Regeneration of porous electrospun membranes embedding alumina nanoparticles saturated with minocycline by UV radiation.

A regeneration method for porous electrospun membranes embedding alumina nanoparticles saturated with minocycline was investigated by UV-LED system. The percentage of adsorption capacities before and after regeneration were used to evaluate regeneration efficiency. The PVDF and PVDF-AlO fiber mats were prepared by electrospinning technique. Scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS) analyses directly confirmed that AlO nanoparticles were generally exposed to the surface of PVDF-AlO fiber mats. Among them, PVDF-AlO 10% fiber mats can effectively adsorb minocycline (remove efficiency >97% in 18 h) with first-order rate constant k = 2.253 ± 0.331 h. The sorption capacity can still keep 81% after five sorption/UV-regeneration circulations. Two successional stages may exist during regeneration: (i) transfer of minocycline from the surface of PVDF-AlO fibers to the DI water, followed by the (ii) decomposition of this compound in aqueous solution by direct and indirect photolysis to yield the intermediate species. The desorption capacity and desorption percentage were 4.39 mg g and 23.30% respectively. The regeneration yields were further enhanced to 94.20% by UV radiation. Minocycline was effectively degraded to intermediate products by direct and indirect photolysis, further degraded into CO, HO, and NO by UV-generated ozone during regeneration. The results indicated that UV radiation was an effective method of regenerating PVDF-AlO fiber mats with low energy requirements. The photochemical byproducts and the reaction sites during regeneration were also determined and recognized.