Magnetically recoverable steel slag/TiO2 visible-light-driven photocatalyst for paraquat degradation

Paraquat is a bipyridylium herbicide with high solubility in water, which is widely used for aquatic weed control. The purposes of the present study were to introduce a navel TiO2-based photocatalyst (SCS@Fe-TiO2) and investigate its performance in paraquat degradation from aqueous solution under visible light. The response surface methodology (RSM) method was used to optimize pH, catalyst dose, initial concentration of paraquat, and irradiation intensity in the photocatalytic process. The characterization results of the photocatalyst revealed that coating Fe-TiO2 onto the SCS has improved its photo-degradation properties. Diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) results showed that not only doping TiO2 by Fe but also coating Fe-TiO2 onto the SCS makes a reduction in the bandgap and electron-hole recombination. Totally, the performance of the photocatalytic process was high (90%-99%) and the effect of the parameters studied on the process was significant (p-value <0.05). The concentration of paraquat and irradiation intensity variables had linear relationships, so increasing the concentration of paraquat reduced the efficiency but the light intensity had the opposite effect. On the other hand, pH and photocatalyst mass had optimum values of 7 and 0.7 g, respectively, so they were the most important variables. HO degrees$$ {\mathrm{HO}}<^>{{}<^>{\circ}} $$ and h(+) played a crucial role in the photo-degradation of paraquat by SCS@Fe-TiO2. SCS@Fe-TiO2 exhibited excellent photocatalytic reactivity for paraquat over 10 cycles. Finally, the SCS@Fe-TiO2 would be a promising photocatalyst for the photo-degradation of paraquat from aqueous solutions under visible light.

Automated summary

This study introduces a new photocatalyst SCS@Fe-TiO2 and investigates its performance in the degradation of paraquat under visible light. The response surface methodology is used to optimize the parameters of the photocatalytic process. The results show that SCS@Fe-TiO2 exhibits excellent photocatalytic reactivity and certain parameters have significant effects on the process.