Bentonite nanoparticles-incorporated ZnO nanofiber mats assembly by electro-centrifuge spinning for efficient photo-degradation of bentazon herbicide: Tuning composition and process optimization

Herein, photocatalytic features and performance of ZnO nanofiber mats spun by electro and electro-centrifuge spinning methods were evaluated by various characterization techniques and the UV-degradation of bentazon herbicide, respectively and then, compared with those of ZnO nanoparticles. Because of higher productivity and more flexibility in loading nanoparticles, the electro-centrifuge spinning method was chosen to fabricate bentonite nanoparticles incorporated ZnO nanofiber mats. The FESEM images clearly indicate the formation of 0D/1D nanoparticle/nanofiber morphologies in samples. XRD, EDX and FTIR analyses confirmed the formation of ZnO and the existence of bentonite. Based on the PL analysis, the bentonite nanoparticles get to inhibit the charge recombination. However, its excessive incorporation causes intense loss of active sites numbers and the surface coverage of ZnO nanofibers which restrict the light absorption as evidenced by FESEM and UV-DRS results. After 2 h irradiation, the efficiency removal of bentazon reached from 85.23% by pure ZnO nano -fibers to 100% by composite nanofiber mats containing 5 wt% bentonite (ZnO-Ben5 (NF-ECS)). Nonetheless, the removal efficiency declines upon further increasing the content of incorporated bentonite. The kinetics study disclosed that the photocatalytic bentazon removal was best fitted with the first order model (R2 = 0.9907) with the maximum rate constant of 0.0243 min-1 over ZnO-Ben5 (NF-ECS). Moreover, RSM-CCD analysis was employed to model and optimize the photocatalytic treatment process. A reduced cubic model (Adj. R2 = 0.9934, p-value <0.0001) was proposed for interpreting the system behavior. Under optimal operating conditions (photocatalyst dosage of 0.33 g.L-1, initial solution pH of 8.92, bentazon concentration of 10.11 ppm and irradiation time of 85.78 min), ZnO-Ben5 (NF-ECS) eliminated approximately 83% of bentazon after four-time recycling, reflecting a sustained great activity.

Automated summary

The photocatalytic features and performance of ZnO nanofiber mats spun by electro and electro-centrifuge spinning methods were evaluated and compared with ZnO nanoparticles. The electro-centrifuge spinning method was chosen to fabricate bentonite nanoparticles incorporated ZnO nanofiber mats due to its higher productivity and flexibility in nanoparticle loading. The incorporation of bentonite nanoparticles inhibited charge recombination, but excessive incorporation resulted in a loss of active sites and restricted light absorption.