Degradation of microcystin algal toxin by 3D printable polymer immobilized photocatalytic TiO₂

Novel and sustainable solutions are needed for surface water treatment. Photocatalytic TiO₂ is studied but is not directly deployable into natural water bodies due to settling and poor recoverability. This research capitalizes on a convergence of the emerging technologies of 3D printing biocompatible polymer (polylactic acid, PLA) composites, nanotechnology, and advanced oxidative processes to immobilize TiO₂ into customizable, high surface area, deployable, and retrievable structures with localized kinetic specificity for harmful algal blooms (HAB). PLA-TiO₂ composites at varying loadings (3–34 %) were extruded as feedstock for fused filament fabrication (FFF) enabling low cost printing design freedom of photocatalyst structures (disks, lattices). Large surface area, 3D lattices were printed as PLA composites with highly loaded (34 % w/w) TiO₂. Prior to HAB cyanotoxin experiments, the photocatalytic performance of the 3D printed PLA-TiO₂ lattice composites (t_1/2 = 0.8 h) under UV light were confirmed comparable to free TiO₂ (t_1/2 = 0.9 h). Under environmentally relevant solar simulation, photocatalysis by printed lattices successfully reduced microcystin (MC) cyanotoxin (t_1/2 = 3 h) faster than photolysis alone (t_1/2 = 36 h). Lattice mediated photocatalysis of MC in presence of cyanobacteria cells (t_1/2 = 11 h) was faster than photolysis (t_1/2 = 58 h) but slower than water-only treatment due to cell activity and light attenuation. PLA-TiO₂ reduces local pH, promoting MC adsorption and degradation. This research is foundational to novel photocatalytic composite optimization for reactive surface area prototyping enabled by 3D printing and scale-up for sustainable water treatment structures, with applicability to traditional and emerging contaminants.