MICROSCAFS® for minocycline elimination from water and real wastewater: Porosity and TiO2 nanoparticles effect

Abstract

We developed and characterized a photocatalytic system utilizing sol–gel synthesized silica-titania microspheres (MICROSCAFS®) with varying interconnected porosities, functioning as a photocatalyst by itself, but also as a support for TiO₂ nanoparticles. This system was employed to remove the antibiotic minocycline from water, including real wastewater from a minocycline production plant, either in batch or flow photoreactor setups. We evaluated the pore size of MICROSCAFS® and found that the combination of medium-sized macropores together with the largest specific surface area (P0/HT) provided the highest adsorption capacity, achieving 13 % in the dark, attributed to the interaction between the positively charged antibiotic and the negatively charged MICROSCAFS®. Photocatalytic activity varied among samples, with P0/HT achieving the highest photodegradation of 73 % after 300  min of solar irradiation in a flow reactor. The immobilization of P25 TiO₂ nanoparticles (P0/HT+P25) optimized the removal, achieving 100 % degradation within 270  min. LC-HRMS/MS analysis identified specific by-products, which were fewer and less toxic than minocycline, and DFT and in-silico toxicity studies corroborate these findings. Scavenger tests highlighted the role of ^•OH, h⁺, and ^•O₂^–, with ^•O₂^– being the primary contributor. This photocatalyst, tested with real wastewater from a pharmaceutical industry, demonstrated effective environmental remediation without the need for expensive separation steps. Flow reactor experiments and a modeling study underscored its potential for continuous pollutant degradation in practical applications.