Synthesis of Spinel Ferrite MFe2O4 (M = Co, Cu, Mn, and Zn) for Persulfate Activation to Remove Aqueous Organics: Effects of M-Site Metal and Synthetic Method

Abstract

Metal species and synthetic method determine the characteristics of spinel ferrite MFe 2 O 4. Herein, a series of MFe 2 O 4 (M = Co, Cu, Mn, Zn) were synthesized to investigate the effect of M-site metal on persulfate activation for the removal of organics from aqueous solution. Results showed that M-site metal of MFe 2 O 4 significantly influenced the catalytic persulfate oxidation of organics. The efficiency of the removal of organics using different MFe 2 O 4 + persulfate systems followed the order of CuFe 2 O 4 > CoFe 2 O 4 > MnFe 2 O 4 > ZnFe 2 O 4. Temperature-programmed oxidation and cyclic voltammetry analyses indicated that M-site metal affected the catalyst reducibility, reversibility of M 2+ /M 3+ redox couple, and electron transfer, and the strengths of these capacities were consistent with the catalytic performance. Besides, it was found that surface hydroxyl group was not the main factor affecting the reactivity of MFe 2 O 4 in persulfate solution. Moreover, synthetic methods (sol-gel, solvothermal, and coprecipitation) for MFe 2 O 4 were further compared. Characterization showed that sol-gel induced good purity, porous structure, large surface area, and favorable element chemical states for ferrite. Consequently, the as-synthesized CuFe 2 O 4 showed better catalytic performance in the removal of organics (96.8% for acid orange 7 and 62.7% for diclofenac) along with good reusability compared with those obtained by solvothermal and coprecipitation routes. This work provides a deeper understanding of spinel ferrite MFe 2 O 4 synthesis and persulfate activation.

Catalytic Activity of CuFe2O4 Spinel Oxide for Liquid‐Phase Oxidation of Cinnamyl Alcohol

“…Figure 3a display the resolved spectra of Fe(II) (2p 3/2 710.1 eV, 2p 1/2 723.5 eV) and Fe(III) (2p 3/2 711.5 eV, 2p 1/2 725.7 eV) coexist on surface of CuFe 2 O 4 samples prepared by sol-gel and coprecipitation method. [28] The strong satellite peaks were also observed for corresponding state of the Fe. It is evident from the area under curve values, that proportion of Fe(III) and Fe(II) in CuFe 2 O 4 by sol-gel which can be attributed to the formation of mixed spinels and Fe oxides of different oxidation states i. e.…”

“…The strong two satellite peaks of Cu 2p 3/2 were observed at 941.6 and 943.4 eV; a satellite peak of Cu 2p 1/2 was noticed at 962.2 eV. [28][29][30][31] It is clearly noticed that Cu 2 + contribution is more in sol-gel method than co-precipitation.…”

“…[27] Based on their surface area and crystalline size of CuFe 2 O 4 ranked as follows: CuFe 2 O 4 -Solgel > CuFe 2 O 4 -Co-precipitation. [28] These results indicated that sol-gel method bequeathed ferrite with a large surface area, which can play a key role in the adsorption capacity of the catalyst.…”

Efficiency and Quantitative Structure-Activity Relationship of Monoaromatics Oxidation by Quinone-Activated Persulfate

“…Persulfate-based oxidation process is widely used in water and soil remediation, in which persulfate is activated to produce sulfate radical anion ( ) as the main active material to degrade recalcitrant organics (Waldemer et al, 2007 ; Xian et al, 2020 ). The common activation methods include thermal energy, transition metal, alkali and UV radiation, etc.…”

A Review of Activation Persulfate by Iron-Based Catalysts for Degrading Wastewater

“…CuFe 2 O 4 is a typical spinel ferrite with a magnetic structure, which has high chemical stability and low metal leaching rate. Taking CuFe 2 O 4 as an example, compared with single transition metal oxides, Fe and Cu elements can play a role in the reaction; respectively, they can also activate PS to produce [46]. Additionally, it was known that CuFe 2 O 4 had the best catalytic effect.…”