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

Abstract

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.

Influencing Factors and Kinetics of Modified Shell Powder/La-Fe-TiO2 Photocatalytic Degradation of Pyridine Wastewater

“…However, when the dosage was increased from 400 to 600 mg/L, the pyridine degradation rate increased from 66.04% to 66.96%. It is speculated that the composite photocatalyst was unable to make full use of the photons generated by UV irradiation when the amount of composite material was low during the reaction, and it cannot produce enough strong oxidizing substances such as hydroxyl radicals, resulting in a lower degradation rate [ 39 ]. With the increase of the amount of added composite material, the composite catalyst could well utilize UV light to produce more photogenerated electrons e − and holes h + , leading to the increase in the degradation rate [ 40 , 41 ].…”

Biodegradable Electrospun Nanofiber Membranes as Promising Candidates for the Development of Face Masks

“…The electrospinning technique is a facile spinning method for preparing nanofibers by using electrostatic field force [64]. Among various nanofiber fabrication methods, electrospinning has been considered the advanced and extensively used technique [65,66]. An electrospinning unit is composed of a syringe pump, a spinneret, a high voltage supplier, and a collector [67] (in Figure 2f).…”