Novel synthesis of nanoscale zero-valent iron from iron ore tailings and green tea for the removal of methylene blue

There are comparatively abundant Fe resources remained in iron ore tailings, which is urgent to be utilized comprehensively. In this work, nanoscale zero-valent iron (T-nZVI) was firstly synthesized with iron ore tailings and green tea as raw materials to realize the efficient removal of methylene blue (MB). The formation process of T-nZVI composite nanoparticles in complex system was investigated, as well as the effect of green tea extract dosage and pH value on its composition, particle size and reactivity. The characterization results indicated that the synthesized T-nZVI nanoparticles were amorphous spherical particles, which were composed of Fe0-Al2O3 core-shell structure capped with organic substance. The removal efficiency of MB by T-nZVI nanoparticles synthesized at optimal conditions could be up to 99.46%, which was better than the nZVI nanoparticles synthesized from chemical reagent. The decolorization mechanism might be related to adsorption, reductive degradation and complex precipitation between MB molecules and T-nZVI nanoparticles. This study proposes a feasible alternative utilization of iron ore tailings to prepare high value-added nanomaterials for wastewater treatment.