Removal of Azo Dyes Reactive Brilliant Red X-3B by Zero-Valent Iron Enhanced by a Weak Magnetic Field: Efficiency and Mechanism

Abstract

The removal kinetics and mechanism of azo dye Reactive Brilliant Red X-3B (X-3B) by a weak magnetic field (WMF)–enhanced zero-valent iron (ZVI) were explored. The results show that the reaction rate of zero-valent iron removal of X-3B was greatly enhanced by the weak magnetic field, and the removal rate increased with the decreasing of pH and initial dye concentration, and increased with the increasing temperature and ZVI dosage. The effect of common coexisting ions was also studied. In the presence of a magnetic field, NO3−, Ca2+, and Mg2+ had certain inhibitory effects on the reaction, while anions CO32−, SO42−, ClO4−, Cl−, HCO3−, and PO43− could significantly promote the removal of dye. In contrast, all kinds of anions and cations could promote the reaction without a magnetic field. Expect these, the degradation process was consistent with the pseudo-first-order kinetic model by fitting the experimental data. The activation energy ware 25.7368 kJ mol−1 in the presence of WMF and 27.9317 kJ mol−1 in the absence of WMF by using the Arrhenius formula. The degradation process was further analyzed by ultraviolet–visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The main mechanism of this reaction involves free radical oxidation, and the main reaction products were lepidocrocite and Fe(OH)3.