Low-energy disinfection under natural light by magnetic Ag Mn1−Fe2O4 in the water: Efficiency and mechanism

Abstract

Abstract Herein, low Ag doping MnFe2O4 (AgxMn1−xFe2O4) was synthesized by an easy sol–gel process and applied for anti-bacteria in the water. Without any special light irradiation, it was found that Ag0.01Mn0.99Fe2O4 (AMFO-0.01) significantly enhanced the antimicrobial activity by a simple contact with the bacteria. The antimicrobial performances under different AMFO-0.01 dosages, initial bacteria concentrations, temperature and pH were conducted. A good stability was still possessed for AMFO-0.01 after an ultrasonic washing. It was uncovered that the interaction between AMFO-0.01 and cell membrane could restrict the activities of bacteria to cause severe membrane injury. The antimicrobial efficiency was not due to the toxicity of elemental Ag or dissolved metal ions. The doping Ag existed as monovalence ions inside the crystal lattice. Continuous electron transfer of Ag(0)/Ag(I) accelerated the electron delivery of Mn(II)/Mn(III), Fe(II)/Fe(III). Such synergistic effect of Ag, Mn, Fe on the surface induced the generation of reactive species (·OH, O2·−, H2O2, 1O2) for the death of bacteria. Considering such easy magnetic separation, room light condition, and high antimicrobial activity of AMFO-0.01, it is a promising candidate in the disinfection application for drinking or waste water treatment.