Upcycling of nickel iron slags to hierarchical self-assembled flower-like photocatalysts for highly efficient degradation of high-concentration tetracycline

The utilization of large-volume nickel–iron slags is largely limited by the existence of heavy metal chromium, resulting in a sharply increase environment problem. Here we report a viable strategy to fully convert nickel–iron slags into self-assembled flower-like silicate photocatalysts. Intriguingly, these decent 3D hierarchical architectures made from wild wastes are composed of core–shell structured silicates. In the meanwhile, nearly 100% chromium is extracted from the slags. Due to the high specific surface area and effective metal coordination sites (i.e., Na+, Mg2+ and Ca2+), the as-obtained silicate catalysts exhibit the extraordinary photocatalytic degradation rate (81.7 %) and the mineralization rate (27 %) of high-concentration tetracycline (100 mg/L) after 30-min Xe lamp irradiation, which are higher than those in most previous reports in terms of degradation and mineralization rates of the high-concentration tetracycline. This simple yet robust strategy to craft 3D self-assembled hierarchical flower-like silicate photocatalysts pave a novel way to the large-scale and value-added consumption of waste residues.