Molten salt synthesis of Z-scheme CeO2/C3N4 photocatalysts with excellent properties for removal of organic pollutants: Characterization, kinetics and mechanisms

Abstract

In this work, we firstly synthesized a CeO2/C3N4 photocatalyst with Z-scheme heterojunction by a facile LiCl–KCl molten salt method. The synthesized catalyst has an excellent quality for removing organic pollution of dyes and antibiotics in wastewater. As an example, the CeCN–1:5 prepared with a mass ratio of Ce2(CO3)3·xH2O:C3H3N6 = 1:5 exhibits a methylene blue (MB) removal capacity of 100% within 90 min and tetracycline (TC) removal capacity of 94.6%. After 4 cycles, the CeCN–1:5 keeps a removal efficiency of nearly 100% in 150 min for MB and 85.7% for TC. The kinetics study reveals that the MB removal process with the CeCN–1:5 fits the modified Elovich model with strong adsorption while TC removal fits the first-order model. The large surface area (238 m2/g) and negative zeta potential (−39.3 mV) of CeCN–1:5 contribute to superior adsorption capacity to MB. However, the adsorption of TC is restricted due to the positive surface/pore potential in acidic solution. CeCN–1:5 has combined Z-scheme heterojunction and exhibits a low recombination rate of electrons (e–)/holes (h+) and the photo-generated active radicals of ·OH/·O2– that promotes the photocatalytic performance. This novel CeO2/C3N4 photocatalyst with an excellent photocatalysis removal activity has an enormous potential for photocatalytic applications.