Antimicrobial resistance and waterborne pathogens require efficient and environmentally compliant disinfection strategies. Cu2+-, Zn2+-, and Mn2+-doped ferrite nanoparticles were evaluated for Escherichia coli inactivation under dark and visible-light conditions. As-prepared ferrites exhibited bactericidal activity mainly driven by divalent metal leaching (up to 18.9 ± 0.9 mg L–1 Zn2+, 18.7 ± 0.1 mg L–1 Mn2+, and 6.2 ± 0.7 mg L–1 Cu2+), producing up to ∼3 log10 reductions in colony-forming units per milliliter (CFU mL–1) but exceeding drinking-water guidelines. Hydrothermal treatment transformed the amorphous ferrites into crystalline nanospinels (≈18–21 nm) and markedly suppressed metal release (<3.6 mg L–1). Under dark conditions, hydrothermally treated ferrites exhibited contact-killing behavior with HT-CuFe2O4, achieving complete bacterial inactivation (6 log10) within 2 h. Under visible light, the photocatalytic activity was enhanced, and HT-CuFe2O4 achieved total E. coli elimination within 0.5 h. Electrochemical analysis confirmed p-type semiconducting behavior, favoring hole-driven oxidation and reactive oxygen species generation. Global solar exposure modeling showed that complete disinfection can be achieved at realistic photon doses, with tropical latitudes requiring the shortest exposure times. These results demonstrate that hydrothermal treatment converts doped ferrites into efficient solar-driven photocatalysts for water disinfection.
Bedoya-Giraldo et al. (Sat,) studied this question.