Enhanced activity of Fe/Mn nanoparticles using a response surface methodology and mechanism for removing oxytetracycline and copper ion

As feed additives, oxytetracycline (OTC) and copper ion (Cu(II)) are often detected in livestock and poultry farming wastewater. To address this issue, firstly, the synthesis conditions of Fe/Mn nanoparticles (Fe/Mn NPs) were initially optimized using a response surface methodology (RSM) to yield highly active Fe/Mn NPs, where the application of RSM significantly increased the Fe/Mn NPs' efficiency in removing co-contamination OTC and Cu(II),respectively, from 45.8 to 86.2% and 14.9-67.2%. Secondly, scanning electron microscope and Nitrogen adsorption-desorption isotherms results showed that Fe/Mn NPs were composed of elliptic particles between 20 and 40 nm, a specific surface area of 59.5 m2 g-1, and a mean pore diameter of 5.27 nm. Fourier infrared spectrometer and X-ray photoelectron spectroscopy analysis revealed that amino, carboxyl and hydroxyl func-tional groups existed on the surface. Zeta potential indicated that Fe/Mn NPs maintained a high negative charge density between pH 1 and 11. These surface properties possessed by the green synthesized Fe/Mn NPs resulted in high adsorption efficiency for co-contamination OTC and Cu(II). Based on this, a removal mechanism based on a combination of complex-bridging effect, pore-filling, hydrogen bonding, surface complexation, ion exchange and electrostatic attraction was proposed. Finally, the assessment of Fe/Mn NPs used in swine wastewater demon-strated that both 99.9% OTC and 55.6% Cu(II) were removed.

Automated summary

By optimizing the synthesis conditions of Fe/Mn nanoparticles (Fe/Mn NPs) using response surface methodology (RSM), the efficiency of Fe/Mn NPs in removing oxytetracycline (OTC) and copper ion (Cu(II)) from livestock and poultry farming wastewater was significantly increased. The Fe/Mn NPs were found to have elliptic shape with amino, carboxyl, and hydroxyl functional groups on the surface, maintaining a high negative charge density between pH 1 and 11. A removal mechanism based on a combination of complex-bridging effect, pore-filling, hydrogen bonding, surface complexation, ion exchange, and electrostatic attraction was proposed. In swine wastewater experiments, Fe/Mn NPs achieved a removal rate of 99.9% for OTC and 55.6% for Cu(II).