Effective activation of peroxymonosulfate by MMT-CuFe2O4 composite in the degradation of methylene blue from aqueous solutions: Characteristics, influence of parameters, and degradation mechanism
Hamed Mohammadi, Nezamaadin Mengelizadeh, Mohammad Reza Zare, Iman Parseh, Majid Hashemi, Majid Yousefi, Parastoo Amiri, Zeinab Khajavi Nasab, Zeinab Habibi, Esmail Mohseni
Abstract
The novel catalyst of copper ferrite loaded on montmorillonite (MMT-CuFe2O4) was prepared by sol-gel method and used as a peroxymonosulfate (PMS) activator in the degradation of methylene blue (MB). Complete degradation of MB was achieved in 5 min using 100 mg/L of MMT-CuFe2O4 nanoparticles in an alkaline medium. The MMT-CuFe2O4/PMS heterogeneous system showed 2-3 times higher efficiency than the PMS and MMT-CuFe2O4 systems alone. Adding low amounts of anions such as chloride, carbonate, and sulfate to the reaction medium reduced the degradation efficiency by 10% due to the production of reactive species with low redox potential. The results also showed that high concentrations of anions can improve the degradation efficiency due to the production of high amounts of radicals. The reusability of the catalyst was investigated in 5 consecutive reaction cycles, and the findings showed that the catalyst can maintain its stability with a dye removal rate ≥90%. The rate of mineralization (TOC removal > 80%), as well as the production of inorganic ions, during the reaction time of 120 min showed that MMT-CuFe2O4 can convert dye molecules into biodegradable compounds (BOD5/COD > 0.4), CO2, NH4+, NO3- and SO42-. The relative growth (76.3%) of lentil root emphasized that the solution treated by a catalytic system has very low toxicity. Trapping experiments showed that sulfate (SO4∙-) and hydroxyl (∙OH) radicals have a significant contribution to the degradation of MB and their oxidation activity occurred in both solid and solution phases. Based on the findings of reactive species identification, a possible mechanism for dye degradation was proposed.