Photo-thermal synergy for boosting photo-Fenton activity with rGO-ZnFe2O4: Novel photo-activation process and mechanism toward environment remediation

Full light photo-Fenton and photo-thermal effect are of great importance but deserve attentions far insufficient in advanced oxidation progresses for extensive environmental remediation. Herein, ultraviolet-visible-near infrared (UV-vis-NIR) light absorbance and photo-thermal conversion were induced into H2O2 activation towards refractory antibiotics elimination from wastewater through green recyclable rGO-ZnFe2O4 developed via ultrasonic method. Interestingly, photo-thermal synergy presents much superior performance than that of solely photoFenton or thermal-Fenton process. Multiple light reflection inner ZnFe2O4 microsphere strengthens UV-vis capture and thermal conversion in degradation reaction. Orbital hybridization and electron rearrangement endow rGO-ZnFe2O4 wide NIR absorbency, fast thermal transfer and photo-generated electrons-holes separation for photo-thermal Fenton progress. Degradation rate of ciprofloxacin on rGO-ZnFe2O4 is found 3 times of ZnFe2O4 under full light exposure which can heat solution from room temperature to 70 degrees;C, while 4 times under NIR irradiation where solution is heated to 46 degrees C. The great differences are mainly originated from photoinduced thermal energy, which in-situ heating active sites to lower H2O2 activation barrier, accelerate Fe2+/Fe3+ cycle and facilitate spread of radicals. Radicals contribute in (OH)-O-center dot > h(+) > O-2(center dot-) under full light irradiation, while perform in h(+) > O-2(center dot-) > (OH)-O-center dot when taking away photo-generated heat. Results based on systematic experiments and theory calculation imply the strong potential of photo-thermal Fenton in pollutants control, which proposes novel strategy in Fenton reaction for environmental remediation with effective utilization of solar energy.

Automated summary

UV-vis-NIR light absorbance and photo-thermal conversion were induced into H2O2 activation using rGO-ZnFe2O4 catalyst, showing superior performance in degradation of refractory antibiotics compared to solely photoFenton or thermal-Fenton processes. The innovative strategy of utilizing solar energy in environmental remediation through photo-thermal Fenton reaction has strong potential in pollutants control.