Degradation of an antibiotic via a photo-Fenton process on block copolymer-nanopatterned iron oxide coated substrates

Abstract

A facile strategy was developed to produce porous iron oxide structures on glass substrates based on block copolymer (BCP) templating. Porous iron oxides with pore sizes of 35 nm, 45 nm and 400 nm were formed based on the solvent vapour annealing of poly(2-vinylpyridine-b-polystyrene (P2VP-b-PS) systems followed by selective infiltration of metal precursor into BCP template and subsequent conversion to (FeIII/FeII) oxides on the glass substrate. The XRD and XPS studies revealed the coexistence of FeIII/FeII. Parameters such as film thickness, polymer concentration and annealing time were varied in order to obtain the best polymer nanopatterns on the substrates, which refers to vertically aligned PS cylinders in a P2VP matrix. An annealing time of 40 min was required to produce vertically aligned PS cylinders of 35 and 45 nm pore sizes, whereas a ∼ 140-fold increase in the annealing time resulted in the formation of the same with 400 nm pore size as measured via AFM and SEM imaging techniques. The iron oxide-covered glass substrates were used in the degradation of a model antibiotic, levofloxacin, via a photo-Fenton process. ∼ 90 % relative degradation of 20 µM aqueous solution of levofloxacin in the presence of 10 mM H2O2 has been achieved by irradiating the solution containing a 1 % wt. iron oxide (FeIII/FeII) loaded glass slide having 400 nm pore diameter for 90 min. No iron leaching from the substrates was observed after 90 min of photo-Fenton process. Therefore, this strategy presents a potential use in the treatment of pharmaceutical wastewater through a heterogenous advanced oxidation process which could be scaled for application.