Recycling metal ions from hot-dip galvanizing wastewater to high-value MOFs: From removal of environmental disturbance via hydrothermal to metal resources

Heavy metal ion pollution in industrial wastewater poses significant threats to human health and the environment. In this study, hot-dip galvanizing wastewater was successfully converted into high-value metal–organic framework (MOF) materials (i.e., Fe-BTC-R and Zn-BTC-R; BTC = benzenetricarboxylic acid), and the restorative capabilities of these materials were evaluated using three dyes, namely methylene blue (MB), malachite green (MG), and crystal violet (CV). For the Fe-BTC-R material, the adsorption capacities of MB and MG were 803.03 and 475.12 mg/g, respectively, while for the Zn-BTC-R material, adsorption capacities of 1798.2 and 381.79 mg/g were obtained for CV and MG, respectively. These results indicate that the adsorption performance of both materials is superior to most conventional adsorbent materials. Furthermore, theoretical calculations and experiments suggested that the mechanism of dye adsorption could be attributed to the synergistic effects of electrostatic attraction, hydrogen bonding, and π–π interactions. Finally, the photocatalytic performances of the materials were simply evaluated using three dyes. Overall, our study not only provides an effective strategy for managing heavy metal salt pollution in wastewater but also contributes to achieving the goals of resource recovery and dye treatment.