Search for: All records

With drinking water regulations forthcoming for per- and polyfluoroalkyl substances (PFAS), the need for cost-effective treatment technologies has become urgent. Adsorption is a key process for removing or concentrating PFAS from water; however, conventional adsorbents operated in packed beds suffer from mass transfer limitations. The objective of this study was to assess the mass transfer performance of a porous polyamide adsorptive membrane for removing PFAS from drinking water under varying conditions. We conducted batch equilibrium and dynamic adsorption experiments for perfluorooctanesulfonic acid, perfluorooctanoic acid, perfluorobutanesulfonic acid, and undecafluoro-2-methyl-3-oxahexanoic acid (i.e., GenX). We assessed various operating and water quality parameters, including flow rate (pore velocity), pH, ionic strength (IS), and presence of dissolved organic carbon. Outcomes revealed that the porous adsorptive membrane was a mass transfer-efficient platform capable of achieving dynamic capacities similar to equilibrium capacities at fast interstitial velocities. The adsorption mechanism of PFAS to the membrane was a mixture of electrostatic and hydrophobic interactions, with pH and IS controlling which interaction was dominant. The adsorption capacity of the membrane was limited by its surface area, but its site density was approximately five times higher than that of granular activated carbon. With advances in molecular engineering to increase the capacity, porous adsorptive membranes are well suited as alternative adsorbent platforms for removing PFAS from drinking water. 

Sunlight irradiation is the predominant process for degrading plastics in the environment, but our current understanding of the degradation of smaller, submicron (<1000 nm) particles is limited due to prior analytical constraints. We used infrared photothermal heterodyne imaging (IR-PHI) to simultaneously analyze the chemical and morphological changes of single polystyrene (PS) particles (∼1000 nm) when exposed to ultraviolet (UV) irradiation (λ = 250–400 nm). Within 6 h of irradiation, infrared bands associated with the backbone of PS decreased, accompanied by a reduction in the particle size. Concurrently, the formation of several spectral features due to photooxidation was attributed to ketones, carboxylic acids, aldehydes, esters, and lactones. Spectral outcomes were used to present an updated reaction scheme for the photodegradation of PS. After 36 h, the average particle size was reduced to 478 ± 158 nm. The rates of size decrease and carbonyl band area increase were −24 ± 3.0 nm h–1 and 2.1 ± 0.6 cm–1 h–1, respectively. Using the size-related rate, we estimated that under peak terrestrial sunlight conditions, it would take less than 500 h for a 1000 nm PS particle to degrade to 1 nm. 

In February 2023, a train derailment in Ohio caused a chemical spill and fires releasing contaminants into the air, soil, waterways, and buildings. 

A portable toilet manufacturer in northwest Indiana (USA) released polyethylene microplastic (MP) pollution into a protected wetland for at least three years. To assess the loads, movement, and fate of the MPs in the wetland from this point source, water and sediment samples were collected in the fall and spring of 2021–2023. Additional samples, including sediment cores and atmospheric particulates, were collected during the summer of 2023 from select areas of the wetland. The MPs were isolated from the field samples using density separation, filtration, and chemical oxidation. Infrared and Raman spectroscopy analyses identified the MPs as polyethylene, which were quantified visually using a stereomicroscope. The numbers of MPs in 100 mL of the marsh water closest to the source ranged from several hundred to over 400,000, while the open water samples contained few microplastics. Marsh surface sediments were highly contaminated with MPs, up to 18,800 per 30.0 g dry mass (dm), compared to core samples in the lower depths (>15 cm) that contained only smaller MPs (<200 µm), numbering 0–480 per 30.0 g (dm). The wide variations in loads of MP contaminants indicate the influence of numerous factors, such as proximity to the point source pollution, weather conditions, natural matter, and pollution sinks, namely sediment deposition. As proof of concept, we demonstrated a novel remediation method using these real-world samples to effectively agglomerate and remove MPs from contaminated waters. 

The inherent physicochemical properties of engineered nanomaterials (ENMs) are known to control the sorption of proteins, but knowledge on how the release of ENMs to the environment prior to protein exposure affects this reaction is limited. In this study, time-resolved, in situ infrared spectroscopy was used to investigate the sorption of a model protein, bovine serum albumin (BSA), onto two different types of titanium dioxide (TiO 2 ) ENMs (catalytic-grade P90 and food-grade E171) in the presence and absence of a simple dissolved organic carbon molecule, oxalate. Infrared spectroscopy results showed that oxalate adsorbed to P90 through chemisorption interactions, but it adsorbed to E171 through physisorption interactions due to the presence of inherent surface-bound phosphates. Secondary structure and two-dimensional correlation spectroscopy analyses showed that BSA interacted with and unfolded on the surface of P90, but not E171, presumably due to the repulsive forces from the negatively charged phosphates on E171. When oxalate was pre-adsorbed to either P90 or E171, the unfolding of BSA occurred, but along different pathways. This suggests both the “outer” surface chemistry ( e.g. , oxalate layers) and the mechanism by which this layer is bound to the ENM play a significant role in the adsorption of proteins. Collectively, the results indicate the exposure of ENMs to natural and engineered environments prior to biological uptake affects the resulting protein corona formation, and thus the transport and bioactivity of ENMs.