Spectrophotometric determination of trace amounts of uranium(VI) in water samples after mixed micelle-mediated extraction

A cloud point extraction process using mixed micelle of the cationic surfactant CTAB and non-ionic surfactant TritonX-114 to extract uranium(VI) from aqueous solutions was investigated. The method is based on the color reaction of uranium with pyrocatechol violet in the presence of potassium iodide in hexamethylenetetramine buffer media and mixed micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g. surfactant concentration, reagent concentration, effect of time) were studied and the analytical characteristics of the method (e.g. limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.20-10.00 ng mL⁻¹ of uranium(VI) ion and the detection limit of the method is 0.06 ng mL⁻¹. The interference effect of some anions and cations was also tested. The method was applied to the determination of uranium(VI) in tap water, waste-water and well water samples.     

Cellulosic-based hydrogel from biomass material for removal of metals from waste water

Abstract

Cellulose and carboxymethyl cellulose (CMC), prepared from rice straw, were used for hydrogel preparation, separately or in a mixture of both of them in a ratios of 1:1, 1:4, 1:9, 2:3 and 3:7 (by weight).They were polymerized with partially neutralized acrylic acid (AA) in the presence of potassium persulphate, as initiator, and vinylsulphone (VS), as cross-linker. Moreover, glutaraldehyde, N,N-methylene bis acrylamide (MBA) and Epichlorohydrin (ECH) were used as cross-linker for the mixture of 1:1 of Cellulose: CMC. The mechanism of the polymerization was studied and the resulted hydrogels were characterized for their appearances, yields percentage, and water absorbencies. The Fourier transform infrared spectroscopy (FT-IR) and XRD analysis were also investigated for the hydrogel samples. Since the textile industry produces large volumes of wastewaters which contain hazardous compounds such as dyes, heavy metals like Cu(II), and surfactants, so we aimed in this research to use the hydrogel samples for Cu²⁺ absorption that can be presented in the wastewater. The FT-IR spectrum, before and after absorption, indicated that the prepared hydrogels were able to absorb the Cu²⁺. The Cu²⁺ ions can be recovered and dried to be reused again as well as the hydrogel samples can be available again for reuse.     

Aminothiozolyl maleamic acid based multi chelating hydrogels for the separation of uranium (VI) ions from aqueous environment

Multi chelating hydrogels (MCHs) were synthesized using a simple radical polymerization method from acrylamide, hydroxyethyl acrylate, and N‐(2‐aminothiozolyl)maleamic acid (AMA) monomers, methylenebisacrylamide (MBA) a cross‐linker, and azobisisobutyronitrile (AIBN) an initiator. The resulting MCHs were characterized with Fourier transform infrared spectroscopy and scanning electron microscopy to confirm the formation and morphological properties. The MCHs were highly swellable in aqueous solutions as well as different pH conditions. MCHs were applied to evaluate uptake behavior of Uranium (VI) ion from aqueous solutions. Batch adsorption studies were performed by varying experimental conditions like contact time, pH, and initial metal ion concentration. The kinetics data was best suited with the second‐order equation model. The equilibrium adsorption data was correlated with Langmuir and Freundlich isotherm models. This study suggests that maximum Uranium (VI) ion uptake has been found to be 288 mg.g^?1 and regenerated for 5 cycles without any significant change. Copyright © 2016 John Wiley & Sons, Ltd.     

Chemically selective membrane optode for Cr(VI) determination in aqueous samples

A methodology for simultaneous preconcentration and determination of Cr(VI) from aqueous samples was developed using a membrane optode formed by physical inclusion of a Cr(VI) selective chromophore 1,5-diphenylcarbazide (DPC) into a plasticized cellulose triacetate matrix. The inclusion of an anion exchanger (Aliquat-336) was found to be effective for immobilization of both DPC and Cr(VI)-DPC complex in the optode matrix itself. The proportionality in intensity of the magenta color on the optodes loaded with varying amounts of Cr(VI) suggests its potential applications for screening of Cr(VI) in aqueous samples by visual colorimetry. On loading high amounts of Cr(VI) in the membrane optode, its color changes from magenta to yellow, which indicates the possibility of using it as a threshold detector for Cr(VI). The membrane optode was optimized in terms of obtaining maximum preconcentration efficiency for Cr(VI) and subsequent stable optical response proportional to the amount of Cr(VI) in the membrane optode sample. The membrane optodes were tested for Cr(VI) determination in tap water and seawater samples. Using this optode, Cr(VI) even at levels of 13.6 ppb could be quantitatively detected. The optodes developed in the present work were found to be stable, cost effective, easy to prepare and efficient for direct preconcentration and determination of Cr(VI) in a variety of aqueous samples using spectrophotometry. However, this membrane optode is for one time use only as the reaction of Cr(VI) with DPC is irreversible.     

Adsorption of U (VI) ions from aqueous solution using silicon dioxide nanopowder

The adsorption kinetics for removal of uranium (V1) from aqueous solution using silicon dioxide nanopowder (nano-SiO₂) was investigated in batch and continuous techniques. Pseudo-first order and pseudo-second order were used to analyze the kinetics of batch experiments. In continuous technique the important parameters (initial concentration, flow rate and bed height) on the breakthrough curves were studied and the adsorption kinetics was analyzed using Thomas and Yoon and Nelson kinetic models. The comparison between the kinetic models was evaluated by the correlation coefficients (r²). The results indicated that the batch experiments fitted well with pseudo second-order kinetic model. The comparison of the experimental breakthrough curve to the breakthrough profile obtained from Thomas and Yoon and Nelson methods showed a satisfactory fit for silicon dioxide nanopowder.     

Application of specific ion interaction theory and parabolic models for the molybdenum(VI) and tungsten(VI) complexes with NTA and IDA at different ionic strengths

The interaction of nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA) with tungsten(VI) (pH 7.5) and molybdenum(VI) (pH 6.00) has been studied in aqueous solutions at 25 ℃, and different ionic strengths (0.1 相似文献   

Evaluation of ammonia buffer containing EDTA as an extractant for Cr(VI) from solid samples

A novel procedure for the extraction of soluble, sparingly soluble and insoluble Cr(VI) from solid samples was presented. EDTA was added to an ammonia buffer commonly used only for the extraction of soluble and sparingly soluble Cr(VI). In the course of extraction in an ultrasonic bath cations which form insoluble chromates are complexed with EDTA while Cr(VI) is transferred to the solution. A concentration of EDTA equal to 0.01 mol L⁻¹ was chosen. The presence of EDTA in the extraction solution enables not only dissolution of insoluble Cr(VI) but also, as reported previously in literature, minimises oxidation of Cr(III) to Cr(VI). The extraction procedure was optimised and applied to Cr(VI) determination in the paint chips real sample. The results obtained were compared with the results obtained using two other extraction procedures. The results show that the novel extraction procedure can be used for the extraction of soluble, sparingly soluble and insoluble Cr(VI) from real solid samples.     

Removal of Cr(VI) from water by cork waste

The biosorption by cork powder is considered as a promising method for heavy metal removal from industrial waste waters such as chromium tanning factories. The aim of this study is to evaluate the efficiency extent of this method using cork powder as a biosorbent for Cr(VI). The Fourier Transform Infrared spectroscopy (FTIR) analysis permits to distinguish the type of functional groups likely to participate in metal binding. A linear form of BET isotherms for all the three used temperatures (i.e., 25, 35 and 45 °C) and a pseudo-second-order equation of adsorption kinetics are obtained. Other experimental results highlight the meaningful influence of parameters such as contact time, pH, concentration of Cr(VI) and the adsorbent particle size on Cr(VI) adsorption. 97% of Cr(VI) has been removed under definite conditions particularly a particle size of diameter d < 0.08 mm and pH of 2–3 values.     

Crystal Structure and Characterisation of Mercury(II) Dichromate(VI)

Summary. Dark-red single crystals of HgCr₂O₇ were grown by reacting HgO and CrO₃ in excess at 200°C for four days. The crystal structure (space group P3₂, Z = 3, a = 7.2389(10), c = 9.461(2) ?, 1363 structure factors, 57 parameters, R[F ²>2σ(F ²)] = 0.0369, wR(F ² all) = 0.0693) was determined from a crystal twinned by merohedry according to (110). It consists of nearly linear HgO₂ units ( (Hg–O) = 2.02 ?) and dichromate units that are linked into infinite chains ‘O₃Cr–O–CrO₃–Hg–O₃Cr–O–CrO₃’ running parallel to the c-axis. Six additional Hg–O contacts between 2.73 and 2.96 ? stabilise the structural arrangement. The dichromate anion exhibits a staggered conformation with a bent Cr–O–Cr bridging angle of 140.7(6)°. Upon heating above 300°C, HgCr₂O₇ decomposes in a two-step mechanism to Cr₂O₃. The title compound was additionally characterised by vibrational spectroscopy.     

Uranyl(VI) and lanthanum(III) thio-diglycolamides complexes: Synthesis and structural studies involving nitrate complexation

New tri-functional ligands of the type R₂NCOCH₂SCH₂CONR₂ (where R = iso-propyl, n-butyl or iso-butyl) were prepared and characterized. The coordination chemistry of these ligands with uranyl and lanthanum(III) nitrates was studied by using the IR, ¹HNMR and elemental analysis methods. Structures for the compounds [UO₂(NO₃)₂(ⁱPr₂NCOCH₂SCH₂CONⁱPr₂)] [UO₂(NO₃)₂(ⁱBu₂NCOCH₂SCH₂CONⁱBu₂)], [La(NO₃)₃(ⁱPr₂NCOCH₂SCH₂CONⁱPr₂)₂] and [La(NO₃)₃(ⁱBu₂NCOCH₂SCH₂CONⁱBu₂)₂] were determined by single crystal X-ray diffraction. These structures show that the ligand acts as a bidentate chelating ligand and bonds through both the carbamoyl groups to the uranyl and lanthanum(III) nitrate groups. Solvent extraction studies show that the ligand can extract the uranyl ion from the nitric acid medium but does not show any ability to extract the americium (III) ion.     

A new experimental approach for liquid-liquid extractive spectrophotometric determination of chromium(VI) in tannery wastewater and alloy samples

In this research work, a new approach is developed for the extractive determination of chromium. The principle of this approach is based on the complexation reaction between 4-(4?-chlorobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (CBIMMT) in dichloromethane as a complexing reagent and chromium(III) in presence of potassium iodide to form a yellow coloured complex at room temperature. The 1:2:2 [Cr(III)-CBIMMT-iodide] ternary complex was quantitatively extracted in dichloromethane from 2.5 mol L^?1 of hydrochloric acid medium which showed maximum absorption intensity at λ_max 411 nm and was stable for more than 72 h. The values of molar absorption coefficient and Sandell’s sensitivity of the complex were found to be 0.7019 × 10⁴ L mol^?1 cm^?1 and 0.00748 µg cm^?2, respectively. The system adheres to Beer’s law from 1.5 to 6.0 µg mL^?1; however, Ringbom’s plot suggests optimal concentration range was 1.8–5.8 µg mL^?1. The limit of detection and limit of quantification of the approach is 0.26 and 0.79 µg mL^?1. This approach was successfully used for the determination of chromium from wastewater effluents from the tannery industries (Kolhapur, MS, India), alloy samples and for separation of it from synthetic mixtures. The present experimental approach is apparently much simpler than the conventional method comprising multistep processes.     

Spectrophotometric Determination of U(VI) with Rifampicin in Soil Samples

A validated spectrophotometric method has been developed for the determination of uranyl ion in soil samples. The method is based on the complexation reaction between uranyl ion and rifampicin in methanol‐water medium at room temperature. The method is followed spectrophotometrically by measuring the absorbance at 375 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 1.35–20.25 μg mL^‐1 with apparent molar absorptivity and Sandell's sensitivity of 8.0 × 10³ L mol^‐1cm^‐1 and 0.042 μg/cm²/0.001 absorbance unit, respectively. The interference of a large number of anions and cations has been investigated and the optimized conditions developed have been utilized for the determination of uranium(VI) in soil samples. The three sigma detection limit (n = 9) for uranyl ion was found to be 0.20 μg mL^‐1. The proposed method was successfully applied to the determination of uranyl ion in soil samples.     

Removal, preconcentration and determination of Mo(VI) from water and wastewater samples using maghemite nanoparticles

Removal and recovery of Mo(VI) from aqueous solutions were investigated using maghemite (γ-Fe₂O₃) nanoparticles. Combination of nanoparticle adsorption and magnetic separation was used to the removal and recovery of Mo(VI) from water and wastewater solutions. The nanoscale maghemite with mean diameter of 50 nm was synthesized by reduction coprecipitation method followed by aeration oxidation. Various factors influencing the adsorption of Mo(VI), e.g. pH, temperature, initial concentration, and coexisting common ions were studied. Adsorption reached equilibrium within <10 min and was independent of initial concentration of Mo(VI). Studies were performed at different pH values to find out the pH at which maximum adsorption occurred. The maximum adsorption occurred at pHs between 4.0 and 6.0. The Langmuir adsorption capacity (q_max) was found to be 33.4 mg Mo(VI)/g of the adsorbent. The results showed that nanoparticle (γ-Fe₂O₃) is suitable for the removal of Mo(VI), as molybdate, from water and wastewater samples. The adsorbed Mo(VI) was then desorbed and determined spectrophotometrically using bromopyrogallol red as a complexation reagent. This allows the determination of Mo(VI) in the range 1.0–86.0 ng mL⁻¹.     

Banana peel: A green and economical sorbent for the selective removal of Cr(VI) from industrial wastewater

This study describes the use of banana peel, a commonly produced fruit waste, for the removal of Cr(VI) from industrial wastewater. The parameters pH, contact time, initial metal ion concentration, and temperature were investigated and the conditions resulting in rapid and efficient adsorption (95% within 10 min) were determined. The binding of metal ions was found to be pH dependent with the optimal sorption occurring at pH 2. The retained species were eluted with 5 mL of 2 M H₂SO₄. To elucidate the mechanism of the process, total amounts of chromium and Cr(VI) were analyzed using flame atomic absorption and ultraviolet–visible (UV–vis) spectroscopic techniques, respectively. The Langmuir and Dubinin–Radushkevich (D–R) isotherms were used to describe the partitioning behavior for the system at different temperatures. Kinetics and thermodynamics of Cr(VI) removal by banana peel were also studied. The influence of diverse ions on the sorption behavior revealed that only Fe(II) ions (of those tested) suppressed the sorption of Cr(VI) ions to some extent. The method was applied for the removal of Cr(VI) from industrial wastewater.     

Nitric oxide removal from flue gas by ferrate(VI)/urea solutions

In this work, nitric oxide absorption process by using ferrate(VI)/urea was proposed. The respective influences of the four factors including pH value, ferrate(VI) concentration, urea concentration, and the temperature and the interactive function of them on nitric oxide absorption were investigated with the response surface methodology (RSM) by central composite design (CCD). The proposed model system showed good consistency with the experiment results, by a correlated coefficient (R²) of 0.9875. In addition, the interactive influences between any two variables were elaborated through analysis of response surface. The optimal parameters were found at pH of 7.1, reaction temperature of 43.8 °C, urea concentration of 6.3 wt%, ferrate(VI) concentration of 4.4 mmol/L for 85.2% NO absorption. Finally, N-containing product analysis shows that nitric oxide was primarily transformed to N₂ and NO₃⁻.     

Equilibrium and kinetics study of Gd(III) and U(VI) adsorption from aqueous solutions by modified Sorrel’s cement

Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol⁻¹, −85.4 J ⋅ mol⁻¹ ⋅,K⁻¹, and −5.4 KJ ⋅ mol⁻¹, respectively, for Gd(III) and 18.9 kJ ⋅ mol⁻¹, 67.8 J ⋅ mol⁻¹ K⁻¹ and −1.3 KJ ⋅ mol⁻¹, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms. The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k ₁and k ₂ have been calculated at different temperatures between 10 and 60^∘C. Form kinetic study, the values of Δ H ^* and Δ S ^* were calculated for Gd(III) and U(VI) at 25^∘C. It is found that Δ H ^* equals −14.8 kJmol⁻¹ and 7.2 kJmol⁻¹ for Gd(III) and U(VI), respectively, while Δ S ^* were found equal −95.7 Jmol⁻¹K⁻¹ and −70.5 Jmol⁻¹K⁻¹ for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI).     

Colorimetric detection of uranium(VI) on building surfaces after enrichment by solid phase extraction

A method for detecting and quantifying uranium(VI) levels on building materials that include concrete, Plexiglas, glass and steel surfaces is presented. Uranium(VI) was extracted from building material surfaces using a pH 2.2 buffer rinse and, subsequently complexed by an organic chelating agent, arsenazo III. The application of a uranium-chelating molecule, arsenazo III, allows for concentration enhancement using C₁₈ solid phase extraction and colorimetric detection of the uranium complex using ultraviolet-visible spectroscopy at 654 nm. The method has a detection limit (based on 3σ) of 40 ng/L (5 ng/cm²) and an overall extraction efficiency greater than 80% for each surface type (concrete, Plexiglas, glass, steel). Methods to prevent interference by metal ions commonly found on building materials are discussed.     

Determination of Cr(III) and Cr(VI) in industrial and environmental liquid samples by EDXRF method

A rapid, sensitive and selective procedure for determination of Cr(III) and Cr(VI) in environmental and industrial liquid samples via preconcentration with ammonium pyrrolidine dithiocarbamate (APDC) and determination by means of the EDXRF was described. The effect of pH in the range of 3-11 on the recovery of Cr(III) and Cr(VI) has been investigated separately and in combination of these two species. The influence of organic matter, carbonate species and elements V, Mn and Fe on the recovery of each chromium specie (separately/in combination) over whole pH range was also tested in order to simulate condition occurring in natural waters that usually contain certain amount of dissolved organic matter and carbonate ions. Cr(VI) and Cr(III) have shown different behaviors in reaction with APDC at different pH ranges and therefore it is possible to separate those two species. It was found that Cr(VI) creates complex with APDC only in the pH range from 3 to 5 with quantitative recovery (app. 98%) at pH 3, but there was no recovery of Cr(III) at that pH. On the contrary, in pH range from 6 to 11, reaction with Cr(III) and APDC reviled that the only reaction product is Cr(OH)₃ instead of the expected Cr(III)-APDC complex. All reaction products were characterized by IR spectroscopy.     

CdSe量子点荧光探针检测生活饮用水中的痕量六价铬

采用胶体化学方法合成还原性谷胱甘肽(GSH)稳定的Cd Se纳米量子点,所合成的Cd Se量子点对痕量的六价铬具有灵敏的荧光猝灭作用。以Cd Se量子点为荧光探针,建立一种简单快速测定生活饮用水中痕量六价铬的检测方法。在0.05~2.0μg·L-1范围内,Cd Se量子点的荧光强度变化值与生活饮用水中六价铬的含量呈线性关系,方法的检出限为0.01μg·L-1,样品测定的相对标准偏差小于5%,加标回收率在97~104%之间。该方法能够快速灵敏检测生活饮用水中的痕量六价铬,具有重现性好,定量准确灵敏等优点。     

Light Promotes the Immobilization of U(VI) by Ferrihydrite

The environmental behaviors of uranium closely depend on its interaction with natural minerals. Ferrihydrite widely distributed in nature is considered as one main natural media that is able to change the geochemical behaviors of various elements. However, the semiconductor properties of ferrihydrite and its impacts on the environmental fate of elements are sometimes ignored. The present study systematically clarified the photocatalysis of U(VI) on ferrihydrite under anaerobic and aerobic conditions, respectively. Ferrihydrite showed excellent photoelectric response. Under anaerobic conditions, U(VI) was converted to U(IV) by light-irradiated ferrihydrite, in the form of UO_2+x (x < 0.25), where •O₂⁻ was the dominant reactive reductive species. At pH 5.0, ~50% of U(VI) was removed after light irradiation for 2 h, while 100% U(VI) was eliminated at pH 6.0. The presence of methanol accelerated the reduction of U(VI). Under aerobic conditions, the light illumination on ferrihydrite also led to an obvious but slower removal of U(VI). The removal of U(VI) increased from ~25% to 70% as the pH increased from 5.0 to 6.0. The generation of H₂O₂ under aerobic conditions led to the formation of UO₄•xH₂O precipitates on ferrihydrite. Therefore, it is proved that light irradiation on ferrihydrite significantly changed the species of U(VI) and promoted the removal of uranium both under anaerobic and aerobic conditions.