Distribution Coefficient Kd Research Articles

SOIL-SOIL SOLUTION DISTRIBUTION COEFFICIENT OF RADIOIODINE IN SURFACE SOILS AROUND SPENT NUCLEAR FUEL REPROCESSING PLANT IN ROKKASHO, JAPAN.

The soil-soil solution distribution coefficient (Kd) of radioiodine in soil samples with various total carbon (TC) contents was measured in a batch sorption experiment using 125I tracer spiked as I-. The log values of Kd-125I and TC concentration in low-TC soils (< 10g kg-1) were positively correlated, whereas those of Kd-125I in TC rich soils (> 10 g kg-1) and dissolved organic carbon (DOC) in liquid phase were negatively correlated. The proportion of 125I in the < 3 kDa fraction in the liquid phase is negatively correlated with the log of DOC, implying that 125I is primarily combined with high-molecular-weight organic matter in soil solutions rich in DOC. The results suggest that Kd-125I in soil with high soil organic material (SOM) content is governed by DOC via the combination of 125I and DOC. In contrast, Kd-125I in soils with a low SOM content was governed by SOM because the anion exchange capacity of SOM was vital for the sorption of 125I-.

Soil heterogeneity influence on the distribution of heavy metals in soil during acid rain infiltration: Experimental and numerical modeling

Acid rain is a global environmental problem that mobilizes heavy metals in soils, while the distribution and geochemical fraction of heavy metals during acid rain infiltration in heterogeneous soils are still unclear. In this study, we performed column experiments to investigate the distribution and geochemical fraction of Cu, Pb, Ni and Cd in heterogeneously layered soils during continuous acid rain infiltration. Chloride ion used as a conservative tracer was found to be uniformly distributed during acid rain infiltration, showing insignificant preferential flow effects in the column. In contrast, however, the distribution of heavy metals was highly non-uniform, especially in the silty soil at the lower part of the column, indicating a heterogeneous distribution of adsorption capacity. In addition, in the control experiments with neutral rain infiltration, uniform distribution of heavy metals was observed, indicating that the heterogeneous distribution of adsorption coefficient during acid rain infiltration was mainly caused by different pH buffering capacities. A numerical model considering water flow and solute transport was developed, where the average water-solid distribution coefficient (Kd) in Layer 2 was only 1.5–12.5% of that in Layer 1 during acid rain infiltration. The model could predict the variation of heavy metal concentrations in soil with the majority of error less than 35%, confirming that different Kd induced the heterogeneous distribution of heavy metals. In addition, the geochemical fraction of heavy metals in the upper coarse sand layer remained stable, while the acid-extractable fractions in the lower loam and silt loam layer gradually increased. Our findings suggest that soil heterogeneity, especially chemical heterogeneity affected by rainfall acidity, has an important influence on the infiltration, migration and geochemical fraction of heavy metals in soils. This study could help guide the risk assessment of heavy metal-contaminated sites that were polluted by acid rain or landfill leachate.

Copper-based metal-organic framework for highly efficient adsorption of lead ions from aqueous solution

A nanomaterial, a copper-based metal organic framework (Cu-BTC MOF), was prepared by a one-step solvothermal synthesis method and applied for the removal of Pb(II) ions from an aqueous solution via adsorption. The Cu-BTC MOF nanomaterial was characterized via x-ray diffraction, Fourier transform infrared, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX), and Brunauer–Emmett–Teller method. TEM and SEM images of the prepared Cu-BTC MOF presented octahedral crystals. Furthermore, EDX spectroscopy showed that the synthesized porous nanomaterial consisted of Cu, O, and C elements. The prepared Cu-BTC MOF was employed as an adsorbent for the removal of Pb(II) ions from an aqueous solution. Adsorption kinetics and adsorption isotherm modeling were conducted in detail. The maximum adsorption capacity values of the Cu-BTC MOF for Pb(II) ions at temperature conditions of 10, 25, and 40 °C were 890.94, 896.04, and 958.37 mg g−1, respectively. The synthesized Cu-BTC MOF showed high distribution coefficient (Kd) values, and it was very effective in extracting Pb(II) ions. In the Pb adsorption process, the molar ratio of Pb adsorption/Cu desorption was found to be close to 1 indicating that ion exchange with Cu ions in the Cu-BTC MOF material occurs and the cation exchange between Pb ions and Cu ions can be considered as a dominant mechanism of the adsorption.

Sorption of two common antihypertensive drugs onto polystyrene microplastics in water matrices.

Recent studies have shown the widespread occurrence of microplastics in multiple environmental compartments. When discharged into the aquatic environment, microplastics interact with other chemicals acting as vectors of organic and inorganic micropollutants. In the present study, we examined the sorption of two commonly used antihypertensive drugs, valsartan (VAL) and losartan (LOS), onto polystyrene (PS) microplastics and we studied the effects of water matrix, solution's pH, salinity, and microplastics' aging on their sorption. According to the results, the sorption of VAL and LOS onto PS is a slow process that reaches equilibrium after 12 days. The sorption of both target micropollutants was pH-dependent and significantly decreased under alkaline conditions. The removal of VAL was enhanced in the presence of 100 mM of Ca2+ while no statistical significant effects were observed when Na+ was added. The increase of salinity either did not affect or decreased the removal of LOS. Lower sorption of both drugs was observed when aged PS was used despite that the specific surface area for aged PS was 39% higher than pristine. Calculation of the sorption distribution coefficient (Kd) for different water matrices showed that the increase of matrix complexity inhibited target compounds' removal and the sorption rate decreased from bottled water > river water ≈ treated wastewater for the two compounds. For VAL, the Kd values ranged between 795 ± 63 L/kg (bottled water) and 384 ± 88 L/kg (river water), while for LOS between 4453 ± 417 L/kg (bottled water) and 3078 ± 716 L/kg (treated wastewater). Both VAL and LOS sorption onto PS microplastics can be described by hydrophobic and electrostatic interactions. The current results indicate that PS particles could affect the transportation of antihypertensive drugs in the aquatic environment causing potential adverse effects on the environment and public health.

Examining sorption of perfluoroalkyl substances (PFAS) in biochars and other carbon-rich materials.

The use of carbon-rich sorbents to remove and/or immobilize perfluoroalkyl substances (PFAS) in contaminated environmental scenarios is attracting increasing interest. The identification of key sorbent properties responsible for PFAS sorption and the development of models that can predict the distribution coefficients (Kd) for PFAS sorption in these materials are crucial in the screening of candidate materials for environmental remediation. In this study, sorption kinetics, sorption isotherms, and the effects of pH, calcium concentration and dissolved organic carbon (DOC) content on PFAS sorption were evaluated in four representative carbon-rich materials: two biochars with contrasting properties, a compost, and charcoal fines rejected by the metallurgical industry. Subsequently, the sorption of seven PFAS with numbers of fluorinated carbons ranging from 4 to 11 was evaluated in a total of ten carbon-rich materials, including activated carbons, so as to build up a Kd prediction model. The sorption of PFAS increased with greater fluorinated chain length, suggesting that hydrophobic interactions play a major role in sorption and electrostatic interactions a minor one. These results were confirmed by a principal component analysis, which revealed that the CORG/O molar ratio and the specific surface area of the material were the two main sorbent properties affecting PFAS sorption. Furthermore, the DOC content in solution had a negative effect on PFAS sorption. Using this information, a simple Kd prediction model applicable to a wide range of materials and PFAS was developed, using only a few easily-derived physicochemical properties of sorbent (CORG/O molar ratio and SSA) and PFAS (number of CF2), and was externally validated with data gathered from the literature.

Utilization of Waste Amine-Oxime (WAO) Resin to Generate Carbon by Microwave and Its Removal of Pb(II) in Water.

Utilising waste amine-oxime (WAO) resin through microwave semi-carbonization, a carbon adsorbent (CA) was obtained to remove Pb(II). After microwave treatment, the pore size of the skeleton structure, three-dimensional porous network, and lamellar pore structure of WAO was improved. The distribution coefficient (Kd) of Pb(II) onto CA is 620 mL/g, and the maximum adsorption capacity of Pb(II) is 82.67 mg/g after 20 min of WAO microwave treatment. The adsorption kinetics and adsorption isotherms conform to the quasi-second-order kinetic equation and Langmuir adsorption isotherm model, respectively. The surface of MT-WAO is negatively charged and the adsorption mechanism is mainly electrostatic interaction. Pb(II) elution in hydrochloric acid solution is more than 98%, and its recovery is high at 318 K and for 1 h.

Experimental study of the sorption properties of natural zeolite-containing tripolite and their ability to purify aqueous solutions contaminated with Ni and Zn.

Sorption properties of natural zeolite-containing tripolite from the Khotynetsky deposit (Russia, Oryol region) were studied to evaluate their possibility to purify ground waters contaminated by technogenic Ni2+ and Zn2+. According to experimental data the total ion-exchange capacity of the natural tripolite sample equaled to 1.79mg-eq/g. The kinetic experiments showed that equilibrium in the studied rock-solution system took place after 500h of interaction. In the range of the used Ni2+ and Zn2+ concentrations (2-10mg/L) after 21days of interaction with natural tropolite suspension, the sorption of the studied ions can be approximated by a linear isotherm, zinc being sorbed much better than nickel: the average values of distribution coefficients (Kd) obtained for 0.003N CaCl2 aquatic solution equaled to 2.7 × 103ml/g for Ni2+ and 6.7 × 103ml/g for Zn2+. Therefore, natural zeolite-containing tripolite of the Khotinetsky deposit can be used for extraction of technogenic Ni2+ and Zn2+ from natural surface and ground waters contaminated by these ions and can be considered as an effective natural sorbent for solving environmental problems.

Efficient removal of europium radionuclides from natural and seawater using mesoporous carbon-based material

Liquid radioactive waste (LRW) presents the most significant environmental hazard due to its high aggregate activity and rapid distribution in the environment. The paper presents the structure and adsorption characteristics features of a new nanocomposite material namely mesoporous carbon (MPC). Characterization studies depicts that the material obtained consisted of bundles of carbon nanotubes coated with a uniform layer of porous carbon shell. The study on the MPC porous structure disclosed that the resulting material possess a combination of micro and mesopores with a predominant size of 1–6 nm and a specific surface area of 2360 m2 g−1. Adsorption characteristics of the MPC were studied using the sorption of 152Eu radionuclide from natural and seawater. Activated charcoal, coconut charcoal, and a gel-type strong-acidic sulfonic cation exchanger were used as reference materials. The synthesized MPC was found to have the distribution coefficients (Kd) of 152Eu over 3 × 106 cm3 g−1, which was 1–3 orders of magnitude higher than for the reference sorbents. The kinetics study of the 152Eu sorption on the MPC showed that the sorption equilibrium was attained in 5 min, three times less than the activated charcoal. High adsorption of MPC is associated with the colloidal of europium species on the developed surface of the carbon sorbent. Results conclude that the synthesized mesoporous carbon material makes a promising adsorbent for removing europium and other radionuclides, namely, cerium, lanthanum, zirconium, plutonium, and americium, from neutral solutions, where those radionuclides exist in either colloidal or pseudo colloidal form.

Particle-scale understanding sorption of phenanthrene on sediment fractions amended with black carbon and humic acid

Black carbon (BC) and humic acid (HA) have been proposed to dominate the sorption behavior of phenanthrene in sediment. Nevertheless, little is known about the sorption mechanism that related to particle-scale by spiking of BC and HA in sediment particle size fractions. In this study, sorption isotherms for phenanthrene were determined in four particle-size sediment fractions (<2 μm, 2–31 μm, 31–63 μm and >63 μm) that amended with BC and HA, or not. The fitting results by Freundlich model indicated that the sediment particle size fractions amended with BC increased the sorption capacity and affinity for phenanthrene. Sediment coarser size fractions (31–63 μm and >63 μm) by spiking of BC contributed higher to sorption capacity factor (KF) and nonlinearity factor (n) than the finer size fractions (2–31 μm and <2 μm). By contrast, the sediment particle size fractions amended with HA enhanced the sorption distribution coefficient (Kd), but reduced the sorption affinity for phenanthrene. All these phenomena are obviously affected by the distribution of heterogeneous organic matter that related to sediment particle-scale. Results of this work could help us better understand the impact of increased BC and HA content in sediments on the sorption of hydrophobic organic pollutants (HOCs) and predict the fate of HOCs in offshore sediments due to tidal action.

Impact of fracture filling materials on selenium sorption in granite

Selenium (Se) sorption behaviors have been widely studied for evaluating radionuclide reactive transport in fractured granite. However, with disparate mineral compositions, the impact of fracture filling materials (FFMs) is often ignored in characterizing radionuclide sorption and migration. This study aims to investigate the contribution of FFMs to the sorption of radionuclide by conducting flow-through experiments with granite, FFMs, and their mixtures (GFMs) separately. The relative contribution of major minerals in these materials is further identified by column experiments with pure minerals. Taking the granite core samples collected from a potentialrepositorysite as an example, the Se(IV) sorption and migration is mainly influenced by biotite and albite in granite samples, and is controlled by smectite and illite in FFMs. The sorption distribution coefficient (Kd) estimated from the individual mineral experiments decreased in the following order: smectite > illite > biotite > K-feldspar > albite > quartz > calcite. When all minerals were mixed, the sorption ability increased with the mass fraction of FFMs. The component additivity model (CAM) was further tested by predicting Kd in different mineral mixtures. The calculated Kd values were lower than those obtained from experimental fitting results. The largest discrepancy occurred when the mass fractions of the granite and FFMs were equal. This implies that CAM has certain limitations in upscaling Kd directly from individual minerals to mineral mixtures, especially when the mass fraction of FFMs is larger than 0.2. The results from this study provide valuable insights for understanding the sorption behaviors of radionuclides in fractured granite.

Chromatographic Purification of Lithium, Vanadium, and Uranium from Seawater Using Organic Composite Adsorbents Composed of Benzo-18-Crown-6 and Benzo-15-Crown-5 Embedded in Highly Porous Silica Beads

The use of the composite adsorbents composed of benzo-15-crown-5 (abbreviated as BC15) and benzo-18-crown-6 (BC18) for the simultaneous recovery of vanadium (V), uranium (U), and lithium (Li) from seawater has been proposed for industrial applications. The adsorption and desorption behavior of these elements on BC15 and BC18 has been examined in various types of aqueous solutions over a wide temperature range. As a result, it was shown that BC15 and BC18 have sufficient adsorption ability for the simultaneous recovery of V, U, and Li from seawater. Moreover, it was seen that the distribution coefficients (Kd) of V decrease with an increase in [HCl]T (subscript T: total concentration), indicating that the anionic V species such as H2V4O134– are exponentially changed into the cationic V species such as V3+, VO2+, and VO2+ under the condition [HCl]T = 1.0 M, and the complexation reactions between BC15 (or BC18) and the initial V structures are inhibited. Besides, it was reasonably shown that the adsorption mechanism is the path through the electrostatic interaction between the anionic V species such as H2V4O134–, and the −C–O–C– single bond that the electron density is eccentrically located in ether functional groups in crown ether rings in BC15 and BC18 (or the −C–OH single bond that the electron density is eccentrically located in bisphenol A in BC15 and BC18). Then, the chromatography experiment of V, U, and Li on BC15 (or BC18) at 298 K was carried out by flowing seawater, 1.0 × 10–2 M HCl, and 1.0 M HCl in sequence. The first peak of V can be separated from the plateau of Li and the first and second peaks of U in the case of the BC15 system. The recovery ratios of V and U were more than 80%. On the other hand, entirely overlapping chromatograms were obtained in the case of the BC18 system, and accordingly, the recovery ratios of V and U were much lower. In short, the separation efficiency of V with BC15 is more pre-eminent than that with BC18. Judging from these results, the durability of BC15 was finally assessed for industrial applications, that is, the aforementioned chromatography experiment was repeatedly carried out to check whether V, U, and Li were stably and mutually separated from seawater or not. The evidence that the recovery performances of V, U, and Li from seawater do not decrease at all after at least five cycle tests was provided. This indicates that this information will be valuable for the development of a practical chromatographic technology to simultaneously recover V, U, and Li from seawater.

Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass

Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed.

Remarkable ability of Pb(II) capture from water by self-assembled metal-phenolic networks prepared with tannic acid and ferric ions

Plant-derived chelators used for heavy metal removal have attracted increasing attention because of their low cost, strong coordination effect, and environmentally benign features. Herein, natural polyphenol-based adsorbents (i.e., TA-Fe7 and TA-Fe12) were prepared using tannic acid (TA) and ferric ions through simple cross-linking self-assembly reactions with pH 7 and 12, respectively. Adsorption isotherms demonstrated that TA-Fe12 showed better adsorption ability towards Pb(II) than TA-Fe7 with a maximum adsorption capacity of 356.1 mg·g−1 at 298 K. Our evaluation of the adsorption affinity indicated that the distribution coefficient Kd of TA-Fe12 for Pb(II) was apparently higher than that of the other cations, revealing the excellent adsorptive selectivity of TA-Fe12 towards Pb(II). The remarkable adsorption capacity of TA-Fe12 can be attributed to the strong coordination between Pb(II) and phenolic hydroxyl groups, ester groups of TA as well as the specific adsorption of Pb(II) on the newly formed hydrous ferric oxides (HFO), demonstrated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Batch cyclic experiments indicated that TA-Fe12 could be employed for repeated use after 10 adsorption–desorption cycles. Fixed-bed tests indicated that the TA-Fe12 column could produce clean water with bed volumes of 9500 and 7860 ([Pb] < 1 mg·L−1) from synthetic Pb(II)-polluted wastewater and simulated electroplating wastewater, which were significantly higher than those of other commercial adsorbents.

Growth and Spectroscopy of Yb:YMgB5O10 Crystal

A transparent Yb:YMgB5O10 single crystal with dimensions up to 25 × 23 × 25 mm and weight 10.337 g was grown using a high-temperature solution growth on dipped seeds technique with a K2Mo3O10 solvent. The Yb3+ concentration was calculated to be 4.7 at.% (NYb = 3.71 × 1020 atoms/cm3) with a distribution coefficient Kd of 0.59. The grown crystal was characterized by means of PXRD, TGA-DSC and ATR-FTIR techniques. The spectroscopic characteristics of the Yb:YMgB5O10 crystal were demonstrated. Absorption cross-section spectra were produced. The luminescence spectra of the Yb:YMgB5O10 crystal were measured in the spectral range of 950–1100 nm. The luminescence kinetics of the 2F5/2 energy level were investigated and the lifetime was determined.

Pharmaceutical pollution of hospital effluents and municipal wastewaters of Eastern Canada

Quantification of drugs residues in wastewaters of different sources could help better understand contamination pathways, eventually leading to effluent regulation. However, limited data are available for hospital-derived wastewaters. Here, an analytical method based on automated on-line solid-phase extraction liquid chromatography tandem mass spectrometry (on-line SPE – UPLC-MS/MS) was developed for the quantification of multi-class pharmaceuticals in wastewaters. Filtrate phase and suspended solids (SPM) were both considered to evaluate the distribution of targeted analytes. Experimental design optimization involved testing different chromatographic columns, on-line SPE columns, and loading conditions for the filtrate phase, and different organic solvents and cleanup strategies for suspended solids. The selected methods were validated with suitable limits of detection, recovery, accuracy, and precision. A total of 30 hospital effluents and 6 wastewater treatment plants were sampled to evaluate concentrations in real field-collected samples. Certain pharmaceuticals were quantified at high levels such as caffeine at 670,000 ng/L in hospital wastewaters and hydroxyibuprofen at 49,000 ng/L in WWTP influents. SPM samples also had high contaminant concentrations such as ibuprofen at 31,000 ng/g in hospital effluents, fluoxetine at 529 ng/g in WWTP influents or clarithromycin at 295 ng/g in WWTP effluents. Distribution coefficients (Kd) and particle-associated fractions (Φ) indicate that pharmaceuticals tend to have better affinity to suspended solids in hospital wastewater than in municipal wastewaters. The results also bring arguments for at source treatment of these specific effluents before their introduction into urban wastewater systems.

Fabrication of 2D nanosheet sorbents through metastable emulsion droplets and subsequent two-step grafting polymerization for efficient blood lead removal in vitro

Hemoperfusion is a powerful and yet simple method for lead poisoning treatment, but creation of safe and effective sorbents with excellent selectivity remains a real challenge. To address this, we here construct 2D nanosheet sorbents (BM-SH) through metastable emulsion droplets and subsequent two-step grafting polymerization for efficient blood lead removal in vitro. Metastable emulsion droplets endow typical nanosized sheet-like structure (thickness of 30 nm) and relatively round shape. The consecutive two grafting processes using hydroxyethyl methacrylate (HEMA) and L-cysteine monomer (D-SH) provide BM-SH with a high density of accessible binding sites towards lead ions (Pb2+). A high adsorption capacity of 390.5 mg g−1 and quick capture 97.35 % of Pb2+ within initial 10 min are obtained, surpassing most of the reported sorbents for lead removal. Besides, adsorption distribution coefficient (Kd) of BM-SH among four coexisting metal ions achieved 7792 mL g−1, showing outstanding selectivity toward Pb2+. Importantly, a possible adsorption mechanism is recognized as coordination with carboxyl, sulfydryl and imino groups from L-cysteine, and mercapto ligand as the key chelating agent may be the reason for high Pb2+ affinity. And what’s more, BM-SH displays good hemocompatibility and high efficiency of blood lead removal rate (above 86 % in vitro).

Radix Astragali residue-derived porous amino-laced double-network hydrogel for efficient Pb(II) removal: Performance and modeling

Valorizing solid waste for heavy metal adsorption is highly desirable to avoid global natural resources depletion. In this study, we developed a new protocol to valorize Radix Astragali residue (one of the Chinese medicine residues) into a low-cost, chemically robust, and highly permeable (ca. 90%) amino-laced porous double-network hydrogel (NH2-CNFs/PAA) for efficient Pb(II) adsorption. The NH2-CNFs/PAA showed (i) excellent Pb(II) adsorption capacity (i.e., 994.5 mg g−1, ~4.8 mmol g−1), (ii) fast adsorption kinetics (kf = 2.01 ×10−5 m s−1), (iii) broad working pH range (2.0–6.0), and (iv) excellent regeneration capability (~15 cycles). (v) excellent performance in various real water matrices on Pb(II) removal. Moreover, its high selectivity (distribution coefficient Kd ~2.4 ×106 mL g−1) toward Pb(II) was owing to the present of abundant amino groups (-NH2). Furthermore, the fix-bed column test indicated the NH2-CNFs/PAA can effectively remove 114.6 bed volumes (influent concentration ~5000 μg L−1) with an enrichment factor 10.9. The full-scale system modeling (i.e., pore surface diffusion model (PSDM)) has been applied to predict the NH2-CNFs/PAA performance on Pb(II) removal. Overall, we have provided an alternative “win-win” scenario that can resolve the Chinese medicine residues disposal issue by valorizing it into high performance gel-based adsorbents for efficient heavy metal removal.

High-efficiency separation of palladium from nitric acid solution using a silica-polymer-based adsorbent isoPentyl-BTBP/SiO2-P

A silica-polymer-based adsorbent (isoPentyl-BTBP/SiO2-P) was prepared via a vacuum impregnation method for efficient and continuous separation of palladium from complex systems. The results revealed that the distribution coefficient (Kd) value of isoPentyl-BTBP/SiO2-P toward Pd in 3 M HNO3 solution was 5226 mL/g, with a maximum adsorption capacity of 31.7 mg/g. Besides, isoPentyl-BTBP/SiO2-P exhibited a superior adsorption selectivity toward Pd to the other 14 coexisting interfering fission product ions, with the separation factor SFPd/M value over 433 in 0.1–6 M HNO3 solution. Moreover, column experiments results demonstrated that isoPentyl-BTBP/SiO2-P can efficiently separate Pd with approximately 100% recovery, from simulated high level liquid waste (HLLW) solutions with multiple competing ions. Finally, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis results revealed strong interactions between nitrogen-containing functional groups (C-NC) and Pd throughout the adsorption process, wherein the NO3− acting as the counterions to balance the charge. In conclusion, isoPentyl-BTBP/SiO2-P has shown promising applications for effectively separating Pd from multi-component and highly acidic environments.

Microplastics as vectors of radioiodine in the marine environment: A study on sorption and interaction mechanism

Radioiodine is one of the long-lived fission products and also an important radionuclide released during nuclear accidents, which generates interest in its environmental fate. Its sorption has been studied in a wide range of materials, but no equivalent study exists for microplastics, an emerging environmental vector. Weathering and biofilm formation on microplastics can enhance radioiodine sorption. For the first time, we're reporting how radioiodine interacts with different types of polyethylene derived microplastics (pristine, irradiated, and biofilm developed microplastics). This study revealed that exposure to radiation and the marine environment significantly alters the physico-chemical properties of microplastics. In particular, in marine-exposed samples, a signature of biofilm development was detected. Speciation study indicates that iodine exists in the iodide form in the studied marine environment. The study revealed that, iodide ions attach to biofilm-developed microplastics via electrostatic, ion-dipole, pore filling, and van der Waals interactions. Pore filling, ion-dipole, and van der Waals interactions may cause iodide binding to irradiated microplastics, whereas pore-filling and van der Waals interactions cause iodide binding to pristine microplastics. The distribution coefficient (Kd) of iodine on microplastics is positively correlated with biofilm biomass, which signifies the role of biofilm in radioiodine uptake. The Kd indicates microplastics are potential iodide accumulators and could be a possible vector in the marine system.

Ultra‐Rapid Removal of Pb(II) Ions by a Nano‐MoS2 Decorated Graphene Aided by the Unique Combination of Affinity and Electrochemistry

AbstractCost‐effective adsorbent materials with high Pb(II) removal efficiency and selectivity are considered necessary for successfully removing Pb(II) contamination from drinking water because of their high‐level toxicity and the ultra‐low safe level of ≤10 ppb in water. This study demonstrates the synthesis and the ultrafast Pb(II) removal capability of a partially reduced graphene oxide‐nano‐molybdenum disulfide composite (prGO‐MoS2). The prGO‐MoS2 exhibits thin sheets of prGO covered more or less uniformly with nano‐MoS2, and the open architecture gives enhanced accessibility to the S2– and oxygen moieties present in prGO‐MoS2. A single treatment of contaminated water samples with prGO‐MoS2 rapidly decreases the concentration of Pb(II) from 10 000 ppb to 0.8642 ppb within ≤3 min with an efficiency of ≥99.99% (4 log reduction value) at a V/m ratio of 2000 mL mg−1. Among the reported materials for Pb(II) removal, prGO‐MoS2 exhibits the fastest removal speed (≤3 min) and the second‐highest adsorption capacity (762 mg g−1), and the highest distribution coefficient (Kd = 6.0 × 108 mL g−1). Here, the high removal performance of Pb(II) by prGO‐MoS2 is delineated based on affinity between Pb(II) and S2− and oxygen moieties, electrochemistry, and the unique structural characteristics.