Hybrid magnetic graphitic nanocomposites towards catalytic wet peroxide oxidation of the liquid effluent from a mechanical biological treatment plant for municipal solid waste

• Published in: Applied catalysis. B, Environmental Vol. 219; pp. 645 - 657
• Main Authors: Ribeiro, Rui S., Rodrigues, Raquel O., Silva, Adrián M.T., Tavares, Pedro B., Carvalho, Ana M.C., Figueiredo, José L., Faria, Joaquim L., Gomes, Helder T.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.12.2017; Elsevier BV
• Subjects: Aromaticity; Bacteria; Bicarbonates; Biochemical oxygen demand; Biodegradability; Biodegradation; Biological effects; Biological treatment; Carbonates; Catalysis; Catalysts; Chemical oxygen demand; Chlorides; Cobalt; Cobalt ferrites; Core-shell nanocomposites; Effluents; Ferrites; Heterogeneous Fenton-like process; Hydrogen ions; Magnetic separation; Magnetite; Mechanical biological treatment; Municipal solid waste; Municipal waste management; Nanocomposites; Nickel; Nitrophenol; Organic carbon; Oxidation; Peroxide; pH effects; Process water; Shells; Solid waste management; Solid wastes; Total organic carbon; Toxicity; Treated water; Wastewater; Wastewater treatment; Water pollution effects; Water treatment; Process water; Core-shell nanocomposites; Mechanical biological treatment; Heterogeneous Fenton-like process; Magnetic separation
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2017.08.013

[Display omitted] •Fe3O4, NiFe2O4 and CoFe2O4 nanoparticles were encapsulated within graphitic shells.•The highest catalytic activity in CWPO is obtained with the hybrid CoFe2O4 catalyst.•Operating pH has a crucial role on the CWPO of the liquid effluent from a MBT plant.•A magnetic separation system was developed for in-situ catalyst recovery after CWPO.•Sequential CWPO reaction/separation runs reveal the high stability of the catalyst. Magnetite, nickel and cobalt ferrites were prepared and encapsulated within graphitic shells, resulting in three hybrid magnetic graphitic nanocomposites. Screening experiments with a 4-nitrophenol aqueous model system (5gL−1) allowed to select the best performing catalyst, which was object of additional studies with the liquid effluent resulting from a mechanical biological treatment plant for municipal solid waste. Due to its high content in bicarbonates (14350mgL−1) and chlorides (2833mgL−1), controlling the initial pH was a crucial step to maximize the performance of the catalytic wet peroxide oxidation (CWPO) treatment. The catalyst load was 0.5gL−1, a very low dosage when compared to the high chemical oxygen demand (COD) of the effluent − 9206mgL−1. At the optimum operating pH (i.e., pH=6), ca. 95% of the aromaticity was converted and ca. 55% of COD and total organic carbon (TOC) of the liquid effluent was removed. The biodegradability of the liquid effluent was enhanced during the treatment by CWPO, as reflected by the 2-fold increase of the five-day biochemical oxygen demand (BOD5) to COD ratio (BOD5/COD), namely from 0.21 (indicating non-biodegradability) to 0.42 (suggesting biodegradability of the treated wastewater). In addition, the treated water revealed no toxicity against selected bacteria. Lastly, a magnetic separation system was designed for in-situ catalyst recovery after the CWPO reaction stage. The high catalyst stability was demonstrated through five reaction/separation sequential experiments in the same vessel with consecutive catalyst reuse.