Porous hydrogel containing Prussian blue nanoparticles for effective cesium ion adsorption in aqueous media

Determination of trace heavy metal ion Tl(I) in water by energy dispersive X-ray fluorescence spectrometry using prussian blue dispersed on solid sepiolite

X-ray fluorescence (XRF) offers the advantage of performing measurements without damaging or consuming the sample, enabling rapid and simultaneous multi-element analysis. It has been widely applied in environmental monitoring, materials science, geology, and medicine, but not in water. Here, a novel method is proposed that combines energy-dispersive X-ray fluorescence spectroscopy (EDXRF) with prussian blue dispersed on solid sepiolite nanomaterials (PB/SEP) and an integrated enrichment-separation device to detect trace heavy metal ion Tl(I) in water environments. The water sample passes through the detachable enrichment component, and subsequently, PB/SEP is used as a solid adsorbent for the pre-enrichment of Tl(I) in the water sample. This process eliminates the cumbersome separation steps and saves analysis time. The research elucidates the impact of sample pH, flow rate, volume, and interfering ions on elemental recoveries, demonstrating that the proposed method offers a low detection limit of 0.057 μg/L, but also maintains high precision, with the RSD of less than 4.39 %. Furthermore, the PB/SEP magnetic nanocomposite was successfully applied to the tap water sample and river water sample with recoveries ranging from 93.5 % to 128.3 %, confirming the accuracy and practicality of the analytical method.

A novel floating adsorbent for cesium based on Shirasu balloon modified with magnetite and Prussian blue

Shirasu balloon (SB) is a hollow glassy sphere produced from volcanic deposits by heating that can float up on water owing to its hollow structure. In this study, a novel adsorbent for the removal of cesium ion in water was developed by the modification of the surface of the SBs with magnetite (Mag) and Prussian blue (PB). The developed adsorbent (PB-Mag-SB) was characterized by elemental analysis, X-ray diffraction, and Fourier transform infrared spectrometry and the magnetism of the adsorbent. From these results and the change in color of the adsorbents, the successful modification of the SBs with magnetite and PB was confirmed. The developed adsorbents were added and mixed with the polluted water. After the adsorption, it could float up on the surface of water due to the buoyancy of the balloon and also be collected by a magnet due to the magnetism of the magnetite formed on the surface of the SB. Furthermore, the removal of Cs from water was achieved by binding site of PB immobilized on the Mag-SB. The PB-Mag-SB could selectively adsorb Cs even in the presence of coexisting cations at high concentrations. The adsorbent remained afloat on the water surface for at least 24 h, and approximately 99% of the adsorbent could be collected within 5 min using a magnet. The introduction of both floating and magnetism properties to the adsorbent makes it easy and selective to collect the adsorbent after the adsorption of pollutants in water. SB is a natural product with a low environmental impact; therefore, the adsorbent based on SB will contribute to the environmental remediation as a novel material for adsorption.

Cesium adsorption from an aqueous medium for environmental remediation: A comprehensive analysis of adsorbents, sources, factors, models, challenges, and opportunities

Considering the widespread and indispensable nature of nuclear energy for future power generation, there is a concurrent increase in the discharge of radioactive Cs into water streams. Recent studies have demonstrated that adsorption is crucial in removing Cs from wastewater for environmental remediation. However, the existing literature lacks comprehensive studies on various adsorption methods, the capacities or efficiencies of adsorbents, influencing factors, isotherm and kinetic models of the Cs adsorption process. A bibliometric and comprehensive analysis was conducted using 1179 publications from the Web of Science Core Collection spanning from 2014 to 2023. It reviews and summarizes current publication trends, active countries, adsorption methods, adsorption capacities or efficiencies of adsorbents, tested water sources, influencing factors, isotherm, and kinetic models of Cs adsorption. The selection of suitable adsorbents and operating parameters is identified as a crucial factor. Over the past decade, due to their notable capacity for Cs adsorption, considerable research has focused on novel adsorbents, such as Prussian blue, graphene oxide, hydrogel, and nanoadsorbents (NA). However, there remains a need for further development of application-oriented laboratory-scale experiments. Future research directions should encompass exploring adsorption mechanisms, developing new adsorbents or their combinations, practical applications of lab-scale studies, and recycling radioactive Cs from wastewater. Drawing upon this literature review, we present the most recent research patterns concerning adsorbents to remove Cs, outline potential avenues for future research, and delineate the obstacles hindering effective adsorption. This comprehensive bibliometric review provides valuable insights into prevalent research focal points and emerging trends, serving as a helpful resource for researchers and policymakers seeking to understand the dynamics of adsorbents for Cs removal from water.

Functionalization of Tailored Porous Carbon Monolith for Decontamination of Radioactive Substances

As the control over radioactive species becomes critical for the contemporary human life, the development of functional materials for decontamination of radioactive substances has also become important. In this work, a three-dimensional (3D) porous carbon monolith functionalized with Prussian blue particles was prepared through removal of colloidal silica particles from exfoliated graphene/silica composite precursors. The colloidal silica particles with a narrow size distribution were used to act a role of hard template and provide a sufficient surface area that could accommodate potentially hazardous radioactive substances by adsorption. The unique surface and pore structure of the functionalized porous carbon monolith was examined using electron microscopy and energy-dispersive X-ray analysis (EDS). The effective incorporation of PB nanoparticles was confirmed using diverse instrumentations such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). A nitrogen adsorption/desorption study showed that surface area and pore volume increased significantly compared with the starting precursor. Adsorption tests were performed with 133Cs ions to examine adsorption isotherms using both Langmuir and Freundlich isotherms. In addition, adsorption kinetics were also investigated and parameters were calculated. The functionalized porous carbon monolith showed a relatively higher adsorption capacity than that of pristine porous carbon monolith and the bulk PB to most radioactive ions such as 133Cs, 85Rb, 138Ba, 88Sr, 140Ce, and 205Tl. This material can be used for decontamination in expanded application fields.

Fluorescence Modulation of Conjugated Polymer Nanoparticles Embedded in Poly(N-Isopropylacrylamide) Hydrogel

A series of conjugated polymers (CPs) emitting red, green, and blue (RGB) fluorescence were synthesized via the Suzuki coupling polymerization. Polymer dots (Pdots) were fabricated by the reprecipitation method from corresponding CPs, in which the Pdot surface was functionalized to have an allyl moiety. The CP backbones were based on the phenylene group, causing the Pdots to show identical ultraviolet-visible absorption at 350 nm, indicating that the same excitation wavelength could be used. The Pdots were covalently embedded in poly(N-isopropylacrylamide) (PNIPAM) hydrogel for further use as a thermoresponsive moiety in the polymer hydrogel. The polymer hydrogel with RGB emission colors could provide thermally reversible fluorescence changes. The size of the hydrogel varied with temperature change because of the PNIPAM’s shrinking and swelling. The swollen and contracted conformations of the Pdot-embedded PNIPAM enabled on-and-off fluorescence, respectively. Fluorescence modulation with 20 to 80% of the hydrogel was possible via thermoreversibility. The fluorescent hydrogel could be a new fluorescence-tuning hybrid material that changes with temperature.

Securely anchored Prussian blue nanocrystals on the surface of porous PAAm sphere for high and selective cesium removal

Prussian blue (PB) has been well known as a pigment crystal to selectively sequestrate the radioactive cesium ion released from aqueous solutions owing to PB cage size similar to the cesium ion. Because the small size of PB is hard to deal with, the adsorbents containing PB have been prepared in the form of composites causing low sequestration efficiency of cesium. In this study, securely anchored PB nanocrystals on the surface of millimeter-sized porous polyacrylamide (PAAm) spheres (PB@PAAm) have been prepared by the crystallization of PB on the Fe³⁺ adsorbed PAAm. The securely anchored PB nanocrystals have been demonstrated to be selective and efficient adsorbents for sequestration of the radioactive cesium. The well-interconnected-spherical pores and millimeter-sized diameter of the PB@PAAm adsorbents facilitated permeation of Cs⁺ into the adsorbent and ease of handling respectively. Especially the well-interconnected-spherical pores allowed that PB@PAAm showed 90% of its maximum Cs⁺ adsorption capacity within 30 min. The PB@PAAm showed an outstanding Cs⁺ capture ability of 374 mg/g, high removal efficiency of 85% even at low concentration of Cs⁺ (10 ng/L), and superior selectivity of Cs⁺ against interference ions of Na⁺, K⁺, Mg²⁺, and Ca²⁺.

More Efficient Prussian Blue Nanoparticles for an Improved Caesium Decontamination from Aqueous Solutions and Biological Fluids

Any release of radioactive cesium-137, due to unintentional accidents in nuclear plants, represents a dangerous threat for human health and the environment. Prussian blue has been widely studied and used as an antidote for humans exposed to acute internal contamination by Cs-137, due to its ability to act as a selective adsorption agent and to its negligible toxicity. In the present work, the synthesis protocol has been revisited avoiding the use of organic solvents to obtain Prussian blue nanoparticles with morphological and textural properties, which positively influence its Cs⁺ binding capacity compared to a commercially available Prussian blue sample. The reduction of the particle size and the increase in the specific surface area and pore volume values compared to the commercial Prussian blue reference led to a more rapid uptake of caesium in simulated enteric fluid solution (+35% after 1 h of contact). Then, after 24 h of contact, both solids were able to remove >98% of the initial Cs⁺ content. The Prussian blue nanoparticles showed a weak inhibition of the bacterial luminescence in the aqueous phase and no chronic detrimental toxic effects.

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.