Perfluorooctanesulfonate (PFOS) is a persistent organic pollutant that is bioaccumulative and toxic. While its use in most countries has been restricted to certain industrial applications due to environmental and health concerns, chrome plating and semiconductor manufacturing facilities are industrial point sources of PFOS-containing wastewater. Current remediation technologies are ineffective at treating these highly concentrated industrial effluents. In this work, UiO-66 metal–organic frameworks (MOFs) of several defect concentrations were studied as sorbents for the removal of PFOS from concentrated aqueous solutions. PFOS sorption isotherms indicated that defective UiO-66, prepared with HCl as a modulator, had a maximum Langmuir sorption capacity of 1.24 mmol/g, which was ∼2× greater than powdered activated carbon (PAC), but ∼2× less than that of a commercial ion-exchange resin. Defective UiO-66 adsorbed PFOS 2 orders of magnitude faster than the ion-exchange resin. Large pore defects (∼16 and ∼20 Å) within the framework were critical to the increased adsorption capacity due to higher internal surface area and an increased number of coordinatively unsaturated Zr sites to bind the PFOS head groups. Of the common co-contaminants in chrome plating wastewaters, chloride ions have a negligible effect on PFOS sorption, while sulfate and hexavalent chromium anions compete for cationically charged adsorption sites. These materials were also effective adsorbents for the shorter-chain homologue, perfluorobutanesulfonate (PFBS). The enhanced PFOS and PFBS adsorptive properties of UiO-66 highlight the advantage of structurally defective MOFs as a water treatment approach toward environmental sustainability.

a b s t r a c tA commercially available Au/TiO 2 catalyst was subjected to a variety of thermal treatments in order to understand how variations in catalyst pretreatment procedures might affect CO oxidation catalysis. Catalytic activity was found to be inversely correlated to the temperature of the pretreatment. Infrared spectroscopy of adsorbed CO experiments, followed by a Temkin analysis of the data, indicated that the thermal treatments caused essentially no changes to the electronics of the Au particles; this, and a series of catalysis control experiments, and previous transmission electron microscopy (TEM) studies ruled out particle growth as a contributing factor to the activity loss. Fourier transform infrared (FTIR) spectroscopy showed that pretreating the catalyst results in water desorption from the surface, but the observable water loss was similar for all the treatments and could not be correlated with catalytic activity. A Michaelis-Menten kinetic treatment indicated that the main reason for deactivation is a loss in the number of active sites with little changes in their intrinsic activity. In situ FTIR experiments during CO oxidation showed extensive buildup of carbonate-like surface species when the pretreated catalysts were contacted with the feed gas. A semi-quantitative infrared spectroscopy method was developed for comparing the amount of carbonates present on each catalyst; results from these experiments showed a strong correlation between the steady-state catalytic activity and amount of surface carbonates generated during the initial moments of catalysis. Further, this experimental protocol was used to show that the carbonates reside on the titania support rather than on the Au, as there was no evidence that they poison Au-CO binding sites. The role of the carbonates in the reaction scheme, their potential role in catalyst deactivation, and the role of surface hydroxyls and water are discussed.

The adsorption of CO on Au/TiO 2 catalysts was examined at room temperature using FTIR transmission spectroscopy. Adsorption was observed as (i) a sharp peak at ∼2100 cm −1 due to CO molecular vibration (the Au−CO peak), and (ii) a broad-band infrared (BB-IR) signal. The Au− CO peak and BB-IR signal are correlated and quantitatively related to the amount of CO adsorbed on the Au nanoparticles. For comparison purposes, we also examined CO adsorption on Au/Al 2 O 3 catalysts. When supported on this nonreducible support, CO adsorption on Au showed only the Au−CO peak; the BB-IR signal was absent. This allowed us to determine that the BB-IR signal observed for CO adsorption on the Au/TiO 2 catalyst is associated with the reducibility of the support. Comparison of the two catalysts also enabled us to determine that the BB-IR signal is due to a decrease in transmission through the powdered catalysts when CO adsorbs on Au/TiO 2 . Consistent with previously published studies, we propose that this BB-IR signal is related to the reversible, partial reduction of the TiO 2 at the Au−TiO 2 interface. This reduction leads to an increase in surface disorder or roughening of TiO 2 particles that produces a decrease in IR transmission through the catalyst (i.e. an increase in IR scattering). These results suggest an efficient CO−Au− TiO 2 adsorbate-induced electronic metal−support interaction (EMSI) that may play an important role in understanding CO reactions on Au/TiO 2 catalysts.

Laser-induced graphene (LIG) is uniquely positioned to advance applications in which electrically conductive carbon coatings are required. Recently, the antifouling, antiviral, and antibacterial properties of LIG have been proven in both air and water filtration applications. For example, an unsupported LIG based filter (pore size: ∼0.3 μm) demonstrated exceptional air filtration properties, while its joule heating effects successfully sterilized and removed unwanted biological components in air despite persisting challenges such as pressure drop, energy consumption, and lack of mechanical robustness.Here, we developed a polyimide (PI) non-woven supported LIG air filter with negligible pressure drop changes compared to the non-woven support material and showed that low electrical current density inactivates aerosolized bacteria. A current density of 4.5 mA/cm 2 did not cause significant joule heating, and 97.2% bacterial removal was obtained. The low-voltage antibacterial mechanism was elucidated using bacterial inhibition experiments on a titanium surface and on an LIG surface fabricated on dense PI films. Complete sterilization was obtained using current densities of ∼8 mA/cm 2 applied for 2 min or ∼ 6 mA/cm 2 for 10 min upon the dense PI−LIG surface. Lastly, >98% bacterial removal was observed using a low-resistance LIG-coated non-woven polyimide air filter at 5 V. However, only very low voltages (∼0.3 V) were needed to remove ∼99% Pseudomonas aeruginosa bacteria and 100% of T4 virus when the LIG-coated filters were hybridized with a stainless steel mesh. Our results show that low current density levels at very low voltages are sufficient for substantial bacterial and viral inactivation, and that these principles might be effectively used in a wide number of air filtration applications such as air conditioners or other ventilation systems, which might limit the spread of infectious particles in hospitals, homes, workplaces, and the transportation industry.

The combined experimental and computational study demonstrates an inverse relationship between phage-nanocomposite conjugate (PNC) size and biofilm eradication potential.