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In response to growing environmental concerns regarding the presence of per- and polyfluoroalkyl substances (PFAS) in landfills, this study explores PFAS permeation through pinhole defects of high-density polyethylene (HDPE) geomembranes (GMs) experimentally. Specifically, this study aims to: (i) investigate the adsorption of PFAS onto HDPE GMs, (ii) evaluate the effectiveness of GMs experimentally in retaining PFAS-laden leachate in the event of a puncture failure, (iii) assess the critical conditions leading to puncture failure of GM using mechanical characterization testing with complementary finite element method (FEM) analyses with the input data from mechanical characterization. Our findings show limited intermolecular attractive interactions between PFAS and GMs, and surfactant properties of PFAS contribute to higher leachate permeation through pinholes. In general, highly fluorinated, short chain PFAS exhibit increased permeation rates, which was attributed to their size and greater propensity to align at the water-air interface. This study underlines the environmental implications of PFAS-laden leachates especially when there are no proper liner systems or leachate collection systems in place underscoring the necessity for modern landfill design and management practices to mitigate environmental risks associated with PFAS. 

Introducing facile regenerability into adsorbent materials can potentially increase sustainability in water treatment systems enabled by extended use. Herein, we detail our recent syntheses of dynamic nanostructured worm-gel materials and their implementation as regenerable adsorbents for water treatment. Photo-controlled atom transfer radical polymerization-induced self-assembly (PhotoATR-PISA) was employed to synthesize various polymer nanostructures, including dispersed spheres, worms, and vesicles, and nanostructured worm-gels, via the synthesis and simultaneous in situ assembly of BAB triblock copolymers. Two dynamic, disulfide-functionalized macroinitiators (SS-MI-1 and 2)with different degree of polymerization and one nondynamic macroinitiator (CC-MI) were synthesized via polymerization of oligo(ethylene glycol methyl ether methacrylate) (OEGMA). PhotoATR-PISA was then implemented via the chain extension fromSS-MI-1, 2 and CC-MI with glycidyl methacrylate (GMA) or benzyl methacrylate (BMA) forming BAB-type triblock copolymer nanoparticles in situ. The final morphology in PhotoATR-PISA was influenced not only by conventional factors such as solids content and block DP but also by unimer exchange rates yielding arrested, nanostructured worm-gels in many instances and arrested vesicle-gels in one instance. These PISA-gel materials were implemented as adsorbents for phenanthrene, a model compound registered as a priority pollutant by the US EPA, from aqueous solutions. The chemical tunability of these materials enabled enhanced, targeted removal of phenanthrene facilitated by π−π interactions, as evidenced by the increased adsorption capacities of PBMA-based PISA-gels when compared to PGMA. Furthermore, the dynamicity of disulfide worm-gels (SS-WG) enabled disulfide exchange-induced regeneration stimulated by UV light. This UV-responsive exchange was investigated for POEGMA macroinitiators as well as dissolved triblock copolymers, dispersed nanoparticles, and SS-WG materials. Finally, the regenerability of the PNT-saturated SS-WG adsorbents induced by UV irradiation (λ = 365 nm) was examined and compared with control worm-gels absent of disulfides, demonstrating enhanced recovery of adsorption capacity under mild irradiation conditions.