Improved humification and Cr(VI) immobilization by CaO and FeO during composting.

The current research studied how FeO nanomaterials (NMs) and CaO affect humification and Cr(VI) immobilization and reduction during the composting of oil-tea Camellia meal and Cr-contaminated soil. The results showed that FeO NMs and CaO successfully construct a Fenton-like reaction in this system. The excitation-emission matrix-parallel factor (EEM-PARAFAC) demonstrated that this Fenton-like treatment increased the generation of humic acids and accelerated the humification. Meantime, RES-Cr increased by 5.91 % and Cr(VI) decreased by 16.36 % in the treatment group with CaO and FeO NMs after 60 days. Moreover, the microbial results showed that FeO NMs and CaO could promote the enrichment of Cr(VI) reducing bacteria, e.g., Bacillus, Pseudomonas, and Psychrobacter, and promote Cr(VI) reduction. This study gives a novel view and theoretical reference to remediate Cr(VI) pollution through composting.