• The HNT/MnFe2O4 catalyst achieves >90% removal of methylene blue across a wide pH range (4–10) with high H2O2 utilization efficiency.
• The catalyst exhibits excellent reusability (less than 10% activity loss after five cycles) and can be easily recovered via magnetic separation.
• The degradation process is resilient to common anions and humic acid; carbonate species even enhance catalytic performance.
• The synergistic effect between halloysite and MnFe2O4, along with the generation of ·OH and ·O2−, underpins the high degradation efficiency for various organic pollutants.