Bulk Solution pH Research Articles

Observation of natural convection and particle ejection from stainless steel single pits

Single pits were visually and electrochemically followed during their growth on a S41500 martensitic SS microelectrode. Solid particles were observed ejecting from the growing pit and after extraction, EDX determined they were mostly iron-based hydroxides/oxides. These particles were carried by fluid flow originating from the pit at a velocity of 21 μm/s. Finite element modeling confirmed the observed flow speeds are achievable by natural convection due to metal ion density gradients. While the pit solution does not experience flow, the bulk solution pH was observed to decrease illustrating how natural convection affects the bulk solution chemistry.

De Novo Design and Characterization of Amphiphilic Peptides with Basic Side Chains for Tailored Interfacial Chemistries.

Lysine-leucine (LK) peptides have been used as model systems and platforms for 2D material design for decades. LK peptides are amphiphilic sequences designed to bind and fold at hydrophobic surfaces through hydrophobic leucine side chains and hydrophilic lysine side chains extending into the aqueous subphase. The hydrophobic periodicity of the sequence dictates the secondary structure at the interface. This robust design makes them ideal candidates for controlling interfacial chemistry. This study presents the de novo design and characterization of two novel peptides: LRα14 and LHα14, which substitute lysine with arginine and histidine, respectively, in the helical LKα14 sequence. This modification is intended to expand the LK peptide platform to a new basic interfacial chemistry. We explore the stability of the new LRα14 and LHα14 designs with respect to changes in pH and salt concentration in bulk solution and at the interface using circular dichroism (UV-CD) and vibrational sum-frequency generation spectroscopy, respectively. Notably, the structural stability of the peptides remains unaffected across a wide range of pH and ionic strength values. At the same time, the variation of side-chain chemistry leads to a wide spectrum of interfacial water structures. By extension of the LK platform to include arginine and histidine, this study broadens the toolbox for designing tailored interfacial chemistries with applications in material and biomedical sciences.

Exploring biorelevant conditions and release profiles of ritonavir from HPMCAS-based amorphous solid dispersions

Development of a release test for amorphous solid dispersions (ASDs) that is in vivo predictive is essential to identify optimally performing formulations early in development. For ASDs containing an enteric polymer, consideration of buffer properties is essential. Herein, release rates of hydroxypropyl methyl cellulose acetate succinate (HPMCAS) and ritonavir from ASDs with a 20% drug loading were compared in phosphate and bicarbonate buffers with different molarities, at pH 6.5. The bioaccessibility of ritonavir from the ASD in the tiny-TIM apparatus was also evaluated and compared to that of the crystalline drug. The surface pH at the dissolving solid: solution interface was evaluated using a pH-sensitive fluorescence probe for HPMCAS and ASD compacts in phosphate and bicarbonate buffers. Drug and polymer were found to release congruently in all buffer systems, indicating that the polymer controlled the drug release. Release was slowest in 10 mM bicarbonate buffer, and much faster in phosphate buffers with molarities typically used in release testing (20-50 mM). Release from the 10 mM bicarbonate buffer was matched in a 5 mM phosphate buffer. The surface pH of HPMCAS and HPMCAS:ritonavir ASDs was found to be lower than the bulk solution pH, where surface pH differences largely explained release rate differences seen in the different buffer systems. Ritonavir was highly bioaccessible from the ASD, as assessed by the tiny-TIM system, and much less bioaccessible when crystalline drug was used. The observations highlight the need for continued development of biorelevant assays tailored for ASD formulation assessment.

Interplay of Drug-Polymer Interactions and Release Performance for HPMCAS-Based Amorphous Solid Dispersions.

The interplay between drug and polymer chemistry and its impact on drug release from an amorphous solid dispersion (ASD) is a relatively underexplored area. Herein, the release rates of several drugs of diverse chemistry from hydroxypropyl methylcellulose acetate succinate (HPMCAS)-based ASDs were explored using surface area normalized dissolution. The tendency of the drug to form an insoluble complex with HPMCAS was determined through coprecipitation experiments. The role of pH and the extent of drug ionization were probed to evaluate the role of electrostatic interactions in complex formation. Relationships between the extent of complexation and the drug release rate from an ASD were observed, whereby the drugs could be divided into two groups. Drugs with a low extent of insoluble complex formation with HPMCAS tended to be neutral or anionic and showed reasonable release at pH 6.8 even at higher drug loadings. Cationic drugs formed insoluble complexes with HPMCAS and showed poor release when formulated as an ASD. Thus, and somewhat counterintuitively, a weakly basic drug showed a reduced release rate from an ASD at a bulk solution pH where it was ionized, relative to when unionized. The opposite trend was observed in the absence of polymer for the neat amorphous drug. In conclusion, electrostatic interactions between HPMCAS and lipophilic cationic drugs led to insoluble complex formation, which in turn resulted in ASDs with poor release performance.

Iodide oxidation by ozone at the surface of aqueous microdroplets.

The oxidation of iodide by ozone occurs at the sea-surface and within sea spray aerosol, influencing the overall ozone budget in the marine boundary layer and leading to the emission of reactive halogen gases. A detailed account of the surface mechanism has proven elusive, however, due to the difficulty in quantifying multiphase kinetics. To obtain a clearer understanding of this reaction mechanism at the air-water interface, we report pH-dependent oxidation kinetics of I- in single levitated microdroplets as a function of [O3] using a quadrupole electrodynamic trap and an open port sampling interface for mass spectrometry. A kinetic model, constrained by molecular simulations of O3 dynamics at the air-water interface, is used to understand the coupled diffusive, reactive, and evaporative pathways at the microdroplet surface, which exhibit a strong dependence on bulk solution pH. Under acidic conditions, the surface reaction is limited by O3 diffusion in the gas phase, whereas under basic conditions the reaction becomes rate limited on the surface. The pH dependence also suggests the existence of a reactive intermediate IOOO- as has previously been observed in the Br- + O3 reaction. Expressions for steady-state surface concentrations of reactants are derived and utilized to directly compute uptake coefficients for this system, allowing for an exploration of uptake dependence on reactant concentration. In the present experiments, reactive uptake coefficients of O3 scale weakly with bulk solution pH, increasing from 4 × 10-4 to 2 × 10-3 with decreasing solution pH from pH 13 to pH 3.

Does Media Choice Matter When Evaluating the Performance of Hydroxypropyl Methylcellulose Acetate Succinate-Based Amorphous Solid Dispersions?

Hydroxypropyl methylcellulose acetate succinate (HPMCAS) is a weakly acidic polymer that is widely used in the formulation of amorphous solid dispersions (ASDs). While the pH-dependent solubility of HPMCAS is widely recognized, the role of other solution properties, including buffer capacity, is less well understood in the context of ASD dissolution. The goal of this study was to elucidate the rate-limiting steps for drug and HPMCAS release from ASDs formulated with two poorly water soluble model drugs, indomethacin and indomethacin methyl ester. The surface area normalized release rate of the drug and/or polymer in a variety of media was determined. The HPMCAS gel layer apparent pH was determined by incorporating pH sensitive dyes into the polymer matrix. Water uptake extent and rate into the ASDs were measured gravimetrically. For neat HPMCAS, the rate-limiting step for polymer dissolution was observed to be the polymer solubility at the polymer-solution interface. This, in turn, was impacted by the gel layer pH which was found to be substantially lower than the bulk solution pH, varying with medium buffer capacity. For the ASDs, the HPMCAS release rate was found to control the drug release rate. However, both drugs reduced the polymer release rate with indomethacin methyl ester having a larger impact. In low buffer capacity media, the presence of the drug had less impact on release rates when compared to observations in higher strength buffers, suggesting changes in the rate-limiting steps for HPMCAS dissolution. The observations made in this study can contribute to the fundamental understanding of acidic polymer dissolution in the presence and absence of a molecularly dispersed lipophilic drug and will help aid in the design of more in vivo relevant release testing experiments.

Electricity facilitates the lithium sorption from salt-lake brine by H3LiTi5O12 nanoparticles: Kinetics, selectivity and mechanism

The rapid consumption of lithium ion (Li+) battery for electronic devices has significantly increased the demand for lithium resource in recent years. The salt-lake brine is considered as the ideal source for Li+ extraction, but the co-existing cations, such as Na+ and K+ limit its recovery efficiency when the adsorption method is applied. In this study, the H3LiTi5O12 nanoparticles (HTO) with a spinel structure were synthesized as Li+-selective adsorbent. The static adsorption experiments showed that the Li+ absorption capacity of HTO was significantly affected by the pH of bulk solution, and exhibited a high separation factor of Li+/Na+ and Li+/K+ at 37 and 16, respectively. When HTO was mixed with activated carbon (AC) and coated on the cathode plate, the Li+ adsorption kinetics (rate constant) was significantly enhanced from 0.18 to 0.25, due to the accelerated rate of the film diffusion driven by the electric field. Density functional theory (DFT) calculation result showed that applying electricity can strengthen the hydrogen bond between Li and O atom on the HTO (111) facet. When the AC mixing ratio was increased from 10% to 50%, the Li+ desorption efficiency increased from 47% to 90%, but at the expense of sacrificing the adsorption capacity, which decreased from 18.1 mg/g to 9.8 mg/g. In terms of the overall recovery efficiency of Li from brine, the weight ratio of HTO:AC at 9:1 was suggested for the electro-sorption method. Finally, the Li+ recovery from actual brine was successfully demonstrated, with 7.1 mg/g of adsorption capacity and well stability.

NS-ZnO@P–Zn nanocomposites catalysts with superior photodegradation of methyl orange through in-situ oxidation and pH-mediated dealloying of equiatomic Al50Zn50 precursors

Mediation of solution pH play a vital role of the formation of porous architectures and dealloying the amphoteric Al50Zn50 precursors. Simultaneous active dissolution of Al and Zn elements in the equiatomic AlZn precursors occurs in dealloying solution pH 1, and porous AlZn structure tend to form due to faster dissolution of Al atoms. Rough porous Zn architectures without ZnO form in dealloying solution pH 13.3 accompanying with prevailed Al dissolution. In bulk solution pH 13, nanocomposites consisting of spindle-shaped ZnO on porous Zn (NS–ZnO@P–Zn) form due to near-electrode pH decrease down to stable pH range of ZnO species basing on in-situ pH monitoring results. In-situ oxidation and dealloying of Al50Zn50 precursors under pH mediation can govern the formation of NS-ZnO@P–Zn nanocomposites. Photodegradation performances of methyl orange by NS-ZnO@P–Zn catalysts under visible-light irradiation are much better than porous AlZn and porous Zn catalysts. NS-ZnO@P–Zn nanocomposites with band-gap of 3.10 eV exhibit superior photodegradation efficiency due to photo-induced charge separation.

Ionic surface propensity controls pH in nanopores

<h2>Summary</h2> To predict many proton-involved reactions in natural and engineered systems, a better understanding of the difference between the solution pH in nanopores and the pH in the bulk solution is critical. However, how the pH in nanopores changes in response to changes in the bulk solution composition remains elusive. Here, the capability of surface-enhanced Raman scattering spectroscopy to measure both pH and ion concentrations enables us to discover a new mechanism: opposite ionic surface propensities induce differences in aqueous concentration and control the pH in nanopores. As further confirmed by our modified Poisson-Boltzmann model, in negatively charged nanopores, anion concentrations are still enhanced, whereas cation concentrations are suppressed. These effects can change the buffer's conjugated acid and base ratio and attract protons to compensate for the excess negative charge in nanopores. Collectively, compared with the bulk solution pH, these factors cause an unexpectedly low pH in nanopores.

Chemistry conditions and corrosion behaviour in simulated crevices of alloy steel

ABSTRACT Control and mitigating crevice corrosion demand a thorough understanding of the prevailing chemistry conditions inside the crevice. To match and predict the dynamics in chemistry conditions occurring inside a crevice appropriately, good crevice models necessitate extensive experimental data. This paper presents the accurate determination of the ionic species in the minute volume of crevice solution and redox potential measurements in fabricated simulated crevices of different dimensions/geometry in different stainless steel alloys. Crevice geometries fabricated from carbon steel (CS) 106 B and stainless steel (SS) 316 materials were exposed to varying water chemistry conditions in a static autoclave at high temperatures. The change in pH, conductivity, ionic concentrations, electrochemical potential and effectof corrosion inhibitors inside the crevice were monitored after exposure in an alkaline medium with and without chloride. Bulk solution pH showed a reduction in alkalinity, conductivity and enhancement in anion concentrations. About 58 times increase in Cl− was measured.

Factors Affecting Hydroxide Ion Concentrations in Bipolar Membranes

The useful lifetime of bipolar ion exchange membranes is often limited by nucleophilic attack by hydroxide ions on the ionic groups and polymer backbone in the anion exchange layers (AELs). This is especially problematic in water treatment applications for making acid and base from salt solutions. This research investigated the effect of bulk electrolyte composition, current density, membrane thickness, ion exchange capacity, and bulk solution pH value on hydroxide ion concentrations inside the AELs of a bipolar membrane. Onedimensional Nernst-Plank equations were solved for the species Na+, Cl-, OH- and H+ within 20-100 μm thick anion and cation exchange layers with fixed charged densities ranging from 0.5-2.0 eq/L. In 1 M NaCl solutions at neutral pH values, hydroxide concentrations in the AEL reached as high as 2.2 M at a current density of 100 mA/cm2. In 1 M NaOH solutions, hydroxide ion concentrations reached as high as 3.77 M. Hydroxide concentrations in the AEL were significantly affected by the ratio of Cl- to hydroxide ions in the bulk electrolyte. Where hydroxide concentrations in the bulk electrolyte were an order of magnitude lower than chloride concentrations, membrane hydroxide concentrations were nearly proportional to the current density. Increases in ion exchange capacity and AEL thickness resulted in increased membrane hydroxide ion concentrations. Membrane concentrations of hydroxide ions can be minimized by operation at low current densities, with high background electrolyte concentrations using thin membranes with low ion exchange capacities and producing base concentrations less than 0.1 M.

Influences of electrode distance and electrolysis time on phosphorus precipitation and composition during electrolysis of anaerobic digestion effluent

Global demand for phosphorus (P) is increasing, which has led to concerns over future drought and has driven efforts to recover P from wastewater streams for reuse. In this study, platinum-coated titanium electrodes were applied to the electrochemical precipitation of P from anaerobic digestion effluent that was collected from a domestic wastewater treatment plant. The influence of the electrode distance on P removal and precipitation was investigated. In addition, the influence of the electrolysis time on the chemical structure and composition of the P precipitate was evaluated from the viewpoint of utilising the P precipitate as fertiliser. Regardless of the electrode distance (10, 5 and 1 mm), PO43−, Ca2+ and Mg2+ were removed. The bulk solution pH increased during electrolysis because of the consumption of generated H+ as HCO3− transitioned to H2CO3 near the anode. A greater increase in the bulk solution pH was observed when the electrode distance was narrowed because of the enhanced H+ consumption. Narrowing the electrode distance reduced the energy consumption for P precipitation. The increase in the bulk solution pH with the narrowing electrode distance changed the dominant P precipitation pathway from onto the cathode to in the bulk solution. X-ray diffraction spectra of the precipitates showed that increasing the electrolysis time transformed amorphous P to hydroxyapatite and struvite. Most P existed in a citric acid-soluble form, which is recommended for use as a slow P release fertiliser. There were no significant changes in the citric acid-soluble P content of the precipitates with increasing electrolysis time. Therefore, increasing the electrolysis time has little influence on the suitability of the precipitate as a slow P release fertiliser.

PH Overpotential for Unveiling the pH Gradient Effect of H + /OH − Transport in Electrode Reaction Kinetics

pH Overpotential for Unveiling the pH Gradient Effect of H ⁺ /OH ⁻ Transport in Electrode Reaction Kinetics

A novel submerged anaerobic osmotic membrane bioreactor coupled to membrane distillation for water reclamation from municipal wastewater

A novel configuration of an osmotic anaerobic membrane bioreactor coupled with membrane-assisted distillation (OMBR-MD) in a single submerged module was proposed for domestic sewage treatment and potabilization. A steady permeate flux was achieved after the 22nd day of monitoring, in which the draw solution (DS) was diluted by the forward osmosis (FO) permeate at the same rate in which it was concentrated by the membrane distillation (MD). Salinity build-up inside the bioreactor contributed to fouling in the FO membrane since it increases the production of soluble microbial products and extracellular polymeric substances. In addition, organic matter accumulated in DS, due to the closed-loop system, may be the main cause for fouling in MD membranes at the latter stages. The OMBR-MD presented great removal for organic matter (91%), phosphorous (95%) and ammonium nitrogen (71%). Alkalinity accumulation within the bioreactor prevented a significant change in bulk solution pH (8.0 – 8.4), reducing the effects of volatile fatty acids production on methanogenic performance. The OMBR-MD removal efficiencies were higher than 96% for all 7 selected pharmaceutical drugs. Additionally, the MD distillate attained eight out of the nine parameters assessed for potable water standards established in Brazilian legislations and recommendations from US EPA, including Escherichia coli. Therefore, the novel OMBR-MD proved to be a feasible alternative for treating municipal wastewater, generating a high-quality distillate.

Electrostatic properties of inner nanopore surfaces of anodic aluminum oxide membranes upon high temperature annealing revealed by EPR of pH-sensitive spin probes and labels

Anodic aluminum oxide (AAO) membranes are versatile nanomaterials that combine the chemically stable and mechanically robust properties of ceramics with homogeneous nanoscale organization that can be tuned to desirable pore diameters and lengths. The AAO substrates feature high surface area that is readily accessible to large and small molecules, making these nanostructures uniquely suited for many possible applications. Examples include templated self-assembly of macroscopically aligned biological membranes and substrates for heterogeneous catalysis. For further development of such applications, one would like to characterize and tune the electrostatic properties of the inner pore surface as well as the local acidity within the nanochannels. Here, we employed electron paramagnetic resonance (EPR) spectroscopy of a small molecule – ionizable nitroxide – as a reporter of the average local acidity in the nanochannels and the local electrostatic potential in the immediate vicinity of the pore surface. The former was achieved by measuring EPR spectra of this molecular probe diffusing in an aqueous phase confined in the AAO nanochannels while for the latter the nitroxide was covalently attached to the hydroxyl group of the alumina surface. We show that the local acidity within the nanochannels is increased by as much as ≈1.48 pH units vs. the pH of bulk solution by decreasing the pore diameter down to ca. 31 nm. Furthermore, the positive surface charge of the as-prepared AAO could be decreased and even switched to a negative surface charge upon annealing the membranes first to 700 °C and then to 1200 °C. For as-prepared AAO, the local electrostatic potential reaches ψ= (163 ± 5) mV for the nitroxide label covalently attached to AAO and located about 0.5 nm away from the surface. Overall, we demonstrate that the acid-based properties of the aqueous volume confined by the AAO nanopores pores can be tuned by either changing the pore diameter from ca. 71 to 31 nm or by thermal annealing to switch the sign of the surface charge. These observations provide a simple and robust means to tailor these versatile high-surface-area nanomaterials for specific applications that depend on acid-base equilibria.

Exploring Microenvironment Acidity Inside the Solvent-Filled Pores of Mesoporous Silica Thin Films via Single-Molecule Spectroscopy

Single-molecule (SM) spectroscopy was used to study the local acidity inside solution-filled silica mesopores. The dual emission, pH-sensitive dye C-SNARF-1 was used as the fluorescent probe. Mesoporous materials were prepared as thin films supported on glass substrates. A microfluidic device was used to seal the upper surface of the films and to allow for their exposure to flowing aqueous solutions of the dye under different pH and ionic strength conditions. Single-molecule data were collected by two-color wide-field fluorescence imaging in the pseudototal internal reflection fluorescence mode. Pairs of fluorescence images were acquired simultaneously in bands centered around 580 and 640 nm, each having a 40 nm bandwidth. The ratio of C-SNARF-1 emission in these two bands (I580/I640) is highly sensitive to pH in bulk solution. The SM data show that C-SNARF-1 remains sensitive to pH in mesoporous materials, but that the emission ratios obtained are often larger than in bulk solution. Results obtained as a...

Application of ammonium bicarbonate buffer as a smart microenvironmental pH regulator of immobilized cephalosporin C acylase catalysis in different reactors.

In a stirred tank reactor, during catalysis with immobilized cephalosporin C acylase (CCA), the microenvironmental pH dropped to 7.2 in a nonbuffered system (with the pH maintained at 8.5 by adding alkali) due to the existence of diffusional resistance. Moreover, the immobilized CCA only catalyzed five batch reactions, suggesting that the sharp pH gradient impaired the enzyme stability. To buffer the protons produced in the hydrolysis of cephalosporin C by CCA, phosphate and bicarbonate buffers were introduced. When CCA was catalyzed with 0.1 M ammonium bicarbonate buffer, no obvious gradient between the bulk solution and intraparticle pH was detected, and the catalysis of 15 batch reactions was achieved. Accordingly, with 0.2 M ammonium bicarbonate buffer in a packed bed reactor, the immobilized CCA exhibited continuous catalysis with high conversion rates (≥95%) for 21 days. Reactions with ammonium bicarbonate buffer showed significant increases in the stability and catalytic efficiency of the immobilized CCA in different reactors compared to those in nonbuffered systems.

Molecular theory of glyphosate adsorption to pH-responsive polymer layers

By means of a molecular-level theory we investigate glyphosate adsorption from aqueous solutions to surface-grafted poly(allylamine) layers. Our molecular model of glyphosate and the polymeric material includes description of size, shape, conformational freedom, and state of protonation of both components. The composition of the bulk solution (pH, salt concentration and glyphosate concentration) plays a critical role to determine adsorption. Adsorption is a non-monotonic function of the solution pH, which can be explained in terms of the pH-dependent protonation behavior of both adsorbate and adsorbent material. Lowering the solution salinity is an efficient way to enhance glyphosate adsorption. This is because glyphosate and salt anions compete for adsorption to the polymer layer. In this competition, glyphosate deprotonation, to increase its negative charge upon entering the polymer layer, plays an critical role to favor its adsorption under a variety of solution conditions. This deprotonation is the result of the higher pH that establishes inside the polymer. Our results show that such pH increase can be controlled, while achieving significant glyphosate adsorption, through varying the grafting density of the material. This result is important since glyphosate degradation by microbial activity is pH-dependent. These polymeric systems are excellent candidates for the development functional materials that combine glyphosate sequestration and in situ biodegradation.

Electrophoretic and potentiometric signatures of multistage CaCO3 nucleation

HypothesisCalcium carbonate nucleation is often a complex and multistep process that is difficult to follow in situ. The time-resolved electrochemical and electrophoretic methods can provide a new insight into the nucleation pathway. ExperimentsHere, we used a combination of speciation calculations with time-resolved electrophoretic and potentiometric methods to monitor calcium carbonate precipitation from a slightly supersaturated solution. FindingsAfter an initial mixing period of three minutes in which metastable CaCO3 phases may have nucleated and subsequently dissolved due to locally-high supersaturations, bulk solution pH and Ca2+ concentrations stabilize before decreasing in tandem with the precipitation of a CaCO3 phase. After an hour, the precipitate is dominated by calcite that grows at the expense of dissolving vaterite. The time-dependent electrokinetic potential shows analogous signatures of multistage nucleation process: initial rapid changes in ζ-potential are followed by much slower equilibration starting about one hour after reagents are mixed. The changes in ζ-potential, solution pH, saturation indexes, and particle morphology are consistent with vaterite to calcite transformation via dissolution of the former and recrystallization of the latter. These findings highlight the potential use of ζ-potential measurements for monitoring polymorphic transformations of carbonate phases in-situ.

Carbon Fiber-Based Flow-Through Electrode System (FES) for Water Disinfection via Direct Oxidation Mechanism with a Sequential Reduction-Oxidation Process.

Flow-through configuration for electrochemical disinfection is considered as a promising approach to minimize the formation of toxic byproducts and energy consumption via the enhanced convective mass transport as compared with conventional flow-by one. Under this hydrodynamic condition, it is essential to ascertain the effect of sequential electro-redox processes with the cathode/anode then anode/cathode arrangements on disinfection performance. Here, carbon fiber felt (CFF) was utilized to construct two flow-through electrode systems (FESs) with sequential reduction-oxidation (cathode-anode) or oxidation-reduction (anode-cathode) processes to systematically compare their disinfection performance toward a model Escherichia coli ( E. coli) pathogen. In-situ sampling and live/dead backlight staining experiments revealed that E. coli inactivation mainly occurred on anode via an adsorption-inactivation-desorption process. In reduction-oxidation system, after the cathode-pretreatment, bulk solution pH increased significantly, leading to the negative charge of E. coli cells. Hence, E. coli cells were adsorbed and inactivated easily on the subsequent anode, finally resulting in its much better disinfection performance and energy efficiency than the oxidation-reduction system. Application of 3.0 V resulted in ∼6.5 log E. coli removal at 1500 L m-2 h-1 (50 mL min-1), suggesting that portable devices can be designed from CFF-based FES with potential application for point-of-use water disinfection.