Strengthening the reactivity of Fe0/(Fe/Cu) by premagnetization: Implications for nitrate reduction rate and selectivity

In order to develop a better Fe0 based system, premagnetization was used to enhance the reactivity of Fe0 particles and Fe/Cu bimetallic particles micro-electrolysis (Fe0/(Fe/Cu)) system for nitrate wastewater treatment. In this study, the significant parameters (i.e., initial pH, premagnetization time and intensity of magnetic field) were optimized firstly. Under the optimal conditions, the premagnetization Fe0/(Fe/Cu) system could obtain a high rate (kobs = 0.732 min−1) and better selectivity ([TN removal]/[NO3−-N removal] ratio = 54.3%) for nitrate reduction, which were much superior to the 7 control experiments (i.e., Fe0/(Fe/Cu) system, premagnetization Fe0 particles and Cu0 particles micro-electrolysis (premagnetization Fe0/Cu0) system, Fe0/Cu0 system, premagnetization Fe0 system, Fe0 system, premagnetization Fe/Cu system and Fe/Cu system). Meanwhile, it was confirmed that the prepared Fe0/(Fe/Cu) could keep the high reactivity even after vacuum drying and longtime storage. Furthermore, the operational life of premagnetization Fe0/(Fe/Cu) system is better than that of Fe0/(Fe/Cu) system (for more than 12.6 L wastewater treatment). The used Fe0/(Fe/Cu) could recover high reactivity after acid washing as well. Moreover, the characteristics of the medium materials before and after employment were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Besides, the reasonable mechanism of premagnetization improving the rate and selectivity for nitrate reduction of Fe0/(Fe/Cu) system was also proposed. The possible reasons why premagnetization process could strengthen both rate and selectivity for nitrate reduction and why premagnetization could strengthen the Fe0/(Fe/Cu) system better were also given. Finally, it was proved that the new developed system not only could effectively treat different pollutants but also is suitable for different quality wastewater treatment. As a conclusion, the premagnetization Fe0/(Fe/Cu) system is a promising Fe0 based technology for wastewater treatment.