Cost-effective PMMA photocatalytic microreactor for nanocatalyst screening and environmental research

Abstract

Photocatalysis offers a sustainable, chemical-free approach for wastewater remediation, yet conventional glass-based reactors remain bulky, catalyst-intensive, and unsuitable for high-throughput material screening. This study presents a low-cost, laser-fabricated poly(methyl methacrylate) (PMMA) microreactor (∼0.6 mL) with immobilized commercial TiO<inf>2</inf> or ZnO nanoparticles, supporting both batch and continuous-flow operation. In batch mode, pseudo-first-order rate constants reached 2.57 × 10⁻² min⁻¹ for TiO<inf>2</inf> and 2.82 × 10⁻² min⁻¹ for ZnO during methylene blue degradation, with >80 % removal achieved within 30 min. Methyl orange degradation followed similar trends with lower rates, reflecting charge and structural effects. The microreactor retained >95 % of initial performance over five reuse cycles, confirming coating stability. Continuous-flow tests demonstrated multifunctionality: ∼75 % Ag⁺ removal and >80 % Escherichia coli inactivation within 15 min. Surface modification with cetyl-trimethyl-ammonium bromide (CTAB) reduced water contact angle from 78° to 26°, boosting TiO<inf>2</inf> photocatalytic efficiency (k = 3.30 × 10⁻² min⁻¹) and enhancing antibacterial performance. ZnO outperformed TiO<inf>2</inf> in both dye degradation and antibacterial assays, with ICP-MS revealing substantial Zn²⁺ leaching contributing to bactericidal activity even in the dark. Compared with conventional reactors operating under similar conditions, the microreactor exhibited higher degradation rates, attributed to enhanced mass transfer, uniform illumination, and reduced reagent and catalyst consumption. The platform's low material cost, facile fabrication, and versatility position it as a promising tool for photocatalyst screening and as a modular element for decentralized water treatment, metal-ion recovery, and environmental disinfection.