Photocatalytic degradation of iohexol by photo-driven double Z heterojunction photocatalyst under strong internal electric field in synergy with peroxymonosulfate (PMS)

• Double Z heterojunction g-C 3 N 4 /Bi 2 O 2 CO 3 /MnWO 4 with strong internal electric field was successfully prepared. • Under visible light irradiation, the double Z-scheme heterojunction g-C 3 N 4 /Bi 2 O 2 CO 3 /MnWO 4 coupled with the activation of PMS efficiently degrades 90.07 % of Iohexol within 40 min. • The catalytic system shows good cycle stability. • By constructing a double Z-scheme heterojunction, the electron transfer within g g-C 3 N 4 /Bi 2 O 2 CO 3 /MnWO 4 can be effectively facilitated, accelerating the electron transfer and enhancing the migration rate of photogenerated carriers. • Activating PMS can generate more reactive free radicals , among which, 1 O 2 and h + are the main reactive radical and · OH, · SO 4 - and · O 2 – provided most of the help for the elimination of Iohexol. This paper describes the preparation of a double Z heterojunction photocatalyst, g-C 3 N 4 /Bi 2 O 2 CO 3 /MnWO 4 (CBCM), with a potent internal electric field using the hydrothermal method. The degradation efficiency can be further improved by combining photocatalytic technology with activated persulfate (PMS) technology. The synthesis of CBCM-7 was validated through XRD and TEM analyses, while XPS provided evidence of electron transfer and the establishment of heterojunctions within its structure. Additionally, PL, PC, and EIS measurements underscored CBCM-7′s proficient rate of photogenerated charge separation and robust charge transfer properties. The experimental results showed that the photocatalytic degradation of the iodinated contrast agent was substantially enhanced by this catalyst coupled with PMS. The degradation rate of Iohexol was up to more than 90 % within 40 min. After the completion of the recycling experiment, the degradation efficiency of this system remained above 80 %. Mechanistic analyses, including EPR tests, indicate that the main active groups generated by the degradation of this dual Z-scheme heterostructured photocatalyst coupled with activated PMS were superoxide radicals and hydroxyl radicals.