Rapid removal of radioactive cesium by polyacrylonitrile nanofibers containing Prussian blue

Amino modified nanofibers anchored to Prussian blue nanoparticles selectively remove Cs+ from water

To improve the selective separation performance of silica nanofibers (SiO2 NFs) for cesium ions (Cs+) and overcome the defects of Prussian blue nanoparticles (PB NPs), PB/SiO2-NH2 NFs were prepared to remove Cs+ from water. Among them, 3-aminopropyltriethoxysilane (APTES) underwent an alkylation reaction with SiO2, resulting in the formation of a dense Si-O-Si network structure that decorated the surface of SiO2 NFs. Meanwhile, the amino functional groups in APTES combined with Fe3+ and then reacted with Fe2+ to form PB NPs, which anchored firmly on the aminoated SiO2 NFs surface. In our experiment, the maximum adsorption capacity of PB/SiO2-NH2 NFs was 111.38 mg/g, which was 31.5 mg/g higher than that of SiO2 NFs. At the same time, after the fifth cycle, the removal rate of Cs+ by PB/SiO2-NH2 NFs adsorbent was 75.36% ± 3.69%. In addition, the adsorption isotherms and adsorption kinetics of PB/SiO2-NH2 NFs were combined with the Freundlich model and the quasi-two-stage fitting model, respectively. Further mechanism analysis showed that the bond between PB/SiO2-NH2 NFs and Cs+ was mainly a synergistic action of ion exchange, electrostatic adsorption and membrane separation.

Constructing porous ZnFC-PA/PSF composite spheres for highly efficient Cs+ removal

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.

Synthesis of Prussian blue-embedded magnetic micro hydrogel for scavenging of cesium from aqueous solutions; Batch and dynamic investigations

A magnetic micro porous structure composite based on alginate and Prussian blue (M-SA-PB) was simply prepared for cesium removal from the aqueous solutions. The gelation and formation of PB proceeded through the same step, which made the PB homogenously distributed and firmly attached to the alginate matrix. The homogenizer was applied to break down the bulky gel structure into micro-ones, and the lyophilizer will provide the porous structure. Batch cesium sorption experiments showed that the adsorption kinetics and isotherms were attributed to the pseudo-second-order model and Langmuir isotherm. Moreover, the Cs-ion is favorably adsorbed on the M-SA-PB composite surface as a monolayer towards Cs, with a maximum adsorption capacity reach of 191.0 mg/g. Furthermore, the M-SA-PB adsorbent showed excellent adsorption selectivity of Cs from multiple-ion solutions. Our work was extended to use the M-SA-PB composite in dynamic cesium sorption. The column studies showed that the removal efficiency of Cs+ increased with increasing bed depth as well as the initial cesium concentration. Finally, as previously mentioned, the M-SA-PB could be considered an excellent Cs+ scavenger employing both batch and dynamic approaches, which makes it a promising adsorbent for practical investigations.

Tuning Surface Energy to Enhance MoS2 Nanosheet Production via Liquid-Phase Exfoliation: Understanding the Electrochemical Adsorption of Cesium Chloride

Environmental pollution caused by radionuclides like Cs-137 and Cs-134 has increased global attention toward public health. Electrochemical adsorption has emerged as a feasible, rapid, and scalable method to treat contaminated water sources. However, graphene and its derivatives have limitations in ion adsorption via physisorption, forming a double layer that restricts the electrode's adsorption capacity. To address this, we propose the use of molybdenum disulfide (MoS2) with its extensive intercalation galleries of MoS2 nanosheets for cesium removal via an electrochemical route. Liquid-phase exfoliation with water and N-methyl-2-pyrrolidone (NMP) was then used to produce MoS2 nanosheets in a scalable quantity (high-yield production). The formation of a mixed solvent possessing relatively equivalent surface energy for exfoliation enabled us to achieve a remarkable exfoliation yield of up to ca. 1.26 mg mL-1, which is one of the highest yields reported to date (without a surfactant being added) and to the best of our knowledge. The 35% v/v of water in NMP displayed a maximum yield while maintaining the structure of the as-exfoliated one. Water exceeding over 66.7% v/v led to the formation of MoO3. Moreover, an insight into the cesium ion removal mechanism through the electrochemical route was demonstrated. It is found that the Cs+ removal follows electrochemical intercalation rather than adsorption. This work aids the understanding of cesium intercalation coupled with a mass-scale production method, which should lead to more efficient and cost-effective removal of radionuclides from contaminated water sources, opening new research avenues in materials and environmental science.

The latest research trends in the removal of cesium from radioactive wastewater: A review based on data-driven and visual analysis

The widespread adoption of nuclear energy has increased the amount of radioactive cesium (Cs) that is discharged into waste streams, which can have environmental risks. In this paper, we provide a comprehensive summary of current advances in aqueous Cs removal by employing a bibliometric analysis. We collected 1580 articles related to aqueous Cs treatment that were published on the Web of Science database between 2012 and 2022. By applying bibliometric analysis combined with network analysis, we revealed the research distribution, knowledge base, research hotspots, and cutting-edge technologies in the field of aqueous Cs removal. Our findings indicate that China, Japan, and South Korea are the most productive countries with respect to Cs removal research. In addition, both historic events and environmental threats might have contributed to research in Asian countries having a higher focus on Cs removal as well as strong international cooperation between Asian countries. A detailed keyword analysis reveals the main knowledge base for aqueous Cs removal and highlights the potential of the adsorption-based method for treating Cs contamination. Furthermore, the results reveal that exploration of functional materials is a popular research topic in the field of Cs removal. Since 2012, novel materials, including Prussian blue, graphene oxide, hydrogel and nanocomposites, have been widely investigated because of their high capacity for Cs removal. On the basis of the detailed information, we report the latest research trends on aqueous Cs removal, and propose future research directions and describe the challenges related to effective Cs treatment. This scientometric review provides insights into current research hotspots and cutting-edge trends in addition to contributing to the development of this crucial research field.

Additive manufacturing of geopolymers with hierarchical porosity for highly efficient removal of Cs. JOURNAL OF HAZARDOUS MATERIALS 2023;443:130161. [PMID: 36327833 DOI: 10.1016/j.jhazmat.2022.130161]

Geopolymers (GPs) have emerged as promising adsorbents for wastewater treatment due to their superior adsorption stability, tunable porosity, high adsorption capacity, and low-energy production. Despite their great promise, developing GPs with well-controlled hierarchical structures and high porosity remains challenging, and the mechanism underlying the ion adsorption process remains elusive. Here we report a cost-effective and universal approach to fabricate Na or K GPs with sophisticated architectures, high porosity, and arbitrary cation species exchange by means of additive manufacturing and a surfactant. The introduction of sodium lauryl sulfate (SLS) enhanced the porosity of the GP adsorbents, yielding NaGP-lattice-10%SLS adsorbent with a high total porosity of 80.8 vol%. Combining static and dynamic adsorption tests, the effects of morphology, surfactant content, and cation species on Cs⁺ adsorption performance were systemically investigated. With an initial Cs⁺ concentration of 900 mg/L, the printed NaGP exhibited a maximum Cs⁺ adsorption capacity of 80.1 mg/g, outperforming other adsorbents reported so far. The quasi-second-order fit of the NaGP adsorbent showed overall higher R² values than the quasi-first-order fit, indicating that the adsorption process was dominated by ion exchange. Combined with first-principles calculations, we verified that the content of water in the GP sod cages also affected the ion-exchange process between Na⁺ and Cs⁺.

Tannic acid-assisted in-situ interfacial formation of Prussian blue-assembled adsorptive membranes for radioactive cesium removal

There is a growing interest in advanced materials that can effectively treat wastewater contaminated with radioactive cesium (¹³⁷Cs), which is an extremely hazardous material. Here, we report a new class of Cs-adsorptive membranes compactly assembled with Cs-adsorptive Prussian blue (PB) particles. The PB particle assembly was formed via an in-situ interfacial reaction between two PB precursors in the presence of tannic acid (TA) as a binder on a porous support. While the interfacial reaction enabled the formation of a defect-less PB network, TA enhanced the PB-PB and PB-support compatibilities, consequently producing a uniform, densely packed PB assembly near the support surface. The fabricated TA-assisted PB membrane (PB/TA-M) synergistically rejected Cs via a combination of adsorption and membrane filtration, although adsorption predominantly determined Cs rejection initially. Hence, the PB/TA-M membrane showed considerably higher Cs removal performance than commercial nanofiltration (NF) and reverse osmosis (RO) polyamide (PA) membranes for a sufficiently long operation time. Furthermore, the PB/TA-M membrane displayed excellent radioactive ¹³⁷Cs removal performance, significantly exceeding those of commercial NF and RO PA membranes due to its higher radiation stability, indicating its viability for application in treating actual radioactive wastewater.

Separation and Removal of Radionuclide Cesium from Water by Biodegradable Magnetic Prussian Blue Nanospheres

As the main component of radioactive wastewater, the cesium ion has seriously endangered the environment and human health. Prussian blue nanoparticles (PB NPs) are used as adsorbents for the purification of cesium-containing wastewater because of their ability to selectively adsorb cesium ions. In this work, novel magnetic Prussian blue nanospheres (MPBNs) were developed from polylactic acid nanospheres as a carrier, loaded with Fe3O4 nanoparticles (Fe3O4 NPs) inside and PB NPs outside for the removal of cesium ions with the help of magnetic separation. Meanwhile, the effects on the adsorption efficiency of MPBNs, such as pH, time, temperature and initial concentration of cesium ion solution, were studied. The adsorption isotherms, kinetic models and adsorption thermodynamics were investigated to research the absorption mechanism. The results showed that MPBNs were spherical with a rough surface, and their particle size, iron content and saturation magnetization were 268.2 ± 1.4 nm, 40.01% and 41.71 emu/g, which can be recovered by magnetic separation. At 293 K, MPBNs could reduce the cesium ion solution from 40 mg/L to 4.8 mg/L, and its cesium ion removal rate and adsorption capacity were 82.46% and 16.49 mg/g, respectively. The optimum pH of MPBNs for cesium ion adsorption was 5~9, the adsorption equilibrium time was 60 min, and the maximum adsorption capacity was 17.03 mg/g. In addition, MPBNs were separated rapidly by an external magnetic field, and the adsorption process was an endothermic reaction. The adsorption isotherm and kinetics of MPBNs were in accordance with the Freundlich model and quasi-second-order fitting model, respectively, and the adsorption process of MPBNs was controlled by the diffusion step in particles. Notably, these MPBNs could be effectively separated from water by a magnetic field, facilitating engineering applications in cesium-containing wastewater.

Reactive oxygen species scavenging nanofibers with chitosan-stabilized Prussian blue nanoparticles for enhanced wound healing efficacy

Chronic inflammatory wounds pose therapeutic challenges in the biomedical field. Polymeric nanofibrous matrices provide extracellular-matrix-like structures to facilitate wound healing; however, wound infection and the subsequent accumulation of reactive oxygen species (ROS) delay healing. Therefore, we herein developed electrospun nanofibers (NFs), composed of chitosan-stabilized Prussian blue (PBChi) nanoparticles (NPs) and poly(vinyl alcohol) (PVA), with ROS scavenging activity to impart antioxidant and wound healing properties. The PBChi NPs were prepared using chitosan with different molecular weights, and their weight ratio with respect to PVA was optimized to yield PBChi-NP-coated PVA NFs with well-defined NF structures. In situ and in vitro antioxidant activity assays showed that the PBChi/PVA NFs could effectively remove ROS. Particularly, PBChi/PVA NFs with a lower chitosan molecular weight exhibited greater antioxidant activity. The hydroxyl radical scavenging activity of PBChi10k/PVA NFs was 60.4 %, approximately two-fold higher than that of PBChi100k/PVA NFs. Further, at the concentration of 10 μg/mL, they could significantly lower the in vitro ROS level by up to 50.7 %. The NFs caused no significant reduction in cell viability, owing to the excellent biocompatibility of PVA with PBChi NPs. Treatment using PBChi/PVA NFs led to faster cell proliferation in in vitro scratch wounds, reducing their size from 202 to 162 μm. The PBChi/PVA NFs possess notable antioxidant and cell proliferation properties as ROS-scavenging wound dressings.

Mechanochemically Synthesized Prussian Blue for Efficient Removal of Cesium Ions from Aqueous Solutions

The adsorptive removal of radioactive cesium [Cs(I)] is important for ensuring a clean aquatic environment. In this work, the adsorption of Cs(I) was carried out using Prussian blue (PB) prepared by mechanochemical synthesis. X-ray diffraction, Fourier-transform infrared spectroscopy, and field-emission scanning electron microscopy results indicated that PB had been successfully synthesized by mechanochemical synthesis. Thermogravimetric analysis, contact angle analysis, inductively coupled plasma atomic emission spectrometry, elemental analysis, and electrophoretic light scattering spectrophotometry confirmed that several defects were formed, explaining the principal mechanism for the efficient adsorption over PB prepared by mechanochemical synthesis. The superior adsorption properties toward Cs(I) make PB prepared by mechanochemical synthesis an attractive candidate material for the efficient, economical, and eco-friendly processes for purifying radioactive wastewater.

A comprehensive review on preparation, functionalization and recent applications of nanofiber membranes in wastewater treatment

The direct discharge of significant amounts of polluted water into water bodies causes adverse ecological and human health effects. This severe deterioration in water quality creates significant challenges to meet the growing demand for clean water. Therefore, the world urgently needs environmentally friendly advanced technology to overcome this global crisis. In this regard, nanofiber-based membrane filtration is a promising technique in wastewater remediation because of their huge surface area, extremely porous structure, amenable pore size/pore size distribution, variety of material choices, and flexibility to modification with other functional materials. However, despite their unique properties, fouling, poor mechanical properties, shrinkage, and deformation are major drawbacks of nanofiber membranes for treating wastewater. This review presents a comprehensive overview of nanofiber membranes' fabrication and function in water purification applications as well as providing novel approaches to overcoming/alleviating the mentioned disadvantages. The review first presents nanofiber membrane preparation methods, focusing on electrospinning as a versatile and viable technique alongside discussing the parameters controlling nanofiber morphology. Afterward, the functionalization of nanofiber membranes by combining them with other nanomaterials, such as metal and metal-oxide nanoparticles, carbon nanotubes, metal-organic frameworks, and biomolecules, were demonstrated and discussed. In addition, nanofiber membranes functionalized with microorganisms were highlighted. Finally, we introduced and discussed in detail the most relevant and recent advances in nanofiber applications in wastewater treatment in the context of removing different pollutants (e.g., heavy metals, nutrients, radioactive elements, pharmaceuticals, and personal care products, dyes, and pesticides). Moreover, the promising antimicrobial ability of nanofiber membranes in removing microorganisms from wastewater has been fully underscored. We believe this comprehensive review could provide researchers with preliminary data and guide both researchers and producers engaged in the nanofiber membrane industry, letting them focus on the research gaps in wastewater treatment.

Effective cesium removal from Cs-containing water using chemically activated opaline mudstone mainly composed of opal-cristobalite/tridymite (opal-CT)

Opaline mudstone (OM) composed of opal-CT (SiO2·nH2O) has high potential use as a cesium (Cs) adsorbent, due to its high specific surface area (SSA). The objective of this study was to investigate the Cs adsorption capacity of chemically activated OM and the adsorption mechanism based on its physico-chemical properties. We used acid- and base-activation methods for the surface modification of OM. Both acid- and base- activations highly increased the specific surface area (SSA) of OM, however, the base-activation decreased the zeta potential value more (- 16.67 mV), compared to the effects of acid-activation (- 6.60 mV) or non-activation method (- 6.66 mV). Base-activated OM showed higher Cs adsorption capacity (32.14 mg/g) than the others (acid: 12.22 mg/g, non: 15.47 mg/g). These results indicate that base-activation generates pH-dependent negative charge, which facilitates Cs adsorption via electrostatic attraction. In terms of the dynamic atomic behavior, Cs cation adsorbed on the OM mainly exist in the form of inner-sphere complexes (IS) containing minor amounts of water molecules. Consequently, the OM can be used as an effective Cs adsorbent via base-activation as an economical and simple modification method.

Prussian blue analogs-based layered double hydroxides for highly efficient Cs+ removal from wastewater

In this work, novel Prussian blue analogs-based layered double hydroxide (PBA@ZnTi-LDH) was in situ synthesized and used for radioactive Cs⁺ removal from wastewater. The results suggested that this PBA@ZnTi-LDH prepared using LDH as skeleton and transition metal source showed higher adsorption capacity (243.9 mg/g) and water stability than conventional PBAs, and promising application in scale-up Cs⁺ removal. Thus, it was granulated by calcium alginate and the PBA@ZnTi-LDH/CaALG exhibited favorable post-separation and fixed-bed adsorption ability at different Cs⁺ concentrations and flow rates, highlighting its application perspective on Cs⁺ removal from various kinds of wastewater. Moreover, the real-world Cs⁺ removal was preliminarily explored using natural complex Cs⁺-containing water. As a result, this stable and easily separated PBA@ZnTi-LDH/CaALG showed high removal efficiency, selectivity and good reusability, which was promising in scale-up Cs⁺ removal from the real-world wastewater.

Assessing of cesium removal from wastewater using functionalized wood cellulosic adsorbent

Sustainable materials are urgently desired for treatment of radioactive cesium (Cs) contaminated water to safe-guard the public health. Apart from the synthetic ligand-based materials, the Mangrove charcoal modified adsorbent was fabricated for assessing of Cs removal from waste sample. The raw charcoal was oxidized using nitrification approach and diverse oxygen containing carboxyl, carbonyl and hydroxyl functional groups were introduced. After modification, the adsorbent characteristics were drastically changed as compared to the charcoal during the measurement of FTIR, N₂ adsorption-desorption isotherms and SEM micrographs. The data clarified that charcoal modified adsorbent was exhibited high Cs transport through the inner surface of the adsorbent based on bonding ability. The adsorbent was shown comparatively slow kinetics to Cs ion; however, the adsorption capacity was high as 133.54 mg/g, which was higher than the crown ether based conjugate materials. The adsorption data were followed to the Langmuir adsorption isotherms and the monolayer coverage was possible due to the data presentation. The presence of high amount of Na and K were slightly interfered to the Cs adsorption by the charcoal modified adsorbent, however; the Na and K concentration was 350-600 folds higher than the Cs concentration. Then the proposed adsorbent was selective to Cs for the potential real radioactive Cs contaminated water. The volume reduction was established rather than desorption and reuses advantages. More than 99% volume reduction was measured by burning of Cs adsorbed adsorbent at 500 °C for ensuring the safe storage and disposal of used adsorbent. Therefore, the charcoal modified adsorbent may open the new door to treat the Cs containing wastewater.

Cesium removal using acid- and base-activated biotite and illite

Biotite and illite have excellent cesium (Cs) adsorption capacity due to their negative charges in addition to adsorption sites of the planar, interlayer, and frayed edge sites (FES). The aim of this study is to investigate the Cs adsorption capacity using acid- and base-activated biotite and illite based on their mineralogical characteristics. The acid-activated biotite and base-activated illite exhibited high Cs removal efficiency from the low-level Cs-containing DI water (97.5 % and 97.3 %, respectively). The acid-activation of biotite increased the specific surface area (SSA, 12.08 → 43.04 m²/g), Fe(III)/Fe(II) ratio (0.56 → 0.76), and wedge zone d-spacing (1.017 → 1.065 nm), while the zeta potential (-4.06 → -4.82 mV) decreased. The base-activation of illite resulted to a decrease in the SSA (22.14 → 18.49 m²/g), zeta potential (-7.68 → -31.64 mV), and Fe(III)/Fe(II) ratio (0.92 → 0.79). However, only acid-activated biotite appeared to have a high capacity of Cs removal from Cs-containing seawater (73.9 %; base-activated illite: 26.1 %). These results indicate that the FES of biotite owing to acid-activation showed better results in regards to Cs adsorption as compared to the pH-dependent negative charges of the base-activated illite.

Enhanced kinetics and super selectivity toward Cs+ in multicomponent aqueous solutions: A robust Prussian blue analogue/polyvinyl chloride composite membrane

Developing effective adsorbents for ¹³⁷Cs removal from complex wastewater systems has been a significant challenge. Although existing spheres adsorbents could improve the post-separation ability and practical operability, the adsorption kinetics are still significantly retarded due to the large intra-particle diffusion resistance. Here, we demonstrate the efficiency of a robust Prussian blue analogue/polyvinyl chloride composite membrane (PPM), which was easily prepared by a simple solvent evaporation method. In virtue of the less dense layer and ion-sieving functionality, it showed enhanced kinetics (5 h) and super selectivity (S_F = 248.3-5388.6) towards Cs⁺. New PPM was robust within a wide pH range (2-10) and exhibited favorable removal capacity (152.8 mg/g), placing it at an outstanding material for Cs⁺ removal among other adsorbents. Moreover, PPM could be simply eluted and reused using a KCl solution as eluent. A study of the adsorption mechanism confirmed an ion-exchange action during the removal process. Thus, PPM is considered to be a promising candidate for the removal of Cs⁺ from multicomponent aqueous solutions.

Brushite-infused polyacrylonitrile nanofiber adsorbent for strontium removal from water

The Fukushima Daiichi nuclear disaster and the decommissioning of over a hundred nuclear reactors worldwide led to the increase in the demand for efficient water treatment technologies to remove radionuclides, such as ⁹⁰Sr. Brushite or dicalcium phosphate dihydrate (DCPD) is a potential adsorbent to remove strontium from water. In this study, composite poly(acrylonitrile) (PAN) nanofiber (NF) adsorbents with DCPD (PAN/DCPD) were prepared, characterized, and investigated for strontium adsorption in water. Material characterization revealed mechanically suitable, hydrophilic, and macroporous composite NF adsorbents with average fiber diameters of <500 nm. As-prepared DCPD powder exhibited a superior strontium uptake capacity of 81.7 mg g^-1 at pH ≅ 10 of aqueous Sr²⁺ solution over its biogenic and synthetic predecessor, hydroxyapatite. Increased DCPD loading resulted in higher adsorption. Maximum Sr²⁺ uptake of PAN/DCPD NF with 70 wt% DCPD loading (PAN/70DCPD NF) was 146 mg g^-1 considering the Sips isotherm model. Kinetic studies revealed that Sr²⁺ removal by PAN/DCPD NF was a chemisorption process which involved ion exchange and surface complexation. PAN/70DCPD NF as a dead-end membrane filter exhibited superior removal efficiency over pure PAN NF. The overall results of this study revealed the potential application of PAN/DCPD NF adsorbent for ⁹⁰Sr removal from water.

Effective removal of cesium from wastewater via adsorptive filtration with potassium copper hexacyanoferrate-immobilized and polyethyleneimine-grafted graphene oxide

As an attractive alternative to radioactive cesium removal, we introduced an adsorptive filtration method using a composite membrane consisting of potassium copper hexacyanoferrate (KCuHCF) and graphene-based support. Polyethyleneimine-grafted reduced graphene oxide (PEI-rGO), used as an immobilizing matrix, was effective not only in distributing KCuHCF inside the composite with the aid of abundant amino-functionality, but also in achieving high water flux by increasing the interlayer spacing of the laminar membrane structure. Due to the rapid and selective cesium adsorption properties of KCuHCF, the fabricated membrane was found to be effective in achieving complete removal of cesium ions under a high flux (over 500 L m^-2 h^-1), which is difficult in a conventional membrane utilizing the molecular sieving effect. This approach offers strong potential in the field of elimination of radionuclides that require rapid and complete decontamination.

Facile Synthesis of Porous Polymer Using Biomass Polyphenol Source for Highly Efficient Separation of Cs+ from Aqueous Solution

In this work, a series of polyphenol porous polymers were derived from biomass polyphenols via a facile azo-coupling method. The structure and morphologies of the polymer were characterized by BET, TEM, SEM, XRD, TGA and FT-IR techniques. Batch experiments demonstrated their potentialities for adsorptive separation of Cs⁺ from aqueous solution. Among them, porous polymers prepared with gallic acid as starting material (GAPP) could adsorb Cs⁺ at wide pH value range effectively, and the optimal adsorption capacity was up to 163.6 mg/g, placing it at top material for Cs⁺ adsorption. GAPP exhibited significantly high adsorption performance toward Cs⁺ compared to Na⁺ and K⁺, making it possible in selective removal of Cs⁺ from ground water in presence of co-existing competitive ions. Moreover, the Cs-laden GAPP could be facilely eluted and reused in consecutive adsorption-desorption processes. As a result, we hope this work could provide ideas about the potential utilization of biomass polyphenol in environmental remediation.

Prussian blue immobilized cellulosic filter for the removal of aqueous cesium

Cesium is a typical radioisotope that has a long half-life and is dangerous and can be emitted in the event of a nuclear accident. Prussian blue (PB), which is known to effectively adsorb cesium, is difficult to separate when it is dissolved in an aqueous system. In this study, PB was immobilized on a filter type support media, cellulose filter (CF), for use as a selective material for cesium adsorption. The commercially available CF was functionalized by the addition of acrylic acid (AA) (i.e., CF-AA) to enhance the PB immobilization, which increased both PB loading and binding strength. The AA functionalization changed the major functional groups from hydroxyl to carboxylic, as confirmed by Fourier-transform infrared spectroscopy. As a result of the surface modification, the PB immobilization increased 1.5 times and reduced detachment of PB during washing. The prepared adsorbent, CF-AA-PB, was tested for its cesium adsorption capability. Cesium adsorption equilibrated within 3 h, and the maximum cesium adsorption capacity was 16.66 mg/g. The observed decrease in the solution pH during cesium adsorption inhibited the overall cesium uptake; however, this was minimized by buffering. The prepared CF-AA-PB was used as a filter material and its potential use as a countermeasure for removing radioactive cesium from a contaminated water stream was demonstrated.

Composite hydrogel particles encapsulated ammonium molybdophosphate for efficiently cesium selective removal and enrichment from wastewater

A novel ammonium molybdophosphate (AMP)/ polyvinyl alcohol (PVA)/ sodium alginate (SA) composite hydrogel (APS) was prepared for Cs⁺ removal and enrichment from radioactive wastewater. Batch experiments with the subject of AMP concentration, pH value, initial Cs⁺ concentration, contact time, temperature, competing ions were investigated. The results showed this APS hydrogel with high permeability and stability could effectively adsorb Cs⁺ at widely broad pH value range and low Cs⁺ concentration within a short time. Adsorption thermodynamic parameters indicated the endothermic and spontaneous nature of the adsorption process, and the Lagergren pseudo-second order model was found to exhibit the best correlation with the adsorption results. Equilibrium data was better described by the Langmuir isotherm equation, and the maximum adsorption capacity of APS hydrogel calculated was in consistent with the experimental results. Furthermore, the APS hydrogel could be easily reused at least five times without obvious decrease in absorption activity and selectivity using ammonia nitrate as the eluent, and what's more, the Cs⁺ concentration in eluent was approximately concentrated for 2 times after single cycle. All the results suggest that the environmental friendly and low-cost APS hydrogel could be used as effective and selective material for Cs⁺ removal and enrichment from wastewater.

Experimental and theoretical investigations of Cs+ adsorption on crown ethers modified magnetic adsorbent

Carboxyl Fe₃O₄ nanoparticles (Fe₃O₄@R-COOH) modified with 18-Crown-6 ether functional groups have been prepared via an amidation reaction and used as bifunctional adsorbent for Cs⁺. The adsorbent has a superparamagnetic property, allowing an easy recycling, and a high capacity of Cs⁺ adsorption on the crown ether. The adsorption isotherms and kinetic behaviors agree well with the Langmuir and the pseudo-second-order models. The material exhibits a high selectivity for Cs⁺ in the solution with co-existing cations (NH₄⁺, Rb⁺, K⁺, Na⁺ and Li⁺). A theoretical calculation according to density functional theory (DFT) is used to estimate the structure of Cs⁺ adsorption on crown ether, demonstrating an exothermic process and showing a good agreement with the experimental observations. The adsorption behavior is affected not only by the size of macrocyclic crown ethers, but also by the chelating symmetry and the binding energy. The newly developed adsorbent has a potential application for removing cesium out of wastewater and salt lakes.

Study of Cu (II), Co (II), Ni (II) and Pb (II) removal from aqueous solutions using magnetic Prussian blue nano-sorbent

In this study magnetic Prussian blue (MPB) was synthesized and applied as sorbent for the efficient removal of heavy metals (Cu (II), Co (II), Ni (II) and Pb (II)) from aqueous solution. The average diameter of nanoparticles was found to be about 15 nm. The experimental results were fitted to Langmuir, Freundlich and Dubinin-Radushkevich models with high regression coefficients. The kinetics data were expressed by pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The influence of initial concentration, sorbent dosage and time on the heavy metals sorption efficiency was studied using response surface methodology (RSM). Analysis of variance (ANOVA) was included to assess the adequacy of the model.

Fabrication of a novel polyvinylidene fluoride membrane via binding SiO2 nanoparticles and a copper ferrocyanide layer onto a membrane surface for selective removal of cesium

A novel polyvinylidene fluoride (PVDF) membrane was fabricated through chemical binding SiO₂ nanoparticles (NPs) and copper ferrocyanide (CuFC) layers onto a membrane surface simultaneously to improve the removal efficiency of Cs. The results indicated that the SiO₂ NPs were strongly deposited onto the membrane surface, and the CuFC layer was firmly attached on the surface of SiO₂ NPs and the membrane. CuFC/SiO₂/PVDF membrane remained stable after the acidic solution and sonication stress treatments. CuFC/SiO₂/PVDF membrane showed good permeate flux and high selectivity on removal of Cs, and adsorbing capacity reached 1440.4 mg m^-2 for Cs. The membrane remained high rejections of Cs in a wide pH, and could be regenerated well by H₂O₂ and N₂H₄. Selective adsorption and electrostatic interaction govern the rejection of Cs. The coexisting cations decreased the rejection of Cs mainly in accordance to the order of cations' hydration radii as K⁺ > Na⁺ > Ca²⁺ > Mg²⁺. In addition, the rejection of Cs could still reach 99.4% in 8 h in the filtration of humic acid solution and natural surface water. The membrane could removal of Cs from water effectively by directly rapid filtration, suggesting it can be applied as promising technology for radioactive wastewater treatment.

Spiderweb-Like Fe-Co Prussian Blue Analogue Nanofibers as Efficient Catalyst for Bisphenol-A Degradation by Activating Peroxymonosulfate

Prussian blue and its analogues (PBA) based nanomaterials have been widely applied to removing pollutants in the recent years. However, easy aggregation and poor recycling largely limit their practical applications. In this work, spiderweb-like Fe-Co Prussian blue analogue/polyacrylonitrile (FCPBA/PAN) nanofibers were prepared by electrospinning and applied to degrading bisphenol-A (BPA) by activating peroxymonosulfate (PMS). Detailed characterization demonstrated that a high loading of FCPBA (86% of FCPBA in FCPBA/PAN) was successfully fixed on the PAN nanofibers. 67% of BPA was removed within 240 min when 500 mg·L⁻¹ PMS and 233 mg·L⁻¹ FCPBA/PAN were introduced in 20 mg·L⁻¹ BPA solution at initial pH of 2.8. Electron paramagnetic resonance (EPR) and radical inhibition experiments were performed to identify the possible degradation mechanism. For comparison, a low loading of FCPBA nanofibers (0.6FCPBA/PAN nanofibers, 43% of FCPBA in FCPBA/PAN) were also prepared and tested the catalytic performance. The results showed that the activity of FCPBA/PAN was much higher than 0.6FCPBA/PAN. Furthermore, a FCPBA/PAN packed column was made as a reactor to demonstrate the reusability and stability of FCPBA/PAN nanofibers, which also exhibited the bright future for the industrial application. This work makes it possible to fabricate efficient PBA nanocatalysts with excellent recyclability and promotes the application of PBA in industrial areas.

Photocatalytic enhancement of cesium removal by Prussian blue-deposited TiO2

After the Fukushima nuclear accident, tremendous efforts were made to treat radiocesium, radiostrontium, and other radioactive materials. For the first time, we demonstrate that a TiO₂ photocatalyst can significantly enhance Cs adsorption by Prussian blue-deposited TiO₂ (PB/TiO₂) under UV irradiation. In this study, we synthesized PB/TiO₂ using the photodeposition method. After the Cs ions were adsorbed on the PB/TiO₂ in darkness, we then exposed the PB/TiO₂ to UV light irradiation. This resulted in a further increase in Cs ion adsorption of more than 10 times the amount adsorbed in darkness. This photocatalytic-enhanced adsorption of Cs ions was not observed on PB mixed with SiO₂, nor under visible light irradiation. We investigated the effects of PB concentration, PB/TiO₂ concentration, and gas purging on both dark and photocatalytic-enhanced adsorption of Cs ions by PB/TiO₂. Based on the results, we suggest that the photocatalytic-enhanced adsorption of Cs ions on PB/TiO₂ is due to photocatalytic reduction of PB, which leads to additional adsorption of Cs ions. The change in solution color before and after the reaction, and the change in solution pH in the dark and during UV irradiation strongly support this suggestion. The photocatalytic-enhanced adsorption of Cs ions was equivalent during radioactive ¹³⁷Cs removal, indicating important applications for pollutant removal from contaminated water.