Rare earth doping: a strategy to enhance the catalytic activity of ZnFe₂O₄ in activating peroxymonosulfate for acetaminophen degradation

In this paper, ZnFe₂O₄ was doped by two rare earth metals (La and Pr), and the as-prepared ZnLa_0.5Fe_1.5O₄ and ZnPr_0.5Fe_1.5O₄ were applied to activate PMS for acetaminophen degradation. ZnLa_0.5Fe_1.5O₄ with the largest oxygen vacancy (O_V) content showed the highest acetaminophen degradation efficacy. About 89.7% of acetaminophen was removed within 60 min in the ZnLa_0.5Fe_1.5O₄/PMS system. Free radical quenching experiments and EPR tests confirmed that SO₄˙^-, ˙OH, O₂˙^- and ¹O₂ were the dominant reactive oxygen species (ROS). The role of La/Pr doping was explored through a series of comparative studies. The results indicated that La doping enhanced the content of oxygen vacancies, accelerated the electron transfer in the system, and thus sharply improved the catalytic performance of ZnFe₂O₄. Furthermore, the reusability, universality and actual water environment adaptability of ZnLa_0.5Fe_1.5O₄ were investigated.