Method of H2 Transfer Is Vital for Catalytic Hydrodefluorination of Perfluorooctanoic Acid (PFOA).

The efficient transfer of H2 plays a critical role in catalytic hydrogenation, particularly for the removal of recalcitrant contaminants from water. One of the most persistent contaminants, perfluorooctanoic acid (PFOA), was used to investigate how the method of H2 transfer affected the catalytic hydrodefluorination ability of elemental palladium nanoparticles (Pd0NPs). Pd0NPs were synthesized through an in situ autocatalytic reduction of Pd2+ driven by H2 from the membrane. The Pd0 nanoparticles were directly deposited onto the membrane fibers to form the catalyst film. Direct delivery of H2 to Pd0NPs through the walls of nonporous gas transfer membranes enhanced the hydrodefluorination of PFOA, compared to delivering H2 through the headspace. A higher H2 lumen pressure (20 vs 5 psig) also significantly increased the defluorination rate, although 5 psig H2 flux was sufficient for full reductive defluorination of PFOA. Calculations made using density functional theory (DFT) suggest that subsurface hydrogen delivered directly from the membrane increases and accelerates hydrodefluorination by creating a higher coverage of reactive hydrogen species on the Pd0NP catalyst compared to H2 delivery through the headspace. This study documents the crucial role of the H2 transfer method in the catalytic hydrogenation of PFOA and provides mechanistic insights into how membrane delivery accelerates hydrodefluorination.

Advanced oxidation processes may transform unknown PFAS in groundwater into known products.

Per- and polyfluoroalkyl substances (PFAS) are a group of fluorinated organic contaminants classified as persistent in the aquatic environment. Early studies using targeted analysis approaches to evaluate the degradation of PFAS by advanced oxidation processes (AOP) in real water matrices may have been misinterpreted due to the presence of undetected or unknown PFAS in these matrices. The aims of the present study were to (1) screen selected commercially available AOPs (UV, UV + H2O2, O3/H2O2) and UV photocatalysis in a pilot system using commercially used and novel photocatalysts (TiO2, boron nitride [BN]) for removing PFAS contaminants and (2) evaluate their role on the conversion of non-detected/unknown to known PFAS compounds in real groundwater used as drinking water supplies. Results indicated that, while AOPs have the potential to achieve removal of the EPA method 533 target PFAS compounds (PFDA [100%], PFNA [100%], PFOA [85-94%], PFOS [25-100%], PFHxS [3-100%], PFPeS [100%], PFBS [100%]), AOPs transformed non-detected/unknown longer-chain PFAS compounds to detectable shorter-chain ones under very high-dose AOP operating conditions, leading to an increase in ∑PFAS concentration ranging from 95% to 340%. As emerging PFAS treatment processes transition from lab-scale investigations of target PFAS to pilot testing of real water matrices, studies will need to consider impact of the presence of non-target long-chain PFAS to transform into targeted PFAS compounds. A promising approach to address the potential risks and unforeseen consequences could involve an increased reliance on adsorbable organic fluorine (AOF) analysis before and after advanced oxidation process (AOP) treatment.

Contrasting Capability of Single Atom Palladium for Thermocatalytic versus Electrocatalytic Nitrate Reduction Reaction.

The occurrence of high concentrations of nitrate in various water resources is a significant environmental and human health threat, demanding effective removal technologies. Single atom alloys (SAAs) have emerged as a promising bimetallic material architecture in various thermocatalytic and electrocatalytic schemes including nitrate reduction reaction (NRR). This study suggests that there exists a stark contrast between thermocatalytic (T-NRR) and electrocatalytic (E-NRR) pathways that resulted in dramatic differences in SAA performances. Among Pd/Cu nanoalloys with varying Pd-Cu ratios from 1:100 to 100:1, Pd/Cu(1:100) SAA exhibited the greatest activity (TOFPd = 2 min-1) and highest N2 selectivity (94%) for E-NRR, while the same SAA performed poorly for T-NRR as compared to other nanoalloy counterparts. DFT calculations demonstrate that the improved performance and N2 selectivity of Pd/Cu(1:100) in E-NRR compared to T-NRR originate from the higher stability of NO3* in electrocatalysis and a lower N2 formation barrier than NH due to localized pH effects and the ability to extract protons from water. This study establishes the performance and mechanistic differences of SAA and nanoalloys for T-NRR versus E-NRR.

Comparing methods to deposit Pd-In catalysts on hydrogen-permeable hollow-fiber membranes for nitrate reduction.

Catalytic hydrogenation of nitrate in water has been studied primarily using nanoparticle slurries with constant hydrogen-gas (H2) bubbling. Such slurry reactors are impractical in full-scale water treatment applications because 1) unattached catalysts are difficult to be recycled/reused and 2) gas bubbling is inefficient for delivering H2. Membrane Catalyst-film Reactors (MCfR) resolve these limitations by depositing nanocatalysts on the exterior of gas-permeable hollow-fiber membranes that deliver H2 directly to the catalyst-film. The goal of this study was to compare the technical feasibility and benefits of various methods for attaching bimetallic palladium/indium (Pd/In) nanocatalysts for nitrate reduction in water, and subsequently select the most effective method. Four Pd/In deposition methods were evaluated for effectiveness in achieving durable nanocatalyst immobilization on the membranes and repeatable nitrate-reduction activity: (1) In-Situ MCfR-H2, (2) In-Situ Flask-Synthesis, (3) Ex-Situ Aerosol Impaction-Driven Assembly, and (4) Ex-Situ Electrostatic. Although all four deposition methods achieved catalyst-films that reduced nitrate in solution (≥ 1.1 min-1gPd-1), three deposition methods resulted in significant palladium loss (>29%) and an accompanying decline in nitrate reactivity over time. In contrast, the In-Situ MCfR-H2 deposition method had negligible Pd loss and remained active for nitrate reduction over multiple operational cycles. Therefore, In-Situ MCfR-H2 emerged as the superior deposition method and can be utilized to optimize catalyst attachment, nitrate-reduction, and N2 selectivity in future studies with more complex water matrices, longer treatment cycles, and larger reactors.

Mechanistic Insight into the Photo-Oxidation of Perfluorocarboxylic Acid over Boron Nitride.

Hexagonal boron nitride (hBN) can photocatalytically oxidize and degrade perfluorocarboxylic acids (PFCA), a common member of the per/polyfluoroalkyl substance (PFAS) family of water contaminants. However, the reaction mechanism governing PFCA activation on hBN is not yet understood. Here, we apply electronic grand canonical density functional theory (GC-DFT) to assess the thermodynamic and kinetic favorability of PFCA photo-oxidative activation on hBN: CnF2n+1COO- + h+ → CnF2n+1· + CO2. The oxidation of all PFCA chains is exothermic under illumination with a moderate barrier. However, the longer-chain PFCAs are degraded more effectively because they adsorb on the surface more strongly as a result of increased van der Waals interactions with the hBN surface. The ability of hBN to act as a photocatalyst is unexpected because of its wide band gap. Therefore, we apply both theoretical and experimental analyses to examine possible defects on hBN that could account for its activity. We find that a nitrogen-boron substitutional defect (NB), which generates a mid-gap state, can enhance UVC (ultraviolet C) absorption and PFCA oxidation. This work provides insight into the PFCA oxidation mechanism and reveals engineering strategies to design better photocatalysts for PFCA degradation.

Hydrodefluorination of Perfluorooctanoic Acid in the H2-Based Membrane Catalyst-Film Reactor with Platinum Group Metal Nanoparticles: Pathways and Optimal Conditions.

PFAAs (perfluorinated alkyl acids) have become a concern because of their widespread pollution and persistence. A previous study introduced a novel approach for removing and hydrodefluorinating perfluorooctanoic acid (PFOA) using palladium nanoparticles (Pd0NPs) in situ synthesized on H2-gas-transfer membranes. This work focuses on the products, pathways, and optimal catalyst conditions. Kinetic tests tracking PFOA removal, F- release, and hydrodefluorination intermediates documented that PFOA was hydrodefluorinated by a mixture of parallel and stepwise reactions on the Pd0NP surfaces. Slow desorption of defluorination products lowered the catalyst's activity for hydrodefluorination. Of the platinum group metals studied, Pd was overall superior to Pt, Rh, and Ru for hydrodefluorinating PFOA. pH had a strong influence on performance: PFOA was more strongly adsorbed at higher pH, but lower pH promoted defluorination. A membrane catalyst-film reactor (MCfR), containing an optimum loading of 1.2 g/m2 Pd0 for a total Pd amount of 22 mg, removed 3 mg/L PFOA during continuous flow for 90 days, and the removal flux was as high as 4 mg PFOA/m2/d at a steady state. The EPA health advisory level (70 ng/L) also was achieved over the 90 days with the influent PFOA at an environmentally relevant concentration of 500 ng/L. The results document a sustainable catalytic method for the detoxification of PFOA-contaminated water.

Utilizing the Broad Electromagnetic Spectrum and Unique Nanoscale Properties for Chemical-Free Water Treatment.

Clean water is critical for drinking, industrial processes, and aquatic organisms. Existing water treatment and infrastructure are chemically-intensive and based on nearly century-old technologies that fail to meet modern large and decentralized communities. The next-generation of water processes can transition from outdated technologies by utilizing nanomaterials to harness energy from across the electromagnetic spectrum, enabling electrified and solar-based technologies. The last decade was marked by tremendous improvements in nanomaterial design, synthesis, characterization, and assessment of material properties. Realizing the benefits of these advances requires placing greater attention on embedding nanomaterials onto and into surfaces within reactors and applying external energy sources. This will allow nanomaterial-based processes to replace Victorian-aged, chemical intensive water treatment technologies.

Adsorption and Reductive Defluorination of Perfluorooctanoic Acid over Palladium Nanoparticles.

Per- and polyfluoroalkyl substances (PFASs) comprise a group of widespread and recalcitrant contaminants that are attracting increasing concern due to their persistence and adverse health effects. This study evaluated removal of one of the most prevalent PFAS, perfluorooctanoic acid (PFOA), in H2-based membrane catalyst-film reactors (H2-MCfRs) coated with palladium nanoparticles (Pd0NPs). Batch tests documented that Pd0NPs catalyzed hydrodefluorination of PFOA to partially fluorinated and nonfluorinated octanoic acids; the first-order rate constant for PFOA removal was 0.030 h-1, and a maximum defluorination rate was 16 µM/h in our bench-scale MCfR. Continuous-flow tests achieved stable long-term depletion of PFOA to below the EPA health advisory level (70 ng/L) for up to 70 days without catalyst loss or deactivation. Two distinct mechanisms for Pd0-based PFOA removal were identified based on insights from experimental results and density functional theory (DFT) calculations: (1) nonreactive chemisorption of PFOA in a perpendicular orientation on empty metallic surface sites and (2) reactive defluorination promoted by physiosorption of PFOA in a parallel orientation above surface sites populated with activated hydrogen atoms (Hads*). Pd0-based catalytic reduction chemistry and continuous-flow treatment may be broadly applicable to the ambient-temperature destruction of other PFAS compounds.

Unified Metallic Catalyst Aging Strategy and Implications for Water Treatment.

Heterogeneous catalysis holds great promise for oxidizing or reducing a range of pollutants in water. A well-recognized, but understudied, barrier to implement catalytic treatment centers around fouling or aging over time of the catalyst surfaces. To better understand how to study catalyst fouling or aging, we selected a representative bimetallic catalyst (Pd-In supported on Al2O3), which holds promise to reduce nitrate to innocuous nitrogen gas byproducts upon hydrogen addition, and six model solutions (deionized water, sodium hypochlorite, sodium borohydride, acetic acid, sodium sulfide, and tap water). Our novel aging experimental apparatus permitted single passage of each model solution, separately, through a small packed-bed reactor containing replicate bimetallic catalyst "beds" that could be sacrificed weekly for off-line characterization to quantify impacts of fouling or aging. The composition of the model solutions led to the following gradual changes in surface composition, morphology, or catalytic reactivity: (i) formation of passivating species, (ii) decreased catalytic sites due to metal leaching under acid conditions or sulfide poisoning, (iii) dissolution and/or transformation of indium, (iv) formation of new catalytic sites by the introduction of an additional metallic element, and (v) oxidative etching. The model solution water chemistry captured a wide range of conditions likely to be encountered in potable or industrial water treatment. Aging-induced changes altered catalytic activity and provided insights into potential strategies to improve long-term catalyst operations for water treatment.

Memory Seeds Enable High Structural Phase Purity in 2D Perovskite Films for High-Efficiency Devices.

2D perovskites are a class of halide perovskites offering a pathway for realizing efficient and durable optoelectronic devices. However, the broad chemical phase space and lack of understanding of film formation have led to quasi-2D perovskite films with polydispersity in perovskite layer thicknesses, which have hindered device performance and stability. Here, a simple and scalable approach is reported, termed as the "phase-selective method", to fabricate 2D perovskite thin films with homogenous layer thickness (phase purity). The phase-selective method involves the dissolution of single-crystalline powders with a homogeneous perovskite layer thickness in desired solvents to fabricate thin films. In situ characterizations reveal the presence of sub-micrometer-sized seeds in solution that preserve the memory of the dissolved single crystals and dictate the nucleation and growth of grains with an identical thickness of the perovskite layers in thin films. Photovoltaic devices with a p-i-n architecture are fabricated with such films, which yield an efficiency of 17.1% enabled by an open-circuit voltage of 1.20 V, while preserving 97.5% of their peak performance after 800 h under illumination without any external thermal management.

Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst.

Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 µg h-1 mgcat.-1 (0.46 mmol h-1 cm-2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N2 due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.

Analysis of Reapplications to Integrated and Independent Plastic Surgery Residency.

BACKGROUND: Plastic surgery is one of the most competitive specialties to match, with integrated plastic surgery having the highest rate of unmatched applicants in all categorical specialties. Unmatched applicants face difficult challenges, especially because there is a lack of data to help inform and guide both reapplicants and their advisors. METHOD: A national survey targeting plastic surgery applicants to both integrated and independent tracks from 2014 to 2020 was conducted in August 2020 to identify reapplicants, their application characteristics, and their outcomes. RESULTS: Eighteen of the 54 (33.3%) integrated reapplicants responded to the survey, as well as 7 of the 42 (16.7%) independent reapplicants. Fifty percent of integrated reapplicants and 43% of independent reapplicants successfully eventually matched. For integrated reapplicants, the mean (SD) number of first cycle invites was the greatest predictor of eventual match success, 9.00 (5.93) invites for reapplicants that eventually successfully matched compared with 2.89 (2.89) for those that remained unmatched, P = 0.025. Integrated reapplicants obtained on average 2.47 less invites during the reapplicant cycle compared with the initial cycle, P = 0.046. A Fisher exact test revealed no differences in match outcomes of those integrated reapplicants who spent time in between cycles pursuing research compared with a preliminary surgical year, P = 0.99. CONCLUSIONS: Reapplication to both integrated and independent plastic surgery may result in worse matching outcomes compared with the initial match. Applicants should attempt to preemptively address potential initial application weaknesses as reapplication after a failed initial attempt may carry disadvantages.

Nano-structural effects on Hematite (α-Fe2O3) nanoparticle radiofrequency heating.

Nano-sized hematite (α-Fe2O3) is not well suited for magnetic heating via an alternating magnetic field (AMF) because it is not superparamagnetic-at its best, it is weakly ferromagnetic. However, manipulating the magnetic properties of nano-sized hematite (i.e., magnetic saturation (Ms), magnetic remanence (Mr), and coercivity (Hc)) can make them useful for nanomedicine (i.e., magnetic hyperthermia) and nanoelectronics (i.e., data storage). Herein we study the effects of size, shape, and crystallinity on hematite nanoparticles to experimentally determine the most crucial variable leading to enhancing the radio frequency (RF) heating properties. We present the synthesis, characterization, and magnetic behavior to determine the structure-property relationship between hematite nano-magnetism and RF heating. Increasing particle shape anisotropy had the largest effect on the specific adsorption rate (SAR) producing SAR values more than 6 × greater than the nanospheres (i.e., 45.6 ± 3 W/g of α-Fe2O3 nanorods vs. 6.89 W/g of α-Fe2O3 nanospheres), indicating α-Fe2O3 nanorods can be useful for magnetic hyperthermia.

Global Rehabilitation Health Worker Certification: Global Agenda, Local Imperative.

Rehabilitation, seen as a disability-specific service needed only by few of the world's population, has not been prioritized in countries and is under-resourced. A rehabilitation-ready health workforce is potentially the most important resource for improving functioning and the quality of life for the 2.41 billion people worldwide needing this care. In April 2019, CGFNS International, Inc., and the Association of Schools Advancing Health Professions (ASAHP) partnered to respond to the World Health Organization's Rehab 2030, which emphasizes the need for global action by professional organizations, development agencies, and civil society to develop and maintain a sustainable workforce for rehabilitation under different healthcare models in different economies. The global certification framework presented in this article provides a mechanism to validate rehabilitation knowledge and practice competence of individual health workers. The impact of certification on upgrading rehabilitation education and upskilling the world's rehabilitation health workforce cannot be overstated.

JP-8 Desulfurization by CuNa-Y zeolite at elevated temperatures has two distinct stages: Chemisorption followed by surface reactions.

This study evaluates the performance of continuous flow adsorbers for adsorptive desulfurization. JP-8 fuel with 2,230 ppmw of sulfur was treated in a flow-through adsorber packed with CuNa-Y zeolite pellets and operating at 180 °C and 200 psig with liquid hourly space velocities (LHSV) from 0.13 to 3.24 h-1. Our results showed that a flow-through adsorber operating at these conditions can effectively reduce the sulfur content of JP-8 to ultra-low values (1-10 ppmw) over the entire LHSV range tested, although the overall performance of the adsorber declined with increasing flow rates as expected. We also observed that the total sulfur removal exceeded the theoretical adsorption limit of our zeolite adsorbent. Detailed characterization of the treated fuel and spent adsorbent via chromatographic and surface analysis techniques revealed that desulfurization occurs in two stages. Sulfur is initially removed via adsorption (chemisorption) on the CuNa-Y zeolite, an assertion supported by simulations with a transient heterogeneous model. As the adsorbent becomes saturated, however, surface chemical reactions start taking place leading to the formation of hydrogen sulfide and polymerization products, and depositing carbon residue on the zeolite. The spent adsorbent was regenerated by treating it with air at 550 or 600 °C, which restored the adsorption capacity of the material to about 90% of its initial value.

Superparamagnetic MOF@GO Ni and Co based hybrid nanocomposites as efficient water pollutant adsorbents.

A series of highly efficient adsorbents were developed using Ni3(BTC)2 and Co3(BTC)2 metal-organic frameworks (MOFs) and Fe3O4 magnetic nanoparticles (MNPs) to functionalize graphene oxide (GO). XRD results show high crystallinity of the prepared nanomaterials and the successful decoration of Ni3(BTC)2 and Co3(BTC)2 MOFs over the GO substrate (BTC = benzene-1,3,5-tricarboxylic acid). SEM and TEM imaging show the successful formation of nanoscale MOFs and Fe3O4 MNPs over GO. IR spectroscopy supports the characterization and successful preparation of the Fe3O4/MOF@GO hybrid composite nanoadsorbents. The prepared composite nanoadsorbents were used to sorb Methylene Blue (MB) as a model for common organic pollutants in water and common ions (Na+, Ca2+, Mg2+, SO42-, SiO32-) from a brackish water model. The adsorbed concentration at equilibrium of MB of the prepared composite nanoadsorbents increases by an average of 30.52 and 13.75 mg/g for the Co and Ni composite, respectively, when compared to the MOFs parent materials. The adsorbed amount of sulfate ions increases by 92.1 mg/g for the Co composite and 112.1 mg/g for the Ni composite, when compared to graphene oxide. This adsorption enhancement is attributed to suppressed aggregation through increased dispersive forces in the MOFs due to the presence of GO, formation of nanoscale MOFs over the GO platform, and the hindering of stacking of the graphene layers by the MOFs. Leaching tests show that the release of Co and Ni ions to water is reduced from 105.2 and 220 mg/L, respectively, in the parent MOF materials to 0.5 and 16.4 mg/L, respectively, in the composite nanoadsorbents. These findings show that the newly developed composite nanoadsorbents can sorb organic pollutants, and target sulfate and silicate anions, which makes them suitable candidates for water and wastewater treatments.

In Situ Electrochemical Generation of Reactive Chlorine Species for Efficient Ultrafiltration Membrane Self-Cleaning.

Reactive membranes based on hydroxyl radical generation are hindered by the need for chemical dosing and complicated module and material design. Herein, we utilize an electrochemical approach featuring in situ generation of reactive (radical) chlorine species (RCS) through anodization of chloride ions for membrane self-cleaning. A hybridized carbon nanotube (CNT)-functionalized ceramic membrane (h-CNT/CM), possessing high hydrophilicity, permeability, and conductivity, was fabricated. Using carbamazepine (CBZ) as a probe, we confirmed the presence of RCS in the electrified h-CNT/CM. The rapid and complete degradation of CBZ in a single-pass ultrafiltration indicates a high localized RCS concentration within the three-dimensional porous CNT interwoven layer. We further demonstrate that the electrogeneration of RCS is a critical prestep for free chlorine (HClO and ClO-) formation. The self-cleaning efficiency of the membrane after fouling with a model organic foulant (alginate) was assessed using an electrified cross-flow membrane filtration system. The fouled h-CNT/CM exhibits a near complete water flux recovery following a short (1 min) self-cleaning with an applied voltage of 3 or 4 V and feed solutions of 100 or 10 mM sodium chloride, respectively. Considering the superior performance of the RCS-mediated self-cleaning compared to conventional membrane chemical cleaning using sodium hypochlorite, our results exemplify an effective strategy for in situ electrogeneration of RCS to achieve a highly efficient membrane self-cleaning.