Organophosphate esters (OPEs) are chemicals being used as flame retardants and plasticizers replacing brominated flame retardants (BFRs). OPEs are utilized in various industries including textile, plastics, building materials, furniture, electronics, and vehicle parts. They are not chemically bound to the polymers, rather attached physically, thus they readily release into the surrounding environment by volatilization, leaching, abrasion and dissolution. Studies show a prolonged exposure and the accumulation of OPEs may elicit various adverse effects linked to a number of negative health effects (immune, developmental, and neurobehavioral). The various OPEs have a wide range of physical and chemical properties rendering them difficult to sample with traditional passive samplers. Only a small spectrum of these compounds was detected successfully by a single passive sampler. The pore size and thickness of the diffusion-limiting membrane of a passive sampler are the key factors in the sample selectivity. This study proposed a graphene-based sampler for its chemical and structural advantages to overcome these limitations. Graphene hydrogel monolith was synthesized from 10 mL of a suspension of 2 mg/mL suspension of graphene oxide and treated to yielding a cylindrical reduced graphene oxide (rGO). Graphene samplers were exposed to known concentrations of OPEs in water for increasing exposure time (1, 2, 4, 8, 16, 32 days). Also tested at different temperature and salinity conditions in a laboratory aquarium setup at 2, 14, and 22 degree Celsius and salinity of 0 and 35 psu. The low density and large feeder pores in the structure of the formulated graphene sampler facilitated fast internal diffusion that partitioning equilibrium were reach for most compounds within 72hrs of exposure. The values of log KGH_W for individual OPEs varied between 2.44 and 4.98. Also, the carbon-based chemistry enabled the adsorption of a wide range of contaminants with variety of substituents using the graphene sampler. In addition, in comparison to traditional carbon forms (e.g. activated carbons), the high purity and slit-shaped mesopores between nanosheets of the graphene sampler allow easy and complete extraction of sorbed chemicals without contamination and avoiding irreversible trapping in the molecular-sized pores common in activated carbons.

Graphene based novel passive samplers for detection of organophosphate esters (OPEs)

ACS Spring 2022

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