RhB-sensitized MIL-125(Ti)/g-C3N4/Bi2O3 composite for adsorption and visible-light photocatalytic removal of drugs from water

To develop photocatalytic materials with good visible light response and the simultaneous removal ability to dyes and drugs, MIL-125(Ti)/g-C3N4/Bi2O3 ternary composite material, abbreviated as MILCB, was synthesized using the hydrothermal method. Then, it was further sensitized with RhB in two ways in a dark environment. During this process, MILCB adsorbed RhB, leading to sensitization and forming the sensitized material for adsorbing and photocatalytic degrading pharmaceuticals. The effect of the mass ratio of (g-C3N4/Bi2O3)/MIL-125 (Ti) on the catalytic capability in visible light was studied. The results showed that RhB-sensitized ternary sample (R-MILCB) exhibited good photocatalytic activity towards drugs when the mass proportion of the g-C3N4/Bi2O3 to MIL-125(Ti) was established at 1:30. The apparent photocatalytic rate constants for the degradation of tetracycline and aureomycin were 3.40 times as well as 1.83 times higher, respectively, for the R-MILCB, compared to MIL-125(Ti). They were also 5.67 times as well as 2.75 times higher, respectively, for the binary composite sample of g-C3N4/Bi2O3, and 2.43 times as well as 1.38 times higher, respectively, for the ternary composite sample of MILCB. The composite material significantly improved visible light utilization after sensitization and exhibited good renewable activity. The tight double Z-scheme heterostructure, formed between three types of semiconductors in ternary composite, and the electron transfer from RhB, provided a clear explanation for the genesis of active species and the subsequent degradation of organic drugs. The development of the dual Z-scheme composites shows considerable potential for the simultaneous as well as cost-effective removal of dyes and pharmaceuticals.