Fabrication and investigation of novel monochloroacetic acid fortified, tripolyphosphate-crosslinked chitosan for highly efficient adsorption of uranyl ions from radioactive effluents

Lanthanum-loaded biochar-based alginate hydrogels for efficient phosphate adsorption from wastewater

In this study, a lanthanum-loaded biochar-based alginate hydrogel (La@SA@BC) was successfully fabricated at an optimal 1:1 mass ratio of lanthanum-loaded biochar to sodium alginate. A maximum phosphate (P) adsorption capacity of 56.5 mg/g was achieved under an adsorbent dosage of 0.9 g/L. The hydrogel demonstrated 90 % P removal efficiency at a pH of 3 and showed minimal adsorption reduction (<10 %) in the presence of competing ions (Cl-, SO42-, NO3-). Kinetic analysis indicated a higher pseudo-second-order model fit (R2 = 0.95) in the adsorption process, suggesting chemisorption as the dominant adsorption mechanism. In addition, the morphology, elemental composition, and surface functional group type analysis confirmed the La@SA@BC hydrogel had a rough, folded surface structure with internal cavities and uniform lanthanum distribution. The diversified characterization results identified electrostatic interactions, ligand exchange, precipitation, Lewis acid-base interactions, and pore filling were the primary routes for P removal. These findings highlight La@SA@BC hydrogel's high selectivity, robust ion tolerance, and strong adsorption capacity, enabling it a promising candidate for remediating P-contaminated water.

High-Efficiency Broad-Spectrum Antibacterial Activity of Chitosan/Zinc Ion/Polyoxometalate Composite Films for Water Treatment

The development of multifunctional films with rapidly killing microorganisms and adsorbing residual antibiotics in wastewater remains a challenging endeavor. In this work, the chitosan/zinc ion/polyoxometalate (CS/Zn2+/POM) multifunctional films were prepared by the freeze-drying method using chitosan, ZnO, and POM. Notably, the CS/Zn2+/POM films exhibited excellent bactericidal properties against Gram-positive/negative bacterial strains including Staphylococcus aureus (S. aureus, 99.80%), Escherichia coli (E. coli, 99.82%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli, 87.76% and ampicillin-resistant E. coli, 99.71%). This may be due to the chelation of Zn2+ with CS disrupting the cell membrane and bringing POM into direct contact with bacteria, leading to bacterial death. In addition, the CS/Zn2+/POM films showed good adsorption performance to a tetracycline (TC) solution (adsorption rate 75.2%). Further studies showed that the main process of tetracycline removal by CS/Zn2+/POM films was controlled by a physical adsorption. This POM-based film material has an important potential for the synthesis of broad-spectrum antimicrobial materials for the removal of residual antibiotics from water pollutants such as tetracycline.

Assembly of protein-directed fluorescent gold nanoclusters for high-sensitivity detection of uranyl ions

Uranium is a key element in the nuclear industry, whose accidental release causes health and environmental problems. In this paper, a protein-directed fluorescent sensor with aggregation-induced emission characteristics (gold nanoclusters@ovalbumin, AuNCs@OVA) was synthesized for the detection of UO22+ with high sensitivity and selectivity. The sensor exhibited good fluorescence stability, and its fluorescence intensity could be selectively enhanced by UO22+. Based on FT-IR and XPS analyses, the increase in fluorescence intensity of AuNCs@OVA after the addition of UO22+ was attributed to aggregation induced by the complexation between UO22+ and the amino, carboxyl, hydroxyl, and phosphate groups of ovalbumin. The detection limit was determined to be 34.4 nM, and the sensor showed excellent ion selectivity for UO22+. In combination with a smartphone program, the sensor could realize the real-time detection of UO22+ in a quantitative and portable way.

Bibliometric insights into the evolution of uranium contamination reduction research topics: Focus on microbial reduction of uranium

Confronting the threat of environment uranium pollution, decades of research have yielded advanced and significant findings in uranium bioremediation, resulting in the accumulation of tremendous amount of high-quality literature. In this study, we analyzed over 10,000 uranium reduction-related papers published from 1990 to the present in the Web of Science based on bibliometrics, and revealed some critical information on knowledge structure, thematic evolution and additional attention. Methods including contribution comparison, co-occurrence and temporal evolution analysis are applied. The results of the distribution and impact analysis of authors, sources, and journals indicated that the United States is a leader in this field of research and China is on the rise. The top keywords remained stable, primarily focused on chemicals (uranium, iron, plutonium, nitrat, carbon), characters (divers, surfac, speciat), and microbiology (microbial commun, cytochrome, extracellular polymeric subst). Keywords related to new strains, reduction mechanisms and product characteristics demonstrated the strongest uptrend, while some keywords related to mechanism and performance were clearly emerging in the past 5 years. Furthermore, the evolution of the thematic progression can be categorized into three stages, commencing with the discovery of the enzymatic reduction of hexavalent uranium to tetravalent uranium, developing in the groundwater remediation process at uranium-contaminated sites, and delving into the research on microbial reduction mechanisms of uranium. For future research, enhancing the understanding of mechanisms, improving uranium removal performance, and exploring practical applications can be considered. This study provides unique insights into microbial uranium reduction research, providing valuable references for related studies in this field.

One particle three targets: Phosphate anion-modified magnetic mesoporous silica with enhanced fluorescence for sensitive detection, efficient adsorption, and repeated removal of uranium (VI) ions

An ideal adsorbent material that combines the multiple capabilities of sensitive detection, efficient adsorption, and repeatable removal of uranium (U) from the environment remains a serious challenge. Herin, a general method was developed for synthesizing a series of phosphate anions (such as: PO43-, P2O74-, P3O105- and P6O186-) modified magnetic mesoporous silica nanoparticles (Fe3O4 @mSiO2-Zn2+ NPs). The mesoporous surfaces and abundant phosphate groups provide potential, powerful uranium-binding sites for capturing U(VI) ions. Especially, the optimum adsorption capacity of Fe3O4 @mSiO2-Zn2+/P3O105- NPs was as high as 885.90 mg·g-1 (298 K), which was higher than that of unmodified or other phosphate anions-modified Fe3O4 @mSiO2-Zn2+ NPs. Meanwhile, P3O105--binding sites and mesoporous surfaces also strongly restrict U(VI) ions' fluorescence vibrational inactivation, the adsorption results in rapid green fluorescence enhancement (within 180 s), and an ultra-low detection limit (4.5 nmol·L-1), which is well below the standard in drinking water of the World Health Organization (WHO). Furthermore, even after 5 cycles, the adsorbent still maintained their original adsorption capacity of 80.21% and displayed excellent selectivity for detecting and removing U(VI) from seawater. Based on these results, the Fe3O4 @mSiO2-Zn2+/P3O105- NPs seem to be a suitable multifunctional adsorbent for the detection, adsorption, and removal of U(VI) from environment.

Development of chitosan biopolymer by chemically modified orange peel for safranin O dye removal: A sustainable adsorbent and adsorption modeling using RSM-BBD

This study aimed to develop a biocomposite (hereinafter, CHI/OP-H2SO4) via the functionalization of chitosan (CHI) biopolymer by chemically modified orange peel (OP-H2SO4). The physicochemical characteristics of CHI/OP-H2SO4 were studied using methods such as pHpzc, XRD, FTIR, BET, and FESEM-EDX. The efficacy of the CHI/OP-H2SO4 biocomposite in removing cationic dye (safranin O, SAF-O) from aqueous solutions was assessed. The Box-Behnken Design (BBD) based on response surface methodology (RSM) was employed to optimize the adsorption performance of CHI/OP-H2SO4, considering factors such as A: CHI/OP-H2SO4 dose (0.02-0.08 g), B: pH (4-10), and C: time (10-60 min). The pseudo-first-order and Freundlich isotherm models align well with the experimental data of SAF-O adsorption by CHI/OP-H2SO4. The excellent adsorption capacity for CHI/OP-H2SO4 was recorded (321.2 mg/g). The notable adsorption of SAF-O onto CHI/OP-H2SO4 is attributed primarily to electrostatic forces between the acidic groups of CHI/OP-H2SO4 and the SAF-O cation, along with H-bonding, and n-π interactions. By transforming waste materials into valuable resources, this approach not only mitigates environmental impact but also produces a promising and sustainable adsorbent for the removal of cationic dyes, exemplified here by the effective removal of SAF-O dye.

Removal of U(VI) from acidic wastewater by persimmon tannin-functionalized chitosan

With sodium tripolyphosphate (STPP) as cross-linker, Persimmon tannin-chitosan microspheres (PT-CS) were synthesized by hydrothermal for removing U(VI) from acidic effluent. The batch experiments indicated that PT-CS adsorbed U(VI) most effectively at pH 1.5, the maximum adsorption capacity for PT-CS was 245 mg/g. Compared to pure CS dissolved at pH 3, PT-CS still maintain high stability at pH 1. Moreover, single system of common metal ions in rare earth wastewater only slightly affected the adsorption of uranium at pH 1.5, but this process was inhibited about 30% at pH 5. Those results indicated that the selectivity of PT-CS for uranium removal could be controlled by regulating the pH and there are excellent potentials for PT-CS using in acid metal water treatment. Its adsorption selectivity and ability to adapt different condition was demonstrated with uraniferous rare earth wastewater treatment. The adsorption for PT-CS to U(VI) were well fitted for both Langmuir isothern and pseudo-secondary kinetic model equations, and that meant chemisorption dominated the removal process. Spectroscopic analyses confirmed that the adsorption of U(VI) occurred via surface complexation by -OH and ion exchange with Na+. Therefore, this study provides a high-efficiency, low-cost, valuable and highly adaptable method for the treatment of acidic uranium-containing effluents.

Synthesis of salicylaldehyde tailored PAMAM dendrimers/chitosan for adsorption of aqueous Hg(II): Performance and mechanism

Water pollution caused by Hg(II) exerts hazardous effect to environmental safety and human health. Herein, a family of salicylaldehyde tailored poly(amidoamine) (PAMAM) dendrimers/chitosan composites (G0-S/CTS, G1-S/CTS, and G2-S/CTS) were prepared and used for the removal of Hg(II) from water solution. The adsorption performance of the as-prepared composites for Hg(II) was thoroughly demonstrated by determining various influencing factors. G0-S/CTS, G1-S/CTS and G2-S/CTS exhibited competitive adsorption capacity and good adsorption selective property for Hg(II). The maximum adsorption capacity of G0-S/CTS, G1-S/CTS and G2-S/CTS for Hg(II) were 1.86, 2.18 and 4.47 mmol‧g-1, respectively. The adsorption for Hg(II) could be enhanced by raising initial Hg(II) concentration and temperature. The adsorption process was dominated by film diffusion processes with monolayer adsorption behavior. The functional groups of NH2, CONH, CN, OH, CO and CN were mainly responsible for the adsorption of Hg(II). G0-S/CTS, G1-S/CTS and G2-S/CTS displayed good regeneration property and the regenerate rate maintained 95.00 % after five adsorption-desorption cycles. The as-prepared adsorbents could be potentially used for the efficient removal of Hg(II) from aqueous solution.

Synthesis and fabrication of segregative and durable MnO2@chitosan composite aerogel beads for uranium(VI) removal from wastewater

To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO2@chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO2 nanospheres but also significantly enhances the porous structure and surface area of MnO2@CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO2@CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO2@CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO2-based adsorbents. The chemisorption process of U(VI) on MnO2@CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO2@CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater.

"One-pot" preparation and adsorption performance of chitosan-based La3+/Y3+ dual-ion-imprinted thermosensitive hydrogel

Temperature-sensitive materials are increasingly of deep interest to researchers. Ion imprinting technology is widely used in the field of metal recovery. In order to solve the problem of rare earth metal recovery, we designed a temperature-sensitive dual-imprinted hydrogel adsorption product (CDIH) with chitosan as the matrix, N-isopropylacrylamide as a thermally responsive monomer, and La³⁺ and Y³⁺ as the co-templates. The reversible thermal sensitivity and ion-imprinted structure were determined by differential scanning calorimetry, Fourier transform infrared spectrometer, Raman spectra, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Scanning electron microscopy and X-ray energy spectroscopy various characterizations and analyses. The simultaneous adsorption amount of CDIH for La³⁺ and Y³⁺ was 87.04 mg/g and 90.70 mg/g, respectively. The quasi-secondary kinetic model and Freundlich isotherms model well described the adsorption mechanism of CDIH. It's worthy to mention that CDIH could be well regenerated through washing with deionized water at 20 °C, with a desorption rate of 95.29 % for La³⁺ and 96.03 % for Y³⁺. And after 10 cycles of reuse, 70 % of the adsorption amount could be maintained, revealing excellent reusability. Furthermore, CDIH expressed better adsorption selectivity to La³⁺ and Y³⁺ than its non-imprinted counterparts in a solution containing six metal ions.

Efficient removal of uranium (VI) from water by a hyper-cross-linked polymer adsorbent modified with polyethylenimine via phosphoramidate linkers

Practical adsorbents with high efficiency are essential to effectively treating wastewater. Herein, a novel porous uranium adsorbent (PA-HCP) having a considerable amount of amine and phosphoryl groups was designed and synthesized by grafting polyethyleneimine (PEI) on a hyper-cross-linked fluorene-9-bisphenol skeleton via phosphoramidate linkers. Furthermore, it was used to treat uranium contamination in the environment. PA-HCP exhibited a large specific surface area (up to 124 m2/g) and a pore diameter of 2.5 nm. Batch uranium adsorptions on PA-HCP were investigated methodically. PA-HCP demonstrated a uranium sorption capacity of >300 mg/g in the pH range of 4-10 (C0 = 60 mg/L, T = 298.15 K), with its maximum capacity reaching 573.51 mg/g at pH = 7. The uranium sorption process obeyed the pseudo-second-order model and fitted well with the Langmuir isothermal. In the thermodynamic experiments, uranium sorption on PA-HCP was revealed to be an endothermic, spontaneous process. Even in the presence of competing metal ions, PA-HCP exhibited excellent sorption selectivity for uranium. Additionally, excellent recyclability can be achieved after six cycles. Based on FT-IR and XPS measurements, both the PO and -NH2 (and/or -NH-) groups on PA-HCP contributed to efficient uranium adsorption as a result of the strong coordination between these groups and uranium. Furthermore, the high hydrophilicity of the grafted PEI improved the dispersion of the adsorbents in water and facilitated uranium sorption. These findings suggest that PA-HCP can be used as an efficient and economical sorbent to remove U(VI) from wastewater.

Amino carboxymethyl chitosan//dialdehyde starch/polyvinyl alcohol double-layer film loaded with ε-polylysine

To develop food packaging with good antibacterial activity and mechanical performance, four amino carboxymethyl chitosan (ACC)//dialdehyde starch (DAS) /polyvinyl alcohol (PVA) films were prepared by Schiff base and hydrogen bond interactions for efficient loading and release of ε-polylysine (ε-PL). The effects of the Schiff base reaction on the physicochemical properties of the films were explored based on the different aldehyde group contents in DAS. The ACC//DAS₄/PVA film exhibited a tensile strength of 62.5 MPa, and the water vapor and oxygen permeability was 8.77 × 10^-3·g·mm/m²·d·kPa and 0.15 × 10³·cm³·mm/m²·d, respectively. By leveraging the Schiff base reaction, the film swelling properties were improved by adjusting the cross-link density, mesh size, and molecular mass between the cross-links. The ACC//DAS₄/PVA film could efficiently load ε-PL with a value of 98.44% and long-term release in a food simulant of 10% ethanol at 25 °C for 120 min. Moreover, the ACC-ε-PL//DAS₄/PVA film was successfully used for salmon preservation.

A magnetic MIL-125-NH2@chitosan composite as a separable adsorbent for the removal of Cr(VI) from wastewater

Metal-organic frameworks (MOFs) are gradually used since of their huge specific surface area and superior pore structure. However, there are problems such as easy aggregation and difficult separation in water treatment. In this study, we prepared composite microspheres (FMCS-1) by modifying MIL-125-NH₂ with Fe₃O₄ and chitosan. The structural characterization and performance analysis of the materials showed that the introduction of chitosan effectively prevents the stacking of MOFs. The magnetic test manifested that Fe₃O₄ solved the problem of the difficult separation of MOFs from water. The removal potential of toxic Cr(VI) was tested by adsorption experiments. The isotherm model indicated that FMCS-1 is a single molecular layer adsorbent with a maximum adsorption capacity of 109.46 mg/g at pH = 2. The adsorption kinetics showed that the adsorption of Cr(VI) by FMCS-1 was chemical adsorption. The acid resistance test demonstrated that FMCS-1 can exist stably in acid solutions. The recycling experiments proved that the adsorbent can be reused and the removal percentage still reaches 50 % after 5 cycles. This work expands the application of MOFs in water treatment and also provides an effective adsorbent for Cr(VI) removal.