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ABSTRACT In this study, we investigate the PFOA removal capabilities ofRhodopseudomonas palustris(R. palustris), a fluoroacetate dehalogenase containing microbe as a potential candidate for achieving bioremediation. In the 50-day PFOA uptake experiment, R. palustris removed 44 ± 6.34 % PFOA after 20 days of incubation, which was then reduced to a final removal of 6.23 ± 12.75 %. Results indicate PFOA was temporarily incorporated into the cell membrane before being released partially into the media after cell lysis. This incorporation might be attributed to the combined effect of hydrophobic interaction between PFOA and the cell membrane and the reduced electrostatic repulsion from the high ion presence in the growth medium. The growth ofR. palustrisduring the PFOA uptake experiment was 9-fold slower than their growth without PFOA. This study also completely defines the toxicity range of PFOA forR. palustristhrough a toxicity assay. Increasing PFOA concentration reduced the microbe growth, with complete inhibition around 200 ppm. For various concentrations of PFOA, R. palustris exhibits interesting diauxic growth behavior. An accelerated growth phase was followed by a temporary death phase in the first 24 hours in the presence of 12.5-100 ppm PFOA, implying a unique adaptation mechanism to PFOA. 

Graphene-based 3D macroscopic aerogels with their hierarchical porous structures and mechanical strength have been widely explored for removing contaminants from water. However, their large-scale manufacturing and application in various water treatment processes are limited by their scalability. In this study, we report a proof-of-concept direct ink writing (DIW) 3D printing technique and subsequent freeze-drying to prepare graphene-biopolymer aerogels for water treatment. To provide appropriate rheology for DIW printability, two bio-inspired polymers, polydopamine (PDA) and bovine serum albumin (BSA), were added to the graphene-based ink. The biopolymers also contributed to the contaminant removal capacity of the resultant graphene-polydopamine-bovine serum albumin (G-PDA-BSA) aerogel. The physicochemical properties of the aerogel were thoroughly characterized from the nano- to macroscale. The 3D printed aerogel exhibited excellent water contaminant removal performance for heavy metals (Cr( vi ), Pb( ii )), organic dyes (cationic methylene blue and anionic Evans blue), and organic solvents ( n -hexane, n -heptane, and toluene) in batch adsorption studies. The electrostatic interaction dominated the removal of heavy metals and dyes while the hydrophobic interaction dominated the removal of organic solvents from water. Moreover, the aerogel showed superb regeneration and reuse potential. The aerogel removed 100% organic solvents over 10 cycles of regeneration and reuse; additionally, the removal efficiencies for methylene blue decreased by 2–20% after the third cycle. The fit-for-design 3D printed aerogel was also effectively used as a bottle-cap flow-through filter for dye removal. The potential and vision of the 3D printing approach for graphene-based water treatment presented here can be extended to other functional nanomaterials, can enable shape-specific applications of fit-for-purpose adsorbents/reactors and point-of-use filters, and can materialize the large-scale manufacturing of nano-enabled water treatment devices and technologies.