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Contamination of groundwater by monovalent anions, for instance, fluoride (F-) and nitrite (NO2-), leaves an adverse impact on human health. This study aims at investigating the feasibility of the application of membrane capacitive deionization (MCDI) combined with a monovalent anion permselective exchange membrane (PSM) for the removal of fluoride from water. In this study, various parameters (anion composition and concentration, pH, operating voltage, flow rate, and time) were studied for the purpose of attaining the maximum selectivity. Evaluation of the selectivity for monovalent anions was performed with the help of a lab-made MCDI with a model aqueous system (F-/SO42-). As revealed by the empirical findings, the removal of both F- and SO42- anions increased with the increase in anion concentration and pH, in addition to the increase in the selectivity for monovalent anions (F-). The removal of anions and selectivity also exhibited an increase with flow rate and operating time. Contrarily, the selectivity declined with the applied voltage. A monovalent anion selectivity of 1.43 was obtained subjected to the conditions of 1.0 V operating voltage, together with 10 min adsorption time and 30 mL/min feed flow rate. The results in this study are capable of helping develop the PSMCDI (permselective exchange membrane capacitive deionization) technology and expand its application for the removal of fluoride from drinking water. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are a class of anionic clay materials. When calcined at a certain temperature range, LDHs decompose into corresponding mixed metal oxides (Ox), which are regarded as promising electrode materials for capacitive deionization (CDI). We have developed a simple yet efficient strategy for in situ assembly of the MgAl-Ox nanosheets on graphene (G). The as-obtained MgAl-Ox/G nanohybrids with numerous channels for the access of anion exhibited high surface area and high electrical conductivity. When used as the anode of CDI cell, MgAl-Ox/G nanohybrids exhibited excellent cycling stability and high electrosorption capacity due to its the memory effect and oxidation resistant property. [ABSTRACT FROM AUTHOR]

An experimental investigation is carried out to study the characteristics of flow boiling oscillation in a vertical minichannel with an inner diameter of 2.15 mm. The working fluid is deionized water at a constant system pressure of 0.101 MPa. The characteristics of flow oscillation with different working conditions are analyzed in this paper. With other constant working conditions, it is found that the oscillation periods of the pressure drop and the wall temperature decrease when the inlet subcooling decreases, while the fluctuation amplitude of pressure drop oscillations changes a little. The effects of heat flux and mass flux on the flow boiling oscillation are discussed with the equilibrium vapor quality (xe). Meanwhile, the xe which is at the onset of flow oscillation is affected by the mass flux. Finally, a new model which is based on the flow instability ratio (FIR) is proposed to predict the onset of boiling a two-phase flow oscillation, and a good agreement is achieved when comparing with the experimental results. [ABSTRACT FROM AUTHOR]

The structure and properties of poly(tert-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-tert-butylstyrene) (tBS-HI-SS-HI-tBS) films were investigated as a function of "wet-dry cycles", where one "cycle" is defined as a 24 h soak in deionized water followed by a 24 h drying period in air. Films were characterized with a variety of complementary measurements that include X-ray scattering, infrared spectroscopy, water uptake, impedance spectroscopy, and tensile tests. We find that cycling drives a structural transition toward increasingly interconnected SS domains, which is favorable for water and ion transport. However, cycling can also induce mechanical deformations that reduce ductility, swelling, and water uptake. The significance of this trade-off is illustrated by comparing the properties for two film thicknesses as a function of cycle number: The ductility of thinner films (15 µm) is lost after four cycles, an effect that is correlated with the appearance of macroscale buckles, and the extent of swelling is also reduced. Therefore, the transport properties reflect a balance between the increased SS domain interactions and reduced water content. The ductility in thick films (30 µm) also declines with cycling, but to a lesser extent, and these systems retain their ability to swell through six cycles. Therefore, the transition to a network-like SS structure enhances both water uptake and transport. These systematic studies demonstrate that successive wet-dry cycles can lead to complex changes in the performance of amphiphilic block copolymer films, which may complicate their design for applications in water treatment or proton-conducting layers in electrochemical devices. [ABSTRACT FROM AUTHOR]

Soft matter-directed self-assembly of amphiphilic inorganic nanoparticles (NPs) has recently emerged as a promising approach to access NP ensembles with superior collective properties. While thiol-terminated molecules are primarily employed to tether the amphiphilic ligand to the metal, concerns remain regarding the stabilities of the resulting NPs and their corresponding aggregates. As an alternative, we report amphiphilic N-heterocyclic carbene (NHC)-functionalized gold nanoparticles (AuNPs). To accomplish this, an amphiphilic NHC-AuI complex based on an asymmetric triethylene glycol-/dodecyl-functionalized benzimidazole was first synthesized and used to prepare the corresponding stable amphiphilic NHC-decorated AuNPs. The resulting NPs were comprehensively characterized using both solution- and solid-state-based techniques such as proton nuclear magnetic resonance spectroscopy, dynamic light scattering, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. By optimizing the self-assembly behavior of these amphiphilic AuNPs in deionized water, ethanol, and their mixtures, we were able to fine-tune the plasmonic properties of the AuNPs in the wide range of 525-640 nm. Furthermore, when treated with thiols, the ensembles showed greater stability compared to their parent discrete AuNP counterparts at room temperature. [ABSTRACT FROM AUTHOR]

Hierarchically porous carbon (HPC) materials with interconnected porous texture are produced from a porous poly(divinylbenzene) precursor, which is synthesized by polymerizing high-internal-phase emulsions. After carbonation, the macroporous structures of the poly(divinylbenzene) precursor are preserved and enormous micro-/mesopores via carbonation with KOH are produced, resulting in an interconnected hierarchically porous network. The prepared HPC has a maximum specific surface area of 2189 m2 g-1. The electrode materials for supercapacitors and capacitive deionization devices employing the formed HPC exhibit a high specific capacity of 88 mA h g-1 through a voltage range of 1 V (319 F g-1 at 1 A g-1) and a superior electrosorption capacity of 21.3 mg g-1 in 500 mg L-1 NaCl solution. The excellent capacitive performance could be ascribed to the combination of high specific surface area and favorable hierarchically porous structure. [ABSTRACT FROM AUTHOR]

Aquaporin proteins are of great interest to the membrane science community because of their unique characteristics of high water permeability and perfect molecular selectivity. Although these characteristics make aquaporins particularly valuable for desalination applications, none of these aquaporin-based membrane designs has been produced at a large scale. In this work, we report on the recently designed and commercially available Aquaporin Inside flat-sheet membrane designed for forward osmosis (FO) by Aquaporin A/S, Lyngby, Denmark. The Aquaporin Inside flat-sheet membrane is the first commercially available thin-film composite (TFC) FO membrane to incorporate aquaporin proteins into its polyamide-based selective layer. The membrane tested, which is a first-generation membrane, achieved water fluxes of 14.0 and 8.8 L m-2 h-1 with low reverse salt fluxes of 4.6 and 4.0 g m-2 h-1 in pressure-retarded osmosis (PRO) and FO modes, respectively, using 1.0 M sodium chloride as the draw solution and deionized water as the feed solution. The membrane structural parameter was calculated to be 630 μm, which is similar to those of existing commercial membrane options for FO. The Aquaporin Inside membrane was found to exhibit water and reverse solute flux performances similar to those of other commercially available varieties, although this membrane represents one of the few TFC membranes that is available to the academic community for FO testing at the time of this writing. [ABSTRACT FROM AUTHOR]

Graphene nanomaterials have many diverse applications, but are considered to be emerging environmental pollutants. Thus, their potential environmental risks and biosafety are receiving increased attention. Bioaccumulation and toxicity evaluations in plants are essential for biosafety assessment. In this study, 13C-stable isotope labeling of the carbon skeleton of graphene oxide (GO) was applied to investigate the bioaccumulation and toxicity of GO in wheat. Bioaccumulation of GO was accurately quantified according to the 13C/12C ratio. Wheat seedlings were exposed to 13C-labeled GO at 1.0 mg/mL in nutrient solution for 15 d. 13C-GO accumulated predominantly in the root with a content of 112 μg/g at day 15, hindered the development and growth of wheat plants, disrupted root structure and cellular ultrastructure, and promoted oxidative stress. The GO that accumulated in the root showed extremely limited translocation to the stem and leaves. During the experimental period, GO was excreted slowly from the root. GO inhibited the germination of wheat seeds at high concentrations (≥0.4 mg/mL). The mechanism of GO toxicity to wheat may be associated with oxidative stress induced by GO bioaccumulation, reflected by the changes of malondialdehyde concentration, catalase activity, and peroxidase activity. The results demonstrate that 13C labeling is a promising method to investigate environmental impacts and fates of carbon nanomaterials in biological systems. [ABSTRACT FROM AUTHOR]

Inspired by the homogeneous catalyst tris(pentafluorophenyl) borane [B(C6F5)3], which acts as a promotor of Si-H bond activation, we developed and studied a method of modifying silicon oxide surfaces using hydrosilanes with B(C6F5)3 as the catalyst. This dedihydrosiloxanation reaction yields complete surface coverage within 10 min at room temperature. Organic monolayers derived from hydrosilanes with varying carbon chain lengths (C8-C18) were prepared on oxidized Si(111) surfaces, and the thermal and hydrolytic stabilities of the obtained monolayers were investigated in acidic (pH 3) medium, basic (pH 11) medium, phosphate-buffered saline (PBS), and deionized water (neutral conditions) for up to 30 days. DFT calculations were carried out to gain insight into the mechanism, and the computational results support a mechanism involving silane activation with B(C6F5)3. This catalyzed reaction path proceeds through a low-barrier-height transition state compared to the noncatalyzed reaction path. [ABSTRACT FROM AUTHOR]

An innovative flow electrode comprising redox-active quinones to enhance the effectiveness of water desalination using flow-electrode capacitive deionization (FCDI) is described in this study. The results show that, in addition to carbon particle contact, the presence of the aqueous hydroquinone (H2Q)/benzoquinone (Q) couple in a flowing suspension of carbon particles enhances charge transfer significantly as a result of reversible redox reactions of H2Q/Q. Ion migration through the micropores of the flow electrodes was facilitated in particular with the desalination rate significantly enhanced. The cycling behavior of the quinoid mediators in the anode flow electrode demonstrated a relatively high stability at the low pH induced, suggesting that the mediator would be suitable for long-term operation. [ABSTRACT FROM AUTHOR]

In this study, the structure of nanoconfined ice and its behavior during the melting process have been investigated. For this purpose, deionized water was inserted into the pores of the ordered carbon structures CMK-3 and CMK-8 having pores of different diameters. The first set of experiments was performed using differential scanning calorimetry (DSC), from which the melting transition temperature of the confined ice was determined. In order to investigate the structure of ice formed inside the mesopores, wide-angle X-ray scattering was used. The measurements were performed at temperatures from 173 K up to and above the pore melting point for each system. The results of the XRD experiments showed features characteristic of both hexagonal, Ih, and cubic, Ic, ice at temperatures below the melting point. The structure of the confined ice corresponds to disordered stacking ice layers, ice Isd, and our results agree well with recent simulations of X-ray diffraction of such ice crystals by Murray and co-workers. [ABSTRACT FROM AUTHOR]

Charging capacitive deionization (CDI) at constant voltage (CV) produces an effluent stream in which ion concentrations vary with time. Compared to CV, charging CDI at constant current (CC) has several advantages, particularly a stable and adjustable effluent ion concentration. In this work, the feasibility of removing fluoride from brackish groundwaters by single-pass constant-current (SPCC) CDI in both zero-volt and reverse-current desorption modes was investigated and a model developed to describe the selective electrosorption of fluoride and chloride. It was found that chloride is preferentially removed from the bulk solution during charging. Both experimental and theoretical results are presented showing effects of operating parameters, including adsorption/desorption current, pump flow rate and fluoride/chloride feed concentrations, on the effluent fluoride concentration, average fluoride adsorption rate and water recovery. Effects of design parameters are also discussed using the validated model. Finally, we describe a possible CDI assembly in which, under appropriate conditions, fluoride water quality targets can be met. The model developed here adequately describes the experimental results obtained and shows how change in the selected system design and operating conditions may impact treated water quality. [ABSTRACT FROM AUTHOR]

The evaporation behavior of toluene and hexane lenses on the surface of deionized (DI) water is studied. The toluene and hexane lenses during evaporation experience an advancing stage and a receding stage. There exists a significant difference of the evaporation behavior between the toluene lenses and the hexane lenses. The lifetime and largest diameter of both the toluene and hexane lenses increase with increasing the initial volume of the lenses. For the evaporation of the toluene lenses, the lifetime and largest diameter of the lenses decrease with increasing the temperature of DI water. The effect of the residual of the oil molecules on the evaporation of toluene lenses at a temperature of 21 °C is investigated via the evaporation of a series of consecutive toluene lenses being placed on the same position of the surface of DI water. The temporal evolution of the toluene lenses placed after the first toluene lens deviates significantly from that of the first toluene lens. Significant increase of the receding speed occurs at the dimensionless time in a range 0.7-0.8. [ABSTRACT FROM AUTHOR]

In order for capacitive deionization (CDI) as a water treatment technology to achieve commercial success, substantial improvements in the operational aspects of the system should be improved in order to efficiently recover the energy stored during the deionization step. In the present work, to increase the energy efficiency of the adsorption-desorption processes, we propose a new operational procedure that utilizes a concentrated brine stream as a washing solution during regeneration. Using this approach, we demonstrate that by replacing the electrolyte during regeneration for a solution with higher conductivity, it is possible to substantially increase round-trip energy efficiency. This procedure was experimentally verified in a flow cell reactor using a pair of carbon electrodes (10² cm geometric area) and NaCl solutions having concentrations between 50 and 350 mmol·L-1. According to experimental data, this new operational mode allows for a better utilization of the three-dimensional structure of the porous material. This increases the energetic efficiency of the global CDI process to above 80% when deionization/regeneration currents ratio are optimized for brackish water treatment. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) is novel capacitive deionization (CDI) technology that exhibits continuous deionization and a high desalting efficiency. A flow-electrode with high capacitance and low resistance is required for achieving an efficient FCDI system with low energy consumption. For developing high-performance flow-electrode, studies should be conducted considering porous materials, conductive additives, and electrolytes constituting the flow-electrode. Here, we evaluated the desalting performances of flow-electrodes with spherical activated carbon and aqueous electrolytes containing various concentrations of NaCl in the FCDI unit cell for confirming the effect of salt concentration on the electrolyte of a flow-electrode on desalting efficiency. We verified the necessity of a moderate amount of salt in the flow-electrode for compensating for the reduction in the performance of the flow-electrode, attributed to the resistance of water used as the electrolyte. Simultaneously, we confirmed the potential use of salt water with a high salt concentration, such as seawater, as an aqueous electrolyte for the flow-electrode. [ABSTRACT FROM AUTHOR]

Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which are anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm-1 at 20 °C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport. [ABSTRACT FROM AUTHOR]

Elevated arsenic (As) in aquifers in close proximity to in situ oil sands extraction in the Cold Lake area, Alberta, Canada is attributed to high temperature steam (~200 °C) injected into oil sands deposits to liquefy bitumen. Heat propagated from hot injection wells alters physicochemical properties of the surrounding sediments and associated porewater. Seven sediments from four different cores drilled up to ~300 m depth collected from different locations in the area were used to study the thermal effect (~200 °C) on As distribution in the sediments and its release into porewater. Sediments were moistened with synthetic aquifer or deionized water according to the moisture regimes present in aquitard, aquifer and fractured zones. Heat application greatly released As in the porewater (500--5200 and 1200--6600 μg L-1) from aquifer and fractured sediments, respectively. Mass balance of As chemical fractionation showed that ~89--100% of As in porewater was released from exchangeable and specifically adsorbed As in the sediments. Heat application also altered As distribution in the sediments releasing As from exchange surfaces and amorphous Fe oxides to soluble As fraction. 'The results provide great insight into As release mechanisms warranting development of strategies to mitigate groundwater As contamination during industrial operation. [ABSTRACT FROM AUTHOR]

Understanding the dopant properties in heavily doped nanoscale semiconductors is essential to design nanoscale devices. We report the deionization or finite ionization energy of dopants in silicon (Si) nanofilms with dopant concentration (ND) of greater than 1019 cm-3, which is in contrast to the zero ionization energy (ED) in bulk Si at the same ND. From the comparison of experimentally observed and theoretically calculated ED, we attribute the deionization to the suppression of metal-insulator transition in highly doped nanoscale semiconductors in addition to the quantum confinement and the dielectric mismatch, which greatly increase ED in low-doped nanoscale semiconductors. Thus, for nanoscale transistors, ND should be higher than that estimated from bulk Si dopant properties in order to reduce their resistivity by the metal-insulator transition. [ABSTRACT FROM AUTHOR]

Removal of environmentally persistent perfluoroalkyl acids (PFAAs), that is, perfluorooctanesulfonate (PFOS) and perfluorocarboxylic acids (PFCAs, C4 ~ C10) were investigated through sorption on four metal hydroxide flocs generated in situ by electrocoagulation in deionized water with 10 mM NaCl as supporting electrolyte. The results indicated that the zinc hydroxide flocs yielded the highest removal efficiency with a wide range concentration of PFOA/PFOS (1.5 µM ~ 0.5 mM) at the zinc dosage <150 mg L-1 with the energy consumption <0.18 Wh L-1. The sorption kinetics indicated that the zinc hydroxide flocs had an equilibrium adsorbed amount (qe) up to 5.74/7.69 mmol g-1 (Zn) for PFOA/PFOS at the initial concentration of 0.5 mM with an initial sorption rate (v0) of 1.01 × 10³/1.81 × 10³ mmol g-1 h-1. The sorption of PFOA/PFOS reached equilibrium within <10 min. The sorption mechanisms of PFAAs on the zinc hydroxide flocs were proposed based on the investigation of various driving forces. The results indicated that the hydrophobic interaction was primarily responsible for the PFAAs sorption. The electrocoagulation process with zinc anode may have a great potential for removing PFAAs from industrial wastewater as well as contaminated environmental waterbody. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising desalination technology, which operates at low pressure, low temperature, requires little infrastructure, and has the potential to consume less energy for brackish water desalination. However, CDI devices consume significantly more energy than the theoretical thermodynamic minimum, and this is at least partly due to resistive power dissipation. We here report our efforts to characterize electric resistances in a CDI system, with a focus on the resistance associated with the contact between current collectors and porous electrodes. We present an equivalent circuit model to describe resistive components in a CDI cell. We propose measurable figures of merit to characterize cell resistance. We also show that contact pressure between porous electrodes and current collectors can significantly reduce contact resistance. Lastly, we propose and test an alternative electrical contact configuration which uses a pore-filling conductive adhesive (silver epoxy) and achieves significant reductions in contact resistance. [ABSTRACT FROM AUTHOR]

A unit is developed for the continuous production of fluoride free water using an electrodeionization (EDI) process. The experiments are carried out with a laboratory-scale unit. The EDI process usually operates in two regimes of enhanced transfer and electroregeneration. The current efficiency decreased in the second regime of the EDI system because of water dissociation. The cation-exchange membrane (CEM) and anion-exchange membrane (AEM) used for the present study are converted from a styrene-divinylbenzene-based interpolymer film by sulfonation and chloromethylation, respectively. Methyl methacrylate-ethylene glycol dimethacrylate-based amphoteric resin synthesized by radical suspension polymerization shows a 4.57 mequiv/g ion-exchange capacity with 57% water uptake. Both the membranes and resins are characterized by the means of chemical and mechanical properties. The membranes and resins show very good electrochemical properties with excellent mechanical stability. The removal of fluoride from three concentrations of tap water streams revealed the significance of the water composition on the performance of the EDI unit with respect to the selectivity of fluoride removal and energy consumption. Three potentials (9, 12, and 15 V/cell pair) are applied in different sets of experiments during EDI, out of which 12 V/cell pair was found to be more efficient with a lower power consumption of 4.6 kwh/kg and 37% current efficiency. [ABSTRACT FROM AUTHOR]

Desalination of high-salinity solutionshas been studied usinga novel experimental technique and a theoretical model. Neutron imaginghas been employed to visualize lithium ions in mesoporous carbon materials,which are used as electrodes in capacitive deionization (CDI) forwater desalination. Experiments were conducted with a flow-throughCDI cell designed for neutron imaging and with lithium-6 chloride(6LiCl) as the electrolyte. Sequences of neutron imageshave been obtained at a relatively high concentration of 6LiCl solution to provide information on the transport of ions withinthe electrodes. A new model that computes the individual ionic concentrationprofiles inside mesoporous carbon electrodes has been used to simulatethe CDI process. Modifications have also been introduced into thesimulation model to calculate results at high electrolyte concentrations.Experimental data and simulation results provide insight into whyCDI is not effective for desalination of high ionic-strength solutions.The combination of experimental information, obtained through neutronimaging, with the theoretical model will help in the design of CDIdevices, which can improve the process for high ionic-strength solutions. [ABSTRACT FROM AUTHOR]

A new approach using a chromatography system equipped with isocratic pumps and an electrolytic eluent generator (EG) is introduced, replacing external pH gradient delivery using conventional gradient systems, in which bottled buffers with preadjusted pH are mixed using a gradient pump. The EG is capable of generating high purity base or acid required for online preparation of the buffer at the point of use, utilizing deionized water as the only carrier stream. Typically, the buffer was generated from online titration of a reagent composed of low molecular weight amines. The reagent was delivered isocratically into a static mixing tee, where it was titrated to the required pH with electrolytically generated base or acid. The required pH gradient was thus conveniently generated by electrically controlling the concentration of titrant. Also, since the pH was adjusted at the point of use, this approach offered enhanced throughput in terms of eluent preparation time and labor, and with a more reproducible pH profile. The performance of the system was demonstrated by running pH gradients ranging from pH 8.2 to 10.9 on a polymer monolith cation-exchange column for high throughput profiling of charge heterogeneity of intact, basic therapeutic monoclonal antibodies. A high degree of flexibility in modulating the key parameters of the pH gradient, including the buffer concentration, the pH gradient slope and the operating pH range was demonstrated. This enabled fine-tuning of the separation conditions for each individual antibody in order to enhance the chromatographic resolution. [ABSTRACT FROM AUTHOR]

Plasma, generated in liquid at atmosphericpressure by a nanosecondpulsed voltage, was used to fabricate hybrid structures from boronnitride nanotubes and gold nanoparticles in deionized water. The pHwas greatly reduced, conductivity was significantly increased, andconcentrations of reactive oxygen and nitrogen species in the waterwere increased by the plasma treatment. The treatment reduced thelength of the nanotubes, giving more individual cuplike structures,and introduced functional groups onto the surface. Gold nanoparticleswere successively assembled onto the functionalized surfaces. Thereactive species from the liquid plasma along with the nanosecondpulsed electric field seem to play a role in the shortening and functionalizationof the nanotubes and the assembly of gold nanoparticles. The potentialfor targeted drug delivery was tested in a preliminary investigationusing doxorubicin-loaded plasma-treated nanotubes which were effectiveat killing ∼99% of prostate cancer cells. [ABSTRACT FROM AUTHOR]

A series of six pharmaceuticals were degraded by continuous wave (CW) and pulsed wave (PW) ultrasound at 205 kHz using deionized water, wastewater effluent, and its isolated organic matter matrices. In deionized water, we observed that hydrophobicity is superior to diffusivity (Dw) for predicting degradation kinetics. Enhancements in degradation kinetics by the PW mode were greatest for the highest Dw (i.e., fluorouracil (5-FU)) and Kow (i.e., lovastatin (LOVS)) compounds, indicating that a pharmaceutical with either high diffusivity and low hydrophobicity or low diffusivity and high hydrophobicity benefits from additional time to populate the bubble--water interface during the silent cycle of PW ultrasound. Degradation of 5-FU and LOVS were inhibited by wastewater effluent to a greater extent than the other pharmaceuticals. In addition, a pulse enhancement (PE) for 5-FU and LOVS was not present in wastewater effluent. Irradiating 5-FU and LOVS in hydrophobic (HPO), transphilic (TPI), and hydrophilic (HPI) fractions of effluent organic matter (EfOM) showed that the TPI fraction reduced the PE the most, followed by the HPI and HPO fractions. The smaller size of the TPI over the HPO fraction and higher hydrophobicity of TPI over HPI implicate both size and hydrophobicity of EfOM in hindering degradation of pharmaceuticals. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging water desalination technique. In CDI, pairs of porous electrode capacitors are electrically charged to remove salt from brackish water present between the electrodes. We here present a novel experimental technique allowing measurement of spatially and temporally resolved salt concentration between the CDI electrodes. Our technique measures the local fluorescence intensity of a neutrally charged fluorescent probe which is collisionally quenched by chloride ions. To our knowledge, our system is the first to measure in situ and spatially resolved chloride concentration in a laboratory CDI cell. We here demonstrate good agreement between our dynamic measurements of salt concentration in a charging, millimeter-scale CDI system to the results of a modified Donnan porous electrode transport model. Further, we utilize our dynamic measurements to demonstrate that salt removal between our charging CDI electrodes occurs on a longer time scale than the capacitive charging time scales of our CDI cell. Compared to typical measurements of CDI system performance (namely, measurements of outflow ionic conductivity), our technique can enable more advanced and better-controlled studies of ion transport in CDI systems, which can potentially catalyze future performance improvements. [ABSTRACT FROM AUTHOR]

Negatively charged DNA can form extremely stable complexes with positively charged ions. These counterions are very difficult to remove from DNA; therefore, little is known about DNA behavior in their deficiency. We investigated whether removal of counterions from the strongly bound counterion layer would elicit any novel DNA properties or behaviors. In order to remove the tightly bound counterions, we used dialysis against deionized water in the presence of a strong (0.6 kV/cm) electric field. The electric field promoted the dissociation of the DNA-counterion complexes, while dialysis facilitated irreversible partitioning of counterions and DNA. Counterintuitively, when deprived of counterions, DNA precipitated from the solution into amorphous aggregates. The aggregates remained stable even when the electric field was turned off but readily redissolved when counterions were reintroduced. The phenomenon is likely explained by attraction of like-charged DNA polyions due to entropic-stabilization of condensed counterion layers. [ABSTRACT FROM AUTHOR]

Understanding the fate and transport of engineered nanoparticles (ENPs) in subsurface environments is required for developing the best strategy for waste management and disposal of these materials. In this study, the deposition and release of quantum dot (QD) nanoparticles were studied in saturated sand columns. The QDs were first deposited in columns using 100 mM NaCl or 2 mM CaC12 solutions. Deposited QDs were then contacted with deionized (DI) water and/or varying Na+ concentrations to induce release. QDs deposited in 100 mM Na+ were easily reversible when the column was rinsed with DI water. Conversely, QDs deposited in the presence of Ca2+ exhibited resistance to release with DI water. However, significant release occurred when the columns were flushed with NaCl solutions. This release behavior was explained by cation exchange (Ca2+ in exchange sites were replaced by Na+) which resulted in the breakdown of calcium bridging. We also studied the effect of aging time on the QD release. As the aging time increased, smaller amounts of QDs were released following cation exchange. However, deposited QDs were subsequently released when the column was flushed with DI water. The release behavior was modeled using a single first-order kinetic release process and changes in the maximum solid phase concentration of deposited QDs with transition in solution chemistry. The results of this study demonstrate that the presence of carboxyl groups on ENPs and divalent ions in the solution plays a key role in controlling ENP mobility in the subsurface environment. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a rapidly emerging desalination technology that promises to deliver clean water while storing energy in the electrical double layer (EDL) near a charged surface in a capacitive format. Whereas most research in this subject area has been devoted to using CDI for removing salts, little attention has been paid to the energy storage aspect of the technology. However, it is energy storage that would allow this technology to compete with other desalination processes if this energy could be stored and reused efficiently. This requires that the operational aspects of CDI be optimized with respect to energy used both during the removal of ions as well as during the regeneration cycle. This translates into the fact that currents applied during deionization (charging the EDL) will be different from those used in regeneration (discharge). This paper provides a mechanistic analysis of CDI in terms of energy consumption and energy efficiencies during the charging and discharging of the system under several scenarios. In a previous study, we proposed an operational buffer mode in which an effective separation of deionization and regeneration steps would allow one to better define the energy balance of this CDI process. This paper reports on using this concept, for optimizing energy efficiency, as well as to improve upon the electro-adsorption of ions and system lifetime. Results obtained indicate that real-world operational modes of running CDI systems promote the development of new and unexpected behavior not previously found, mainly associated with the inhomogeneous distribution of ions across the structure of the electrodes. [ABSTRACT FROM AUTHOR]

Orderedmorphologies in disulfonated poly(arylene sulfide sulfonenitrile) (SPSN) copolymers were generated via thermal annealing followedby multiblock copolymer synthesis. While SPSN random copolymers (R-SPSN)showed featureless morphologies, the SPSN multiblock copolymers (B-SPSN)exhibited cocontinuous lamellar morphologies with a center-to-centerinterdomain size of up to 40 nm. In spite of the well-ordered, interconnectedhydrophilic domains, the water self-diffusion coefficient (e.g., D= (0.7–2.0) × 10–10m2s–1) and proton conductivity (e.g., σ= 0.16–0.20 S cm–1in deionized water at30 °C) through B-SPSN were lower than those of the correspondingR-SPSN (e.g., D= (3.5–3.9) × 10–10m2s–1and σ= 0.21 S cm–1) due to the relatively lower wateruptake of the B-SPSN after thermal annealing. The reduced water uptakeof B-SPSN was beneficial to reduction of peroxide degradation rate.Thermal annealing produced significant gains in morphological orderingand finer control over desired membrane properties for proton conductionapplications. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) represents a new promising membrane technology for liquid separation driven by the osmotic pressure of aqueous solution. Organic polymeric FO membranes are subject to severe internal concentration polarization due to asymmetric membrane structure, and low stability due to inherent chemical composition. To address these limitations, this study focuses on the development of a new kind of thin-film inorganic (TFI) membrane made of microporous silica xerogels immobilized onto a stainless steel mesh (SSM) substrate. The FO performances of the TFI membrane were evaluated upon a lab-scale cell-type FO reactor using deionized water as feed solution and sodium chloride (NaCl) as draw solution. The results demonstrated that the TFI membrane could achieve transmembrane water flux of 60.3 L m-2 h-1 driven by 2.0 mol L-1 NaCl draw solution at ambient temperature. Meanwhile, its specific solute flux, i.e. the solute flux normalized by the water flux (0.19 g L-1), was 58.7% lower than that obained for a commercial cellulose triacetate (CTA) membrane (0.46 g L-1). The quasi-symmetry thin-film microporous structure of the silica membrane is responsible for low-level internal concentration polarization, and thus enhanced water flux during FO process. Moreover, the TFI membrne demonstrated a substantially improved stability in terms of mechanical strength, and resistance to thermal and chemical stimulation. This study not only provides a new method for fabricating quasi-symmetry thin-film inorganic silica membrane, but also suggests an effective strategy using this alternative membrane to achieve improved FO performances for scale-up applications. [ABSTRACT FROM AUTHOR]

Identical molecules move with identical velocities when placed in a uniform electric field within a uniform electrolyte. Here we report that homogeneous DNA does not obey this fundamental rule. While most DNA moves with similar velocities, a fraction of DNA moves with velocities that vary within a multiple-fold range. The size of this irregular fraction increases several orders of magnitude when exogenous counterions are added to DNA. The irregular fraction decreases several orders of magnitude when DNA counterions are removed by dialysis against deionized water in the presence of a strong electric field (0.6 kV/cm). Dialysis without the field is ineffective in decreasing the size of irregular fraction. These results suggest that (i) DNA can form very stable complexes with counterions, (ii) these complexes can be dissociated by an electric field, and (iii) the observed non-uniform velocity of DNA is caused by electric-field-induced slow dissociation of these stable complexes. Our findings help to better understand a fundamental property of DNA: its interaction with counterions. In addition, these findings suggest a practical way of making electromigration of DNA more uniform: removal of strongly bound DNA counterions by electro-dialysis against deionized water. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous carbon electrodes. In front of each electrode, an ion-exchange membrane is positioned, and between them, a spacer is situated, which transports the water to be desalinated. In this work, we demonstrate for the first time that up to 83% of the energy used for charging the electrodes during desalination can be recovered in the regeneration step. This can be achieved by charging and discharging the electrodes in a controlled manner by using constant current conditions. By implementing energy recovery as an integral part of the MCDI operation, the overall energy consumption can be as low as 0.26 (kW-h)/m3 of produced water to reduce the salinity by 10 mM, which means that MCDI is more energy efficient for treatment of brackish water than reverse osmosis. Nevertheless, the measured energy consumption is much higher than the thermodynamically calculated values for desalinating the water, and therefore, a further improvement in thermodynamic efficiency will be needed in the future. [ABSTRACT FROM AUTHOR]

The increasing demand for low-cost and high-efficient materials capable of solar energy generation is central in the development of a green energy economy. To this end, we propose a new and simple strategy to synthesize monodisperse cube-like single-crystal anatase TiO2 with high yield and no impurity. Using inexpensive ultra pure TiCl4 (>99.9%) as precursor, followed by deionized water washing or ion exchange procedure, the chloride ions can be removed and cube-like anatase TiO2 with high purity and narrow size distribution can be obtained after a solvothermal process. A high light-to-electricity conversion yield of 7.06% was achieved using the as-prepared TiO2 nanocrystals as the photoanode of dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (TAT) was produced by condensation of acetonitrile and trioxane as a low cost precursor for the production of 1,3,5,7-tetranitro-octahydro-1,3,5,7-tetrazocine (HMX). However, 1,3,5-triacetyl-hexahydro-s-triazine (TRAT) was also produced as a byproduct. To develop an efficient and economical method for the separation of TAT and TRAT, the solubilities of TAT and TRAT in ethyl acetate, methanol, acetonitrile and deionized water were investigated at temperatures between 298 K and 318 K. TAT was found to be relative insoluble in ethyl acetate with a maximum solubility of about 0.0295 mol/kg ethyl acetate at 318 K, which was an order of magnitude lower than that of TRAT (0.371 mol/kg ethyl acetate). TRAT was also relatively insoluble in water (0.712 mol/kg water). Accordingly, a method for the separation of TAT and TRAT based on recrystallization in ethyl acetate and precipitation by deionized water was developed. TAT was recrystallized from ethyl acetate with a purity of 97.9 %, and TRAT was recovered from the ethyl acetate filtrate by addition of water with a purity of 98.9 %. [ABSTRACT FROM AUTHOR]

We demonstrate a new procedure for separation of single-strandedDNA (ssDNA) fragments that are anchored to the surface of a gold electrodeby end hybridization. The new separation procedure takes advantageof the strong yet evolving nonuniform electric field near the goldsurface in contact with a buffer solution gradually being dilutedwith deionized water. Separation of short ssDNA fragments is demonstratedby monitoring the DNA at the gold surface with in situfluorescence measurement. The experimental results can be rationalizedwith a simple theoretical model of electric double layer that relatesthe strength of the surface pulling force to the ionic concentrationof the changing buffer solution. [ABSTRACT FROM AUTHOR]

Uranium is the main source for nuclear energy but also one of the most toxic heavy metals. The current methods for uranium removal from water present limitations, such as narrow pH operating range, limited tolerance to high salt concentrations, or/and high cost. We show here that a layered sulfide ion exchanger K2MnSn2S6 (KMS-1) overcomes these limitations and is exceptionally capable in selectively and rapidly sequestering high (ppm) as well as trace (ppb) quantities of UO22+ under a variety of conditions, including seawater. KMS-1 can efficiently absorb the naturally occurring U traces in seawater samples. The results presented here reveal the exceptional potential of sulfide-based ion-exchangers for remediating of uranium-containing wastes and groundwater and for extracting uranium from the sea. [ABSTRACT FROM AUTHOR]

A thermal-initiated polymerization procedure is describedfor thecontrolled preparation of monodispersed polyacrylamide (PAM) hydrogelmicrospheres. A coaxial microfluidic device was designed to disperseuniform drops (∼500 μm) of acrylamide monomer aqueoussolution into n-octane. Using a delay loop immersedinto a heat bath, the polymerization is initiated and carried outin separate droplets. Combining the improvement of heat transfer inthe microfluidic device and the sufficient addition of n-octane, the controllable preparation can still be achieved at 95°C, much higher than 20–60 °C as reported prevalently.Herein, the PAM microspheres can be prepared within 2 min or less,with the CV of diameter less than 4%. Furthermore, based on this controllablereaction platform, PAM microspheres were prepared at various reactiontemperatures (higher than 90 °C) and monomer solution compositionsto investigate the fundamental rules of controlling on their skeletonstructure and absorbent capacity in deionized water. [ABSTRACT FROM AUTHOR]

The kinetics and efficiencies of arsenite and arsenate removal from water were evaluated using polyaluminum granulates (PAG) with high content of aluminum nanoclusters. PAG was characterized to be meso- and macroporous, with a specific surface area of 35 ± 1 m2 g-1. Adsorption experiments were conducted at pH 7.5 in deionized water and synthetic water with composition of As-contaminated groundwater in the Pannonian Basin. As(III) and As(V) sorption was best described by the Freundlich and Langmuir isotherm, respectively, with a maximum As(V) uptake capacity of 200 μmol g-1 in synthetic water. While As(III) removal reached equilibrium within 40 h, As(V) was removed almost entirely within 20 h. Micro X-ray fluorescence and electron microscopy revealed that As(III) was distributed uniformly within the grain, whereas As(V) diffused up to 81 μm into PAG. The results imply that As(V) is adsorbed 3 times faster while being transported 105 times slower than As(III) in Al hydroxide materials. [ABSTRACT FROM AUTHOR]

The cholesterol-lowering pharmaceutical gemfibrozil is a relevant environmental contaminant because of its frequency of detection in U.S. wastewaters at concentrations which have been shown to disrupt endocrine function in aquatic species. The treatment of gemfibrozil solutions with sodium hypochlorite yielded a 4'-chlorinated gemfibrozil analog (chlorogemfibrozil). In the presence of bromide ion, as is often encountered in municipal wastewater, hypobromous acid generated through a halogen exchange reaction produced an additional 4'-brominated gemfibrozil product (bromogemfibrozil). Standards of chloro- and bromogemfibrozil were synthesized, isolated and characterized using mass spectrometry and NMR spectroscopy. Mass spectrometry was used to follow the in situ halogenation reaction of gemfibrozil in deionized water and wastewater matrices, and to measure levels of gemfibrozil (254 ± 20 ng/L), chlorogemfibrozil (166 ± 121 ng/L), and bromogemfibrozil (50 ± 11 ng/L) in advanced primary wastewater treatment effluent treated by chlorination. Chlorogemfibrozil demonstrated a significant (p < 0.05) reduction in the levels of 11-ketotestosterone at 55.1 μg/L and bromogemfibrozil demonstrated a significant (p < 0.05) reduction in the levels of testosterone at 58.8 μg/L in vivo in Japanese medaka in a 21 day exposure. These results indicated that aqueous exposure to halogenated degradates of gemfibrozil enhanced the antiandrogenicity of the parent compound in a model fish species, demonstrating that chlorination may increase the toxicity of pharmaceutically active compounds in surface water. [ABSTRACT FROM AUTHOR]

Genistein and daidzein are two estrogenic compounds derived from plants, especially legumes. This research begins to explore their environmental fate, focusing on direct and indirect photolysis. UV-visible spectra for both compounds at varying pH values were taken, the pKa values for both compounds were measured, and UV-visible spectra for each protonation state were determined. The loss of both compounds in deionized water was observed upon exposure to natural sunlight, and the quantum yields were determined for each protonation state. In Mississippi River water, direct photolysis does not account for all of the loss of genistein and daidzein. The mechanism of indirect photolysis was probed using quenchers and sensitizers, and results suggest that daidzein is transformed mainly via direct photolysis and singlet oxygenation, while genistein is transformed mainly via reaction with triplet-state natural organic matter. The parameters determined in this study will allow for estimation of the concentration of genistein and daidzein in sunlit surface waters, which will allow for assessment of any risks posed to aquatic wildlife. [ABSTRACT FROM AUTHOR]

A multispecies biofilm model is developed for simultaneous reduction of nitrate and perchlorate in the H2-based membrane biofilm reactor. The one-dimension model includes dual-substrate Monod kinetics for a steady-state biofilm with five solid and five dissolved components. The solid components are autotrophic denitrifying bacteria, autotrophic perchlorate-reducing bacteria, heterotrophic bacteria, inert biomass, and extracellular polymeric substances (EPS). The dissolved components are nitrate, perchlorate, hydrogen (H2), substrate-utilization-associated products, and biomass-associated products (BAP). The model explicitly considers four mechanisms involved in how three important operating conditions (H2 pressure, nitrate loading, and perchlorate loading) affect nitrate and perchlorate removals: (1) competition for H2, (2) promotion of PRB growth due to having two electron acceptors (nitrate and perchlorate), (3) competition between nitrate and perchlorate reduction for the same resources in the PRB: electrons and possibly reductase enzymes, and (4) competition for space in the biofilm. Two other special features are having H2 delivered from the membrane substratum and solving directly for steady state using a novel three-step approach: finite-difference for approximating partial differential and/or integral equations, Newton-Raphson for solving nonlinear equations, and an iterative scheme to obtain the steady-state biofilm thickness. An example result illustrates the model's features. [ABSTRACT FROM AUTHOR]

Based on continuous electrodeionization (CEDI) technology, a novel hybrid electrochemical acidification process has been developed to extract large quantities of CO2from seawater. This indirect approach acidifies seawater to recover CO2from bicarbonate. The electrolytic regeneration of cation exchange resin allowed simultaneous and continuous ion exchange and regeneration to occur within the cell along with control of the seawater pH. Lowering seawater pH was found to be proportional to the applied current to the cell, and the CO2in the acidified seawater was readily removed at pH less than 6.0. In addition, the cell produced a portion of hydrogen gas without additional energy penalties. [ABSTRACT FROM AUTHOR]

We report on the efficient removal of heavy metal ions from simulated wastewater with a nanostructured assembly. The nanoassembly was obtained via direct assembling the performed anisotropic layered double hydroxide nanocrystals (LDH-NCs) onto the surface of carbon nanospheres (labeled as LDH-NCs@CNs). It was found that the maximum adsorption capacity of the nanoassembly toward Cu2+ was ∼19.93 mg g-1 when the initial Cu2+ concentration was 10.0 mg L-1, displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Cu2+ removal was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared building unit of the assembly, including LDH-NCs, CNs, and the assembly, as well as Cu2+-adsorbed assembly, were carefully examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Cu2+ removal with the assembly of LDH-NCs@CNs was proposed. Comparison experiments show that the adsorption capacity of the resulting LDH-NCs@CNs assembly was much higher than its any building unit alone (CNs or LDH-NCs), exhibiting the deliberation of the assembly on water decontamination. This work provides a very efficient, fast and convenient approach for exploring promising nanoassembly materials for water treatment. [ABSTRACT FROM AUTHOR]

The aluminum Keggin polycation (Al13) has been identified as an effective specie for neutralization and coagulation of anionic contaminants in water. In this study, we compare efficacy of the aluminum Keggin-ion to the analogues containing a single Ga-atom or single Ge-atom (GaAl12 and GeAl12, respectively) substituted into the center of the polycation in water-treatment studies. We investigated removal of bacteriophage (model viruses), Cryptosporidium, dissolved organic carbon (DOC), and turbidity. In every study, the order of contaminant removal efficacy trends GaAl12 > Al13 > GeAl12. By ESI MS (electrospray ionization mass spectrometry), we noted the GaAl12 deprotonates least of the three aluminum polycations, and thus probably carries the highest charge, and also optimal contaminant-neutralization ability. The ESI MS studies of the aluminum polycation solutions, as well as solid-state characterization of their resulting precipitates both reveal some conversion of Al13 to larger polycations, Al30 for instance. The GaAl12 does not show any evidence for this alteration that is responsible for poor shelf life of commercial prehydrolyzed aluminum coagulants such as polyaluminum chloride. Based on these studies, we conclude that substitution of a single Ga-atom in the center of the aluminum Keggin polycation produces an optimal water-treatment product due to enhanced shelf life and efficacy in neutralization of anionic contaminants. [ABSTRACT FROM AUTHOR]

A new concept in speciation analysis based on the diffusive gradients in thin films (DGT) technique is described. By use of two sets of DGT devices, one set with perfluorosulfonated ionomer (Nafion) diffusive membranes and the other with polyacrylamide, anionic and uncharged analytes can be fractionated on the basis of charge. The dual device method is applied to speciation analysis of dissolved inorganic arsenic species. Over the environmentally significant pH range, inorganic As" exists as neutral H3AsO3, whereas Asv is present as anionic H2AsO4- and HAsO42-. The measured diffusion coefficient of AsIII Through the negatively charged Nafion membrane is significantly larger than that of the Asv species, whereas diffusion rates are similar through polyacrylamide diffusive gels. Hence, after simultaneously deploying DGT devices with and without Nafion membranes, measurement of the amount of accumulated As in each type of device enables the concentration of both oxidation states to be determined. [ABSTRACT FROM AUTHOR]

Evaluates a class of bifunctional anion-exchange resins with improved selectivity and sorption kinetics for removing pertechnetate from contaminated groundwater. Effectiveness in removal of low levels of TcO4-; Laboratory experiments with ammonium groups.

Presents an experimental data on a simple, low-cost vapor-sparging technique to detritiate water using the isotopic exchange process. Capitalization on isotopic disequilibrium between tritiated wastewater and a tritium free and water vapor feed stream; Monitoring of deuterium and oxygen-18.

A simple, qualitative demonstration of the vapor pressure lowering of aqueous solutions is presented. The demonstration consists of comparing two liquids, deionized water and a salt solution, in closed, glass containers. The difference in the degree of condensation inside of the two containers illustrates the difference in the vapor pressures of the two systems. [ABSTRACT FROM AUTHOR]

The article points to a smart, conservation-minded approach to synthesizing zeolites, materials that have applications, among others, in water purification. Dissolved water pollutants often have very unexpected origins. The molecular assemblies of aluminosilicates collectively known as zeolites have found applications as water purifiers through their ability to exchange ions contained in their inorganic structural framework and to absorb toxic solutes. This might in the future provide affordable means of water desalination or decontamination for developing countries and help to alleviate the looming global water crisis.