Photocatalytic degradation of microcystins from a field-collected cyanobacterial assemblage by 3D printed TiO2 structures using artificial versus solar irradiation

• Published in: Journal of environmental management Vol. 371; p. 123208
• Main Authors: Calomeni-Eck, Alyssa J., Kennedy, Alan J., McQueen, Andrew D., Ballentine, Mark L., Fernando, Brianna M., May, Lauren R., Melby, Nicolas L.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2024
• Subjects: 3D print; Harmful algal bloom; Immobilization; Photocatalysis; Toxins; Treatment; 3D print; Immobilization; Harmful algal bloom; Toxins; Treatment; Photocatalysis
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2024.123208

Microcystins (MCs) from freshwater cyanobacteria cause adverse effects to humans and ecological receptors through multiple exposure routes requiring adaptable and diverse treatment technologies. Photocatalysis of MCs using TiO2 is a promising technology; however, TiO2 photocatalysts as unbound nanoparticles in suspension are impractical to deploy. 3D Printing (3DP) provides a means to immobilize TiO2, producing deployable photocatalyst structures with extensive geometric freedom. The objective of this proof-of-concept experiment was to incrementally increase the environmental complexity (e.g., broad-spectrum fluorescent lamps and outdoor solar; filtered cell lysate and algal assemblage as the source of MCs) while comparing photocatalysis rates of MCs by 3DP TiO2 structures using polylactic acid (PLA) as the binder. Degradation half-lives of MCs were shorter in TiO2 embedded in 3DP PLA relative to PLA-only controls with differences in half-lives ranging from 3.6 to 10h. The one exception was the outdoor solar and an algal assemblage, where significant differences could not be discerned due to the already rapid photolysis rates. Ultimately, photocatalysis rates (half-life = 1.9–11.6h) were comparable to those previously published for TiO2 3DP structures in a laboratory environment and TiO2 fixed-films (half-life = 2–13h) demonstrating feasibility of 3DP to immobilize TiO2 photocatalysts under a range of conditions. This is the first time that MC concentrations from a field-collected HAB were photocatalytically degraded in both solar simulated light and sunlight using a custom-made advanced photocatalytic nano-composite with enhanced performance through high surface area design enabled by 3D printing. These data inform future development of scalable, retrievable, and operationally flexible structures with immobilized TiO2.
•Demonstrates feasibility of 3D printed immobilized photocatalysts.•Provided environmental relevance with natural solar irradiation + algal assemblage.•Microcystin (MC) photocatalysis observed for printed TiO2 polymer structures.•Rates faster for TiO2 vs controls, except for combined effects solar + assemblage.•Equal rates due to photocatalysis and photolysis for combined solar + assemblage.