Controllable synthesis of Bi2SiO5/Bi4Si3O12 heterostructure and it's specific adsorption and photocatalytic performance

Nanosheets of Bi2SiO5/Bi4Si3O12 composite material was prepared by a one-step hydrothermal method with HNO3 solution as the solvent. In the same hydrothermal condition, the nanosheets of Bi2SiO5 and hollow spherical of Bi4Si3O12 were prepared by substituting HNO3 solution with ethylene glycol and benzyl alcohol as solvent, respectively. The obtained materials were characterized by the XRD, XPS, SEM, TEM, BET, UV–vis spectroscopy and PL. The Bi2SiO5, Bi2SiO5/Bi4Si3O12 and Bi4Si3O12 photocatalysts were applied to remove 17α-ethynylestradiol (EE2), and the EE2 removal rates were 47.6%, 99.4% and 25.4% after 12 min of UV-light irradiation, respectively. Photocatalytic activity of Bi2SiO5/Bi4Si3O12was better than that of Bi2SiO5 and Bi4Si3O12, because that heterojunction of Bi2SiO5/Bi4Si3O12 had the matching band structure between Bi2SiO5 and Bi4Si3O12, the carrier separation efficiency and transport efficiency were improved. The Bi2SiO5/Bi4Si3O12 shows the highest reaction rate, which is 9.69, 26.41, 27.29 and 124.96 times higher than that of Bi2SiO5, Bi4Si3O12, P25 and EE2 photolysis, respectively. The effects of pH value and photocatalyst dosage were optimized for removing EE2 in water. The possible photocatalytic mechanism was proposed based on the trapping photocatalytic experiments and the energy band positions. Surprisingly, the Bi2SiO5/Bi4Si3O12 photocatalyst had specific adsorption performance on EE2 comparing to BPA due to the EE2 has stronger hydrophobicity than BPA, while it can photodegrade both EE2 and bisphenol A (BPA). Results in this work provide new insights for controlled synthesized the Bi2SiO5, Bi2SiO5/Bi4Si3O12 and Bi4Si3O12 only by changing the solvent in hydrothermal process. The Bi2SiO5/Bi4Si3O12 possess a synergistic effect of adsorption and photocatalysis for hydrophobic organic molecules, which indicates that it can be used as an efficient material for removing hydrophobic molecules. Meanwhile, Bi2SiO5/Bi4Si3O12 composite was considered a promising photocatalyst for removing all kinds of Endocrine Disrupting Chemicals (EDCs) organic pollutants.