Degradation of Minocycline by the Adsorption–Catalysis Multifunctional PVDF–PVP–TiO2 Membrane: Degradation Kinetics, Photocatalytic Efficiency, and Toxicity of Products

The photocatalytic degradation of minocycline was studied by using polyvinylidene fluoride–polyvinylpyrrolidone–TiO2 (PVDF–PVP–TiO2) fiber mats prepared by an electrospinning technology. The influences of the TiO2 dosage, minocycline concentrations, inorganic anions, pH values, and dissolved organic matter (DOM) concentrations on the degradation kinetics were investigated. A mass of 97% minocycline was degraded in 45 min at 5% TiO2 dosage. The corresponding decomposition rate constant was 0.069 min−1. The inorganic anions affected the minocycline decomposition in the order of HCO3− > Cl− > SO42− > NO3−, which was confirmed by the results of electron spin resonance (ESR) spectra. The lowest electrical energy per order (EEO) was 6.5 Wh/L. Over five cycles, there was no change in the photocatalytic performance of the degrading minocycline. Those investigations suggested that effective degradation of minocycline could be reached in the PVDF–PVP–TiO2 fiber mats with a low energy consumption, good separation and, good recovery. Three photocatalytic decomposition pathways of minocycline were proposed: (i) hydroxyl substitution of the acylamino group; (ii) hydroxyl substitution of the amide group, and (iii) a cleavage of the methyl groups and further oxidation of the amino group by OH. Potential risks caused by TP159 and TP99 should not be ignored, while the TP90 are nontoxic. Tests indicated that the toxicity of the photocatalytic process may be persistent if minocycline and its products were not mineralized completely.

A new air PM2.5 filtrative lamp with a combination of fabric filter and TiO2 coating mop

Air particle cleaning in developing countries in Southeast Asia has become important especially regarding local respiratory health. One of possible solutions is air filtration which is normally used but at high cost. Therefore, this study aims to develop low cost air PM2.5 filtration using integrated lamp, and then investigate filtration performance of adaptive lamp. The integration of fabric filter and floor lamp is designed with fan unit driving force, and then photocatalytic process is applied for increasing air purificative performance. Tests are set in 2.5 m width × 2.5 m length × 2.5 m height bedroom within three regimes: (A) existing filter, (B) integrating fabric filter lamp and (C) adapting TiO2 fiber mop to filter lamp. Based on EPA standard, no regime examined exceeds NAAQs at 35 μg/m3, while regime C with fan speed 2 m/s shows the best performance of air purification. Then the MERV level of filtrative lamp demonstrates MERV15 and MERV16 to identify regime B lamp with 3 m/s fan speed and C lamp with 2 m/s fan speed respectively.