Reducing environmental burden of electroplating wastewater treatment by ternary cooperation of zero-valence iron, manganese, and graphitic biochar

Abstract

Iron-based technology is one of the most practical approaches to remove toxic metals from electroplating wastewater, but faces the problem of low efficiency and requires energy/chemical-demanding steps for safe disposal. Here we develop an efficient material by combining iron and manganese particles with biochar for sustainable decontamination. The formed graphitic biochar layer prevents the embedded zero-valence iron from fast passivation and facilitates the electron transfer, boosting their ability to reduce pollutants and making the iron up to 24 times more efficient than common iron-based materials. Meanwhile, the manganese oxides undergo a 0.02 Å lattice expansion, improving their ability to trap toxic metals. The carbon, iron, and manganese form stable chemical bonds that lock in pollutants, eliminating the need for costly and carbon-intensive stabilization process before landfill disposal. This approach cuts greenhouse gas emissions by 71.8–89.7% compared to conventional treatments and produces only 2.1–3.5% CO2 compared to other iron-based methods. Our strategy can innovate mineral-carbon composite designs and suggest a more sustainable path for industrial wastewater treatment. Iron-based technology is useful for wastewater treatment but suffers from performance and sustainability issues. Here, zero-valence iron and manganese oxide were embedded in graphitic biochar through a combined hydrothermal-pyrolysis process for sustainable water decontamination.