Ion-Imprinted Polymers: Synthesis, Characterization, and Adsorption of Radionuclides

Advancements in mercury detection using surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs): a review

Mercury (Hg) contamination remains a major environmental concern primarily due to its presence at trace levels, making monitoring the concentration of Hg challenging. Sensitivity and selectivity are significant challenges in the development of mercury sensors. Surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs) are two distinct analytical methods developed and employed for mercury detection. In this review, we provide an overview of the key aspects of SERS and IIP methodologies, focusing on the recent advances in sensitivity and selectivity for mercury detection. By examining the critical parameters and challenges commonly encountered in this area of research, as reported in the literature, we present a set of recommendations. These recommendations cover solid and colloidal SERS substrates, appropriate Raman reporter/probe molecules, and customization of IIPs for mercury sensing and removal. Furthermore, we provide a perspective on the potential integration of SERS with IIPs to achieve enhanced sensitivity and selectivity in mercury detection. Our aim is to foster the establishment of a SERS-IIP hybrid method as a robust analytical tool for mercury detection across diverse fields.

"Ion-imprinting" strategy towards metal sulfide scavenger enables the highly selective capture of radiocesium

Highly selective capture of radiocesium is an urgent need for environmental radioactive contamination remediation and spent fuel disposal. Herein, a strategy is proposed for construction of "inorganic ion-imprinted adsorbents" with ion recognition-separation capabilities, and a metal sulfide Cs2.33Ga2.33Sn1.67S8·H2O (FJSM-CGTS) with "imprinting effect" on Cs+ is prepared. We show that the K+ activation product of FJSM-CGTS, Cs0.51K1.82Ga2.33Sn1.67S8·H2O (FJMS-KCGTS), can reach adsorption equilibrium for Cs+ within 5 min, with a maximum adsorption capacity of 246.65 mg·g-1. FJMS-KCGTS overcomes the hindrance of Cs+ adsorption by competing ions and realizes highly selective capture of Cs+ in complex environments. It shows successful cleanup for actual 137Cs-liquid-wastes generated during industrial production with removal rates of over 99%. Ion-exchange column filled with FJMS-KCGTS can efficiently treat 540 mL Cs+-containing solutions (31.995 mg·L-1) and generates only 0.12 mL of solid waste, which enables waste solution volume reduction. Single-crystal structural analysis and density functional theory calculations are used to visualize the "ion-imprinting" process and confirm that the "imprinting effect" originates from the spatially confined effect of the framework. This work clearly reveals radiocesium capture mechanism and structure-function relationships that could inspire the development of efficient inorganic adsorbents for selective recognition and separation of key radionuclides.

Simultaneously Recovery of Thorium and Tungsten through Hybrid Electrolysis-Nanofiltration Processes

The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular, thorium. The radioactive element thorium has unexpectedly accessible domestic applications (filaments of light bulbs and electronic tubes, welding electrodes, and working alloys containing aluminum and magnesium), which lead to its appearance in electrical and electronic waste from municipal waste management platforms. The current paper proposes the simultaneous recovery of waste containing tungsten and thorium from welding electrodes. Simultaneous recovery is achieved by applying a hybrid membrane electrolysis technology coupled with nanofiltration. An electrolysis cell with sulphonated polyether-ether-ketone membranes (sPEEK) and a nanofiltration module with chitosan-polypropylene membranes (C-PHF-M) are used to carry out the hybrid process. The analysis of welding electrodes led to a composition of W (tungsten) 89.4%; Th 7.1%; O2 2.5%; and Al 1.1%. Thus, the parameters of the electrolysis process were chosen according to the speciation of the three metals suggested by the superimposed Pourbaix diagrams. At a constant potential of 20.0 V and an electrolysis current of 1.0 A, the pH is varied and the possible composition of the solution in the anodic workspace is analyzed. Favorable conditions for both electrolysis and nanofiltration were obtained at pH from 6 to 9, when the soluble tungstate ion, the aluminum hydroxide, and solid thorium dioxide were formed. Through the first nanofiltration, the tungstate ion is obtained in the permeate, and thorium dioxide and aluminum hydroxide in the concentrate. By adding a pH 13 solution over the two precipitates, the aluminum is solubilized as sodium aluminate, which will be found after the second nanofiltration in the permeate, with the thorium dioxide remaining integrally (within an error of ±0.1 ppm) on the C-PHF-M membrane.

Novel oligonucleotide-based sorbent for the selective extraction of cadmium from serum samples

The objective was to develop a sorbent functionalized with aptamers for the selective extraction of cadmium from biological samples. Two oligonucleotide sequences reported in literature as specific to cadmium were covalently grafted on activated Sepharose, with grafting yields of 45%. Once the supports packed in cartridges, a thorough study of the percolation conditions favoring Cd(II) retention was performed, demonstrating the importance of the nature of this medium. A high selectivity was reached when applying the optimal conditions as a recovery of 85% was obtained using the sorbent functionalized with one of the specific aptamers and only 1% on the control sorbent grafted with a scramble sequence. A high specificity was also obtained as recoveries for most of other ions were lower than 15%. The capacity of this oligosorbent estimated to 180 ng of Cd(II) for 30 mg of support was perfectly adapted to the trace analysis of Cd(II). The extraction procedure was then applied to a serum sample which was first subjected to acid precipitation. The initial concentration of cadmium in the serum was estimated to 1.83 µg/L using standard addition method and an extraction yield of 75 ± 1.6% was measured. Comparison of these results with those obtained without oligoextraction (recovery of 57%) showed a significant reduction of matrix effects in ICP-MS thanks to the use of the oligosorbent, underlining its interest for a more reliable quantification of Cd(II). This result was confirmed by performing the oligoextraction protocol on a certified serum.

Microbial involvement in iodine cycle: mechanisms and potential applications

Stable iodine isotopes are essential for humans as they are necessary for producing thyroid gland hormones. However, there are hazardous radioactive iodine isotopes that are emitted into the environment through radioactive waste generated by nuclear power plants, nuclear weapon tests, and medical practice. Due to the biophilic character of iodine radionuclides and their enormous biomagnification potential, their elimination from contaminated environments is essential to prevent the spread of radioactive pollution in ecosystems. Since microorganisms play a vital role in controlling iodine cycling and fate in the environment, they also can be efficiently utilized in solving the issue of contamination spread. Thus, this paper summarizes all known on microbial processes that are involved in iodine transformation to highlight their prospects in remediation of the sites contaminated with radioactive iodine isotopes.

Design of a New Phthalocyanine-Based Ion-Imprinted Polymer for Selective Lithium Recovery from Desalination Plant Reverse Osmosis Waste

In this study, a novel technique is introduced that involves the combination of an ion-imprinted polymer and solid-phase extraction to selectively adsorb lithium ions from reverse osmosis brine. In the process of synthesizing ion-imprinted polymers, phthalocyanine acrylate acted as the functional monomer responsible for lithium chelation. The structural and morphological characteristics of the molecularly imprinted polymers and non-imprinted polymers were assessed using Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption data for Li on an ion-imprinted polymer showed an excellent fit to the Langmuir isotherm, with a maximum adsorption capacity (Qm) of 3.2 mg·g-1. Comprehensive chemical analyses revealed a significant Li concentration with a higher value of 45.36 mg/L. Through the implementation of a central composite design approach, the adsorption and desorption procedures were systematically optimized by varying the pH, temperature, sorbent mass, and elution volume. This systematic approach allowed the identification of the most efficient operating conditions for extracting lithium from seawater reverse osmosis brine using ion-imprinted polymer-solid-phase extraction. The optimum operating conditions for the highest efficiency of adsorbing Li+ were determined to be a pH of 8.49 and a temperature of 45.5 °C. The efficiency of ion-imprinted polymer regeneration was evaluated through a cycle of the adsorption-desorption process, which resulted in Li recoveries of up to 80%. The recovery of Li from the spiked brine sample obtained from the desalination plant reverse osmosis waste through the ion-imprinted polymer ranged from 62.8% to 71.53%.

"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.

Thorium Removal, Recovery and Recycling: A Membrane Challenge for Urban Mining

Although only a slightly radioactive element, thorium is considered extremely toxic because its various species, which reach the environment, can constitute an important problem for the health of the population. The present paper aims to expand the possibilities of using membrane processes in the removal, recovery and recycling of thorium from industrial residues reaching municipal waste-processing platforms. The paper includes a short introduction on the interest shown in this element, a weak radioactive metal, followed by highlighting some common (domestic) uses. In a distinct but concise section, the bio-medical impact of thorium is presented. The classic technologies for obtaining thorium are concentrated in a single schema, and the speciation of thorium is presented with an emphasis on the formation of hydroxo-complexes and complexes with common organic reagents. The determination of thorium is highlighted on the basis of its radioactivity, but especially through methods that call for extraction followed by an established electrochemical, spectral or chromatographic method. Membrane processes are presented based on the electrochemical potential difference, including barro-membrane processes, electrodialysis, liquid membranes and hybrid processes. A separate sub-chapter is devoted to proposals and recommendations for the use of membranes in order to achieve some progress in urban mining for the valorization of thorium.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

A Modern Computer Application to Model Rare Earth Element Ion Behavior in Adsorptive Membranes and Materials

The following paper offers a modern REE 1.0 computer application designed to model the behavior of REE ions in adsorptive materials and membranes. The current version of the application is based on several models, such as the Lagergren pseudo-first order, pseudo-second-order and Elovich kinetic models, and the intraparticle diffusion model, the diffusion-chemisorption model, and the Boyd model. The application has been verified on a sample of four different types of adsorptive materials and membranes. The proposed application allowed the analysis of kinetics, but also the mechanisms of the adsorption process, especially those responsible for the rate-determining steps. It was found that Lagergren pseudo-second-order kinetic model was the best-fit model to describe the adsorption behavior of REE ions onto the novel materials and membranes. Other models determined the process of chemisorption was in force for the analyzed cases, and the mechanisms controlling the adsorption processes are diffusion-chemisorption and adsorption is mostly controlled by film diffusion. Additionally, characteristic parameters, such as q_e designated from two different models, showed very similar values, which indicates the correctness of the analysis.

Amphiphilic ligand in situ assembly of uranyl active sites and selective interactions of molybdenum disulfide

Removal of radioactive uranyl ions (UO₂²⁺) from water by effective adsorbents is highly desired but remains a challenge. UO₂²⁺ are easily combined with H₂O, and the polarization of H₂O affects the complexation between UO₂²⁺ and the adsorbent. Thus, it is necessary to reconstruct the UO₂²⁺ active site to improve the adsorption capacity. Herein ，an amphiphilic ligand, namely N, N-dimethyl-9-decenamide (NND), is successfully prepared. NND replace H₂O in [UO₂(H₂O)₅]²⁺ by hydrogen bonding, thereby enhancing the adsorption capacity of MoS₂ particles in the reconstituted UO₂²⁺ active sites. The predicted maximum adsorption capacity increased from 50.7 to 500.7 mg g^- 1 (by a factor of 9.87) with the presence of NND, which is higher than other functional group-modified MoS₂ adsorbents. Furthermore, NND and MoS₂ can retain UO₂²⁺ uptake under extreme conditions including high acid-base and gamma irradiation. Theoretical Calculations of NND through H bonding produces an increased amount of charge transfer and a reduced adsorption energy between UO₂²⁺ and MoS₂, which weakens the polarization effect of H₂O. The findings showed that NND appeared to be a promising amphiphilic to improve the adsorption efficiency of UO₂²⁺ from water.

Synthesis of N-isopropyl acrylamide copolymerized acrylic acid caped with Dibenzo-18-crown-6 composite for selective separation of Co-60 radioisotope from radioactive liquid waste containing Cs-137

A new selective polymeric composite capped with crown ether was successfully synthesized using N-isopropyl acrylamide copolymerized acrylic acid paired with Dibenzo-18-crown-6, P(NIPAm-Co-AA-DB 18C-6), by Gamma irradiation and ultrasonic homogenizer polymerization. Scanner electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering were used to characterize the selected polymeric composite's chemical and physical constitution. SEM shows a rough irregular surface, and FTIR spectra confirmed the function groups of P(NIPAm-Co-AA-DB 18C-6). Moreover, a systematic study of monomer and crown ether concentration was investigated to enhance the composite's performance. The behavior of the synthetic composite toward the selective separation of Co-60 from Cs-137 in a binary system was evaluated. Effects of pH, contact time, and initial ion concentration were investigated in a batch mode and the maximum capacity reached 108.0 mg/g for Co-60 and 82.0 mg/g for Cs-137. Four Kinetic models were investigated (pseudo-first-order, pseudo-second-order, Elovich, and Intra-particle diffusion). Regarding the calculated parameters, pseudo-second-order and Elovich models are the most describing the sorption process, indicating the chemisorptions process. Six adsorption isotherms were examined, two-parameter models (Langmuir, and Freundlich) and three-parameter models (Redlich-Peterson, Khan, Sips, and Hills). The best-fitted isotherm was identified using three error methodological approaches: the correlation coefficient (R2), the chi-square test (χ2), and the root-mean-square error. Isotherm models fit the experimental values in the following sequence: Khan > Rdlish-Peterson > Hills > Sips. Finally, an application for column separation was conducted, and Co-60 was completely separated from Cs-137 by 0.1 M HNO3. These findings indicate promising applications in the successive separation of Co-60 from radioactive liquid waste containing Cs-137 from Egyptian reactors.

Graphical abstract

Electrochemical Sensors Based on Au Nanoparticles Decorated Pyrene-Reduced Graphene Oxide for Hydrazine, 4-Nitrophenol and Hg2+ Detection in Water

Monitoring hazardous chemical compounds such as hydrazine (N2H4), 4-nitrophenol (4-NP) and Hg2+ in natural water resources is a crucial issue due to their toxic effects on human health and catastrophic impact on the environment. Electrochemical nanostructured platforms integrating hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are of great interest for such a purpose. In this work, disposable screen-printed carbon electrodes (SPCEs) have been modified with a hybrid nanocomposite formed by reduced graphene oxide (RGO), functionalized by 1-pyrene carboxylic acid (PCA), and decorated by colloidal Au NPs. These hybrid platforms have been tested for the electrocatalytic detection of N2H4 and 4-NP by differential pulse voltammetry and have been modified with an electropolymerized film of Hg2+ ions imprinted polycurcumin for the electroanalytical detection of Hg2+ by DPV. LODs, lower and in line with the lowest ones reported for state-of-the-art electrochemical sensors, integrating similar Au-graphene < nanocomposites, have been estimated. Additionally, good repeatability, reproducibility, and storage stability have been assessed, as well as a high selectivity in the presence of a 100-fold higher concentration of interfering species. The applicability of the proposed platforms for the detection of the compounds in real complex matrices, such as tap and river water samples, has been effectively demonstrated.

Magnetic nanocomposites based on Zn,Al-LDH intercalated with citric and EDTA groups for the removal of U(vi) from environmental and wastewater: synergistic effect and adsorption mechanism study

The efficient removal of U(vi) ions from contaminated natural waters and wastewaters of industrial processing plants by novel magnetic nanocomposites based on magnetite and Zn,Al-layered double hydroxides intercalated with citric and EDTA groups (Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA) was shown. These adsorbents were obtained using co-precipitation and ion-exchange techniques. The infrared spectroscopy confirmed the existence of O-containing groups on the surfaces of Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA, which could provide active sites in the interlayer of the adsorbents for the pollutants removal. The intercalation of Zn,Al-LDH with chelating EDTA-groups significantly increased the adsorption capacity toward U(vi) ions (131.22 mg g-1) compared to citric moieties in a wide range of pH (3.5-9.0). The maximum adsorption capacities of U(vi) at pH 7.5 were 81.12 mg g-1 for Fe3O4/Zn,Al-LDH/EDTA and 21.6 mg g-1 for Fe3O4/Zn,Al-LDH/Cit. The higher adsorption capacity of Fe3O4/Zn,Al-LDH/EDTA vs. the citric sample might be explained by high affinity of LDH-supports and high-activity of the chelating groups in formation of the complexes in the interlayer space of the magnetic nanocomposite. The removal of U(vi) by the magnetic nanocomposites occurred due to interlayer complexation and electrostatic interactions. The cations (Na+, K+, Ca2+), HCO3 - and fulvic acid anions being typical for natural waters were practically not affected upon the removal of U(vi) from aqueous media. The adsorption performance of Fe3O4/Zn,Al-LDH/EDTA nanocomposites was evaluated in the analysis of environmental and wastewater samples with recoveries in the range of 95.8-99.9%. This superior intercalation performance of LDH-supports provides simple and low-cost adsorbents, providing a strategy for decontamination of radionuclides from wastewater.

Surface ion-imprinted brewer's spent grain with low template loading for selective uranyl ions adsorption from simulated wastewater

Efficient removal of uranyl ions from wastewater requires excellent selectivity of the adsorbents. Herein, we report a new strategy using a high monomer/template molar ratio of 500:1 to prepare surface ion-imprinted brewer's spent grain (IIP-BSG) for selective U(VI) removal using binary functional monomers (2-hydroxyethyl methacrylate and diethyl vinylphosphonate) with high site accessibility and easy template removal. IIP-BSG exhibits a maximum U(VI) adsorption capacity of 165.7 mg/g, a high selectivity toward U(VI) in the presence of an excess amount of Eu(III) (Eu/U molar ratio = 20), a good tolerance of salinity, and a high reusability. In addition, mechanism studies have revealed electrostatic interaction and a coordination of uranyl ions by carboxyl and phosphoryl groups, the predominant contribution of high-energy (specific) sites during selective adsorption, and internal mass transfer as the rate-controlling step of U(VI) adsorption. Furthermore, IIP-BSG shows great potentials to separate U(VI) from lanthanides in simulated nuclear wastewater (pH₀ = 3.5) and selectively concentrate U(VI) from simulated mine water (pH₀ = 7.1). This study proves that the ion-imprinting effect can be achieved using a very low template amount with reduced production cost and secondary pollution, which benefits large-scale promotion of the ion-imprinted materials for selective uranyl ions removal.

Uranium Determination in Waters, Wine and Honey by Solid Phase Extraction with New Ion Imprinted Polymer

An analytical method for uranium determination in waters, wine and honey was developed based on solid phase extraction (SPE) with new ion imprinted polymer. The sorbent was synthesized using 4-(2-Pyridylazo)resorcinol (PAR) as a ligand via dispersion polymerization and characterized by SEM for morphology and shape of polymer particles and nitrogen adsorption–desorption studies for their surface area and total pore volume. The kinetic experiments performed showed that the rate limiting step is the complexation between U(VI) ions and chelating ligand PAR incorporated in the polymer matrix. Investigations by Freundlich and Langmuir adsorption isotherm models showed that sorption process occurs as a surface monolayer on homogeneous sites. The high extraction efficiency of synthesized sorbent toward U(VI) allows its application for SPE determination of U(VI) in wine and honey without preliminary sample digestion using ICP-OES as measurement method. The recoveries achieved varied: (i) between 88 to 95% for surface and ground waters, (ii) between 90–96% for 5% aqueous solution of honey, (iii) between 86–93% for different types of wine. The validity and versatility of proposed analytical methods were confirmed by parallel measurement of U in water samples using Alpha spectrometry and U analysis in wine and honey after sample digestion and ICP-MS measurement. The analytical procedure proposed for U determination in surface waters is characterized with low limits of detection/quantification and good reproducibility ensuring its application for routine control in national monitoring of surface waters. The application of proposed method for honey and wine samples analysis provides data for U content in traditional Bulgarian products.

A Core-Shell Amino-Functionalized Magnetic Molecularly Imprinted Polymer Based on Glycidyl Methacrylate for Dispersive Solid-Phase Microextraction of Aniline

A core-shell amino-functionalized glycidyl methacrylate magnetic molecularly imprinted polymer (MIP) was synthesized by the suspension polymerization/surface imprinting method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mercury porosimetry, nitrogen gas adsorption–desorption, and elemental analysis. This MIP was used as the sorbent in dispersive solid-phase microextraction (DSPME) of aniline from textile wastewater prior to high-performance liquid chromatography-mass spectrometry (HPLC-MS) measurements. Since aniline is toxic and a probable human carcinogen, its determination in water is of great significance. This is a challenging task because aniline is usually present at trace levels. The effects of different DSPME variables on the preconcentration efficiency have been studied by using the Plackett–Burman screening design of experiments (DoE) followed by response surface methodology optimization using the Box-Behnken design. Thus, DoE enabled the investigation of several variables simultaneously. Under optimized conditions, aniline was effectively and selectively separated by a small amount of the DSPME sorbent and detected in real textile wastewater samples. The method detection limit of 1 ng mL−1 was attained, with good method linearity and acceptable recovery and precision. The results showed that the studied MIP could be a reliable DSPME sorbent for efficiently analyzing trace aniline in real wastewater samples.

Separation of anthropogenic radionuclides from aqueous environment using raw and modified biosorbents

In this study, two types of biosorbents were used to remove ¹³⁷Cs and plutonium isotopes from aqueous solutions - moss (Ptilium crista - castrensis) and oak sawdust (Quercus robur), both in the form of natural and modified state. Sorbent modification significantly increases the sorbent surface area (for moss sorbents - from 4.0 to 47.2 m²/g, and for sawdust sorbents - from 1.1 to 26.3 m²/g), pore volume (from 10^-3 to 10^-2), concentration and amount of basic cations and anions, as well as active functional groups on the sorbent surface. The main functional groups on the surface of natural sorbents modified with iron hydroxide interacting with analytes are carboxyl and hydroxyl groups. For carbonized sawdust and its subsequent activation with concentrated HCl, in addition to carboxyl and hydroxyl groups, acetyl groups also become active. Carbonated sawdust treated with HCl showed the highest average removal efficiency and sorption capacity for radiocesium and plutonium isotopes in laboratory column experiments - for ¹³⁷Cs ∼78.6% and ∼196.6 Bq/g and for ^239+240Pu ∼83% and ∼41.5 Bq/g, respectively. The moss and moss modified with iron hydroxide also showed good properties of adsorbing plutonium isotopes in field (in-situ) experiments. The best results on the sorption of ¹³⁷Cs in field experiments were shown by carbonated sawdust activated with HCl, and for isotopes of plutonium - the raw moss and moss modified with iron hydroxide. The results of the study showed that sorbents can be used not only for purification of water from plutonium isotopes but allow the operational sampling and more accurate measurement of radiocesium and plutonium isotopes in the fresh water reservoirs by the dynamic flow method.

Novel Chemoresistive Sensor for Sensitive Detection of Pb2+ Ions Using an Interdigital Gold Electrode Fabricated with a Reduced Graphene Oxide-Based Ion-Imprinted Polymer

This study presents novel chemoresistive reduced graphene oxide-ion-imprinted polymer (IIP-rGO)-based sensors for detection of lead (Pb2+) ions. The ion-imprinted polymer was synthesized by bulk polymerization and modified with a variable amount of rGO incorporated to form an IIP-rGO composite. The amount of rGO in the polymer matrix affected the sensor's relative response, and 1:3 mass ratio produced excellent results, with a consistent trend as the concentration of Pb2+ ions increased in the solution. The decrease in relative resistance (ΔR/R o) followed an exponential decay relationship between the ΔR/R o response and the concentration of Pb2+ ions in aqueous solutions. After solving the exponential decay function, it is observed that the sensor has the upper limit of ΔR/R o >1.7287 μg L-1, and the limit of detection of the sensor is 1.77 μg L-1. A nonimprinted polymer (NIP)-based sensor responded with a low relative resistance of the same magnitude although the concentration was varied. The response ratio of the IIP-based sensor to the NIP-based sensor (ΔR/R o)IIP/(ΔR/R o)NIP as a function of the concentration of Pb2+ ions in the solution shows that the response ratios recorded a maximum of around 22 at 50 μg L-1 and then decreased as the concentration increased, following an exponential decay function with the minimum ratio of 2.09 at 200 μg L-1 but never read 1. The sensor showed excellent selectivity against the bivalent cations Mn2+, Fe2+, Sn2+, and Ti2+. The sensor was capable of exhibiting 90% ΔR/R o response repeatability in a consecutive test.