Sorption behavior of U(VI), ~(234)U(VI) and ~(238)U(VI) onto fracture-filling clays in Beishan granite, Gansu: Application to selecting the site of high-level radwaste repository in China

Knowing the transport of uranium and radionu-clides through the environment is important for as-sessing the risk posed by long-term disposal of rad-waste. Granitic rocks have been selected as a host-rock type for the first high-level radwaste repository in China. According to the Chinese High-level Rad-waste Management Program, high-level radwaste (HLW) will be buried at 800―1000 m depth in a granitic pluton in Northwest China and, specifically, in the A granitic complex of Beishan area,…     

Removal of Congo Red from Aqueous Solution by Sorption on Organified Rectorite

Batch sorption technique was carried out for the removal of anionic dye Congo red (CR) from aqueous solution using raw rectorite (R‐REC) and organified rectorite (CTA⁺‐REC) modified by cetyltrimethylammonium bromide (CTAB) as adsorbents. The effects of organification degree of CTA⁺‐REC as well as the process parameters including the pH of dye solution, sorption time, and initial dye concentration on adsorption capacity for CR were investigated and the sorption kinetics was also evaluated. The results showed that the sorption behaviors of R‐REC and CTA⁺‐REC for CR followed pseudo‐second‐order kinetic model and the sorption equilibrium data perfectly obeyed the Langmuir isotherm. The thermodynamic parameters including entropy of sorption (ΔS⁰), enthalpy of sorption (ΔH⁰), and Gibbs free energy of sorption (ΔG⁰) were obtained and analyzed. Fourier transform infrared study revealed that a chemisorption process occurred between CR and CTA⁺‐REC. REC modified by cationic surfactants showed the higher adsorption capacities for CR compared to R‐REC and in theory would be used as an efficient and promising adsorbent for the removal of anionic dyes in wastewater treatment.     

Influence of Carbon and Microbial Community Priming on the Attenuation of Uranium in a Contaminated Floodplain Aquifer

The capacity for subsurface sediments to sequester radionuclide contaminants, such as uranium (U), and retain them after bioremediation efforts are completed is critical to the long‐term stewardship of re‐mediated sites. In U bioremediation strategies, carbon amendment stimulates bioreduction of U(VI) to U(IV), immobilizing it within the sediments. Sediments enriched in natural organic matter are naturally capable of sequestering significant U, but may serve as sources to the aquifer, contributing to plume persistence. Two types of organic‐rich sediments were compared to better understand U release mechanisms. Sediments that were artificially primed for U removal were retrieved from an area previously biostimulated while detrital‐rich sediments were collected from a location never subject to amendment. Batch incubations demonstrated that primed sediments rapidly removed uranium from the groundwater, whereas naturally reduced sediments released a sizeable portion of U before U(VI)‐reduction commenced. Column experiments confirmed that U release persisted for 65 pore volumes in naturally reduced sediments, demonstrating their sink‐source behavior. Acetate addition to primed sediments shifted the microbial community from sulfate‐reducing bacteria within Desulfobacteraceae to the iron‐reducing Geobacteraceae and Firmicutes, associated with efficient U(VI) removal and retention, respectively. In contrast, Geobacteraceae communities in naturally reduced sediments were replaced by sequences with similarity to Pseudomonas spp. during U release, while U(VI) removal only occurred with enrichment of Firmicutes. These investigations stress the importance of characterizing zones with heterogeneous carbon pools at U‐contaminated sites prior to the determination of a remedial strategy to identify areas, which may contribute to long‐term sourcing of the contaminants.     

Sorption behavior of nonylphenol on marine sediments: effect of temperature, medium, sediment organic carbon and surfactant

The sorption behavior of nonylphenol (NP, a toxic endocrine disruptor) on marine sediments was studied in detail through a series of kinetic and thermodynamic sorption experiments. The results showed that the sorption reaction of NP on marine sediments reached equilibrium in 1.5 h and that it accorded well with the non-linear Ho-McKay pseudo-second-order model. The sorption isotherms of NP on H₂O-treated sediments could be well described by the Linear isotherm model, while the sorption isotherm on H₂O₂-treated sediments could be well fitted with the Freundlich isotherm model. A positive correlation was found between the distribution coefficient (K_d) and the sediment organic carbon contents. The medium salinity showed a positive relation with the K_d and a negative relation with the dissolved organic carbon (DOC). Hexadecyl trimethyl ammonium bromide (CTAB) enhanced the sorption amount of NP the most, while sodium dodecylbenzenesulfonate (SDBS) enhanced it the least. The sorption reaction of NP on marine sediments was a spontaneous, physical, exothermic and entropy-decreasing process.     

Treatment of a Trifluraline Effluent by Means of Oxidation‐Coagulation with Fe(VI) and Combined Fenton Processes

The amination water (AW) effluent stream from the industrial production of the trifluraline herbicide was submitted to an oxidation‐coagulation treatment with potassium ferrate, combined with advanced oxidation processes. The experimental results obtained by analysis of variance (ANOVA) for the oxidation‐coagulation‐Fenton process, evaluating the variables pH (A), Fe(VI) concentration (B), and H₂O₂ concentration (C), demonstrated that the regression equation resulting from the Response Surface Methodology (RSM) experimental design, for the quadratic model, was η_Abs (%) = 36.9– 21.58A + 8.37A² + 1.36B + 0.92B² + 1.08C + 1.52C² + 1.27AB – 1.34AC + 1.33BC. The maximum absorptiometric color reduction occurred at pH 3, with corresponding maximum amounts of iron and hydrogen peroxide. The absorptiometric color and COD reduction were 96% and 57%, respectively. For the oxidation‐coagulation‐photo‐Fenton process, the analyzed variables were pH (A), Fe(VI) concentration (B), H₂O₂ concentration (C), and temperature (D). The regression equation resulting from the quadratic model was η_Abs (%) = 38.3 – 20.2A + 8.12A² – 0.27B + 3.73B² + 0.3C + 3.6C² + 1.67D + 3.1D² + 1.72AB + 0.51AC – 1.82AD + 0.74BC – 1.11BD + 0.03CD. The ANOVA response showed that the highest absorptiometric color reduction occurred at pH 3, with respective maximum amounts of iron and hydrogen peroxide at 60°C. The maximum efficiencies achieved by the proposed treatment process for the trifluraline effluent stream were 95% and 85%, for absorptiometric color and COD reduction, respectively.     

Development of U–Pb dating of uraninite using a secondary ion mass spectrometer: Selection of reference material and establishment of calibration method

A method for U–Pb isotopic dating using secondary ion mass spectrometer (SIMS) was developed for uraninite. Correlation between ²⁵¹(UO)⁺/²³⁵U⁺ and ²⁰⁶Pb⁺/²³⁵U⁺ obtained by a sensitive high‐resolution ion microprobe (SHRIMP) was adopted for a calibration from secondary ion ratios (Pb⁺/U⁺) to the atomic abundance ratios (Pb/U). In this study, a uraninite sample (²⁰⁶Pb/²³⁸U = 0.1647) collected from Faraday mine, Bancroft, Canada, is used as a reference material for the U–Pb calibration. The established method was applied to three uraninite samples collected from the Chardon, Ecarpière, and Mistamisk mines. The calibrated ²⁰⁶Pb^*/²³⁸U ratios of the three uraninites show correlation with Pb/U elemental ratios obtained using an electron probe microanalyzer (EPMA) (correlation coefficients: 0.98, 0.99, and 0.97, respectively), which indicates the reliability of the SHRIMP calibration method used in this study. The analysis of Ecarpière uraninite provides concordant U–Pb data, and a weighted average of the ²⁰⁶Pb^*/²³⁸U age is 287 Ma ±8 Ma (95 % conf.) which is consistent with the previous chronological results by SIMS. Mistamisk uraninite provides discordant U–Pb data with the upper and lower intercept ages of 1 729 and 421 Ma, which correspond to uraninite formation in association with the Hudsonian orogeny and the remobilization of uranium as pitchblende, respectively. The U–Pb age of Chardon uraninite (315 Ma) is consistent with the igneous activity of Mortagne granite, but is older than the previously reported age (264 Ma). Marcasite in the Chardon uraninite altered to goethite under the oxidizing condition, which indicates that U–Pb system in the uraninite crystallized at 315 Ma was disturbed under the oxidizing condition. The established calibration method using Faraday uraninite is useful for U–Pb isotopic dating on the scale of a few micrometers to tens of micrometers, which make it possible to obtain the accurate age of uraninite.     

Synthesis and Characterization of Poly(2‐hydroxyethylmethacrylate‐hydroxyapatite) a Novel Composite for the Removal of Lead(II) from Aqueous Solutions

In the present study, a novel adsorbent, poly (2‐hydroxyethylmethacrylate‐hydroxyapatite) [P(HEMA‐Hap)], was prepared and characterized. The synthesis was achieved by means of free‐radical polymerization and a number of structural characterization methods, including FT‐IR, XRD, TGA, SEM, BET‐porosity, and swelling tests. Pb²⁺ adsorption was performed using a series of pH, time, and temperature ranges. The reusability of the composite was also tested. The results obtained indicated that the novel adsorbent is able to bind Pb²⁺ ions with strong chemical affinity. The adsorption results were fitted to the classic Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) sorption models. Thermodynamic parameters obtained demonstrated that the sorption process was spontaneous (ΔG < 0), endothermic (ΔH > 0), as expected. The process was also consistent with the pseudo‐second‐order model, and chemical adsorption was determined to be the rate‐controlling step. It was also shown that the composite could be used for five consecutive adsorption processes.     

Bi‐Solute Sorption of Estrogens at Low Concentration: Two‐ and Three‐Parametric Analysis

Competitive sorption of estriol (E3) and 17α‐ethinylestradiol (EE2) was studied on activated charcoal. Better sorption of E3 (88.9%) and EE2 (69.5%) was observed with single‐solute sorption system than with bi‐solute sorption system. Single‐solute sorption kinetics of E3 and EE2 were evaluated with two (Langmuir and Freundlich) and three (dual mode and Song) parameter models. Freundlich model (R², 0.9915 (E3); 0.9875 (EE2)) showed good prediction compared to other models for single‐solute sorption. Adsorption capacity documented reduced efficacy (86.4% (E3); 65.9% (EE2)) due to induced competitive behavior between the estrogens in aqueous phase. Bi‐solute adsorption kinetics of E3 and EE2 were described by IAST with two and three parameter models. Among these models, IAST‐Freundlich model (R², 0.9765 (E3); 0.9985 (EE2)) was best in predicting bi‐solute sorption of E3 and EE2 by activated charcoal. All these models showed favorable representation of both single‐ and bi‐solute sorption behaviors.     

Removal of Chromium from Synthetic Effluent using Nymphaea rubra

In the present work, biosorption of Cr(VI) by Nymphaea rubra was investigated in batch studies. Batch experiments were conducted to study the effect of initial sorbent dosage, solution pH and initial Cr(VI) concentration. The results showed that the equilibrium uptake capacity was increased with decrease in biomass dosage. The Cr(VI) removal was influenced by the initial chromium compound concentration. Langmuir and Freundlich adsorption isotherm models were used to represent the equilibrium data. The Freundlich isotherm model was fitted very well with the equilibrium data when compared to Langmuir isotherm model. The sorption results were analyzed for pseudo‐first order and pseudo‐second order kinetic model. It was observed that the kinetic data fitted very well with the pseudo‐second order rate equation when compared to the pseudo‐first order rate equation. Fourier transform infrared spectrum showed the presence of different functional groups in the biomass. The surface morphology of the sorbent was exemplified by SEM analysis. Aquatic weeds seem to be a promising biosorbent for the removal of chromium ions from water environment. This paper reports the research findings of a laboratory‐based study on the removal of Cr(VI) from the synthetic solution using the dried stem of N. rubra as a biosorbent.     

Surface complexation at hydrous fluorapatite

The adsorption of H⁺, OH^– and ARS (Alizarin Red S) onto hydrous fluorapatite surfaces and Ca²⁺—ARS complexation in solution were studied by means of combined potentiometric and spectrophotometric titrations, as well as zeta potential and FT-IR measurements. Corresponding equilibrium constants of surface and solution reactions are determined. The application in flotation processes is discussed.     

Cloud Point Extraction for the Preconcentration of Silver and Palladium in Real Samples and Determination by Atomic Absorption Spectrometry

A cloud point extraction procedure is presented for the preconcentration and simultaneous determination of Ag⁺ and Pd²⁺ in various samples. After complexation with 2‐((2‐((1H‐benzo[d]imidazole‐2‐yl)methoxy)phenoxy)methyl)‐1H‐benzo[d]imidazol (BIMPI), which was used as a new chelating agent, analyte ions were quantitatively extracted to a phase rich in Triton X‐114 following centrifugation, and determination was carried out by flame atomic absorption spectrometry (FAAS). Under the optimum experimental conditions (i. e., pH = 7.0, 15.0·10^–5 mol/L BIMPI and 0.036% (w/v) Triton X‐114), calibration graphs were linear in the range of 28.0–430.0 μg/L and 57.0–720.0 μg/L with detection limits of 10.0 and 25.0 μg/L for Ag⁺ and Pd²⁺, respectively. The enrichment factors were 35.0 and 28.0 for Ag⁺ and Pd²⁺, respectively. The method has been successfully applied to evaluate these metals in some real samples, including waste water, soil and hydrogenation catalyst samples.     

A Dynamic Model to Simulate Arsenic,Lead, and Mercury Contamination in the Terrestrial Environment During Extreme Floods of Rivers

Beside damages of infrastructure in industrial regions, extreme floods can cause contamination with particle‐bound pollutants, e. g., due to erosion of soils and sediments. In order to predict contamination with inorganic pollutants, the transport and fate of arsenic, lead, and mercury during a fictive flood event of River Vereinigte Mulde in the region of Bitterfeld (Germany) with 200 years recurrence time was modeled. The finite element model system Telemac2D, which is subdivided into a hydrodynamic (Telemac‐2D), a transport (Subief‐2D), and a water quality module (wq2subief) was applied. The transport and water quality model models were calibrated using results of sediment trap exposures in the floodplain of River Vereinigte Mulde. Model results exhibited that the spatial patterns of particle‐associated arsenic and lead concentrations significantly changed. Extended, mostly agriculturally used areas showed arsenic and lead concentrations between 150 and 200 mg kg^–1 and 250 and 300 mg kg^–1, respectively, while urban areas were to a great extent spared from high contamination with arsenic and lead. Concentrations of particle‐associated mercury showed a pattern distinct from those of arsenic and lead. Outside of small patches with concentrations up to 63 mg kg^–1, concentrations of particle‐associated mercury remained close to zero. Differences in the spatial patterns of the three pollutants regarded mainly arise from significantly different initial and boundary conditions. Sensitivity analyses of initial and boundary conditions revealed a high sensitivity of particle‐bound pollutant concentrations, whereas the sensitivities of concentrations of suspended sediments and soluble pollutants were mediocre to negligible.     

Cr(VI) Immobilization Process in a Cr‐Spiked Soil by Zerovalent Iron Nanoparticles: Optimization Using Response Surface Methodology

The response surface methodology involving the five‐level central composite design (CCD) was employed to model and optimize the Cr(VI) immobilization process in a Cr‐spiked soil using starch‐stabilized zerovalent iron nanoparticles (ZVIn). ZVIn were synthesized via a borohydride reduction method and characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). All Cr(VI) immobilization experiments were conducted in a batch system. The variables for the CCD optimization were the ZVIn dosage (% w/w), reaction time (min), and initial Cr(VI) concentration in soil (mg/kg). The predicted response values by the second‐order polynomial model were found to be in good agreement with experimental values (R² = 0.968 and adj‐R² = 0.940). The optimization result showed that the Cr(VI) immobilization efficiency presented the maximal result (90.63%) at the following optimal conditions: ZVIn dosage of 1.5% w/w, reaction time of 60 min, and an initial Cr(VI) concentration of 400 mg/kg.     

Development of Polymeric and Polymer‐Based Hybrid Adsorbents for Chromium Removal from Aqueous Solution

Ferric oxide‐loaded hybrid sorbents are environmentally benign and exhibit sorption behaviors for chromium removal from waters. In the current study, glycidyl methacrylate‐based polymer (GMD) and nanosized ferric oxide loaded glycidyl methacrylate‐based polymer (GMDFe) were prepared and assayed to examine the effect of ferric oxide loading on chromium sorption from aqueous solution for the first time from the equilibrium and kinetic points of view. The experimental equilibrium data, suitably fitted by the Langmuir and Freundlich isotherms, have shown that ferric oxide loaded hybrid sorbent exhibits higher adsorption capacity than glycidyl methacrylate‐based polymer (GMD). The Langmuir isotherm model was found to be the most suitable one for the Cr(VI) adsorption. The maximum adsorption capacities of GMD and GMDFe sorbents were determined at pH 4 as 109.54 and 157.52 mg/g, respectively. A series of column experiments was carried out to determine the breakthrough curves. The column was regenerated by eluting Cr(VI) using NaOH (10% w/v) solution after adsorption studies.     

Dynamic,Mechanistic, and Thermodynamic Modeling of Zn(II) Ion Biosorption onto Zinc Sequestering Bacterium VMSDCM

The surface of the bacterial cells before the biosorption of Zn(II) ion has been found rough, heterogeneous, and non‐crystalline together with tremendous protrusions and negatively charged functional groups. The bacterium was characterized as rod shaped with Gram‐negative type of cell wall structure. In reaction dynamics, pseudo‐second‐order kinetics with higher linear correlation coefficient (R²) ranging between 0.97 and 0.99, lower sum of square errors (SSE) (0.035–0.081) and chi (χ²) (0.0013–0.009) provided a better explanation of sorption of Zn(II) ion on bacterium surface as compared to pseudo‐first‐order model. The removal of Zn(II) was governed by both film and intra‐particle diffusion at onset and later stage of sorption of metal ion on the surface of bacterial cells. The R² (0.92–0.94) for intra‐particle diffusion model was quite higher with lower values of SSE (9.56–16.33) and chi (χ²) (11.26–19.65) against the Bangham's model. The positive value of ΔH (16.628 × 10^?6 kJ/mol) and ΔS (5320.90 kJ/mol/K) showed that the biosorption of Zn(II) ion across liquid phase on bacterial surface was endothermic with increased randomness at solid–liquid interface. The negative values of ΔG demarcated the whole process as spontaneous in nature. In the present work, the distribution coefficient was found to be > 0.5 at various temperature ranges. At the attainment of equilibrium, the residual concentration of Zn(II) ion in liquid phase was around 0.6 mg/L, which was much below the limit described by United States Environmental Protection Agency (USEPA), i.e. 5 mg/L.     

Removal of Heavy Metals from Synthetic Mixture as well as Pharmaceutical Sample Via Cation Exchange Resin Modified with Rhodamine B: Its Thermodynamic and Kinetic Studies

A new sorbent was prepared by loading rhodamine B on Amberlite IR‐120. Various physico‐chemical parameters such as effects of adsorbate concentration, contact time, pH, and temperature on the sorption of the dye have been studied. Thermodynamic parameters (ΔH° and ΔS°) were also evaluated for the sorption of dye. Kinetic studies revealed that the sorption of the dye was best fit for pseudo‐second‐order kinetic. The metal ion uptake in different solvent systems has been explored through column studies. On the basis of distribution coefficient (K_d), some heavy metal ions of analytical interest from binary mixtures have been separated. The limit of detection (LOD) for the Ni²⁺ and Fe³⁺ metal ions was 0.81 and 0.60 µg L^?1, and the limit of quantification (LOQ) was found to be 2.72 and 2.0 µg L^?1. This sorbent has also been successfully applied in the analysis of multivitamin formulation. The applicability of the modified resin in the separation of heavy metals constituting real and synthetic samples has been explored.     

Pulsating of the generalized ion and neutral polar winds

A three-dimensional, time-dependent model of the ion and neutral polar winds was used to study their dynamic evolution during the May 4, 1998 magnetic storm. The simulation tracked the dynamics of five species (O⁺, H⁺, H_s, O_s, and electrons) and covered a 9-h period. During the storm, D_st decreased to −210 nT, Ap reached 300, and K_p was elevated. The IMF B_z component was southward at the start of the storm and for several hours thereafter and then turned northward. However, the magnetospheric energy input to the ionosphere exhibited a 50-min oscillation, with the plasma convection and particle precipitation patterns expanding and contracting in a periodic manner. As a consequence, the ion and neutral polar winds pulsated with an approximate 50-min period. The H⁺ and O⁺ ions displayed cyclic upflows and downflows in the topside ionosphere as well as a highly structured spatial distribution that varied with time. The vertical flux of the neutral H_s atoms was upward at the top of the ionosphere, but the magnitude varied in a cyclic manner in response to the oscillating stormtime energy input. The vertical flux of neutral O_s atoms was downward at the top of the ionosphere and varied significantly with the stormtime energy input. For H⁺, O⁺, and H_s, the maximum total (integrated) vertical flux during the storm was upward at the top of the ionosphere, with values of 8–9×10²⁵ particles/s for H⁺, 2–4×10²⁶ particles/s for O⁺, and 2–3×10²⁷ particles/s for H_s. The corresponding total vertical O_s flux was predominately downward, with only localized areas with positive fluxes.     

Sorption behavior of phenanthrene in Yangtze estuarine sediments: sequential separation

In the present study, phenanthrene was chosen as the probe compound for determining the sorption of PAHs in sediments from Yangtze estuary and nearby coastal area, China. Sorption isotherms were fitted well by the Freundlich and dual models, respectively. Selected sediments were further sequentially separated to remove the carbonate and organic carbon (OC). Calculated OC sorption capacity values based on both H₂O₂ oxidization and 375 °C combustion methods were similar and comparable to the K_oc values estimated by the empirical linear sorption equations. Both sorption models and sorption data using sequentially separated samples achieve the similar conclusions: (1) the partition behavior dominated by OC in sediments with f_oc > 0.01; (2) for sediments with 0.001 < f_oc < 0.01, OC dominated sorption at relatively high aqueous concentration; whereas mineral phase adsorption dominated sorption at lower concentration especially when C_w/S_w was in the range of 0.0001-0.001 in natural aqueous system.     

Removal and Recovery of Molybdenum from Aqueous Solutions by Adsorption onto Surfactant‐Modified Coir Pith,a Lignocellulosic Polymer

Coconut coir pith, a lignocellulosic polymer, is an unwanted by‐product of the coir fiber industry. The pith was used as a biosorbent for the removal of Molybdenum(VI) after modification with a cationic surfactant, hexadecyltrimethylammonium bromide. The optimum pH for maximum adsorption of Mo(VI) was found to be 3.0. Langmuir, Freundlich and Dubinin Radushkevich isotherms were used to model the adsorption equilibrium data and the system was seen to follow all three isotherms. The Langmuir adsorption capacity of the biosorbent was found to be 57.5 mg g^–1. Kinetic studies showed that the adsorption generally obeyed a second‐order kinetic model. Desorption studies showed that the recovery of Mo(VI) from the spent adsorbent was feasible. The effect of foreign anions on the adsorption of Mo(VI) was also examined.     

Dynamics of microelement concentrations in bottom sediments of the marginal filter (Razdol’naya R.–Amur Bay)—Result of biogeochemical processes

Atomic-emission spectroscopy was used to determine the concentrations of Be, Ga, Nb, Ta, Y, Zr, Hf, Sc, Mo, U, and Th in subcolloidal, medium-pelite, coarse-pelite, fine-aleurite, and coarse-aleurite fractions of bottom sediments of Razdol’naya R. marginal filter. The concentrations of examined elements are maximal for the subcolloidal sediment fraction. The average concentration (n = 10) of elements in the soil and fluvial sediments (upstream of the mixing zone) were calculated and taken as background concentrations. The highest concentrations of Y, Be, U was shown to correspond to sediments in the zone of fresh and sea water mixing, which is accompanied by flocculation and sorption on Fe and Mn hydroxides and clay minerals (hydromica in fluvial sediments, and smectite in marine sediments).