Photocatalyst water treatment research receives considerable attention. Novel methods to prototype and improve additively manufactured (AM) photocatalyst structures is desirable. We present two photocatalyst applications to treat polyaromatic hydrocarbons (PAHs) and harmful algal blooms (HABs). These contaminants cause ecosystem and human health impacts and are directly and indirectly anthropogenically sourced, respectively. Photocatalytic TiO2 nanoparticles offer a sustainable treatment strategy by generating reactive oxygen species under natural solar or artificial UV radiation. The associated free radical effects are localized, short-lived, and not expected to have adverse implications on nearby non-target organisms. However, free TiO2 nanoparticles rapidly agglomerate and settle out of the photoactive zone and are not retrievable once deployed. This research investigates the unique solution of immobilizing TiO2 (76% anatase) by compounding it into transparent thermoplastic polylactic acid (PLA), which was chosen due to its greater biocompatibility (relative to petroleum-derived polymers) due to its plant-derived monomer (e.g., sugarcane, corn). The PLA-TiO2 composite (23% TiO2 w/w) was 3D printed using a desktop fused filament fabrication printer into disks and high surface area lattice geometries, which were submerged in freshwater. Exploratory studies indicated &gt;90% reduction in methylene blue (1 mg/L) under ReptiSun® 5.0 bulbs (2 W/m2 UV; 280-400 nm), confirming the printed PLA-TiO2 retained comparable dye degradation efficacy to free TiO2 after 10 h UV exposure. PAH exposures, sourced from elutriation of contaminated sediment, indicated that while UV alone degraded PAH analytes, the TiO2 composite significantly increased the degradation kinetics of fluoranthene, pyrene and chrysene. The composites were also tested to reduce the Microcystin toxin (quantified by ELISA) released from a Microcystis aeruginosa HAB. While cells grew in the light lacking photocatalyst, the photocatalyst composites significantly (p &lt; 0.05) reduced cell density (&gt;85%), resulting in optically clear test solution. The PLA-TiO2 composites also reduced microcystin from 30 µg/L to below detection (and toxicity thresholds). Further investigations on this on-demand, retrievable, and reusable AM technology include photocatalyst loading optimization, treatment kinetics quantification, and scale-up.

Additively manufactured polymer photocatalyst composites reduce organic contaminants and harmful algal bloom toxins

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.