Soft Chemical Synthesis And Visible-light Induced Photocatalytic Activity Bi₂Fe₄O₉ Semiconductor Photocatalyst

At present, people are faced with all kinds of environmental problems. In order to protect the ecological balance, to achieve sustainable developments, controlling environmental pollution has become a major issue. So the AOP products, with a good application prospect in the field of environmental protection, have become a-research focus now.This thesis mainly studies the soft chemical synthesis processes of semicondctor catalyst Bi2Fe4O9 and the synergistic effect between the semiconductor photocatalysis and Fenton-like reaction. The main research contents are summarized as follows:1. Bi2Fe4O9 sub-micron-sized plates have been synthesized by a template free hydrothermal method at low temperature with different mineralizer concentrations, reaction temperatures and molar ratios of Bi3+ and Fe3+. The samples were characterized through XRD, SEM, UV-vis spectroscopy. The results show that the pure phase Bi2Fe4O9 could be obtained with NaOH as mineralizer at high concentration and rection temperature above 10 M,>130℃ The obtained catalyst exhibited good performance in acid photo-fenton-like system. In this chapter, the influence of different surfactants was also investigated.2. By the sol-gel method (with water and ethylene glycol as solvent), adding different surfactants,-pure phase Bi2Fe4O9 nanopowders were successfully snthesized. The results show that, during the sol-gel process, calcination temperature, composition of solvent and different surfactants may impact the structure, morphology and optical properties of the samples. When using water as solvent and citric acid as the chelating agent, the heat treatment temperature should be at 700℃. When using ethylene glycol as solvent, the precursor can quickly heated to 700℃. The addition of some surfactants can enhance catalytic degradation of performance.3. Using the coprecipitation method, we prepared some samples with the KOH solution and ammonia as precipitants, respectively. It was confirmed that, with ammonia as the precipitating agent, Bi2Fe4O9 can be synthesized by calcined at 700℃ for 2 h. The particulate morphology was observed with average diameter of 200 nm. In the Photo-Fenton-like system, more than 80% of the target contamination could be degraded in 3h. With KOH as the precipitant, it is easy to get BiFeO3 and Bi25FeO40. In this thesis, we also studied the photocatalytic performance of the two common bismuth ferrite powders.