Hydrothermal synthesizing sludge-based magnetite catalyst from ferric sludge and biosolids: Formation mechanism and...

Sludge-based magnetite catalyst (SBMC) containing Fe₃O₄ was synthesized by hydrothermal (HT) of biosolids and ferric sludge, which is a promising wasted sludge recycling way. The protein and carbohydrate, main representative compounds in biosolids, were used to explore the SBMC formation mechanism. A part of carbohydrate and the produced Maillard reaction products (MRPs) derived from two substrates via Maillard reaction (MR) were confirmed to participate in Fe³⁺ reduction. The MR accompanied by substrates humification, making MRPs own strong chelation activity. The MRPs (50-100 kDa) reflected the strongest relative reducing and chelation activity, mainly involving in Fe₃O₄ synthesis. Furthermore, the SBMC was verified as an efficient Fenton-like catalyst for aniline with 77.9% removal efficiency. The OH and O₂^- both contributed to the degradation, differing from only OH playing function in traditional Fenton-like system, implying biochar in SBMC could mediate the reactive oxygen species generating by Fe₃O₄, and benefit its catalytic performance.