3 years ago

Novel ZnS/Carbon Nanofiber Photocatalyst for Degradation of Rhodamine 6G: Kinetics Tracking of Operational Parameters and Development of a Kinetics Model

Novel ZnS/Carbon Nanofiber Photocatalyst for Degradation of Rhodamine 6G: Kinetics Tracking of Operational Parameters and Development of a Kinetics Model
Parvin Gharbani, Ali Mehrizad
A novel nanocomposite in the role of photocatalyst was prepared by composition of zinc sulfide (ZnS) nanoparticles with carbon nanofibers (CNFs) and was characterized. The XRD, EDX, and FE-SEM analysis revealed that ZnS is successfully embedded in CNFs matrix. The DRS results indicated that supporting of ZnS by CNFs led to a decrease of the band gap energy. The photocatalytic degradation of a hazardous xanthine dye, Rhodamine 6 G (Rh-6G), by the prepared ZnS/CNFs composite was examined from the kinetics point of view. Nonlinear regression analysis was used to develop a mathematical kinetics model based on the Langmuir–Hinshelwood mechanism, and an empirical equation was obtained for the estimation of apparent pseudo-first-order rate constant (kap) as a function of operational parameters (viz. initial dye concentration, ZnS/CNFs content, pH, and irradiation intensity). Based on the results, kap increased with an increase ZnS/CNFs content, pH, and UV light intensity, whereas it decreased by increasing the initial Rh-6G concentration. Moreover, a new kinetics model was obtained based on proposed elementary steps to determine kap. In the final stage of the work, intermediate materials produced within photocatalytic degradation of Rh-6G dye were detected by GC-MS analysis. Novel zinc sulfide/carbon nanofiber (ZnS/CNF) composite in the role of photocatalyst was prepared and used toward degradation of Rhodamine 6 G (Rh-6G). Photocatalytic studies were performed from the kinetics point of view, and it was found that the rate of degradation obeys the Langmuir–Hinshelwood pseudo-first-order kinetics model. A new kinetics model was obtained based on the proposed elementary steps, and the obtained results indicated that the trapping of valence band holes occurs faster than e−/h+ recombination. Active degradation of Rh-6G by ZnS/CNFs was performed, which inset photograph indicates the reduction of dye from pink to colorless.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/php.12795

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