In-Situ-Generated Fluoride-Assisted Rapid Dissolution of Uranium Oxides by Ionic Liquids.

A quantitative, rapid, endothermic dissolution of U3O8 in C4mim·PF6 (1-alkyl-3-methyl imidazolium hexafluorophosphate) has been achieved within 2 h at 65 °C by in situ generated fluoride ions by pre-equilibrating the ionic liquid with suitable concentrations of nitric acid. The efficiency of the dissolution followed the trend: UO3 > UO2 > U3O8. The fluoride generation was found to increase with the concentration of nitric acid being equilibrated, the water content of the ionic liquid, and also the time of equilibration. The rate of dissolution of U3O8 followed the trend: C4mim·PF6> C6mim·PF6 > C8mim·PF6. The maximum loading observed for the present case was 200 mg mL-1 which is considered to be quite high with an ionic liquid. The effects of different acid pre-equilibration (HClO4, HCl) on F- generation and subsequent dissolution characteristics have also been investigated. The in situ F- generation, as well as U3O8 dissolution, were found to predominantly follow a pseudo-second-order rate kinetics, while the rate constants for U3O8 dissolution were found to be higher than that of F- generation. The dissolved uranium was successfully electrodeposited on a Cu plate, as confirmed by EDXRF, while the formation of UO2 was revealed from the XRD pattern of the deposit.

Remarkably High Separation of Neodymium from Praseodymium by Selective Dissolution from their Oxide Mixture using an Ionic Liquid Containing aß-Diketone.

A simple, efficient, direct and economical method for the mutual separation of Nd and Pr was developed by the selective dissolution of Nd2O3 from their oxide mixtures in an ionic liquid containing 2-thenoyltrifluoroacetone (HTTA) resulting in an unprecedented separation factor (ßNd/Pr)>500, which is 277 times more than the thus far reported ßNd/Pr values. The proposed mechanism was supported by DFT computations.

Experimental and Theoretical Insight into the Ionic Liquid-Mediated Complexation of Trivalent Lanthanides with ß-Diketone and Its Fluorinated Analogue.

A multitechnique approach with theoretical insights has been employed to understand the complexation of trivalent lanthanides with two ß-diketones, viz. 1-phenyl-1,3-butanedione (L1) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (L2), in an ionic liquid (C6mim·NTf2). UV-vis spectral analysis of complexation using Nd3+ revealed the predominance of ML2+ and ML4- species. The stability constants for the PB complexes were higher (ß2 ∼ 10.45 ± 0.05, ß4 ∼ 15.51 ± 0.05) than those for the TPB (ß2 ∼ 7.56 ± 0.05, ß4 ∼ 13.19 ± 0.06). The photoluminescence titration using Eu3+ corroborated the same observations with slightly higher stability constants, probably due to the higher ionic potential of Eu3+. The more asymmetric (AL2ML4 ∼ 5.2) Eu-L2 complex was found to contain one water molecule in the primary coordination sphere of Eu3+ with more covalency of the Eu3+-O bond (Ω2L1 = 8.5 × 10-20, Ω4L1 = 1.3 × 10-20) compared to the less asymmetric Eu-L1 complex (AL1ML4 ∼ 3.5) with two water molecules having less Eu-O covalency (Judd-Offelt parameters: Ω2L1 = 7.3 × 10-20, Ω4L1 = 1.0 × 10-20). Liquid-liquid extraction studies involving Nd3+ and Eu3+ revealed the formation of the ML4- complex following an 'anion exchange' mechanism. The shift of the enol peak from 1176 to 1138 cm-1 on the complexation of the ß-diketones with Eu3+ was confirmed from the FTIR spectra. 1H NMR titration of the ß-diketones with La(NTf2)3 evidenced the participation of α-H of the ß-diketones and protons at C2, C4, and C5 positions of the methylimidazolium ring. For the ML2 complex, 4 donor O atoms are suggested to coordinate to the trivalent lanthanides with bond distances of 2.3297-2.411 Å for La-O, 2.206-2.236 Å for Eu-O, and 2.217-2.268 Å for Nd-O, respectively, while for the ML4 complex, 8 donor O atoms were coordinated with bond lengths of 2.506-2.559 Å for La-O, 2.367-2.447 Å for Eu-O, and 2.408-2.476 Å for Nd-O. The Nd3+ ion was higher by 9.7 kcal·mol-1 than that of the La3+ ion for the 1:4 complex. The complexation energy with L1 was quite higher than that with L2 for both 1:2 and 1:4 complexes. Using cyclic voltammetry, the redox behavior of trivalent lanthanides Eu and Gd with ß-diketonate in ionic liquid medium was probed and their redox energetic and kinetic parameters were determined.

Ionic Liquid Assisted Exothermic Complexation of Trivalent Lanthanides with Fluorinated ß Diketone: Multitechnique Approach with Theoretical Insight.

The complexation of the betadiketone,1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione (HFOD) was studied with trivalent lanthanide ions, viz. Nd3+, La3+, and Eu3+ in several methylimidazolium-based ionic liquids (Cnmim•NTf2, where, n = 4,6,8). In C6mim•NTf2, predominant formation of ML2+ and ML4- species was evidenced from the UV-vis absorption (Nd3+) as well as luminescence (Eu3+) spectral studies with log ß2 ≈ 5.88 ± 0.04, log ß4 ≈ 10.95 ± 0.06. The formation constants followed the trend C4mim•NTf2 > C6mim•NTf2 > C8mim•NTf2. The asymmetry factors for the ML2+ and ML4- species were found to be 1.2 and 1.59, respectively. The ML4- complex was found to have one primary coordination sphere water molecule with enhanced covalency between Eu3+ and O from HFOD (Judd Offelt constants Ω2 and Ω4 ≈ 17.2 and 2.35) compared to Eu3+aq, yet comparable to other ß diketones. Complexation-induced temperature increase was confirmed by calorimetric measurements, indicating the exothermic complexation reaction (ΔHcomplexation ≈ -13.7 kJ mol-1), which is also spontaneous in nature (ΔG ≈ -68.1 kJ mol-1), with an enhancement in the entropy values. Due to complexation, the shifts in the peak positions (1686.66 cm-1, 1633.53 cm-1) associated with ß diketone/ketone functional groups were evidenced. Density functional theory (DFT) calculation was performed to optimize the structural parameters including bond distance, bond angles, and energetics associated with the complexation.

Evaluation of a Phosphinate Functionalized Ionic Liquid for the Separation of Nb and Ta from Nitric Acid Feed Conditions.

A 'green' single-step separation process, involving a phosphonium phosphinate functionalized ionic liquid (FIL) in C8mim·NTf2, has been developed for highly encouraging improvements in the mutual separation of Nb and Ta with a maximum separation factor of ∼48 at 2 M nitric acid. The separation factor in C4mim·NTf2 was found to be somewhat lower compared to that seen in C8mim·NTf2. In C8mim·NTf2, the extraction proceeded via the neutral NbOF3(R4P+)(R2POO-) and TaOF3(R4P+)(R2POO-) species predominated by a 'solvation' mechanism at 2 M HNO3, where both the cationic and anionic parts of the FIL took part in the metal ion extraction. However, in the case of C4mim·NTf2, the extraction proceeded via a cation exchange mechanism involving the mono-positive species viz. [NbO(R2POO-)2]+IL, [TaO(R2POO-)2]+IL. Only the phosphinate group of the FIL was directly involved in the binding to the metal ion. The charge neutrality was maintained by the exchange of the C4mim+ ion from the ionic liquid phase to the aqueous phase. The processes were spontaneous, exothermic involving outer sphere complexation. The radiolytic stabilities of the C8mim·NTf2-based solvent systems were poorer than those of the solvents based on C4mim·NTf2. Aqueous solutions of EDTA-guanidine carbonate or DTPA-guanidine carbonate showed promising back extraction ability though three contacts of these organic phases were required for more than 99.99% stripping of the metal ion. The reusability of these solvent systems was evaluated. After four consecutive cycles, a maximum of only 8% reduction in the extraction efficiency of Ta was noticed, while for Nb it was less than 4% for Nb.

Experimental and Theoretical Investigation on the Extractive Mass Transfer of Eu3+ Ions Using Novel Amide Ligands in 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide.

Novel amide ligands in the ionic liquid (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) were utilized for the liquid-liquid biphasic mass transfer of Eu3+ ions from aqueous acidic waste solution. The cation exchange mechanism was found to be operative with the formation of [Eu(NO3)2L3]+ species (L = 4-chloro-N-(1-methyl-1H-pyrazol-3-yl)picolinamide). However, the presence of an inner-sphere water molecule was revealed by density functional theory (DFT) calculations. The viscosity-induced slower kinetics was evidenced during mass transfer, which was improved by increasing temperature. The process was exothermic in nature. The improvement in the kinetics of extractive mass transfer at higher temperatures is evinced by a reduction in the distribution ratio value. The spontaneity of the reaction was evidenced through the negative Gibbs free energy value, whereas the process enhances the entropy of the system, probably by releasing water molecules at least partially during complexation. The structures of bare ligands and complexes have been optimized by using DFT calculations. A high value of complexation energy, solvation energy, and associated enthalpy and free energy change reveal the efficacy in binding Eu with O and N donor atoms. In addition, natural population analysis, atoms-in-molecules analysis, and energy decomposition analysis have been employed to explore the nature of bonding existing in Eu-O and Eu-N bonds.

Chemical characterization of automobile windshield glass samples for major, minor, and trace elemental concentration determination by INAA and its comparison with ED-XRF and DC Arc AES in terms of analytical capabilities and possible applications for glass forensics.

Automobile (car) windshield glass fragments serve as important forensic evidentiary materials and their chemical characterization mainly at minor and trace concentration levels is a key step in forensic investigations. For such glass analysis as well as for forensics, direct solid sample analysis by suitable analytical technique(s) is very important. In view of this, instrumental neutron activation analysis (INAA) using high flux neutrons from research reactor was utilized for chemical characterization of car windshield glass samples. Energy dispersive X-ray fluorescence (ED-XRF) and direct current arc carrier distillation atomic emission spectroscopy (DC Arc AES) methods were also utilized for the analysis of all glass samples for evaluating their analytical capabilities with respect to INAA. A comparative evaluation was carried out with respect to accuracy, precision, and detection limits under quality assurance/quality control (QA/QC). The methods were validated by analyzing certified reference materials (CRMs) G-2 and RGM-1 from USGS and NIST standard reference material (SRM) of sodalime glass (SRM 610). Concentrations of seventeen elements (Na, Ca, Sc, Cr, Fe, Co, Zn, Rb, Zr, Ba, La, Hf, Ce, Eu, Yb, Sm, and Th) were determined in all analyzed glass samples by INAA at major, minor, and trace concentration levels, indicating its capability for potential applications to forensic studies. Grouping study of these automobile glasses was carried out utilizing concentrations of transition elements and rare earth elements (REEs) in conjunction with statistical cluster analysis. In addition, it has been highlighted that some of the transition elements as well as REEs are important markers/discriminating elements for same brand automobile glasses obtained from two different sources/origins.

Carbonate treated coffee powder (CTCP) for selective sorption of Pu4+ over Am3+, Np4+, NpO22+, and PuO22+ from aqueous acidic solution: Investigation on mechanism, kinetics, thermodynamics, stripping and radiolytic stability.

An attempt was made for understanding the sorption behaviour of different actinide ions Pu4+, PuO22+, Am3+, Np4+, and NpO22+ on carbonate treated exhausted coffee powder (CTCP). Very efficient sorption of Pu4+ over other actinide ions from aqueous acidic medium was observed. Almost 4 h were required for achieving equilibrium. Experimental results for Pu+4 were fitted into different sorption isotherm model: Langmuir isotherm, Freundlich isotherm, D.R, isotherm and Temkin isotherm. Based on the linear regression, it was found that, Freundlich isotherm was predominantly operative. Pseudo 2nd order kinetics was found to be effective for the sorption of Pu+4. More than 80 % of loaded Pu4+ was found to desorb by 0.25 M oxalic acid solution. CTCP exhibited relatively good radiation stability. Sorption of Pu+4 on CTCP was exothermic, and spontaneous in nature. The sorption process was simple, cost effective and environmentally benign, as it did not involve any sophisticated, multi-step, sorbent synthesis.

Simple, Fast, and Selective Dissolution of Eu2O3 in an Ionic Liquid as a Sustainable Paradigm for Lanthanide-Actinide Separations in Radioactive Waste Remediation.

The liquid-liquid extraction (LLE) process for lanthanide-actinide separation from the nuclear fuel cycle has several drawbacks such as, the requirement of cooling for decay heat control, the handling of large volumes of toxic volatile organic compounds (VOCs), and secondary waste generation. Alternatively reprocessing without spent fuel cooling is done by pyroprocessing, which uses high-temperature corrosive molten salts and requires elevated temperature, and is an energy-intensive process. In recent years, some of the shortcomings of both LLE and pyroprocessing are overcome by the use of room temperature ionic liquids (RTILs) as the solvents. In the present work, an attempt was made to exploit the potential of the neoteric, less-corrosive, low-VOC RTILs toward direct dissolution-based separations at ambient conditions. The present paper involves the selective dissolution of Eu2O3 in an RTIL, i.e., C4mim·NTf2 containing 2-thenoyltrifluoroacetone (HTTA) within ca. 30 min at ambient conditions; while the dissolution of AmO2 and UO2 were found to be very poor, making this an attractive method for lanthanide-actinide separation, a key step in radioactive waste management, i.e., an actinide partitioning and transmutation strategy. The quantitative dissolution of Eu2O3 from simulated spent nuclear fuel with different Eu2O3 loading was also shown. Water plays a crucial role in deciding the kinetics of dissolution and amount of the dissolved oxide. The combination of X-ray absorption, fluorescence, and UV-vis spectroscopic studies suggested the formation of the dehydrated anionic complex Ln(TTA)4- to play pivotal role in the oxide dissolution process. The structure of the complex was analyzed by density functional theory and extended X-ray absorption fine structure. The mechanism of oxide dissolution was proposed and electrochemical studies were performed to understand the possible recovery option using electrodeposition of the dissolved Eu3+.

An insight into the sequestration of tetra and hexavalent actinides by tri ethoxysilyl-amino-propyl-3-oxa-glutaramic acid (SAPOGA) functionalized titania.

Silyl-amino-propyl-3-oxa-glutaramic acid (SAPOGA) functionalized titania has been synthesized for highly efficient solid phase sequestration of thorium and uranyl ions from an aqueous acidic waste stream. The XRD pattern suggested that the grafting was performed on the anatase phase, leading to a rougher surface resulting in better interaction with actinides. The successful grafting of SAPOGA bridging was confirmed using spectroscopic methods. The Langmuir isotherm and the intraparticle diffusion-based kinetics model were found to be operative with sorption capacities of 231 mg g-1 and 458 mg g-1 and rate constants of 51 mg g-1 min-1 and 48 mg g-1 min-1 for U and Th, respectively. The entropy driven sequestration process was thermodynamically favourable (ΔGU = -6.0 kJ mol-1 and ΔGTh = -9.1 kJ mol-1) and endothermic in nature. The experimentally corroborated complexation pattern was assisted by density functional theory (DFT) calculations, which gave further insight into the metal-ligand interaction.

Understanding the Mechanism of Cs Accumulation on Stainless Steel Suspended in Nuclear High-Level Liquid Waste.

In a nuclear facility, the surface of stainless steels (SS) was found to be contaminated during the processing of radioactive liquid waste. Their safe and secure disposal is highly challenging to the nuclear industry. If the fundamental property of steel corrosion could be evaluated, successful decontamination and effective decommissioning strategies could be planned. Although individual radionuclide contamination behavior on SS metal was studied, till date, SS contamination behavior under the exposure of high-level liquid waste (HLLW) was unexplored. In view of this, investigations were carried out to understand the nature of contamination in SS 304L alloy under the exposure of simulated HLLW (SHLLW). For understanding of radionuclide adsorption behavior on structural materials, scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy have been utilized for SS 304L. The solutions were analyzed using inductively coupled plasma optical emission spectroscopy to calculate the changes in the elemental composition of the solution and corrosion behavior of SS. The passivation of SS coupons was observed in the presence of HNO3 due to enrichment of Cr at the surface. The deposition of Cs and Mo was noticed, while SS coupons were exposed to SHLLW. At 3 M HNO3 and room temperature, the SS surface is mildly passivated by Cr enrichment by formation of a Cr oxide layer on the SS surface. However, the passive layer was not thick enough to attenuate the signal from the substrate below the passivated layer. Hence, Fe0 and Cr0 were also found along with Cr3+ and Fe3+ (in small quantity). When temperature was elevated to 70 °C, the SS surface was completely covered with the Cr oxide layer, and hence no Cr0 signal was observed. The small signal of Fe0 indicated that the signal from the substrate surface is present below the passive layer. During the passivation process, Cr diffused toward the passive layer, thereby producing a Cr-depleted layer below the passive layer (Cr0 signal was not seen). In the case of SHLLW at 70 °C, the surface was fully covered by Cr3+, Mo6+, and Cs+. Fe and Ni were not observed at all. This finding will help to design an effective corrosion inhibitor and suitable decontamination agent. In addition to that, this information was found to be useful in designing high-performance novel and modern age reactor materials with improved characteristics.

Mechanism unravelling for highly efficient and selective 99TcO4 - sequestration utilising crown ether based solvent system from nuclear liquid waste: experimental and computational investigations.

Selective and efficient separation of pertechnetate (TcO4 -) from nuclear waste is desirable for the safe and secure management of radioactive waste. Here, we have projected dibenzo-18-crown-6 ether (DB18C6) in a highly polar nitrobenzene medium for enhancing the removal efficiency of 99Tc from reprocessing plant low level waste (LLW). An effort was made to determine the stoichiometry of metal-ligand complex by slope ratio method, revealing that one ligand (DB18C6) binds with one TcO4 - moiety. Optimum ligand concentration for 99Tc extraction was evaluated. Relevant interference of the anions was studied systematically. The effect of solution pH was analysed on the extraction efficiency of 99Tc. A kinetic study was carried out for maximum extraction of metal ions. A quantitative stripping study was also achieved for metal ions with a suitable stripping solution. After evaluation of all essential parameters, selectivity and feasibility studies were finally carried out with actual low level reprocessing plant waste to demonstrate a laboratory scale process for effective separation of TcO4 - ions. Density functional theory (DFT) calculations were carried out to understand the nature of the complexation of TcO4 - ion with DB18C6 in different solvents systems and to elucidate the key aspect behind ionic selectivity and enhanced the 99Tc extraction efficiency of DB18C6 in the studied diluent systems. The ΔE and ΔG values for different modeled complexation reactions were evaluated systematically. From the calculated free energy of complexation of TcO4 - with DB18C6, it was observed that the consideration of explicit solvent plays a vital role in predicting the experimental selectivity.

Correction: Mechanism unravelling for highly efficient and selective 99TcO4 - sequestration utilising crown ether based solvent system from nuclear liquid waste: experimental and computational investigations.

[This corrects the article DOI: 10.1039/D1RA07738D.].

Application of 3D magnetic nanocomposites: MXene-supported Fe3O4@CS nanospheres for highly efficient adsorption and separation of dyes.

Due to the presence of several hydroxyl and amino groups on the surface, chitosan (CS) has been reported to be a potential candidate to solve the pollution caused by dyes in different industrial wastewater. However, it is associated with the recycling issues. Nano-Fe3O4 has the advantages of easy magnetic separation and surface functionalization, which can improve the efficiency as well as selectivity of separation. However, its tendency for agglomeration can reduce the adsorption capacity. MXene can provide suitable support for both CS and Fe3O4 to construct new MXene@Fe3O4@CS composites. In this study, MXene@Fe3O4@CSmagnetic nanosphere was synthesized by ultrasonic self-assembly to remove Congo red (CR). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared (FT-IR) spectroscopy were employed to characterize the nanocomposites. According to the batch experiments, the adsorption kinetics were found to predominantly follow quasi-secondary rate kinetics. The adsorption followed Langmuir isotherm model. The adsorption process was found to be endothermic, entropy-driven, and thermodynamically spontaneous process. The adsorption capacity for CR was estimated as 620.22 mg·g-1.

User Control of Personal mHealth Data Using a Mobile Blockchain App: Design Science Perspective.

BACKGROUND: Integrating pervasive computing with blockchain's ability to store privacy-protected mobile health (mHealth) data while providing Health Insurance Portability and Accountability Act (HIPAA) compliance is a challenge. Patients use a multitude of devices, apps, and services to collect and store mHealth data. We present the design of an internet of things (IoT)-based configurable blockchain with different mHealth apps on iOS and Android, which collect the same user's data. We discuss the advantages of using such a blockchain architecture and demonstrate 2 things: the ease with which users can retain full control of their pervasive mHealth data and the ease with which HIPAA compliance can be accomplished by providers who choose to access user data. OBJECTIVE: The purpose of this paper is to design, evaluate, and test IoT-based mHealth data using wearable devices and an efficient, configurable blockchain, which has been designed and implemented from the first principles to store such data. The purpose of this paper is also to demonstrate the privacy-preserving and HIPAA-compliant nature of pervasive computing-based personalized health care systems that provide users with total control of their own data. METHODS: This paper followed the methodical design science approach adapted in information systems, wherein we evaluated prior designs, proposed enhancements with a blockchain design pattern published by the same authors, and used the design to support IoT transactions. We prototyped both the blockchain and IoT-based mHealth apps in different devices and tested all use cases that formed the design goals for such a system. Specifically, we validated the design goals for our system using the HIPAA checklist for businesses and proved the compliance of our architecture for mHealth data on pervasive computing devices. RESULTS: Blockchain-based personalized health care systems provide several advantages over traditional systems. They provide and support extreme privacy protection, provide the ability to share personalized data and delete data upon request, and support the ability to analyze such data. CONCLUSIONS: We conclude that blockchains, specifically the consensus, hasher, storer, miner architecture presented in this paper, with configurable modules and software as a service model, provide many advantages for patients using pervasive devices that store mHealth data on the blockchain. Among them is the ability to store, retrieve, and modify ones generated health care data with a single private key across devices. These data are transparent, stored perennially, and provide patients with privacy and pseudoanonymity, in addition to very strong encryption for data access. Firms and device manufacturers would benefit from such an approach wherein they relinquish user data control while giving users the ability to select and offer their own mHealth data on data marketplaces. We show that such an architecture complies with the stringent requirements of HIPAA for patient data access.

Application of hybrid MOF composite in extraction of f-block elements: Experimental and computational investigation.

An attempt was made to understand the sorption behaviour of UO22+, Th4+ and Eu3+ on novel hybrid metal-organic framework composites, FeBDC@CoBDC. The XRD pattern revealed the composite nature of the hybrid MOF materials, while FTIR and Raman spectroscopic analyses evidenced the presence of different functional moieties. The thermal stability of the hybrid MOF composites was investigated through thermogravimetric analysis. The sorption predominantly followed Langmuir isotherm with sorption capacity of 189 mg g-1, 224 mg g-1 and 205 mg g-1 for UO22+, Th4+ and Eu3+ respectively. The sorption proceeded through chemisorption following pseudo 2nd order rate kinetics. The processes were found to be thermodynamically favourable and endothermic in nature. However, they were entropically driven. Multiple contacts of complexing agents were necessary for quantitative elution of f-elements from loaded MOF. The MOF showed moderate stability towards radiation exposure. DFT calculation was used for the optimization of structures, estimation of bond length and estimation of binding energy. In hybrid MOF composites, the Fe atom was having six coordination with 4 O atoms of BDC moieties and 2 O atoms of -OH groups. The O atoms of BDC and -OH groups were coordinated to Eu, Th and U atoms during their sorption.

Novel Poly(ionic liquid) Augmented Membranes for Unconventional Aqueous Phase Applications in Fractionation of Dyes and Sugar.

Poly(ionic) liquid (PIL) augmented membranes were fabricated through self-polymerization of 2-vinyl pyridine and 4-vinyl pyridine followed by dopamine triggered polymerization and bridging with inert polyamide support. The resulting membranes acquired a positive surface charge with a high degree of hydrophilicity. Fourier transformed Infra-red (FTIR) and Energy dispersive X-ray (EDX) spectroscopic investigation revealed the successful augmentation of PIL surface layer, whereas surface morphology was investigated through scanning electron microscopy (SEM) imaging. This manuscript demonstrates pi electron-induced separation of dyes with the trend in permeability: Coomassie Brilliant Blue G (CBBHG) > Remazol Brilliant Blue R (RBBR) > Eichrome Black T (EBT) > Congo Red (CR). CBBG exhibited extended conjugation over large aromatic domain. RBBR and EBT were associated withtheelectron-donating -NH2 group and electron-withdrawing -NO2 group, respectively, hence pi electron density on aromatic ring varied. The steric repulsion between two pairs of ortho hydrogens (Hs) in biphenyl moieties of CR resulted in deviation of planarity and hence aromaticity leading to the lowest permeability. The sugar fractionation followed the trend: Galactose > Mannose > Fructose > Glucose > Xylose. More hydroxyl (-OH) groups in sugars and their conformational alignment in the same direction, exhibited more lone pair of electrons leading to more interaction with PIL and hence better permeability. Pentose showed poorer permeation than hexose, whereas aldose showed better permeation than ketose.

Remote Performance Modulation of Ultrafiltration Membranes by Magnetically and Thermally Responsive Polymer Chains.

Ultrafiltration membranes, that respond to an external magnetic field and local temperature have been developed. Surface-initiated activator-generated electron transfer (AGET) atom transfer radical polymerization (ATRP) has been used to graft poly(N-isopropylacrylamide) (PNIPAm) from the surface of 300 kDa regenerated cellulose membranes. The polymerization initiator was selectively attached to the entire membrane surface, only the outer membrane surface or only the inner pore surface. A superparamagnetic nanoparticle was attached to the end of the polymer chain. The DI water flux as well as the flux and rejection of bovine serum albumin were investigated in the absence and presence of a 20 and 1000 Hz oscillating magnetic field. In an oscillating magnetic field, the tethered superparamagnetic nanoparticles can cause movement of the PNIPAm chains or induce heating. A 20 Hz magnetic field maximizes movement of the chains. A 1000 Hz magnetic field leads to greater induced heating. PNIPAm displays a lower critical solution temperature at 32 °C. Heating leads to collapse of the PNIPAm chains above their Lower Critical Solution Temperature (LCST). This work highlights the versatility of selectively grafting polymer chains containing a superparamagnetic nanoparticle from specific membrane locations. Depending on the frequency of the oscillating external magnetic field, membrane properties may be tuned.

Application of Zwitterions in Forward Osmosis: A Short Review.

Forward osmosis (FO) is an important desalination method to produce potable water. It was also used to treat different wastewater streams, including industrial as well as municipal wastewater. Though FO is environmentally benign, energy intensive, and highly efficient; it still suffers from four types of fouling namely: organic fouling, inorganic scaling, biofouling and colloidal fouling or a combination of these types of fouling. Membrane fouling may require simple shear force and physical cleaning for sufficient recovery of membrane performance. Severe fouling may need chemical cleaning, especially when a slimy biofilm or severe microbial colony is formed. Modification of FO membrane through introducing zwitterionic moieties on the membrane surface has been proven to enhance antifouling property. In addition, it could also significantly improve the separation efficiency and longevity of the membrane. Zwitterion moieties can also incorporate in draw solution as electrolytes in FO process. It could be in a form of a monomer or a polymer. Hence, this review comprehensively discussed several methods of inclusion of zwitterionic moieties in FO membrane. These methods include atom transfer radical polymerization (ATRP); second interfacial polymerization (SIP); coating and in situ formation. Furthermore, an attempt was made to understand the mechanism of improvement in FO performance by zwitterionic moieties. Finally, the future prospective of the application of zwitterions in FO has been discussed.

Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review.

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.