Degradation of oxytetracycline using microporous and mesoporous photocatalyst composites: Uniform design to explore factors

Microporous ZSM-5 and mesoporous MCM-41 loaded with TiO2 were synthesized to remove oxytetracycline in aqueous solutions. The adsorption of oxytetracycline showed that MCM-41 had higher adsorption capacity than ZSM-5 and that this capacity changed little after TiO2 loading. Four factors affecting photocatalytic degradation were investigated by uniform design; these factors included the initial pH of oxytetracycline solution, reaction temperature, dosage of catalysts, and TiO2 content of catalysts. Single-factor experiment confirmed that experimental values agreed with predicted ones by the regression formula of the uniform design. After recycling and reuse for five cycles, the composites retained their degradation performance. Both adsorption and photocatalytic degradation experiments indicated that MCM-41 was more suitable than ZSM-5 for loading TiO2 to remove oxytetracycline because of the former's better absorption properties. The biomass at the stationary growth phase and the maximum specific growth rate of Escherichia coli were used to assess toxicity during photocatalytic degradation, which linearly decreased with increased oxytetracycline degradation efficiency.