Continuous Flow Cell Research Articles

Effects of process factors on the performance of electrochemical disinfection for wastewater in a continuous-flow cell reactor.

Although electrochemical disinfection has been shown to be an effective approach to inactivate bacteria in saline water, the effects of process parameters and reactor designfor its application in low-salinity water have not been well understood. In this study, factorial experiments were performed to investigate the direct and confounded effects of applied current (5-20 mA), contact time (2.5-20 min), anode surface area (185-370 cm2), and chloride concentration (50-400 mg L-1) on thedisinfection efficiency in fresh water andthe secondary effluent of municipal wastewater. An electrochemical disinfection reactor cell with an internal volume of 75 cm3 was designed and fabricated. Residence time distribution analysis showed thatthe internal mixing of the reactor is similar to that of adispersedplug-flow reactor. All studied process parameters showed significant effect on the kill efficiency, with the applied current and contact time having the most dominant effect. Although theeffect of chloride concentration, which isresponsible for electrochemical production of free chlorine in water, isstatistically significant, it isnot as prominent as those reported for high salinity water. A synergistic effect between chloride concentration and anode surface area was identified, leading to high kill efficiency (99.9%, 3 log kill) at low current density (0.0135 mA cm-2). Response surface modeling results suggested that a scaled-up disinfection reactor can be designed using large anode surface area with long contact time for high chloride water (400 mg L-1) or high current density with short contact time for low chloride water (50 mg L-1). The power requirement of a portable system treating 37.85 m3 day-1 (10,000 gpd) of municipal wastewater was estimated to be 1.9 to 8.3 kWto achieve a 3 log kill, depending on the reactor design.

Continuous Flow Microbial Flow Cell with an Anion Exchange Membrane for Treating Low Conductivity and Poorly Buffered Wastewater

The authors acknowledge funding by the Environmental Security Technology Certification Program via cooperative research agreement W9132T-16-2-0014 through the US Army Engineer Research and Development Center and funding by the Pennsylvania State University.

Electrochemical Oxidative Functionalization of Arylalkynes: Access to α,α‐Dibromo Aryl Ketones

AbstractA general and effective protocol to synthesize α,α‐dibromo aryl ketones has been developed via an electrochemical oxidative method. The reaction proceeds smoothly at room temperature in an undivided cell without the addition of external oxidants. In the reaction process, LiBr acts as both bromine source and supporting electrolyte. This electrooxidation strategy has good substrate applicability and functional group compatibility. Moreover, the reaction could be scaled up efficiently in a continuous flow cell. The target product could undergo further functionalization for the synthesis of some useful heterocyclic compounds.magnified image

Highly Efficient Electrochemical Oxidation of Alcohols in a Flow Electrochemical Column Cell Modified with Au Nanoparticle Catalyst

Electrosynthesis is a powerful means for obtaining a variety of useful chemical products without employing toxic or otherwise hazardous chemical reagents and under relatively mild conditions. However, conventional batch-type cells suffer from a low productivity due to narrow two-dimensional reaction fields in the electrochemical system. To overcome this problem, we utilized continuous-flow column cell[1]. Although it was developed for a highly sensitive coulometric analysis of trace chemical substances in 1968, it is also expected to conduct rapid and quantitative bulk electrolysis due to its large electrode area and continuous-flow system. This flow cell consisted of a working electrode compartment and a counter electrode compartment, separated by an ion permeable Vycor® glass tube (Figure 1 (a)). A bundle of carbon fiber threads was tightly packed as a working electrode in the continuous-flow column cell, and a Pt spiral wire was used as a counter electrode. During several decades, the bulk gold has been considered as less active material, but at nanoscale, it exhibits surprisingly physicochemical and catalytic properties[2]. Therefore, in this work, the carbon fiber surface was also functionalized with Au nanoparticle catalyst to promote an electrochemical oxidation of alcohols.As a result, we have successfully demonstrated an efficient electrocatalytic oxidation of benzyl alcohol to provide benzaldehyde and benzoic acid with high current efficiencies in alkaline media. Moreover, it was also found that the selectivity of benzaldehyde was influenced by the added base amounts, and increased up to 97% by decreasing the amounts. We will also report the results of electrochemical oxidation of other alcohols.

Acquired factor XIII deficiency in patients under therapeutic plasma exchange: A poorly explored etiology.

Factor XIII (FXIII) deficiency may cause bleeding under certain clinical circumstances. Therapeutic plasma exchange (TPE) may lead to a transient deficiency. To describe the clinical evolution of patients with acquired FXIII deficiency secondary to TPE. We respectively studied a cohort of consecutive patients from 2014 to 2019 who were treated with TPE with FXIII levels <50%. The FXIII was measured after the start of the TPE course, on days between the TPE sessions, due to suspected acquired deficiency. All TPE were performed using continuous flow cell separator. In all cases, the initial replacement fluid applied was albumin. Apheresis procedures were held at 24to 48 hours intervals. Eighteen patients were included, 13 of them were recipients of kidney transplants. The main TPE prescription was humoral rejection. Median FXIII at diagnosis (measured on days between sessions of the TPE course) was 19%(IQR17-25). The median of apheresis procedures before measurement of FXIII was 3(IQR2-4). Among the total cohort, 10 patients suffered hemorrhages. None of the patients without history of kidney transplants had bleeding (n = 5), however, 10/13 with kidney transplants did. Five kidney transplant patients received therapy with FXIII concentrate because of life-threatening bleeding. In all cases, the bleeding stopped within the first 24 hours. All patients had their FXIII levels measured again after finishing the TPE course, with normal results. TPE is an under-diagnosed cause of acquired FXIII deficiency since routine coagulation tests remain unaltered. It might cause major bleeding, particularly in patients with a recent history of surgery like kidney transplants.

Tracking leukemic T-cell transcriptional dynamics in vivo with a blood-based reporter assay.

Transcriptional dynamics of cancer cells govern cell fate decisions and are therapeutically actionable drug targets. In this study, we engineered a circulating cancer cell line that secretes a luciferase reporter to capture constitutive and circadian clock-driven transcription dynamics over the course of a day. Engineered human leukemic T cells (Jurkat) were observed to rhythmically secrete luciferase in a continuous flow cell culture system. When transplanted invivo, engineered leukemic cells caused circadian plasma luciferase activity and had expected pathological signs of leukemic disease. This technique is rapid and noninvasive, requiring only a few microliters of media or blood, and can aid in investigating relationships between invivo cancer cell signaling and behavior, such as diet or sleep.

HG-ICP-OES Technique, a Useful Tool for Arsenic Determination in Soft Water

This paper presents a fast, sensitive, linear and precise method for the determination of arsenic (As) at trace levels, from different types of water (drinking, mineral, surface water and groundwater) using hydride generation and optical emission spectrometry with inductively coupled plasma (HG-ICP-OES). In order to generate the hydride, the initial pretreatment of the samples with a mixture of potassium iodide and ascorbic acid is necessary, in hydrochloric acid medium for reducing the As5+ to As3+ ions and for the subsequent formation of the hydride from As3+ ions and sodium borohydride, in a continuous-flow cell. The quantification limit of the method (LOQ = 0.43 �g/L), the precision (3.41%), the recovery yield (95%) and the measurement uncertainty of 24% frame the method within the limits imposed by the acceptance criteria of an analytical method for arsenic determination. The proposed method was tested on several types of water, the obtained results being compared to those obtained by applying two sensitive and selective alternative methods using ICP-MS, respectively ultrasonic nebulizer and ICP-OES.

In Situ Observation of the pH Gradient near the Gas Diffusion Electrode of CO2 Reduction in Alkaline Electrolyte.

The local pH variation near the surface of CO2 reduction electrodes is important but hard to study. We develop a continuous-flow Raman electrochemical cell that enables the first experimental study of the local pH near a CO2 reduction gas diffusion electrode under reaction conditions. At zero current, CO2 chemically reacts with the 1 M KOH electrolyte at the interface to form HCO3- and CO32-. The local pH on the cathode surface is 7.2, and the HCO3- concentration profile extends a distance of 120 μm into the electrolyte, which verifies that the nominal overpotential reduction from using alkaline electrolyte originates from the Nernst potential of the pH gradient layer at the cathode/electrolyte interface. The CO2-OH- neutralization reaction and the pH gradient layer still persist, albeit to a reduced extent, at CO2 reduction current densities up to 150 mA/cm2.

A Continuous Flow Cell for High‐Temperature/High‐Pressure Electroorganic Synthesis

AbstractA flow electrolysis cell that enables operation at high temperatures and pressures has been designed and developed. The cell, with a cylindrical shape and concentric electrodes, can be easily assembled using commercially available fluidic components. The compact design of the device permits easy temperature control using a commercial column heater. Temperatures ranging from −10 °C to +150 °C and pressures up to 70 bar have been successfully applied for long operation periods. The cell performance has been evaluated using the anodic methoxylation of N‐formylpiperidine as a model. Very high conversions and selectivities have been achieved with single‐pass processing, and high productivities of 73 mmol/h with electrolyte recycling. The high pressure and temperature capabilities of the cell have been used to demonstrate the negative effect that re‐dissolved hydrogen gas can have on hydrogen‐releasing electrochemical reactions in undivided cells, owing to undesired anodic oxidation of hydrogen.

SUN-358 INDICATIONS, EFFICACY AND SAFETY OF THERAPEUTIC APHERESIS IN NEPHROLOGY PATIENTS

Therapeutic Apheresis (TA) serves as a rescue therapy in many patients with kidney diseases and these indications have expanded dramatically in the past few years. Rapid removal of undesirable antibodies and immune complexes remains the prime rationale for adopting plasmapheresis as a therapy. However, there is limited data available regarding the indications, efficacy and safety of TA in nephrology patients. This was a retrospective analysis of TA performed in adult and pediatric nephrology patients at a tertiary healthcare centre from January 2011 to December 2018. The study population included all consecutive patients admitted in the Department of Nephrology; both adult and pediatric, who were thought to benefit from TPE. All the procedures were performed on a continuous flow cell separator Com.Tec (Fresenius Kabi, Germany) with PL1 or P1R kit using central venous access. Conventional therapeutic plasma exchange was performed using PL1 kit whereas cascade plasmapheresis and immunoadsorption were performed using P1R kit. For cascade, Evaflux plasma fractionator (Kawasumi Laboratories, Japan) was used and for immunoadsorption, Glycosorb – ABO (Glycorex Transplantation AB, Sweden) or Adsopak (Pocard, Moscow) adsorbers were used. Informed consent was obtained from the patient or guardians prior to each procedure. Demographic details, clinical condition, ASFA category and clinical response were noted. Procedure parameters such as blood and plasma volume processed, anticoagulant used, time taken for the procedure, volume and type of replacement fluid administered and adverse reaction events were noted. All procedures and adverse reaction management were done according to departmental standard operating procedures. A total of 190 patients (63 females and 127 males) underwent 842 sessions of TA for different indications. 184 and 658 procedures were performed for 24 pediatric and 166 adult patients respectively. Mean age of presentation in pediatric age group was 9.21±1.22 years while in adults it was 43.08±3.41 years. 639 procedures (75.89%) were conventional plasma exchanges, 182 were cascade plasmapheresis (21.61%) and 21 were immunoadsorption (2.49%). Mean blood urea and serum creatinine prior to initiation of plasmapheresis of all indications except desensitization was 158.78±5.65mg/dl and 4.95±1.08mg/dl while at the time of termination it was 73.05±3.42mg/dl and 3.34±1.15mg/dl respectively. Replacement fluid was plasma in 303 procedures (35.98%), 5% albumin in 412 (48.93%) and combination of plasma and 5% albumin in 127 procedures (15.08%). Acid Citrate Dextrose was the preferred anticoagulant. As per departmental standard operating procedure, patients with body weight <20 kg i.e. 25 procedures (2.96%) required priming of kit with albumin or red cells. Patient outcome in terms of survival was 76.84%; 79.16% in pediatric and 74.69% in adult age group. Thirty-nine procedures (4.63%); 12 in pediatric and 27 in adults were associated with adverse events in the form of shivering(12), urticaria(3) and catheter related complications(6). Findings of this study highlight the efficacy and safety of TA in different nephrological indications for pediatric and adult nephrology patients.

Optimization of nanocomposite membrane for vacuum membrane distillation (VMD) using static and continuous flow cells: Effect of nanoparticles and film thickness

Abstract In this study, the effects of incorporation of nanoparticles (NPs), including 7 nm TiO2, 200 nm TiO2, and hydrophilic and hydrophobic SiO2 with a mean diameter in the range of 15–20 nm, and their concentrations on the membrane properties and vacuum membrane distillation (VMD) performance were evaluated. The effect of membrane thickness and support materials were also investigated. The membranes were characterized extensively in terms of water contact angle, liquid entrance pressure of water (LEPw), scanning electron microscopy, surface roughness, and pore size. While the best polyvinylidene fluoride (PVDF) nanocomposite membranes with 200 nm TiO2 NPs were obtained at 2 wt% NPs concentration, the optimal NPs concentration was 5% when 7 nm TiO2 was integrated. Using a nanocomposite membrane containing 2 wt% TiO2 − 200 nm NPs, a VMD flux of 3.2 kg/m2h and a LEPw of 34 psi were obtained with 99.99% salt rejection. Furthermore, it was observed that decreasing the membrane thickness would increase the portion of the finger-like layer in the membrane and reduce the spongy-like layer when hydrophilic NPs were used. Using continuous flow VMD, a flux of 3.1 kg/m2h was obtained with neat PVDF membranes, which was higher than the flux obtained by the static VMD with the same membrane at the same temperature and vacuum pressure. The fluxes of both static and continuous flow cells VMD increased with temperature. Furthermore, it was evident that the continuous flow cell VMD at 2 L per minute yielded higher flux than the static cell VMD at any given temperature, indicating strong effects of turbulence provided in the continuous flow cell VMD.

Electrochemical CO2 Reduction in a Continuous Non-Aqueous Flow Cell with [Ni(cyclam)]2.

A significant number of molecular catalysts have been developed for electrochemical CO2 reduction with high efficiency and selectivity; however, testing of these electrocatalysts in an application-ready system is lacking. Here, we present an example of a nonaqueous flow cell electrolyzer with [Ni(cyclam)]2+ as the homogeneous electrocatalyst for CO2 reduction. Using ferrocene as a sacrificial electron donor and ammonium salts as both electrolyte and proton donor, efficient catalytic CO2 reduction is achieved. The nonaqueous design shows high selectivity for the reduction of CO2 to CO (>80%) and achieves high current densities with a graphite felt working electrode (up to 50 mA·cm-2 with 0.5 M proton donor in MeCN solution), producing >40 mL·h-1 of CO. The choice of a molecular electrocatalyst, solvent, and proton donor are the key factors for achieving high activity with an efficient flow electrolyzer and the eventual development of a viable continuous process.

Antimicrobial activity and toxicity of glass ionomer cement containing an essential oil.

The aim of this study was to evaluate the antimicrobial activity and toxicity of glass ionomer cement (GIC) modified with 5-methyl-2-(1-methylethyl)phenol (thymol) against Streptococcus mutans in silico and in vitro. The antimicrobial activity of thymol on GIC modified with concentrations of 2% (GIC-2) and 4% (GIC-4) was evaluated in a model of planktonic cell biofilm using agar diffusion test, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), dynamic biofilm (continuous flow cell parallel), and bacterial kinetics. Conventional GIC (GIC-0) was used as a control. Thymol toxicity was evaluated in Artemia salina and in silico using Osiris® software. Differences between groups were estimated by analysis of variance, followed by Tukey post hoc test, with a 5% significance level. The results of the agar diffusion test between groups were not significantly different (P≥0.05). Thymol had potential bacteriostatic and bactericidal activity against Streptococcus mutans with respect to planktonic growth, with MIC of 100 µg/mL and MBC of 400 µg/mL. The groups GIC-0, GIC-2, and GIC-4 reduced the biofilm by approximately 10, 85, and 95%, respectively. Bacterial kinetics showed efficiency of the modified GICs for up to 96 h. GIC with thymol was effective against S. mutans, with significant inhibition of the biofilms. Analyses in silico and using Artemia salina resulted in no relevant toxicity, suggesting potential for use in humans. GIC-2 was effective against S. mutans biofilm, with decreased cell viability.

A retrospective study of autologous stem cell mobilization by G-CSF in combination with chemotherapy in patients with multiple myeloma and lymphoma.

Factors affecting peripheral blood hematopoietic stem cell (PBSC) mobilization and collection were investigated in patients with multiple myeloma (MM) and lymphoma who were undergoing chemotherapy. Clinical data from 128 patients, including 53 MM and 75 malignant lymphoma (7 Hodgkin's lymphoma and 68 non-Hodgkin's lymphoma) cases were retrospectively analyzed. Autologous PBSCs were mobilized using granulocyte-colony stimulating factor (G-CSF) during chemotherapy, and collected using a continuous flow cell separation instrument. The yields of CD34+ cells per kilogram of patient body weight <2.0×106/kg, >2.0×106/kg or >5.0×106/kg were defined as a failure, a success or ideal mobilization, respectively. In MM and lymphoma patients, the success rates of CD34+ cell acquisition were 73.6 (39/53) and 58.7% (44/75), the ideal rates were 43.4 (23/53) and 30.7% (23/75), and the failure rates were 26.4 (14/53) and 41.3% (31/75), respectively. Univariate and multivariate statistical analysis revealed that negative factors for PBSC mobilization in patients with MM were lenalidomide treatment, multiple chemotherapies, incomplete disease remission and low-level blood hemoglobin; in patients with lymphoma, the negative factors were the histological disease type, incomplete disease remission, being beyond the first-line of previous chemotherapy, multiple chemotherapies, chemotherapy with the HyperCVAD-B mobilization scheme, high-dose MTX/Ara-c (methotrexate/cytarabine) treatment, prolonged administration of G-CSF and low-hematocrit levels. In the present study, different factors influencing PBSC mobilization and collection in MM and lymphoma cases were identified. PBSC mobilization yielded sufficient CD34+ cell counts both in MM and lymphoma patients; however, the failure rates were relatively high.

Catalyst-Electrolyte Interactions in Aqueous Reline Solutions for Highly Selective Electrochemical CO2 Reduction.

Achieving high product selectivities is one challenge that limits viability of electrochemical CO2 reduction (CO2 R) to chemical feedstocks. Here, it was demonstrated how interactions between Ag foil cathodes and reline (choline chloride + urea) led to highly selective CO2 R to CO with a faradaic efficiency of (96±8) % in 50 wt % aqueous reline at -0.884 V vs. the reversible hydrogen electrode (RHE), which is a 1.5-fold improvement over CO2 R in KHCO3 . In reline the Ag foil was roughened by (i) dissolution of oxide layers followed by (ii) electrodeposition of Ag nanoparticles back on cathode. This surface restructuring exposed low-coordinated Ag atoms, and subsequent adsorption of choline ions and urea at the catalyst surface limited proton availability in the double layer and stabilized key intermediates such as *COOH. These approaches could potentially be extended to other electrocatalytic metals and lower-viscosity deep eutectic solvents to achieve higher-current-density CO2 R in continuous-flow cell electrolyzers.

Electrocatalytic reduction of CO2 over dendritic-type Cu- and Fe-based electrodes prepared by electrodeposition

Abstract The identification of the role of nano-morphology of electrodes for the reduction of CO2, particularly in determining the selectivity towards > C1 products of reduction, is still a challenge. We show here for the first time how a dendritic-type nano-morphology and related fractal dimension plays a crucial role in determining the selectivity for electrodes based on Cu and Fe. The electrodes, prepared by electrodeposition of Cu or Fe on metal substrates (Cu, Ti, Al, Fe, Fe-Cr-Ni alloy) or carbon-based gas diffusion layers (GDL), were tested in a continuous flow cell at constant potential (−1.5 V vs. Ag/AgCl) or at the onset potential of the first cathodic peak determined by cyclic voltammetry. Results showed that the dendritic-type nano-morphology influences positively not only the activity to formic acid, but especially the selectivity to gas products (i.e. CH4 and CO) and to higher carbon-chain liquid products (i.e. ethanol, isopropanol, acetic acid) when smoother edges and denser surface sites are present. Tests at the onset potential show very high total carbon Faradaic efficiency (FE) for Fe electrodeposited on GDL and Ti (about 92–95%). The lowest onset potential (−0.3 V) is observed for Cu on GDL, showing over 80% total carbon FE and almost 60% FE to formic acid.

In Situ Monitoring of Nanoparticle Formation during Iridium‐Catalysed Oxygen Evolution by Real‐Time Small Angle X‐Ray Scattering

AbstractReal‐time Small Angle X‐Ray Scattering (SAXS) has been used to investigate the homogeneity of a series of molecular iridium complexes during water oxidation catalysis in aqueous NaIO4 solution through a continuous flow cell. The results obtained for the unstable [Cp*Ir(OH2)3]2+ precursor forming amorphous IrOx nanoparticles (NPs) in‐situ validate and complement previous Dynamic Light Scattering (DLS) studies by providing enhanced sensitivity for small particle sizes and increased temporal resolution under realistic reaction conditions. Correlating particle formation profiles with O2 evolution traces allowed homogeneous catalysis to be clearly distinguished from heterogeneous catalysis. A series of seven pyridine−alkoxide Cp*Ir complexes are shown to be fully homogeneous by SAXS, validating previous studies and confirming their catalysis to be molecular in nature throughout the reaction.

Supporting‐Electrolyte‐Free Electrochemical Methoxymethylation of Alcohols Using a 3D‐Printed Electrosynthesis Continuous Flow Cell System

AbstractWe describe the development of a novel low‐cost small‐footprint 3D‐printed electrosynthesis continuous flow cell system that was designed and adapted to fit a commercially available Electrasyn 2.0. The utility and effectiveness of the combined flow/electrochemistry system over the batch process was demonstrated in the development of an improved and supporting‐electrolyte‐free version of our anodic methoxymethylation of alcohols.

Design and optimization of an electrocoagulation reactor for fluoride remediation in underground water sources for human consumption

• Electrocoagulation process for fluoride removal was evaluated. • Progressive scale-up procedure involving three pilot reactors was employed. • An optimized electrochemical reactor in a unique design was used. • The final fluoride concentration of 1.4 mg/L was attained within 10 min. • Kinetics of remediation process fitted by the Variable Order Kinetic model. Fluoride remediation in underground waters of volcanic origin was performed at laboratory scale using an electrocoagulation (EC) technique. The natural waters from certain volcanic springs on the island of Tenerife (Canary Islands, Spain) contain average fluoride concentrations in excess of 7 mg/L. Thus, it is necessary to treat the water for fluoride mitigation below the maximum acceptable concentration of 1.5 mg/L according to Spanish regulations for drinking water. The design and optimization of a sustainable process was accomplished using a progressive scale-up procedure involving three pilot reactors with different configurations and effective working volumes. A bipolar electrode cell design using aluminum electrodes was used in all cases. The good performance of the process was confirmed by reducing the fluoride concentration from 7.35 to 1.4 mg/L. The following optimized operating conditions were determined for a continuous flow cell system: current density, 10 mA/cm 2 ; residence time, 10 min; and, half-period of polarity reversal, 1 min. Furthermore, the kinetics of the remediation process can be fitted using the Variable Order Kinetic (VOK) model, with a power relationship between fluoride concentration and residence time in the EC reactor.

Use of electrospun threads in immobilized cell reactors for continuous ethanol production

Saccharomyces cerevisiae immobilized in electrospun Pluronic F127 dimethacrylate (FDMA) was successfully employed for the production of ethanol in an immobilized cell reactor. Yeast cells were immobilized into fibers formed through the process of electrospinning and cross-linking. The threads had an average diameter of 0.88 μm and were used in continuous-flow immobilized cell reactors. The immobilized cell reactors were able to maintain a high ethanol yield of >90% from day 4 through to the end of the time course at day 14. The reactor was able to achieve a maximum ethanol yield of 94.3%. This study shows that the use of electrospinning is a promising method for continuous ethanol production through immobilized cell-based continuous flow reactors.