Charles-François de Lannoy

Electrically conductive membranes (ECMs) have emerged as a multifunctional separation technology that integrates membrane filtration with electrochemical reactions. Physical stability remains a critical challenge for ECMs synthesized by coating polymer membranes with conductive materials. In this article, polydopamine (PDA) and polyethyleneimine (PEI) were used to facilitate the synthesis of significantly more stable ECMs using poly(vinylidene fluoride) (PVDF) ultrafiltration membranes and carbon nanotubes (CNTs). Four different synthesis methods were compared in terms of the final surface stability and separation properties: (1) CNTs deposited on PEI-crosslinked PDA-coated PVDF membranes, (2) PEI-crosslinked CNTs deposited on PDA-coated PVDF, (3) PDA, PEI and CNTs sequentially deposited layer-by-layer on PVDF, and (4) PEI-crosslinked PDA deposited on CNT-coated PVDF. The results revealed that method 1 generated ECMs with the greatest physical stability, highest electrical conductivity (18,518 S/m), and sufficient permeability (395.2 L/(m2·h·bar). In comparison, method 2 resulted in membranes with the highest permeability (2128.5 L/(m2·h·bar), but with low surface conductivity (502 S/m) and poor physical stability (i.e., 53–75% lower peel-off forces compared to other methods). Overall, methods 1, 3, and 4 can be used to make highly conductive membranes with a 97–99% removal of methyl orange by electrochemical degradation at −3 V.

Electrochemical membranes (ECMs) are an emerging multifunctional separation technology that enables simultaneous contaminant filtration and reaction due to their electrically conductive porous surface coatings. Physical coating stability remains a technical challenge for ECMs, which are largely based on carbonaceous nanomaterials or metallic thin films. In this research, binding chemistry based on polydopamine (PDA) and polyethylenimine (PEI) was developed to prepare physically stable ECMs. Poly(vinylidene fluoride) (PVDF) ultrafiltration membranes were coated with PEI cross-linked PDA followed by the deposition of carboxyl-functionalized single/double-walled carbon nanotubes (SW/DWCNTs-COOH). Fabricated membranes were characterized for their structural, physicochemical, electrochemical, and separation properties. In a batch electrochemical system, the membranes achieved >99.2 …

BACKGROUNDAerosol barrier enclosure systems have been designed to prevent airborne contamination, but their safety has been questioned. A vacuum tent was designed with active continuous suctioning to minimize risks of aerosol dispersion. We tested its efficacy, risk of rebreathing, and usability on a bench, in healthy volunteers, and in an ergonomic clinical assessment study.METHODSFirst, a manikin with airway connected to a breathing simulator was placed inside the vacuum tent to generate active breathing, cough, and CO2 production; high-flow nasal cannula (HFNC) was applied in the manikin’s nares. Negative pressure was applied in the vacuum tent’s apex port using wall suction. Fluorescent microparticles were aerosolized in the vacuum tent for qualitative assessment. To quantify particles inside and around vacuum tent (aerosol retention), an airtight aerosol chamber with aerosolized latex …

Electrochemical membranes (ECMs) and porous electrodes have gained much attention in a broad range of applications including water and wastewater treatment, energy production and storage, and carbon dioxide capture. Lab scale batch experiments (electrochemical stirred cells) are the baseline for developing ECMs and porous electrodes. We observed electrochemical dissolution of metal fasteners (alligator clips), used to hold porous conductive and non‐conductive membranes in batch electrochemical cells, despite being kept outside the electrolyte. The electrolyte migrated through the porous membranes by the action of capillary forces, forming a closed electrochemical circuit with the metal fasteners. This unexpected leaching can lead to misleading results for electrochemical experiments on porous electrodes and ECMs. In this study, we compared (1) porous membranes versus non‐porous electrodes …

Wastewater generated from e-waste leaching is rich in precious metals including gold, silver and platinum. Conventional precipitation and solvent extraction are chemically intensive separations with concerning environmental externalities. Sorbents, in particular carbon nanotubes, have low chemical consumption, and have shown promise for gold adsorption due to their high specific surface area and chemical functionalization potential. However, regenerating sorbents used to adsorb Au is hazardous requiring strong acids. Herein, we delineate the effect of various functional groups on the sidewalls of multiwall carbon nanotubes (MWCNTs) on gold adsorption, and we introduced an acid-free electrochemical technique for Au elution from MWCNTs. Pristine MWCNTs (P-MWCNTs), carboxylic functionalised MWCNTs (COOH-MWCNTs) and amide functionalised MWCNTs (NH 2-MWCNTs) were compared for their …

Importance Masks reduce transmission of SARS-CoV2 and other respiratory pathogens. Comparative studies of the fitted filtration efficiency of different types of masks of are few.   Objective To describe the fitted filtration efficiency against small aerosols (0.02 – 1 µm) of medical and non-medical masks and respirators when worn, and how this is affected by user modifications (hacks) and by overmasking with a cloth mask.   Design We tested a 2-layer woven-cotton cloth mask of a consensus design, ASTM-certified level 1 and level 3 masks, a non-certified mask, KF94s, KN95s, an N95 and a CaN99.   Setting Closed rooms with ambient particles supplemented by salt particles.   Participants 12 total participants; 21 – 55 years, 68% female, 77% white, NIOSH 1 to 10.   Main Outcome and Measure Using standard methods and a PortaCount 8038, we counted 0.02–1µm particles inside and outside masks and respirators, expressing results as the percentage filtered by each mask. We also studied level 1 and level 3 masks with earguards, scrub caps, the knot-and-tuck method, and the effects of braces or overmasking with a cloth mask.   Results Filtration efficiency for the cloth mask was 47-55%, for level 1 masks 52-60%, for level 3 masks 60-77%. A non-certified KN95 look-alike, two KF94s, and three KN95s filtered 57-77%, and the N95 and CaN99 97-98% without fit testing. External braces and overmasking with a well-fitting cloth mask increased filtration, but earguards, scrub caps, and the knot-and-tuck method did not.   Limitations Limited number of masks of each type sampled; no adjustment for multiple comparisons.   Conclusions and Relevance …

Catalytic membrane microreactors (CMMRs) are an exciting new technology that combine catalysis with membranes by seeding the high internal surface area of membranes with catalysts. This enables the continuous purification and production of organic compounds with high catalytic activity, while maintaining nanocatalyst size and stability. This study reports a simple two-step batch reaction approach for synthesizing stable Pd-immobilized catalytic membranes to transform 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in a flow-through CMMR system. The product (4-AP) is an essential intermediate for the polymer and solvent chemical industry. Pd-immobilized membranes exhibited strong catalytic activity for 4-NP reduction in the presence of NaBH 4, with 4-fold higher reduction (79.7%) and 2-fold higher reduction rate (1.08 mol m− 2 h− 1) as compared to control membranes without catalysts. The catalytic …

Wettability plays a significant role in controlling multiphase flow in porous media for many industrial applications, including geologic carbon dioxide sequestration, enhanced oil recovery, and fuel cells. Microfluidics is a powerful tool to study the complexities of interfacial phenomena involved in multiphase flow in well-controlled geometries. Recently, the thiolene-based polymer called NOA81 emerged as an ideal material in the fabrication of microfluidic devices, since it combines the versatility of conventional soft photolithography with a wide range of achievable wettability conditions. Specifically, the wettability of NOA81 can be continuously tuned through exposure to UV–ozone. Despite its growing popularity, the exact physical and chemical mechanisms behind the wettability alteration have not been fully characterized. Here, we apply different characterization techniques, including contact angle measurements, X …

Emerging contaminants in potable waters and wastewaters are a global concern exacerbated by industrial growth. Graphene-based nanomaterials (e.g., rGO) incorporated at a membrane’s surface have been shown to enhance separation performance by increasing adsorption and altering membrane pore size. However, rGO surface-deposited membranes demonstrate low water fluxes and poor stability due to high rGO interlayer packing density and nanosheet swelling. Herein, a cationic polyelectrolyte cross-linked rGO nanocomposite membrane was developed to address these issues. These membranes were formed by a layer of iron doped rGO (rGO–Fe) cross-linked with hyperbranched polyethylenimine (HPEI) vacuum-deposited onto a polydopamine (PDA) coated polyethersulfone (PES) ultrafiltration membrane. The HPEI cross-linking of iron-doped rGO was accomplished by 1) activating the carbonyl …

Despite the significant increase in research on mask filtration testing since the COVID-19 pandemic, there remains considerable ambiguity regarding which parameters affect particle filtration efficiency (PFE) and how differences in standard testing protocols can lead to divergent PFE values. We evaluated the PFE (and differential pressure) of several common face masks and community face mask materials including woven cotton, spunbond polypropylene, and meltblown polypropylene, testing in accordance with ASTM F2100/2299 standards for medical masks, using polystyrene latex (PSL) aerosol, as well as NIOSH standards for respirators, using NaCl aerosol. In both cases, PFE was measured with and without aerosol charge neutralization, which is used to bring the particle population to a known, equilibrium bipolar charge distribution. Aerosols of either composition that were untreated (not neutralized) led to …

Bimetallic nanocatalysts are of great interest due to their greater activity, selectivity, and chemical and electrochemical stability, compared to their monometallic counterparts. Bimetallic nanocatalysts formed from abundant and inexpensive elements provide greater opportunities for applications over noble metal catalysts. In this study, inexpensive Ni-Cu bimetallic catalytic membrane microreactors (CMMRs) were synthesized in a simple two-step process to catalytically degrade the environmental pollutant, 4-nitrophenol (4-NP), and produce the valuable feedstock, 4-aminophenol (4-AP). Ni-Cu nanoparticles were either produced by a replacement reduction reaction or a co-reduction reaction, producing either bimodal or integrated nanostructures, respectively, as demonstrated by transmission electron microscopy (TEM), while the electronic reconfiguration between bimetallic systems was verified by X-ray …

Transition-metal phosphides (TMPs) are emerging electrocatalysts for both hydrogen evolution and the conversion of reactants/contaminants by various electrochemical reactions. TMPs are promising catalysts because they are earth abundant, have high electrical conductivity, and have high chemical stability. In this seminal work, a low-priced nickel phosphorus (Ni-P) ultrafiltration membrane was fabricated and used for electrochemical reductive dechlorination of chlorophenols. Amorphous Ni-P nanoparticles were grown on an ultrafiltration poly(ether sulfone) (PES) membrane via electroless deposition. The prepared Ni-P membrane was used as a cathode for electrochemical reductive dechlorination of 2-chlorophenol (2-CP) in flow-through mode. It was observed that a dechlorination efficiency of 42.7%, a reaction rate constant of 1.621 min–1, and a Faradaic efficiency of 24.5% were achieved at an optimized …

The prevalence of organic micropollutants (OMPs) and their persistence in water supplies have raised serious concerns for drinking water safety and public health. Conventional water treatment technologies, including adsorption and biological treatment, are known to be insufficient in treating OMPs and have demonstrated poor selectivity toward a wide range of OMPs. Pressure-driven membrane filtration has the potential to remove many OMPs detected in water with high selectivity as a membrane’s molecular weight cutoff (MWCO), surface charge, and hydrophilicity can be easily tailored to a targeted OMP’s size, charge and octanol–water partition coefficient (Kow). Over the past 10 years, polymeric (nano)composite microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes have been extensively synthesized and studied for their ability to remove OMPs. This review discusses the fate and transport …

This study investigated the abilities of electrochemically active bacteria (EAB) as bio-catalysts for Pb(II) bioreduction in an attached growth reactor. Electrically conductive carbon nanofibers (CNF) were used as bacterial scaffolds to facilitate electron transfer between EAB and Pb(II). Our results demonstrated that the CNF attached growth reactor can remove > 80% and > 90% of Pb(II) from solution at 0.5 mg/L and 5.0 mg/L concentrations, respectively, and maintained Pb(II) levels < 0.10 mg/L over repeated Pb(II) dosages dosed at all concentrations. Experimental measurements by SEM-EDX and ICP-OES provided evidence that Pb(II) was reduced to Pb0, suggesting that Pb(II) was adsorbed onto CNFs, and subsequently bioreduced. Numerical modelling was used to estimate Pb(II) concentrations along the CNFs via capturing Pb(II)’s diffusive transport, and the removal mechanisms governed by EAB and CNF …

Pollutant leaching from wildfire-impacted peatland soils (peat) is well-known, but often underestimated when considering boreal ecosystem source water protection and when treating source waters to provide clean drinking water. Burning peat impacts its physical properties and chemical composition, yet the consequences of these transformations to source water quality through pollutant leaching has not been studied in detail. We combusted near-surface boreal peat under simulated peat smoldering conditions at two temperatures (250 °C and 300 °C) and quantified the concentrations of the leached carbon, nutrients and phenols from 5 g peat L−1 reverse osmosis (RO) water suspensions over a 2-day leaching period. For the conditions studied, measured water quality parameters exceeded US surface water guidelines and even exceeded EU and Canadian wastewater/sewer discharge limits including chemical …

Biofouling detection enables the adoption of effective cleaning strategies for biofouling prevention. This work investigates the use of electrical impedance spectroscopy (EIS) to monitor the biofilm development and the use of electric fields to mitigate biofouling on the surface of gold-coated membranes. The multi-bacterial suspension was injected into a two-electrode crossflow filtration system where the permeate flux and impedance spectra were recorded to monitor the biofilm growth. Permeate flux declined over time while the impedance at low frequency regions (<10 Hz) rapidly decreased with fouling at the early stages of fouling, and then gradually decreased as biofilm matured. The normalized diffusion-related impedance (Rd), an EIS-derived parameter, was extracted to determine the sensitivity of EIS detection. We observed that impedance-based detection was more sensitive to changes as compared to the …

The objective of this study was to characterize commercially-available cotton fabrics to determine their suitability as materials for construction of cloth masks for personal and public use to reduce infectious disease spread. The study focused on cottons because of their widespread availability, moderate performance and they are recommended for inclusion in home-made masks by international health authorities. Fifty-two cottons were analyzed by electron microscopy to determine fabric characteristics and fabric weights. Sixteen fabrics were selected to test for breathability and to construct 2-ply cotton masks of a standard design to use in quantitative fit testing on a human participant. Cotton mask fitted filtration efficiencies (FFEs) for 0.02–1 μm ambient and aerosolized sodium chloride particles ranged from 40 to 66% compared with the mean medical mask FFE of 55±2%. Pressure differentials across 2-ply materials ranged from 0.57 to > 12 mm H2O/cm2 on samples of equal surface area with 6 of 16 materials exceeding the recommended medical mask limit. Models were calibrated to predict 2-ply cotton mask FFEs and differential pressures for each fabric based on pore characteristics and fabric weight. Models indicated cotton fabrics from 6 of 9 consumer categories can produce cloth masks with adequate breathability and FFEs equivalent to a medical mask: T-shirt, fashion fabric, mass-market quilting cotton, home décor fabric, bed sheets and high-quality quilting cotton. Masks from one cloth mask and the medical mask were re-tested with a mask fitter to distinguish filtration from leakage. The fabric and medical masks had 3.7% and 41.8 …

Water issues in Indigenous communities of “Canada” are rooted in the settler-nation’s history of colonialism. Conventional approaches to water management have failed to provide Indigenous communities with water security and limit Indigenous self-determination. Innovative and community-led approaches to water monitoring and management can help promote Indigenous water governance. The Co-Creation of Indigenous Water Quality Tools (CCIWQT) research project is a Haudenosaunee-led approach to improving water security in Six Nations of the Grand River (Six Nations). In alignment with the needs and priorities of Six Nations and underpinned by Haudenosaunee values, the goal of CCIWQT is to develop a broad range of “tools” that can assist in enhancing the community's control over their water management. These tools are being developed through a novel interpretation of co-creation. For CCIWQT …

The surface properties of electrically conductive membranes (ECMs) govern their advanced abilities. During operation, these properties may differ considerably from their initially measured properties. Depending on their operating conditions, ECMs may undergo various degrees of passivation. ECM passivation can detrimentally impact their real time performance, causing large deviations from expected behaviour based on their initially measured properties. Quantifying these changes will enable consistent performance comparisons across the active and electrically conductive membrane research field. As such, consistent methods must be established to quantify ECM membrane properties. In this work, we proposed three standardized methods to assess the electrochemical, chemical, and physical stability of such membrane coatings: 1) electrochemical oxidation, 2) surface scratch testing, and 3) pressurized …

A range of conductive materials have been used to develop electrically conductive membranes (ECMs) for use in various applications, including fouling mitigation, selectivity enhancement, electrochemical degradation of contaminants, and surface sensing capabilities. ECMs have been fabricated both as stand-alone porous materials and as composite materials wherein the conductive material is supported on a conventional membrane. In this meta-analysis, we classify composite ECMs from 111 studies based on their physical properties and specific applications in order to identify their material limitations, performance trends, and avenues for future work. During this analysis, two major challenges were identified: the wide variety of test conditions (98 unique pollutants across 193 different experiments) used by researchers, which makes it difficult to perform cross-study comparisons, and a very limited body of ECM …