rabbits. Therefore, the stable coloading of drugs by β-CD-POF(I), leading to enhanced antimicrobial effects, provides a new strategy for treating URT infections.

Iodide ion-imprinted chitosan beads for highly selective adsorption for nuclear wastewater treatment applications

Iodide ions from radioactive iodine isotopes are common contaminants present in nuclear wastewater from nuclear power plants which are considered hazardous contaminants to be released in water sources even at low concentrations due to their association with metabolic disorders, therefore its removal from the nuclear wastewater effluents is necessary. Chitosan beads are natural and cost-efficient adsorbents that have been used for ion removal from wastewater. However, issues of poor selectivity persist in achieving high-efficiency iodide ion removal. In this study, ion-imprinted chitosan beads (IIC) have been synthesized using the phase-inversion method, IIC beads were modified by cross-linking with epichlorohydrin (IIC-EPI) and modified by cross-linking with epichlorohydrin and silicon dioxide nanoparticles (IIC-SiO2-EPI). Through 4 h of batch adsorption experiments, IIC beads achieved a maximum adsorption capacity (Qe) of 0.65 mmol g-1 and showed more preference for the iodide ions compared to the non-imprinted chitosan beads which achieved a maximum adsorption capacity of 0.27 mmol g-1 at pH 7. While the modified beads IIC-EPI and IIC-SiO2-EPI beads have boosted the adsorption capacities to 0.72 mmol g-1 and 0.91 mmol g-1. Scanning electron microscopic cross-sectional images have shown more pores and cavities than the surface images which agrees with the multilayer heterogeneous diffusion suggested by the Freundlich adsorption isotherm, that the experimental data has fitted. Adsorption kinetic data have fitted the Pseudo-second-order model as well as the Weber and Morris intraparticle model, which suggest an intraparticle pore diffusion adsorption mechanism, with the involvement of the physical electrostatic interactions with the cationic chitosan surface.

Adsorption Characterization of Cu(II) and Cd(II) by a Magnetite-Chitosan Composite: Kinetic, Thermodynamic and Equilibrium Studies

Optimizing the use of magnetite-chitosan composites for heavy metal adsorption has been of great interest due to their environmental friendliness. To gain insights into their potential with green synthesis, this study analyzed one of these composites through X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Adsorption properties were then explored via static experiments to evaluate the pH dependence, isotherms, kinetics, thermodynamics and regeneration adsorption of Cu(II) and Cd(II). Results disclosed that the optimum pH of adsorption was 5.0, the equilibrium time was about 10 min, and the capacity for Cu(II) and Cd(II) reached 26.28 and 18.67 mg/g, respectively. The adsorption amount of cations increased with temperature from 25 °C to 35 °C and decreased with further increase in temperature from 40 °C to 50 °C, which might be related to the unfolding of chitosan; the adsorption capacity was above 80% of the initial value after two regenerations and about 60% after five regenerations. The composite has a relatively rough outer surface, but its inner surface and porosity are not obvious; it has functional groups of magnetite and chitosan, and chitosan might dominate the adsorption. Consequently, this research proposes the value of maintaining green synthesis research to further optimize the composite system of heavy metal adsorption.

Effect of different synthesis methodologies on the adsorption of iodine

Radioactive nuclides such as cesium, ruthenium, and iodine are difficult to remove in radioactive wastewater, which could be removed by coprecipitation of special chemical precipitants. In this study, dynamic Cu/Ag-mordenite (Cu/Ag-MOR) material was synthesized to be treated as the precipitant to selectively adsorb the iodine ion (I^-) through controlled chemisorption combined with physical adsorption. XRD, XPS, and FTIR characterization demonstrated the successful modification of the MOR carrier surface by Cu/Ag particles and the high selectivity of the active component Cu (I) on the dynamic Cu/Ag-MOR material. SEM, TEM, and BET methods were used to characterize the Cu/Ag-MOR material, demonstrating these results: the MOR carried a stable porous structure, which allowed the silver to be well dispersed on its surface. The silver improved the copper distribution by being well-coated by the copper species. Furthermore, the analysis of the factors influencing the chemical plating of copper showed that the pH, the concentration of EDTA-2Na and the temperature all influenced the deposition rate of Cu₂O. The activation energy for Cu₂O deposition in dynamic Cu/Ag-MOR was 20.31 kJ/mol. The highest removal of I^- in the presence of dynamic Cu/Ag-MOR could reach 99.1% in the adsorption tests. The adsorption kinetics was under a proposed second-order model, with chemisorption being the controlling step of the reaction. The adsorption/desorption experiments demonstrated the reusability of the nano-sorbent. It was also demonstrated that dynamic Cu/Ag-MOR materials showed good applicability in complex situations where multiple pollutants co-exist.

Viologen-functionalized magnetic material for the removal of Iodine and benzanthracene in an aqueous solution

The development of magnetically active adsorbents for effective iodine removal would be highly desirable to address environmental pollution and remediation. Herein, we demonstrated the synthesis of Vio@SiO₂@Fe₃O₄ as an adsorbent via surface functionalisation of electron-deficient bipyridium (viologen) units on the surface of magnetically active silica-coated magnetite (Fe₃O₄) core. This adsorbent was characterised thoroughly using various analytical techniques, such as field emission scanning electron microscopy (FESEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR), field emission transmission electron microscopy (FETEM), Brunauer-Emmett-Teller (BET) analysis and X-ray photon analysis (XPS). The removal of triiodide from the aqueous solution was monitored via the batch method. It revealed that the complete removal was achieved upon stirring for 70 min. The thermally stable and crystalline Vio@SiO₂@Fe₃O₄ displayed efficient removal capacity even in the presence of other competing ions and at different pHs. The adsorption kinetics data were analysed following the pseudo-first-order and pseudo-second-order models. Further, the isotherm experiment showed that the maximum uptake capacity of iodine is 1.38 g/g. It can be regenerated and reused over multiple cycles to capture iodine. Further, Vio@SiO₂@Fe₃O₄ displayed a good removal capacity toward toxic polyaromatic, Benzanthracene (BzA) pollutant with an uptake capacity of 2445 μg/g. This effective removal of toxic pollutants iodine/benzanthracene was attributed to the strong non-covalent electrostatic and π-π interaction with electron-deficient bipyridium units.

Mn3O4@polyaniline nanocomposite with multiple active sites to capture uranium(VI) and iodide: synthesis, performance, and mechanism

A major challenge for radioactive wastewater treatment and associated environmental remediation is how to simultaneously remove cationic and anionic radionuclides. Herein, a series of Mn₃O₄@polyaniline (Mn₃O₄@PANI) nanocomposites were successfully prepared and used to remove U(VI) and I^- from aqueous solution, two highly concomitant species in nuclear pollution settings. Batch adsorption experiments reveal that the component Mn₃O₄ is predominantly responsible for U(VI) removal, but PANI for I^-. The nanocomposite with 24.2 wt% Mn₃O₄ possesses high removal percentages (> 85%) either for U(VI) or I^- over a wide pH range, fast removal kinetics, and excellent adsorption selectivity at high concentrations of competing ions. Benefiting from the contributions of the two components and the high adsorption affinities, the nanocomposite achieves the simultaneous removal to coexisting U(VI) and I^-, with a maximum adsorption capacity 102.6 mg/g for U(VI) and 126.1 mg/g for I^-. X-ray photoelectron spectroscopy (XPS) results reveal that the U(VI) adsorption occurs via coordination bonding with Mn-O, -NH- , and =N- groups in the nanocomposite, whereas I^- adsorption proceeds mainly through I anionic species exchange with Cl^- and interactions with π-bonds in PANI, as well as the electrostatic attraction onto Mn₃O₄. Considering the excellent performance and multiple active sites, the Mn₃O₄@PANI nanocomposite is promising to remove practical radioactive U(VI) and I^-.

Emerging periodate-based oxidation technologies for water decontamination: A state-of-the-art mechanistic review and future perspectives

With the ever-increasing severity of the ongoing water crisis, it is of great significance to develop efficient, eco-friendly water treatment technologies. As an emerging oxidant in the advanced oxidation processes (AOPs), periodate (PI) has received worldwide attention owing to the advantages of superior stability, susceptible activation capability, and high efficiency for decontamination. This is the first review that conducts a comprehensive analysis of the mechanism, pollutant transformation pathway, toxicity evolution, barriers, and future directions of PI-based AOPs based on the scientific information and experimental data reported in recent years. The pollutant elimination in PI-based AOPs was mainly attributed to the in situ generate reactive oxygen species (e.g., ^•OH, O(³P), ¹O₂, and O₂^•-), reactive iodine species (e.g., IO₃^• and IO₄^•), and high-valent metal-oxo species with exceptionally high reactivity. These reactive species were derived from the PI activated by the external energy, metal activators, alkaline, freezing, hydroxylamine, H₂O_2, etc. It is noteworthy that direct electron transport could also dominate the decontamination in carbon-based catalyst/PI systems. Furthermore, PI was transformed to iodate (IO₃^-) stoichiometrically via an oxygen-atom transfer process in most PI-based AOPs systems. However, the production of I₂, I^-, and HOI was sometimes inevitable. Furthermore, the transformation pathway of typical micropollutants was clarified, and the in silico QSAR-based prediction results indicated that most transformation products retained biodegradation recalcitrance and multi-endpoint toxicity. The barriers faced by the PI-based AOPs were also clarified with potential solutions. Finally, future perspectives and research directions are highlighted based on the current state of PI-based AOPs. This review enhances our in-depth understanding of PI-based AOPs for pollutant elimination and identifies future research needs to focus on the reduction of toxic byproducts.

Synthesis and applications of bismuth-impregnated biochars originated from spent coffee grounds for efficient adsorption of radioactive iodine: A mechanism study

The adsorption of radioactive iodine, which is capable of presenting high mobility in aquatic ecosystems and generating undesirable health effects in humans (e.g., thyroid gland dysfunction), was comprehensively examined using pristine spent coffee ground biochar (SCGB) and bismuth-impregnated spent coffee ground biochar (Bi@SCGB) to provide valuable insights into the variations in the adsorption capacity and mechanisms after pretreatment with Bi(NO₃)₃. The greater adsorption of radioactive iodine toward Bi@SCGB (adsorption capacity (Q_e) = 253.71 μg/g) compared to that for SCGB (Q_e = 23.32 μg/g) and its reduced adsorption capability at higher pH values provide evidence that the adsorption of radioactive iodine with SCGB and Bi@SCGB is strongly influenced by the presence of bismuth materials and the electrostatic repulsion between their negatively charged surfaces and negatively charged radioactive iodine (IO₃^-). The calculated R² values for the adsorption kinetics and isotherms support that chemisorption plays a crucial role in the adsorption of radioactive iodine by SCGB and Bi@SCGB in aqueous phases. The adsorption of radioactive iodine onto SCGB was linearly correlated with the contact time (h^1/2), and the diffusion of intra-particle predominantly determined the adsorption rate of radioactive iodine onto Bi@SCGB (C_{stage II} (129.20) > C_{stage I} (42.33)). Thermodynamic studies revealed that the adsorption of radioactive iodine toward SCGB (ΔG° = -8.47 to -7.83 kJ/mol; ΔH° = -13.93 kJ/mol) occurred exothermically and that for Bi@SCGB (ΔG° = -15.90 to -13.89 kJ/mol; ΔH° = 5.88 kJ/mol) proceeded endothermically and spontaneously. The X-ray photoelectron spectroscopy (XPS) analysis of SCGB and Bi@SCGB before and after the adsorption of radioactive iodine suggest the conclusion that the change in the primary adsorption mechanism from electrostatic attraction to surface precipitation upon the impregnation of bismuth materials on the surfaces of spent coffee ground biochars is beneficial for the adsorption of radioactive iodine in aqueous phases.

Multifunctional chitosan ferrogels for targeted cancer therapy by on-demand magnetically triggered drug delivery and hyperthermia

A facile method for the synthesis of chitosan ferrogels for magnetically triggered drug release and hyperthermia treatment is presented. The glyoxal crosslinked, dried ferrogels (magnetic bioaerogels) have been characterized by FTIR, XRD, TGA and VSM analyses and they possess unique characteristics such as high porosity, ultra-low density and superparamagnetism (M_s up to 56 emu g^-1). In addition, they present high drug (Doxorubicin, DOX) loading efficiency (~40 %), tumor-specific pH-responsive swelling, excellent biodegradation, remotely switchable drug release and high magnetic hyperthermia potential (42 °C within 4 min). Almost complete degradation of the ferrogels occurs in 3 months under physiological conditions (pH = 7.4), while the tumor-specific microenvironment (pH = 5.6) accelerates the degradation rate, where it occurs in ~8 weeks. Furthermore, an enhancement in drug release (by 30 %) was observed in 60 min, when subjected to a magnetic field of 50 mT. Excellent biocompatibility and promising cell-material interactions have been exhibited by the ferrogels, substantiated by MTT assay, cytoskeleton staining and confocal imaging. The viability has been drastically reduced for DOX-loaded samples due to the action of the released drug; validating the efficacy of DOX loaded ferrogels. The system presented, therefore, holds multi-functionalities enabling smart cancer treatment.

Combination of Micelle Collapse and CuNi Surface Dissolution for Electrodeposition of Magnetic Freestanding Chitosan Film

Magnetic chitosan hydrogel has aroused immense attention in recent years due to their biomedical significance and magnetic responsiveness. Here, A new electrodeposition method is reported for the fabrication of a novel CuNi-based magnetic chitosan freestanding film (MCFF) in an acidic chitosan plating bath containing SDS-modified CuNi NPs. Contrary to chitosan’s anodic and cathodic deposition, which typically involves electrochemical oxidation, the synthetic process is triggered by coordination of chitosan with Cu and Ni ions in situ generated by the controlled surface dissolution of the suspended NPs with the acidic plating bath. The NPs provide not only the ions required for chitosan growth but also become entrapped during electrodeposition, thereby endowing the composite with magnetic properties. The obtained MCFF offers a wide range of features, including good mechanical strength, magnetic properties, homogeneity, and morphological transparency. Besides the fundamental interest of the synthesis itself, sufficient mechanical strength ensures that the hydrogel can be used by either peeling it off of the electrode or by directly building a complex hydrogel electrode. Its fast and easy magnetic steering, separation and recovery, large surface area, lack of secondary pollution, and strong chelating capability could lead to it finding applications as an electrochemical detector or adsorbent.

Recovery, regeneration and sustainable management of spent adsorbents from wastewater treatment streams: A review

Adsorption is the most widely adopted, effective, and reliable treatment process for the removal of inorganic and organic contaminants from wastewater. One of the major issues with the adsorption-treatment process for the removal of contaminants from wastewater streams is the recovery and sustainable management of spent adsorbents. This review focuses on the effectiveness of emerging adsorbents and how the spent adsorbents could be recovered, regenerated, and further managed through reuse or safe disposal. The critical analysis of both conventional and emerging adsorbents on organic and inorganic contaminants in wastewater systems are evaluated. The various recovery and regeneration techniques of spent adsorbents including magnetic separation, filtration, thermal desorption and decomposition, chemical desorption, supercritical fluid desorption, advanced oxidation process and microbial assisted adsorbent regeneration are discussed in detail. The current challenges for the recovery and regeneration of adsorbents and the methodologies used for solving those problems are covered. The spent adsorbents are managed through regeneration for reuse (such as soil amendment, capacitor, catalyst/catalyst support) or safe disposal involving incineration and landfilling. Sustainable management of spent adsorbents, including processes involved in the recovery and regeneration of adsorbents for reuse, is examined in the context of resource recovery and circular economy. Finally, the review ends with the current drawbacks in the recovery and management of the spent adsorbents and the future directions for the economic and environmental feasibility of the system for industrial-scale application.