Facile and low-cost fabrication of ZnO/biochar nanocomposites from jute fibers for efficient and stable photodegradation of methylene blue dye

Abstract

The present work demonstrates the fabrication of ZnO loaded on biomass porous carbon through pyrolysis of jute fibers pretreated by Zn(OAc)2. XRD, Raman SEM, TEM, XPS and physical adsorption of nitrogen were used to characterize the products. Dark adsorption and photocatalytic degradation of methylene blue (MB) was run to evaluate their activities for removal of organic pollutants. It was demonstrated that the composition and structure of ZnO/JFC composites depended on the ratios of jute fibers to zinc salt. Through adjusting the mass ratio between raw materials, a fine composite of ZnO monocrystalline nanorods embedded on the porous carbon walls was obtained, which exhibited a much better efficiency for MB decolorization. The removal of MB was found to be pH dependent, and the optimized removal efficiency reached to 99% and the mineralization level was over 93% at pH 7.0 following 30 min under UV illumination. The kinetic studies showed the decolorization of MB followed pseudo first-order kinetics, and the rate constants were determined using the Langmuir–Hinshelwood model, indicating KLH = 0.024 L∙mg−1and kc = 4.01 mg∙L−1 min−1. Moreover, the ZnO nanorods/JFC composite was stable and showed a high efficiency of over 80% during seven cycles of utilization and regeneration. Examination for the real sample contaminated by MB proved that the presence of metal ions and other organic pollutants hardly affected its photocatalytic ability. It was demonstrated that ZnO/JFC composites could be fabricated through simultaneous pyrolysis of jute fibers and zinc acetate. These composites were provided with the advantages of high photocatalytic efficiency, convenient recycling and long-term stability, and were expected to be applied in environmental engineering and manufacturing for organic dyes removal.