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Amine-functionalized graphene oxide/zinc hexacyanoferrate (amino-rGO/ZnHCF) composites were successfully synthesized for the removal of Cs+ from radioactive liquid waste. Their morphologies, surface areas, pore sizes, functional groups, and thermal stabilities were investigated by field-emission transmission electron microscopy, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, and thermogravimetry. Adsorption experiments revealed high adsorption capacities at pH 5–7 and stability below pH 9. The dependence of the synthesized composites on the pseudo-second-order model and the Temkin model was also observed. The results of this study indicate that the new amino-rGO/ZnHCF composites are good adsorbent candidates for Cs removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

The effect of Tf2N−, as a common anion in aqueous and ionic liquid (IL) phases, on Cs extraction in the IL system was investigated using C2mimTf2N as an IL and DCH18C6 as an extractant. The "common anion (Tf2N−) effect" operated via the movement of Cs+·Tf2N− from the aqueous phase into the IL phase by extraction in the form of Cs+·extractant·Tf2N−, without any traditional cation exchange. The extraction product was recovered as a precipitate using a small amount of IL, which facilitated precipitation via supersaturation. [ABSTRACT FROM AUTHOR]

The spontaneous reductive decomposition behavior of HMnO4 in water as a function of the initial HMnO4 concentration and reaction temperature was investigated. The decomposition of HMnO4 was fast in the early stage of the reaction and thereafter slowed down significantly, regardless of the initial HMnO4 concentration. The loss of HMnO4 by spontaneous reductive decomposition increased with increasing reaction temperature. Based on the experimental results and the classical nucleation theory, a mathematical model was developed using a combination of two first-order reactions representing the nucleation and crystal growth of MnO2 to predict the spontaneous reductive decomposition behavior of HMnO4. [ABSTRACT FROM AUTHOR]

Zinc hexacyanoferrate functionalized magnetic carbon nanotube composites were synthesized to be used as adsorbents for the selective removal of Cs. The synthesized adsorbents exhibited a high adsorption capacity that could be successfully improved by increasing the loading of zinc hexacyanoferrate, which plays a major role in selectively adsorbing and removing Cs from the adsorbent surface. Although the saturation magnetization value for the synthesized adsorbents decreased with increasing zinc hexacyanoferrate loading, the adsorbents could be sufficiently separated by using a permanent magnet. [ABSTRACT FROM AUTHOR]

Selective separation of Cs from liquid radioactive waste by 'precipitation' was observed in a hydrophobic ionic liquid containing the Cs-selective extractant dicyclohexano-18-crown-6. The precipitate was formed by the cation exchange mechanism, which simplified the treatment of Cs after extraction. Solid-liquid extraction is a more economical extraction system than liquid-liquid extraction because it uses smaller quantities of ionic liquids. This work showed the possibility of developing a new method for removing Cs from liquid radioactive waste using solid-liquid phase separation instead of the conventional liquid-liquid separation in an ionic liquid extraction system. [ABSTRACT FROM AUTHOR]

In this study, copper ferrocyanide-functionalized, multi-walled carbon nanotubes (MWCNT-CuFCs) were synthesized. The MWCNT-CuFCs exhibited a high capacity for sorbing Cs from aqueous solutions because of their strong affinity for Cs and high specific surface area. The sorption capacity of the MWCNT-CuFCs for Cs was dependent upon the initial pH of the solution. The sorption ability of the MWCNT-CuFCs for Cs was maintained even in the presence of co-existing ions (K and Na). To determine the degree of Cs desorption from the MWCNT-CuFCs, a column-based desorption experiment was performed. [ABSTRACT FROM AUTHOR]

In order to evaluate hydrate-based desalination (HBD), experiments with seawater samples were carried out at various conditions (i.e. hydraulic pressure, washing step, and hydrate-forming gas). Before and after the hydrate process, cations (Na + , K + , Mg 2 + , Ca 2 + , and B 3 + ) and anions (Cl − and SO 4 2 − ) were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC). In a single stage of CO 2 hydrate process without any pretreatment, 71%–94% of each cation was removed in the following order: K + > Na + ≈ Mg 2 + ≈ Ca 2 + > B 3 + and 73%–83% of each anion was removed. When the brines on the surface of hydrate pellets were removed, the ion removal efficiency increased above 4%. It was also found that the desalting efficiency depended on the hydrate-forming gas (CO 2 > CH 4 ) and the hydraulic pressure (6–10 MPa) to produce hydrate pellets. In this study, the removal efficiency of cations and anions in a real seawater sample using HBD processes were reported for the first time. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ph-MSs with different compositions were synthesized via co-condensation. [•] Adsorption affinity of Ph-MS for BPA increased with surface hydrophobicity at low concentration. [•] Ph-MS exhibited good characteristics as a recyclable adsorbent. [•] The selective adsorption behavior of Ph-MS was investigated using several organic adsorbates. [•] Both hydrophilic and hydrophobic interactions were involved in the adsorption of Ph-MS. [ABSTRACT FROM AUTHOR]

Abstract: Sorptive removal of Co2+, Sr2+ and Cs+ from aqueous solution by phosphate-modified montmorillonite (PMM) was studied considering the influencing factors (initial metal ion concentrations, initial solution pH and temperature). The Freundlich, Langmuir and Dubinin–Radushkevich (DR) models were used to fit single-solute sorption data. The Freundlich model was the best, indicating heterogeneous surface property of PMM. The maximum sorption capacity (q mL) of Langmuir model was in the order of Cs+ >Co2+ >Sr2+. The mean sorption energy (E) values of DR model (<8kJ/mol) at pH 5 for all metals indicated physical sorption. However, Cs+ sorption mainly occurred by chemical sorption. In bi-solute competitive sorption, the sorption of one metal ion was suppressed by the presence of competing metal ion. The Sheindorf–Rebhun–Sheintuch (SRS) model, the extended Freundlich model (EFM), the modified extended Langmuir model (MELM) and the IAST-Freundlich model predicted the competitive sorption adequately. Sorptions of Co2+ and Sr2+ were strongly dependent on the initial solution pH but that of Cs+ was not. The calculated thermodynamic parameters such as ΔH, ΔS, and ΔG showed that sorptions of Co2+ and Sr2+ onto PMM were endothermic, whereas that of Cs+ was exothermic and that all sorption occurred spontaneously. [Copyright &y& Elsevier]

In the solidification process using asphalt as a medium, nitrate oxidizes the medium and makes it unstable. Therefore, in order to efficiently remove nitrate from wastewater, a magnetic adsorbent was synthesized (m-MWCNTs), and physicochemical properties of m-MWCNTs were confirmed by SEM, TEM, XRD, FT-IR, BET, and VSM analyses. In the process of synthesizing m-MWCNTs, the amount of magnetite introduced on the surface of MWCNTs could be controlled by increasing the concentration of the chemical agent that becomes the Fe precursor. In addition, the amount of nitrate adsorption increased with higher magnetite content on the surface of MWCNTs. The adsorption process followed the Langmuir model and pseudo-second-order kinetics. In nitrate adsorption using m-MWCNTs, pH was the main condition to determine the adsorption amount, and as the pH increased, the amount of nitrate adsorption decreased. Thermodynamic experiments revealed that the adsorption of nitrate by m-MWCNTs is an endothermic and spontaneous process. [Display omitted] • Magnetic MWCNTs (m-MWCNTs) was synthesized successfully for removal of nitrate. • Increasing Fe 3 O 4 loading on MWCNTs surface leads to an increase in nitrate adsorption capacity. • Adsorption of nitrate by m-MWCNTs was favorable in acidic conditions. [ABSTRACT FROM AUTHOR]

Anionic dyes are one of the most serious contaminants in water as these molecules are known to be toxic to many living organisms. Herein, we report the development of functionalized polyvinylidene fluoride membranes modified with chitosan-coated iron oxide nanomaterials (Fe-PVDF) for the efficient treatment of anionic dye-contaminated water. Aqueous solutions of anionic dyes could be captured rapidly by passing through the functionalized membrane under reduced pressure. Under neutral conditions, Fe-PVDF showed a maximum removal capacity of 74.6 mg/g for Evans blue (EB) through the adsorption process. In addition, the adsorption capacity was significantly enhanced up to 434.78 mg/g under acidic conditions. The adsorption process for EB matched well with the Langmuir model, indicating monolayer adsorption of the dye to the membrane surface. Moreover, Fe-PVDF can be reusable by a simple washing step in an alkaline solution, and thus, the composite membrane was applied several times without a significant decrease in its adsorption performance. The same composite membrane was further applied to the removal of five other different anionic dyes with high efficiencies. The adsorption mechanism can be explained by the electrostatic interaction between the positively charged chitosan and the negatively charged dye as well as the affinity of the sulfate groups in dye molecules for the surface of the iron oxide nanoparticles. The easy preparation and rapid decolorization procedures make this composite membrane suitable for efficient water treatment., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Chromium is a toxic and carcinogenic heavy metal that originates from various human activities. Therefore, the effective removal of chromium from aqueous solutions is an extremely important global challenge. Herein, we report a chitosan-coated iron oxide nanoparticle immobilized hydrophilic poly(vinylidene) fluoride membrane (Chi@Fe 2 O 3 -PVDF) which can potentially be used for efficient removal of hexavalent chromium(VI) by a simple filtration process. Membrane filtration is an easy and efficient method for treating large volumes of water in a short duration. The adsorption experiments were conducted by batch and continuous in-flow systems. The experimental data showed rapid capture of hexavalent chromium (Cr(VI)) which can be explained by the pseudo-second-order kinetic and Langmuir isotherm model. The nanocomposite membrane exhibited high adsorption capacity for Cr(VI) (14.451 mg/g in batch system, 14.104 mg/g in continuous in-flow system). Moreover, its removal efficiency was not changed significantly in the presence of several competing ions, i.e., Cl - , NO 3 - , SO 4 2- , and PO 4 3- . Consequently, the Chi@Fe 2 O 3 -PVDF-based filtration process is expected to show a promising direction and be developed as a practical method for wastewater treatment.

Ciprofloxacin (CPX), a widely used antibiotic, was removed by synthesizing graphene oxide/calcium alginate-polyacrylamide (GO/Ca-Alg 2 -PAM) beads, a three-dimensional double-network complex. The synthesis of GO/Ca-Alg 2 -PAM beads was performed by crosslinking and cation exchange mechanisms with graphene oxide (GO), sodium alginate (Na-Alg), and polyacrylamide (PAM). The properties of GO/Ca-Alg 2 -PAM beads were confirmed using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and a thermogravimetric analysis. Furthermore, isothermal adsorption experiments were performed and fitted using three isothermal adsorption models (Langmuir, Freundlich, and Temkin). The adsorption isotherm experimental data fit well with the Langmuir isotherm model with a q m value of 6.846 mg/g. In addition, the spontaneous reaction of the CPX adsorption using GO/Ca-Alg 2 -PAM was confirmed by temperature-dependent experiments.

Composite beads consisting of Ca alginate mixed with zinc ferrocyanide (ZnFC) and Cyanex 272 were synthesized in order to selectively adsorb Cs + and Co 2+ from water. Their physicochemical properties of the synthesized composite beads were characterized using various techniques, including FESEM, EDX, FTIR, and TGA. The ZnFC/Cyanex 272/alginate (ZCA) composite beads were then tested as an adsorbent for the selective removal of Cs + and Co 2+ from an aqueous solution. The adsorption capacity increased with increasing ZnFC and Cyanex 272 contents. The adsorption process followed the Langmuir model and pseudo-second-order kinetics. The ZCA composite beads exhibited excellent selectivity toward Cs + and Co 2+ even in the presence of competitive cations (K + , Na + , Fe 2+ , and Ni 2+ ). The adsorption capacity of the ZCA composite beads for Cs + and Co 2+ was almost maintained after three times of adsorption-desorption process., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A novel blend of membranes made of Nafion ® and poly(vinylpyrrolidone) (PVP) was prepared and characterized to investigate its applicability in proton exchange membrane fuel cells (PEMFCs). In addition to being effectively proton conductive, the membranes exhibited better mechanical strength, chemical stability, and adequate water retention ability, as well as ion exchange capacity comparable to that of cast Nafion ® membrane. The data obtained from an electrochemical impedance spectroscopy (EIS) fitting of the fuel cells revealed the membrane electrode assemblies (MEAs) made of 0.5 wt.% PVP/Nafion ® had lower ohmic and charge transfer resistance compared with that of the Nafion ® membrane. The intermolecular interactions and morphology of these membranes were assessed using Fourier-transform infrared spectroscopy and field-emission scanning electron microscopy. The results of the performance curve indicate that the introduction of PVP as a modifier played a vital role in improving membrane performance. Accordingly, this solution-casted polymer electrolyte membrane with suitable PVP content offers a simple way to improve electrochemical, mechanical, and chemical properties, and thereby promises the prospect of use in low-temperature PEMFCs.

A Zn(II)-based metal-organic framework (MOF) compound and MnO 2 were used to prepare ZnO x -MOF@MnO 2 composites for selective Sr 2+ removal in aqueous solutions. The ZnO x -MOF@MnO 2 composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller surface area analysis. The functional groups, morphologies, thermal stabilities, and specific surface areas of the composites were suitable for Sr 2+ adsorption. A maximum adsorption capacity of 147.094 mg g -1 was observed in batch adsorption experiments, and the sorption isotherms were fit well by the Freundlich model of multilayer adsorption. Adsorption reached equilibrium rapidly in kinetic experiments and followed the pseudo-second-order kinetic model. The adsorption capacity of the ZnO x -MOF@MnO 2 composite with the highest MnO 2 content was high over a wide pH range, and the composite was highly selective toward Sr 2+ in solutions containing coexisting competing ions. Also, it has a good reusability for removing Sr 2+ ., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Sulfated titania-silica (SO4(2-)-/TiO2-SiO2) composites were prepared by a sol-gel method with sulfate reaction and characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The nanometric diameter and geometry of the sulfated titania-silica (STS) was investigated by transmission electron microscopy (TEM). A small amount of the STS composite in the range of 0.5-3 wt% was then added as reinforcing into the Nafion membrane by water-assisted solution casting method to prepare STS reinforced Nafion nanocomposite membranes (STS-Nafion nanocomposite membranes). The additional functional groups, sulfate groups, of the nanocomposite membrane having more surface oxygenated groups enhanced the fuel cell membrane properties. The STS-Nafion nanocomposite membranes exhibited improved water uptake compared to that of neat Nafion membranes, whereas methanol uptake values were decreased dramatically improved thermal property of the prepared nanocomposite membranes were measured by thermogravimetric analysis (TGA). Furthermore, increased ion exchange capacity values were obtained by thermoacidic pretreatment of the nanocomposite membranes.

Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWCNTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.