Flow-through Design Research Articles

Bioconcentration of Per- and Polyfluoroalkyl Substances and Precursors in Fathead Minnow Tissues Environmentally Exposed to Aqueous Film-Forming Foam-Contaminated Waters.

Exposure to per- and polyfluoroalkyl substances (PFAS) has been associated with toxicity in wildlife and negative health effects in humans. Decades of fire training activity at Joint Base Cape Cod (MA, USA) incorporated the use of aqueous film-forming foam (AFFF), which resulted in long-term PFAS contamination of sediments, groundwater, and hydrologically connected surface waters. To explore the bioconcentration potential of PFAS in complex environmental mixtures, a mobile laboratory was established to evaluate the bioconcentration of PFAS from AFFF-impacted groundwater by flow-through design. Fathead minnows (n = 24) were exposed to PFAS in groundwater over a 21-day period and tissue-specific PFAS burdens in liver, kidney, and gonad were derived at three different time points. The ∑PFAS concentrations in groundwater increased from approximately 10,000 ng/L at day 1 to 36,000 ng/L at day 21. The relative abundance of PFAS in liver, kidney, and gonad shifted temporally from majority perfluoroalkyl sulfonamides (FASAs) to perfluoroalkyl sulfonates (PFSAs). By day 21, mean ∑PFAS concentrations in tissues displayed a predominance in the order of liver > kidney > gonad. Generally, bioconcentration factors (BCFs) for FASAs, perfluoroalkyl carboxylates (PFCAs), and fluorotelomer sulfonates (FTS) increased with degree of fluorinated carbon chain length, but this was not evident for PFSAs. Perfluorooctane sulfonamide (FOSA) displayed the highest mean BCF (8700 L/kg) in day 21 kidney. Suspect screening results revealed the presence of several perfluoroalkyl sulfinate and FASA compounds present in groundwater and in liver for which pseudo-bioconcentration factors are also reported. The bioconcentration observed for precursor compounds and PFSA derivatives detected suggests alternative pathways for terminal PFAS exposure in aquatic wildlife and humans. Environ Toxicol Chem 2024;43:1795-1806. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

High permeation, biodegradable hydrogel based flow-through reactor for water disinfection with controlled silver release

Innovative disinfection strategies for clean water access demand manufacturing and operational simplicity, offering benefits for technology adoption. A hydrogel reactor composed of chitosan/graphene oxide/nano-Ag (CS/GO/Ag) achieves complete disinfection of real water resources contaminated with natural and biomedical contaminants, present concomitantly at higher contamination levels (104-106 CFU mL−1). The hydrogel exhibits remarkable mechanical stability and maintains shape without permanent deformation through dynamic swelling behaviour. Its open-ended, porous network allows rapid water permeation with tuneable hydrophilicity to maximize hydrogel-water interactions for disinfection. Hydrogel is reusable while achieving complete disinfection and maintains a controlled silver release (87.4 ppb, 0.07 % rate) within safety limits through restricted oxidative-dissolution of immobilized AgNPs. A distinct species-specific disinfection potential was observed for completely eradicating four natural/biomedical pathogens within 120 min. The CS/GO/Ag hydrogel employs a multifaceted mechanism to combat bacteria and appears virtually non-toxic to humans along with desirable soil biodegradability, promising safer and sustainable use. In continuous-flow, the hydrogel disinfected over 30 L of contaminated water (initial count, 105 CFU mL−1) without regeneration. A consistent disinfection performance across various natural water resources, easy flow-through design, and the suitability of Weibull model highlights CS/GO/Ag hydrogel’s potential for large-scale disinfection, effectively addressing water purification challenges.

Development of an open-source flow-through cyclic voltammetry cell for real-time inline reaction analytics

A low volume flow-through cyclic voltammetry cell design that can be readily constructed from commercial fluidic components enables rapid inline monitoring of redox active species.

Rapid desorption and analysis for illicit drugs and chemical profiling of fingerprints by SICRIT ion source.

Forensic analysis can encompass a wide variety of analytes from biological samples including DNA, blood, serum, and fingerprints to synthetic samples like drugs and explosives. In order to analyze this variety, there are various sample preparation techniques, which can be time-consuming and require multiple analytical instruments. With recent advancements in ambient ionization mass spectrometry (MS), plasma-based dielectric barrier discharge ionization (DBDI) sources have demonstrated to cover a wide range of these analytes. The flow-through design of this source also allows for easy connection to a thermal desorption type of sample introduction. We present an in-house built thermal desorption device where the sample is introduced via a glass slide, which gets heated and transferred to the DBDI-MS with nitrogen for identification and semi-quantification. Using a glass slide as an inexpensive sampling device, detection limits as low as 20 pg for fentanyl are demonstrated. Additionally, a very precise (>96% accuracy) identification of persons based on the chemical profile of their fingerprints is possible, establishing a direct analytical link of the drug trace to the individual in one measurement. We compared the DAG, TAG, sterol, and (semi-)volatile region of the averaged fingerprint spectra over multiple days, showing the best model accuracy for identification based on the DAG region. The combination of thermal desorption and DBDI-MS minimized sample preparation, leading to an ultrasensitive and rapid analysis of illicit drug traces and the identification of underlying personas based on fingerprints.

Development and Optimization of a Chamber System Applied to Maize Net Ecosystem Carbon Exchange Measurements

Net ecosystem carbon exchange (NEE) in agricultural land represents a significant source of global greenhouse gas (GHG) emissions. While there are various tools for measuring NEE in agricultural fields, the chamber method remains the sole tool at the plot scale. In this research, we evaluated the NEE of maize plants at the nodulation stage using the flow-through chamber method. Many existing flow-through chamber systems directly introduce gases, leading to collisions with plants and subsequent turbulence inside the chamber. Turbulence can extend the time required to achieve a steady state. We modified the traditional flow-through chamber design to minimize turbulence in the measurement zone. Our modifications were validated by modeling the chamber and maize plants and by conducting fluid simulation experiments. In the analysis of our comparative field measurements between the two chamber designs, the use of the improved system notably shortened the time required to reach the steady state, increased the measurement frequency, and reduced the influence of changing environmental factors on the readings. Enhancing the measurement frequency is crucial for ensuring long-term accuracy. By reducing turbulence in the chamber, we anticipate improvements in the precision of NEE measurements in agricultural research, which could significantly contribute to an accurate assessment of the global carbon cycle.

Faster bipolar capacitive deionization with flow-through electrodes

Capacitive deionization (CDI) is an emerging technology in water cleaning applications. Bipolar electrode modules are promising for upscaling CDI systems by applying a high voltage over a stack of cells. Previous experiments indicate around 3 times faster removal rate can be achieved with a 5-cell stack of flow-between electrodes. In this work, we present the first flow-through bipolar CDI design. Surprisingly, the effective average salt adsorption rate (ASAR) of a 5-cell stack was around 10 times higher per electrode mass. The flow-through design allows for faster ion transport to match the higher charging rate. Also, the floating electrodes discharge near-instantaneous by internal short-circuit upon the removal of potential, leaving almost twice as much time for charging in a cycle. Resistance is lowered due to the removal of internal compartments in the design, and the benefits of flow-through devices outweigh any potential higher energy cost of mass transport. The high voltage at the extreme electrodes poses a risk of electrode oxidation but optimized device operation controls this risk by constraining the voltage locally. For the same reason, the device is best adapted for the deionization of moderate to low ionic concentrations, such as river water, well water, or municipal water. In summary, this work provides a simpler yet highly effective way of scaling up CDI for water-cleaning applications.

A General Strategy to Synthesize Fluidic Single Atom Electrodes for Selective Reactive Oxygen Species Production.

Fine-tuning the geometric and electronic structure of catalytic metal centers via N-coordination engineering offers an effective design for the electrocatalytic transformation of O2 to singlet oxygen (1O2). Herein, we develop a general coordination modulation strategy to synthesize fluidic single-atom electrodes for selective electrocatalytic activation of O2 to 1O2. Using a single Cr atom system as an example, >98% 1O2 selectivity can be achieved from electrocatalytic O2 activation due to the subtle engineering of Cr-N4 sites. Both theoretical simulations and experimental results determined that "end-on" adsorption of O2 onto the Cr-N4 sites lowers the overall activation energy barrier of O2 and promotes the breakage of Cr-OOH bonds to form •OOH intermediates. In addition, the flow-through configuration (k = 0.097 min-1) endowed convection-enhanced mass transport and improved charge transfer imparted by spatial confinement within the lamellar electrode structure compared to that of batch reactor (k = 0.019 min-1). In a practical demonstration, the Cr-N4/MXene electrocatalytic system exhibits a high selectivity toward electron-rich micropollutants (e.g., sulfamethoxazole, bisphenol A, and sulfadimidine). The flow-through design of the fluidic electrode achieves a synergy with the molecular microenvironment that enables selective electrocatalytic 1O2 generation, which could be used in numerous ways, including the treatment of environmental pollution.

Mechanisms of interfacial catalysis and mass transfer in a flow-through electro-peroxone process

To investigate the catalytic mechanism and mass transfer efficiency in the removal of amitriptyline using an electro-peroxide process, a CuFe2O4-modified carbon cloth cathode was prepared and utilized in a reaction unit. The results demonstrated a remarkable efficacy of the system, achieving 91.0% amitriptyline removal, 68.3% mineralization, 41.2% mineralization current efficiency, and 0.24 kWh/m3 energy consumption within just five minutes of treatment. The study revealed that the exposed Fe atoms of the ferrite nanoparticles, with a size of 22.7 nm and 89.7% crystallinity, functioned as mediators to bind the adsorbed O atoms. The 3dxy, 3dxz, and 3d2z orbitals of Fe atoms interacted with the 2pz orbital of O atoms of H2O2 and O3 to form σ and π bonds, facilitating the adsorption-activation of H2O2 and O3 into hydroxyl radicals. These hydroxyl radicals (∼ 1.15 × 1013 mol/L) were distributed at the cathode-solution interface and rapidly consumed along the direction of liquid flow. The flow-through cathode design improved the mass transfer of aqueous O3 and in-situ generated H2O2, leading to an increased yield of hydroxyl radicals, as well as the contact time and space between hydroxyl radicals and amitriptyline. Ultimately, this resulted in a higher degradation efficiency of the system.

A gravity-independent single-phase electrode reservoir for capillary electrophoresis applications.

Capillary electrophoresis (CE) holds great promise as an in situ analytical technique for a variety of applications. However, typical instrumentation operates with open reservoirs (e.g., vials) to accommodate reagents and samples, which is problematic for automated instruments designed for space or underwater applications that may be operated in various orientations. Microgravity conditions add an additional challenge due to the unpredictable position of the headspace (air layer above the liquid) in any two-phase reservoir. One potential solution for these applications is to use a headspace-free, flow-through reservoir design that is sealed and connected to the necessary reagents and samples. Here we demonstrate a flow-through HV reservoir for capillary electrophoresis that is compatible with automated in situ exploration needs, and which can be electrically isolated from its source fluidics (in order to prevent unwanted leakage current). We also demonstrate how the overall system can be rationally designed based on the operational parameters for CE to prevent electrolysis products produced at the electrode from entering the capillary and interfering with the CE separation. A reservoir was demonstrated with a 19 mm long, 1.8 mm inner diameter channel connecting the separation capillary and the HV electrode. Tests of these reservoirs integrated into a CE system show reproducible CE system operation with a variety of background electrolytes at voltages up to 25 kV. Rotation of the reservoirs, and the system, showed that their performance was independent of the direction of the gravity vector. This article is protected by copyright. All rights reserved.

Investigation of the effect of different flow-through cell design on the release of prolonged release tablets

Investigation of the effect of different flow-through cell design on the release of prolonged release tablets

Atomic H*-mediated electrochemical removal of low concentration antimonite and recovery of antimony from water

Compounds containing antimony (Sb) are broadly used as starting materials for a wide range of industrial products, leading to serious water pollution associated with Sb rock mining as well as Sb leaching. Herein, we proposed an innovative design of an electrified membrane consisted of bimetallic palladium and iron nanoparticles (Pd-Fe NPs) supported on conductive carbon nanotube (CNT) networks. The nanohybrid filter enabled effective generation and retainment of atomic hydrogen (H*) under an electric field, which further contributed to the complete electroreduction of antimonite (Sb(III)). The highest atomic H* yield and Sb(III) removal kinetics were identified once a potential of −1.0 V vs. Ag/AgCl was exerted. Compared to the pristine CNT, Pd-CNT and Fe-CNT filters, the reaction rate constant of the Pd/Fe-CNT filter was increased 5.15-, 2.39-, and 1.76-fold, respectively for electrochemical removal of Sb(III). The results denoted that the superior performance of the Pd/Fe-CNT nanohybrid filter originated from: (1) the flow-through design, which enhanced mass transport, (2) the bimetallic design, which increased the catalytic activity, and (3) the collective contribution from atomic H*-mediated indirect reduction and direct electron transfer reduction mechanisms. The robust system performance occurred over a broad range of pH values, a variety of water matrices and can withstand several cycles of experiments. Our findings highlight an effective electro-filtration strategy to induce atomic H*-mediated electrochemical removal and recovery of Sb from water.

Wiring of bilirubin oxidases with redox polymers on gas diffusion electrodes for increased stability of self-powered biofuel cells-based glucose sensing

A new redox polymer/bilirubin oxidase (BOD)-based gas diffusion electrode was designed to be implemented as the non-current and non-stability limiting biocathode in a glucose/O2 biofuel cell that acts as a self-powered glucose biosensor. For the proof-of-concept, a bioanode comprising the Os-complex modified redox polymer P(VI-co-AA)-[Os(bpy)2Cl]Cl and FAD-dependent glucose dehydrogenase to oxidize the analyte was used. In order to develop an optimal O2-reducing biocathode for the biofuel cell Mv-BOD as well as Bp-BOD and Mo-BOD have been tested in gas diffusion electrodes in direct electron transfer as well as in mediated electron transfer immobilized in the Os-complex modified redox polymer P(VI-co-AA)-[Os(diCl-bpy)2]Cl2. The resulting biofuel cell exhibits a glucose-dependent current and power output in the concentration region between 1 and 10 mM. To create a more realistic test environment, the performance and long-term stability of the biofuel cell-based self-powered glucose biosensor has been investigated in a flow-through cell design.

Flow-through Battery Electrode for Grid-Scale Energy Storage

In order to combat climate change by switching from fossil fuels to renewable sources of energy generation, there is a critical need for the development of new energy storage technologies. A robust network of energy storage facilities is essential for the stability of a grid powered primarily by wind and solar. Given the scale of the need for energy storage, it is necessary for the storage technology to be low-cost, safe, and recyclable at the end of its life. At Lawrence Berkeley National Lab, we have developed a technology capable of achieving these goals. Our system is a novel flow-battery that uses a combination of strategies to address each of the above criteria. We use an aqueous (non-flammable) electrolyte and earth-abundant materials to keep projected chemical, manufacturing, and operation costs relatively low and to reduce safety concerns. Our newly developed flow-through electrode design further reduces projected manufacturing and operation costs and simplifies material recovery/recycling. Based on our prototype, the chemical cost of storage is projected to be $59/kWh compared with $66/kWh and $154/kWh for lithium ion and vanadium redox flow batteries respectively. As energy storage facilities become larger and larger, these savings from low up-front costs and efficient recycling will become increasingly important for keeping the cost of renewable energy storage affordable.

Flow-Through Design for Enhanced Redox Flow Battery Performance

The high capital cost, driven by the poor performance, still hinders the widespread application of vanadium redox flow batteries. This work compares two different cell designs to demonstrate that the electrolyte flow velocity and pattern is of critical importance to increase the overall battery performance. The Oriented-Distribution-Path (ODP) cell design includes inlet and outlet distribution channels, while the Multi-Distribution-Path (MDP) design does not. The introduction of the distribution channels in the ODP caused the electrolyte flow pattern through the electrode to be less uniform. However, the latter reduced the concentration polarization under high current density and low flow rate conditions. In a charge-discharge cycle comparison, the MDP displayed the highest cell energy efficiency at 80 mA cm−2 and at a flow rate of 300 cm3 min−1. However, the best overall performance was obtained using the ODP at 80 mA cm−2 and a flow rate of 10 cm3 min−1. This work demonstrates that the highest system energy efficiency is achieved when using low flow rates together with a cell design that promotes a high pressure drop. The insights of this study apply to other chemistries making it useful to define guidelines for designing energy-efficient redox flow batteries.

Electrochemical Flow Reactor for Cement Clinker Production

Cement is the most widely used manmade materials today, about one ton is produced every year per person on Earth (1). Production process contributes to about 5% of industrial energy consumption and about 8% (8.2Gton/year) of global CO2 emissions [ref]. In conventional manufacturing process, calcination of CaCO3 (limestone) is obtained in a kiln using energy input from non-renewable sources producing CaO. Carbon dioxide emission come from both the decomposition reaction and from the combustion of the fuel necessary to provide heat to the system (calcination and sintering reactions happen at high temperature, between 900 and 1500°C). As a result, about one ton of CO2 is released for every ton of cement produced.An effort towards the decarbonization of this industrial process is necessary and urgently needed (2). However, the recent scientific efforts to reduce CO2 emissions of the cement industry have mainly focused on the use of supplementary cementitious materials, but less on direct decarbonation of the cement manufacturing process in the kiln. For the latter, only one related work exists by Ellis et al. that describes a proof-of-concept of an alternative route to produce cement clinker via electrochemical means (3). In this electrochemical calcination, water and limestone are introduced into an electrochemical H-cell based on the concept of the bipolar membrane. This electrochemical reaction (that could be supplied by renewable sources) produces a precursor of the actual clinker in the form of calcium hydroxide, Ca(OH)2, which is an intermediate that requires less energy than calcium carbonate for the conversion to CaO and ultimately to cement production. H2 and O2 gases are obtained as by products, that can be used in fuel cells, together with carbon dioxide, which can be easily captured and sequestrated or employed in novel CO2 electrolysis cells. This pioneering article demonstrates the possibility of an alternative electrochemical route, but shows low voltage efficiencies and in its nature, being confined in the H-cell makes scale-up or flow-through process not possible.Here we present a novel flow-through concept for Ca(OH)2 production using a bipolar membrane flow-through reactor design. A single cell electrolyzer with serpentine flow field was used. A microfluidic spacer was introduced into the middle compartment between the two membranes and KCl electrolyte was supplied to remove the precipitate Ca(OH)2, as it forms (Fig. 1a). In this configuration acid and calcium carbonate were supplied on the anode and on cathode no flow was supplied. We show a yield of 300 mg of Ca(OH)2, with a faradaic efficiency of around 50%. Presence of calcium hydroxide in the products is confirmed by FT-IR spectroscopy (Fig 1d). We show how the yield of the reaction is the same for different current densities (Fig 1b and c), and through modelling effort we conclude that the process is limited by availability of calcium ions at the cathodic side due to the limited solubility of limestone in water.As an upgrade to this design, we also investigated the possibility to introduce the electrochemical production of clinker in a reverse bipolar electrolyzer. In this configuration, water splitting occurs in in the spacer under the potential difference set between anode and cathode. Calcium carbonate is then introduced on the acidic side (cathode), and it reacts in the spacer producing Ca(OH)2. At the same time, hydrogen and oxygen are produced at the two catalyst layers as useful byproducts. This configuration requires a lower potential to occur, and also its kinetic and thermodynamic environment is more favorable than the Case 1 electrolyzer (Fig. 1e). Additional design will be explored of CO2 electrolysis (Case 3 of Fig. 1e), adding useful products to the reaction and at the same time removing carbon dioxide from the atmosphere, “neutralizing” the amount produced by CaCO3 decomposition. In all these configurations the resulting Ca(OH)2 was analyzed for its purity and further synthesized into CaO using high temperature kiln. Figure 1

Novel strategy for the efficient degradation of organic contaminants using porous graphite electrodes: Synergistic mechanism of anodic and cathodic reactions

The co-activation of persulfate (PS) using electricity and carbon is a novel method used in sulfate radical-based advanced oxidation processes. However, the full utilisation of the synergistic effects between diverse reactions on both electrodes to achieve high PS activation and efficient removal of contaminants remains challenging. In this study, we designed porous graphite to serve as two electrodes and a continuous-flow reactor; this system resulted in internal PS activation and the degradation of organics within a specified “confined space”. With the enhancement of mass and electron transfer in the reactor, the model contaminant metronidazole (MNZ) was successfully degraded with a removal efficiency of 94.79%. The flow-through design remarkably outperformed the flow-by design, which reflected the stronger restrain of side reactions, larger electrochemical active surface area, higher active-site exposure, lower charge-transfer resistance, and higher diffusion coefficient of porous graphite electrodes. Kinetic experiments, radical scavenging experiments, and electron paramagnetic resonance tests carried out in split cells demonstrated that direct electron transfer, ∙OH oxidation, and non-radical oxidation with active PS* and 1O2 collectively contributed to the degradation of MNZ in the anode; SO4−∙ oxidation played the most significant role in the cathodic cell. Finally, the broad applicability of the reactor was confirmed by the treatment of diverse water matrixes and wastewater containing various persistent organic contaminants, showing great potential for practical applications.

Numerical Modeling for Sensitive and Rapid Molecular Detection by Membrane-Based Immunosensors.

Rapid, simple, and sensitive point-of-care testing (POCT) has attracted attention in recent years due to its excellent potential for early disease diagnosis and health monitoring. The flow-through biosensor design is a candidate for POCT that utilizes the small-sized pores of a porous membrane as a recognition space where it emits a signal comparable to that of a conventional enzyme-linked immunosorbent assay within 35 min of detection time. In this paper, we present a numerical model for this immunosensing technology to systematically design an improved recognition system. The model considers mass transfer into the pore (convection and diffusion), the kinetics between the immobilized receptor and the target molecule, and the flow conditions, successfully leading to a bottleneck step (capture of secondary antibody) in sandwich-type detection. Our simulation results also show that this problem can be solved by adopting both appropriate receptors and analytical conditions. Eventually, the requirements to achieve the sensitivity required for POCT were fulfilled, which will allow for further development of immunosensing devices for disease detection.

Performance of the graphite felt flow-through electrode in hexavalent chromium reduction using a single-pass mode

Flow-through electrodes generally outcompete traditional parallel-plate electrodes in current efficiency and mass transfer. High-performance electrode materials can be costly and complicated to fabricate, hindering their wide application. In this study, we used commercial graphite felt (GF) as the cathode of a flow-through electrochemical cell to investigate its potential in treating Cr(VI) solution through electroreduction. The flow-through design with the porous GF electrode allowed sufficient contact surface with Cr(VI) and single-pass tests demonstrated a high reduction efficiency (95~100%) [117 mg/L~3 mg/L Cr(VI)] under acidic conditions. Slow flow rate and high current promoted electroreduction of Cr(VI). The presence of other metal ions could further improve Cr(VI) reduction at low flow rates due to enhanced conductivity in dilute solutions and generation of low valent ions as reducing agents. At fast flow rates, competition of these ions for reduction decreased Cr(VI) reduction efficiency. Moreover, an acidic environment prevented the coating of an insoluble layer on the GF surface and promoted durable performance, with a lower energy consumption [0.46 kWh for treating 100 L 117 mg/L Cr(VI) solution per unit area of GF]. This work demonstrated the potential of Cr(VI) detoxification using GF cathodes in flow-through electrochemical cell.

A novel electrocatalytic filtration system with carbon nanotube supported nanoscale zerovalent copper toward ultrafast oxidation of organic pollutants

In this study, we designed an integrated electrochemical filtration system for catalytic activation of peroxymonosulfate (PMS) and degradation of aqueous microcontaminants. Composites of carbon nanotube (CNT) and nanoscale zero valence copper (nZVC) were developed to serve as high-performance catalysts, electrode and filtration media simultaneously. We observed both radical and nonradical reaction pathways, which collectively contributed to the degradation of model pollutants. Congo red was completely removed via a single-pass through the nZVCCNT filter (τ <2 s) at neutral pH. The rapid kinetics of Congo red degradation were maintained across a wide pH range (from 3.0–7.0), in complicated matrixes (e.g., tap water and lake water), and for the degradation of a wide array of persistent organic contaminants. The superior activity of nZVCCNT stems from the boosted redox cycles of Cu2+/Cu+ in the presence of an external electric field. The flow-through design remarkably outperformed the conventional batch system due to the convection-enhanced mass transport. Mechanism studies suggested that the carbonyl group and electrophilic oxygen of CNT served as electron donor and electron acceptor, respectively, to activate PMS to generate •OH and 1O2via one-electron transport. The electron-deficient Cu atoms are prone to react with PMS via surface hydroxyl group to produce reactive intermediates (Cu2+-O-O-SO3−), and then 1O2 will be generated by breaking the coordination bond of the metastable intermediate. The study will provide a green strategy for the remediation of organic pollution by a highly efficient and integrated system based on catalytic oxidation, electrochemistry, and nano-filtration techniques.

Simultaneous decontamination of arsenite and antimonite using an electrochemical CNT filter functionalized with nanoscale goethite

The co-presence of arsenic (As) and antimony (Sb) in water bodies has been commonly reported. The toxicity of As and Sb varies with different speciation. Herein, we designed a dual-functional electrochemical filter toward “one-step” detoxification and sequestration of highly toxic As(III) and Sb(III). The key to this technology is a functional anodic filter consists of nanoscale goethite and carbon nanotubes (CNT). Results showed that 97.9% As(III) and 91.9% Sb(III) transformation and 86.4% Astotal and 70.1% Sbtotal removal efficiency can be obtained over 2 h continuous filtration under optimized conditions. The Astotal removal kinetics and efficiency enhanced with flow rate and applied voltage (e.g., the Astotal removal efficiency increased from 62.9% at 0 V to 86.4% at 2.5 V). This enhancement in kinetics and efficiency can be explained by the synergistic effects of the flow-through design, plentiful exposed sorption sites, electrochemical reactivity, and nanoscale goethite. Moreover, the proposed technology works effectively across a wide pH range. Only negligible inhibition was observed in the presence of nitrate, chloride, and carbonate. Exhausted hybrid filters can be effectively regenerated by using chemical wash with NaOH solution. This study not only revealed the different adsorption behaviors of As(III) and Sb(III) on the hybrid filters, but also provided new insights into rational design of continuous-flow filters toward simultaneous decontamination of As(III) and Sb(III).