Preconcentration and determination of copper and cadmium ions with 1,6-bis(2-carboxy aldehyde phenoxy)butane functionalized Amberlite XAD-16 by flame atomic absorption spectrometry

A new chelating resin, covalently linked 1,6-bis(2-carboxy aldehyde phenoxy)butane with the Amberlite XAD-16 was synthesized and used for preconcentration of Cu(II) and Cd(II) prior to their determination by flame atomic absorption spectrometry (FAAS). It was characterized by elemental analyses and Fourier Transform Infrared Spectroscopy (FT-IR). Cu(II) and Cd(II) ions were quantitatively preconcentrated on minicolumn loaded with synthesised resin at pH 4.00 and 6.00, respectively. They were eluated with 5 mL of 0.5 mol L⁻¹ HCl. Recoveries of Cu(II) and Cd(II) were found to be 100 ± 2.15, 100 ± 1.40 (N = 5), the limits of detection of Cu(II) and Cd(II) in the determination by FAAS (3s, N = 20) were found to be 0.33 and 1.19 μg L⁻¹, respectively. The effect of foreign ions on the recovery has been investigated. The proposed method has been applied for the determination of Cu(II) and Cd(II) ions to the real samples collected from Tigris river water in Diyarbak?r and Elaz?? cities in Turkey. Standard addition method and analysis of the certified reference material (NCS-DC 73350) was employed to check the accuracy of the method.     

Modified native cellulose fibers--a novel efficient adsorbent for both fluoride and arsenic

Native cellulose fibers were surface modified by poly(N,N-dimethyl aminoethyl methacrylate) (PDMAEMA) to generate an anion adsorbent, which was characterized by scanning electron microscopy, fourier transform infrared spectroscopy and elemental analyzer. This adsorbent had high efficiency in removal of F⁻, AsO₂⁻ and AsO₄³⁻ from aqueous solutions, even at low initial concentrations. Adsorption kinetics showed that the adsorption equilibrium could be reached within 1 min. The distribution coefficient did not change with adsorbent dose, indicating the adsorption was a homogenous process. Langmuir, Freundlich and Temkin models were used to fit the adsorption isotherms. Based on the parameters calculated from the models, the adsorption capacity was in the order of AsO₄³⁻ ? AsO₂⁻ > F⁻, and the adsorption was a favorable process. Compared with Freundlich and Temkin models, the isotherms followed Langmuir model a little better.     

Development of chemically engineered porous metal oxides for phosphate removal

In this study, the application of ordered mesoporous silica (OMS) doped with various metal oxides (Zr, Ti, Fe and Al) were studied for the removal of (ortho) phosphate ions from water by adsorption. The materials were characterized by means of N₂ physisorption (BET), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The doped materials had surface areas between 600 and 700 m² g⁻¹ and exhibited pore sizes of 44–64 Å. Phosphate adsorption was determined by measurement of the aqueous concentration of orthophosphate using ultraviolet–visible (UV–vis) spectroscopy before and after extraction. The effects of different metal oxide loading ratios, initial concentration of phosphate solution, temperature and pH effects on the efficiency of phosphate removal were investigated. The doped mesoporous materials were effective adsorbents of orthophosphate and up to 100% removal was observed under appropriate conditions. ‘Back extracting’ the phosphate from the doped silica (following water treatment) was also investigated and shown to have little adverse effect on the adsorbent.     

Tailoring NiO Nanostructured Arrays by Sulfate Anions for Sodium‐Ion Batteries

In this contribution, a novel sulfate‐ion‐controlled synthesis is developed to fabricate freestanding nickel hydroxide nanoarrays on Ni substrate. As an inorganic morphology‐controlled agent, SO₄²⁻ ions play a critical role in controlling the crystal growth and the nanoarray morphologies, by modulating the growth rate of adsorbed crystal facets or inserting into the metal hydroxide interlayers. By controlling the SO₄²⁻ concentration, the nanostructured arrays are tailored from one‐dimensional (1D) Ni(SO₄)_0.3(OH)_1.4 nanobelt arrays to hierarchical β ‐ Ni(OH)₂ nanosheet arrays. With further graphene oxide modification and postheat treatment, the obtained NiO/graphene hybrid nanoarrays show great potential for high‐performance sodium‐ion batteries, which exhibit a cyclability of 380 mAh g⁻¹ after undergoing 100 cycles at 0.5 C and reach a rate capability of 335 mA h g⁻¹ at 10 C.     

Choice of the Optimum Composition of the Solution Fuel for a Homogeneous Reactor and of Termoxid Sorbent for Recovering <Superscript>99</Superscript>Mo

T-52 sorbent was chosen for recovering ⁹⁹Mo from low-enriched uranium fuel of a homogeneous solution reactor, because this sorbent exhibits the maximal ⁹⁹Mo distribution coefficient in sorption from solutions containing 150–360 g L^–1 uranium. The use of sulfate and nitrate solutions for producing and recovering ⁹⁹Mo from the fuel of a homogeneous solution reactor was compared. The optimum composition of the solution fuel of a commercial reactor for ⁹⁹Mo production was suggested: nitric acid uranium solution (20% ²³⁵U, 100–200 g L^–1, 1 M HNO₃).     

Recovery of platinum, tin and indium from spent catalysts in chloride medium using strong basic anion exchange resins

This work describes a route for platinum recovery from spent commercial Pt and PtSnIn/Al₂O₃ catalysts using strong basic mesoporous and macroporous anion exchange resins (Cl⁻ form). The catalysts were leached with aqua regia (75 °C, 20-25 min). Platinum adsorption was influenced by the presence of other metals which form chlorocomplexes (tin, indium) and also base metals (aluminum). However, it was possible to overcome this fact by a sequential desorption procedure. Aluminum was selectively removed from the resins by elution with 3 mol L⁻¹ HCl. Platinum was desorbed passing 1 mol L⁻¹ Na₂S₂O₃ (pH 9). Tin was removed by elution with 0.1 mol L⁻¹ ascorbic acid. Indium was removed using 0.1 mol L⁻¹ EDTA as eluent. Desorption efficiency exceeded 99% for all metals. Metals were recovered in high yields (>98 wt%).     

Fluoride removal performance of glass derived hydroxyapatite

A novel sodium calcium borate glass derived hydroxyapatite (G-HAP) with different ranges of particle size was prepared by immersion sodium calcium borate glass in 0.1 M K₂HPO₄ solution by the ratio of 50 g L⁻¹ for 7 days. The unique advantage of G-HAP for the adsorption of fluoride ions in solutions was studied. The effects of size and quantity of particles, pH value and adsorption time on adsorption performance were investigated. The maximum adsorption capacity was 17.34 mg g⁻¹ if 5 g L⁻¹, <100 μm G-HAP was added to a solution with an initial pH value of 6.72 and the adsorption time was 12 h. The results showed that the micro-G-HAP could immobilize F⁻ in solution more effectively than commercial nano-HAP, which makes potential application of the G-HAP in removing the fluoride ions from wastewater. The adsorption kinetics and isotherms for F⁻ could be well fitted by a second order kinetic model and Freundlich isotherm model respectively, which could be used to describe the adsorption behavior. The mechanism of G-HAP in immobilizing F⁻ from aqueous solutions was investigated by the X-ray diffraction (XRD), infrared spectra (IR) and scanning electron microscopy (SEM).     

Uranium Sorption from Sulfate Solutions with Polyampholytes

Sorption of uranium from sulfate solutions with amino carboxylic, amino phosphonic poly-ampholytes was studied in relation to the pH and concentrations of sulfuric acid, ammonium sulfate, and themetal. The sorption is satisfactorily described by the equation K _d = KC _e ^Z, similar to the Freundlich isotherm equation. The mechanism of uranium sorption on ampholytes is suggested on the basis of calculated data on the ionic state of uranium in sulfate solutions, analytical data, and IR spectra.     

Removal of fluoride from aqueous media by Fe3O4@Al(OH)3 magnetic nanoparticles

A novel magnetic nanosized adsorbent using hydrous aluminum oxide embedded with Fe₃O₄ nanoparticle (Fe₃O₄@Al(OH)₃ NPs), was prepared and applied to remove excessive fluoride from aqueous solution. This adsorbent combines the advantages of magnetic nanoparticle and hydrous aluminum oxide floc with magnetic separability and high affinity toward fluoride, which provides distinctive merits including easy preparation, high adsorption capacity, easy isolation from sample solutions by the application of an external magnetic field. The adsorption capacity calculated by Langmuir equation was 88.48 mg g^?1 at pH 6.5. Main factors affecting the removal of fluoride, such as solution pH, temperature, adsorption time, initial fluoride concentration and co-existing anions were investigated. The adsorption capacity increased with temperature and the kinetics followed a pseudo-second-order rate equation. The enthalpy change (ΔH⁰) and entropy change (ΔS⁰) was 6.836 kJ mol^?1 and 41.65 J mol^?1 K^?1, which substantiates the endothermic and spontaneous nature of the fluoride adsorption process. Furthermore, the residual concentration of fluoride using Fe₃O₄@Al(OH)₃ NPs as adsorbent could reach 0.3 mg L^?1 with an initial concentration of 20 mg L^?1, which met the standard of World Health Organization (WHO) norms for drinking water quality. All of the results suggested that the Fe₃O₄@Al(OH)₃ NPs with strong and specific affinity to fluoride could be excellent adsorbents for fluoride contaminated water treatment.     

Preparation and electrochemical properties of lamellar MnO2 for supercapacitors

Lamellar birnessite-type MnO₂ materials were prepared by changing the pH of the initial reaction system via hydrothermal synthesis. The interlayer spacing of MnO₂ with a layered structure increased gradually when the initial pH value varied from 12.43 to 2.81, while the MnO₂, composed of α-MnO₂ and γ-MnO₂, had a rod-like structure at pH 0.63. Electrochemical studies indicated that the specific capacitance of birnessite-type MnO₂ was much higher than that of rod-like MnO₂ at high discharge current densities due to the lamellar structure with fast intercalation/deintercalation of protons and high utilization of MnO₂. The initial specific capacitance of MnO₂ prepared at pH 2.81 was 242.1 F g⁻¹ at 2 mA cm⁻² in 2 mol L⁻¹ (NH₄)₂SO₄ aqueous electrolyte. The capacitance increased by about 8.1% of initial capacitance after 200 cycles at a current density of 100 mA cm⁻².     

Potentiodynamical deposition of nanosized manganese oxides as high capacitance electrochemical capacitors

Nanosized manganese oxides powders were potentiodynamically deposition onto the Pb substrates by anodic oxidation in 0.5 mol L⁻¹ MnSO₄ and 0.5 mol L⁻¹ H₂SO₄ mixed solution at 40 °C. The chemical composition of the sample was determined by complex titration with ethylene diamine tetraacetic acid and redox titration. X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and chronopotentiometry were employed to characterize the materials. The highest specific capacitance of the MnO_x composite electrode was up to 420 F g⁻¹ in 1.0 mol L⁻¹ Na₂SO₄ electrolyte at the scan rate 5 mV s⁻¹. The synthesized nanosized manganese oxide exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

Potentiodynamical co-deposited manganese oxide/carbon composite for high capacitance electrochemical capacitors

Manganese oxide/carbon composite materials were prepared by introducing the carbon powders into the potentiodynamical anodic co-deposited manganese oxide in 0.5 mol L^− 1 MnSO₄ and 0.5 mol L^− 1 H₂SO₄ mixed solution at 40 °C. The surface morphology and structure of the composite material were examined by scanning electron microscope and X-ray diffraction. Cyclic voltammetry tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of manganese oxide and carbon. These composite materials with rough surface, which consisted of approximately amorphous manganese oxide, were confirmed to possess the ideal capacitive property. The highest specific capacitance of manganese oxide/carbon composite electrode was up to 410 F g^− 1 in 1.0 mol L^− 1 Na₂SO₄ electrolyte at the scan rate 10 mV s^− 1. The synthesized composite materials exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

Removal of acid orange 7 by guava seed carbon: A four parameter optimization study

The preparation of carbon from waste materials is a recent and economic alternative for the removal of dyes. In this study four samples of carbon were obtained by thermal treatment at 1000 °C using as precursor the guava seed with different particle sizes. The Taguchi method was applied as an experimental design to establish the optimum conditions for the removal of acid orange 7 in batch experiments. The chosen experimental factors and their ranges were: pH (2–12), temperature (15–35 °C), specific surface area (50–600 m² g⁻¹) and adsorbent dosage (16–50 mg ml⁻¹). The orthogonal array L₉ and the larger the better response category were selected to determine the optimum removal conditions: pH 2, temperature 15 °C, S_esp 600 m² g⁻¹ and dosage 30 mg ml⁻¹. Under these conditions a total removal of acid orange 7 was achieved. Moreover, the most significant factors were the carbon specific surface area and the pH. The influence of the different factors on the adsorption of acid orange 7 from solution is explained in terms of electrostatic interactions by considering the dye species and the character of the surface.     

Electron spin resonance spectra of Gd3+ ions in K2SO4-ZnSO4 glasses

Electron spin resonance (ESR) spectra of Gd³⁺ ions doped in K₂SO₄-ZnSO₄ glasses have been studied on an X-band ESR spectrometer at different temperatures (–120 to 150 C). The ESR spectrum at room temperature exhibits three prominent features with effectiveg-values of 5.6, 2.83 and 2.02. The spectra are similar to the U spectra familiar in many oxide and fluoride glasses, indicating very low and disordered site symmetries with a broad distribution of crystal fields. Remarkable changes have been observed in the spectrum with changes in the temperature, concentration and glass composition. The broadening of theg 2.02 line with increasing Gd³⁺ ion content indicates that the dipole-dipole interaction between the resonant centres increases with increase in Gd³⁺ ion content. A weak band at 36350cm^–1 is observed in the optical absorption spectrum of 0.5mol% Gd³⁺ in K₂SO₄-ZnSO₄ glass which has been assigned to the transition⁸S_7/2⁶P_7/2.     

Microwave enhanced Fenton-like process for the treatment of high concentration pharmaceutical wastewater

This paper explored a novel process for wastewater treatment, i.e. microwave enhanced Fenton-like process. This novel process was introduced to treat high concentration pharmaceutical wastewater with initial COD loading of 49,912.5 mg L⁻¹. Operating parameters were investigated and the optimal condition included as follows: microwave power was 300 W, radiation time was 6 min, initial pH was 4.42, H₂O₂ dosage was 1300 mg L⁻¹ and Fe₂(SO₄)₃ dosage was 4900 mg L⁻¹, respectively. Within the present experimental condition used, the COD removal and UV₂₅₄ removal reached to 57.53% and 55.06%, respectively, and BOD₅/COD was enhanced from 0.165 to 0.470. The variation of molecular weight distribution indicated that both macromolecular substances and micromolecular substances were eliminated quite well. The structure of flocs revealed that one ferric hydrated ion seemed to connect with another ferric hydrated ion and/or organic compound molecule to form large-scale particles by means of van der waals force and/or hydrogen bond. Subsequently, these particles aggregated to form flocs and settled down. Comparing with traditional Fenton-like reaction and conventional heating assisted Fenton-like reaction, microwave enhanced Fenton-like process displayed superior treatment efficiency. Microwave was in favor of improving the degradation efficiency, the settling quality of sludge, as well as reducing the yield of sludge and enhancing the biodegradability of effluent. Microwave enhanced Fenton-like process is believed to be a promising treatment technology for high concentration and biorefractory wastewater.     

Low-temperature synthesis of δ-MnO2 with large surface area and its capacitance

δ-MnO₂ was synthesized by a facile low-temperature hydrothermal method with a mixed system of KMnO₄ and CO(NH₂)₂ at 90 °C for 24 h. The obtained product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N₂ adsorption-desorption. Results showed that the as-synthesized product had a layered structure and a high specific surface area of 230 m² g^− 1. Electrochemical characterization indicated that the prepared material exhibited an ideal capacitive behavior with the initial capacitance value of 265 F g^− 1 in 1 mol L^− 1 Na₂SO₄ aqueous solution at a scan rate of 5 mV s^− 1 and excellent cycling behavior.     

Synthesis,characterization and ion exchange properties of zirconium(IV) tungstoiodophosphate,a new cation exchanger

Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L⁻¹ sodium tungstate, potassium iodate and 1 mol L⁻¹ orthophosphoric acid to aqueous solution of 0·1 mol L⁻¹ zirconium(IV) oxychloride. Its ion exchange capacity for Na⁺ and K⁺ was found to be 2·20 and 2·35 meq g⁻¹ dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb²⁺ from other metal ions.     

Sorption of actinide ions onto mesoporous phosphorus-containing silicas

Equilibrium and kinetic characteristics of template mesoporous silicas containing phosphonic acid residues in sorption of various actinide ions were studied. The sorption equilibrium involving these sorbents is attained within 20 min after introducing the sorbent into the solution. The calculated values of the internal diffusion coefficient \((\bar D)\) and half-exchange time (τ_0.5) in sorption of uranium were ～3.5 × 10^?16 m² s^?1 and ～390 s, respectively. Mesoporous phosphorus-containing silicas efficiently sorb from acid solutions uranyl ions, Th(IV), and Pu(IV). In sorption of uranium from sulfuric acid solutions, the capacity of the sorbents is 125–132 mg g^?1, and in sorption from nitric acid solutions (0.5–3.0 M HNO₃), 276–299 mg g^?1. In sorption of Th(IV) from nitric acid solutions, the capacity of the sorbents is 60–66 mg g^?1. In sorption of microamounts of ²³⁹Pu(IV), the distribution coefficient reaches 4500 cm³ g^?1. Phosphorus-containing silicas in nitric acid solutions do not noticeably sorb ²⁴¹Am, which allows using them for efficient separation of the Pu/Am pair with the separation factor of no less than 2 × 10₃.     

Adsorptive removal of fluoride from aqueous solution using orange waste loaded with multi-valent metal ions

Adsorption gels for fluoride ion were prepared from orange waste by saponification followed by metal loading. The pectin compounds contained in orange waste creates ligand exchange sites once it is loaded with multi-valent metal ions such as Al³⁺, La³⁺, Ce³⁺, Ti⁴⁺, Sn⁴⁺, and V⁴⁺ to be used for fluoride removal from aqueous solution. The optimum pH for fluoride removal depends on the type of loaded metal ions. The isotherm experiments showed the Langmuir type monolayer adsorption. Among all kinds of metal loaded gels tested, Al loaded gel appeared to exhibit the most favorable adsorption behavior. The adsorption kinetics of fluoride on loaded gel demonstrated fast adsorption process. The presence of NO₃⁻, Cl⁻ and Na⁺ ions has negligible effect on fluoride removal whereas SO₄²⁻ and HCO₃⁻ retarded the fluoride removal capacity in some extent. Fluoride removal at different adsorbent doses showed that fluoride concentration can be successfully lowered down to the acceptable level of environmental standard. The fluoride adsorption mechanism was interpreted in terms of ligand exchange mechanism. The complete elution of adsorbed fluoride from the gel was successfully achieved using NaOH solution.     

An Ion-Crosslinked Supramolecular Hydrogel for Ultrahigh and Fast Uranium Recovery from Seawater

Large-scale uranium extraction from seawater is a crucial but challenging part of nuclear power generation. In this study, a new ion-crosslinked supramolecular Zn²⁺–poly(amidoxime) (PAO) hydrogel that can super-efficiently adsorb uranium from seawater is explored. By simply mixing two solutions of zinc chloride and PAO, a supramolecular Zn²⁺–PAO hydrogel is achieved via the interaction between zinc cations and amidoxime anions. In contrast with existing amidoxime-functionalized hydrogel-based adsorbents having low PAO contents and fiber-based adsorbents with weak hydrophilicity, the PAOs can be directly crosslinked using a small quantity of superhydrophilic zinc ion. Thus, a supramolecular hydrogel is formed, having both a high content of well-dispersed PAOs and good hydrophilicity. Relative to reported adsorbents, this low-cost hydrogel membrane exhibits outstanding uranium adsorption performance, reaching 1188 mg g^-1 of M_U/M_{dry gel} in 32 ppm uranium-spiked water. More importantly, after immersion in natural seawater for only 4 weeks, the uranium extraction capacity of the Zn²⁺–PAO hydrogel membrane reaches 9.23 mg g^-1 of M_U/M_{dry gel}. This work can provide a general strategy for designing a new type of supramolecular hydrogel, crosslinked by various bivalent/multivalent cation-crosslinkers and even many other superhydrophilic supramolecular crosslinkers, for the high-efficient and massive extraction of uranium from seawater.