Amorphous Fe2O3 nanoparticles embedded into hypercrosslinked porous polymeric matrix for designing an easily separable and recyclable photocatalytic system

Abstract

The use of polymer sorbents in wastewater treatment can generate large-scale secondary waste due to the oxidation of the polymer matrix, stemming from the ionogenic functional groups or impurities. In this work, amorphous Fe2O3 nanoparticles were embedded into a porous non-ionogenic polymer matrix (Porolas) using two different Fe(III) salts (iron nitrate and iron oxalate) for designing an easily separable and recyclable photocatalytic system. The Fe2O3-Porolas composites were prepared by a simple method: an impregnation of the Porolas by Fe(III) salts and calcination at 250 °C for 1 h. The sorption capacity and photocatalytic activity of the Fe2O3-Porolas composites were evaluated by the removal of methylene blue (MB) from model-contaminated water under UV light irradiation in the presence of oxalic acid. The characterization results, particularly from X-ray photoelectron spectroscopy and Mössbauer spectroscopy, confirmed the formation of highly dispersed amorphous Fe2O3 nanoparticles that are embedded in the Porolas matrix. An increase in the content of the embedded Fe2O3 nanoparticles decreased specific surface area (SBET), MB sorption capacity, and apparent photodegradation rate constant (kapp) but increased the photodegradation efficiency of MB. The enhancement in MB removal can be attributed to the photocatalytic activities of the Porolas and Fe2O3 nanoparticles (heterogeneous photocatalysis), sorption effect, and leaching of Fe ions in aqueous solution (homogeneous photocatalysis). The scaffold network of the Porolas and highly dispersed Fe2O3 nanoparticles additionally contributed to the enhancement of photocatalytic activity of the Fe2O3-Porolas composite. Almost complete decolorization of MB (96–98%) and more than 97% TOC were achieved in this study, confirming simultaneous mineralization of both MB and OA in aqueous solution. The Fe2O3-Porolas composite can be easily prepared and inexpensive to design an easily separable and recyclable photocatalytic system for wastewater treatment.