Optimization of magnetic polyurethane composite PU/OA@Fe3O4 synthesis for enhanced treatment of municipal wastewater using response surface methodology

Abstract

A novel magnetic polyurethane (PU) composite, PU/OA@Fe3O4 (MPU), was synthesized using oleic-acid-coated Fe3O4 nanoparticles. The response surface method based on the Box-Behnken design was employed to optimize the synthesis of MPU. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetry, and saturated magnetization were employed to characterize the MPU. The conditions for optimal synthesis of MPU were as follows: 0.65 g of catalyst A, 0.42 g of catalyst B, 2.11 g of organic silicon resin FS-05, and a toluene diisocyanate index of 112. The saturated magnetization of MPU at an OA@Fe3O4 of 8% and 10% were 21.19 and 32.83 emu/g, respectively. The improvement in removal performance of a sequencing batch biofilm reactor with MPU compared to conventional PU was also investigated. Removal of ammonia nitrogen, total nitrogen, chemical oxygen demand, and total phosphorus were all improved, compared to PU, by 11.73%, 9.13%, 11.22%, and 10.34%, respectively. At the end of the experiment, total and volatile biomass of MPU were 542 and 375 mg/g, respectively, which were 30 and 100 mg/g greater than those of PU. In addition, the biofilms growing on MPU contained considerably more proteins and tightly bound extracellular polymeric substances than those growing on PU.