Effective activation of peroxymonosulfate by CoCr-LDH for removing organic contaminants in water: from lab-scale to practical applications.

In this study, CoCr layered double hydroxide material (CoCr-LDH) was prepared and used as an effective catalyst for peroxymonosulfate (PMS) activation to degrade organics in water. The prepared CoCr-LDH material had a crystalline structure and relatively porous structure, as determined by various surface analyses. In Rhodamine B (RhB) removal, the most outstanding PMS activation ability belongs to the material with a Co:Cr molar ratio of 2:1. The removal of RhB follows pseudo-first-order kinetics (R2 > 0.99) with an activation energy of 38.23 kJ/mol and efficiency of 98% after 7 min of treatment, and the total organic carbon of the solution reduced 47.2% after 10 min. The activation and oxidation mechanisms were proposed and the RhB degradation pathways were suggested with the key contribution of O2•- and 1O2. Notably, CoCr-LDH can activate PMS over a wide pH range of 4 - 9, and apply to a wide range of organic pollutants and aqueous environments. The material has high stability and good recovery, which can be reused for 5 cycles with a stable efficiency of above 88%, suggesting a high potential for practical recalcitrant water treatment via PMS activation by heterogeneous catalysts.

A comprehensive study on the heterogeneous electro-Fenton degradation of tartrazine in water using CoFe2O4/carbon felt cathode.

In this study, cobalt ferrite coated carbon felt (CoFe2O4/CF) was synthesized by solvothermal method and applied as cathode for electro-Fenton (EF) treatment of tartrazine (TTZ) in water. The materials were characterized by SEM, XRD, FTIR, CV, and EIS to explore their physical, chemical, and electrical properties. The effects of solvothermal temperature and metal content on the TTZ removal were examined, showing that 220 °C with 2 mM of Co and 4 mM of Fe precursors were the best synthesis condition. Various influencing factors such as applied current density, pH, TTZ concentration, and electrolytes were investigated, and the optimal condition was found at 8.33 mA cm-2, pH 3, 50 mgTTZ L-1, and 50 mM of Na2SO4, respectively. By radical quenching test, , 1O2, and HO were recognized as the key reactive oxygen species and the reaction mechanism was proposed for the EF decolorization of TTZ using CoFe2O4/CF cathode. The reusability and stability test showed that the highly efficient CoFe2O4/CF cathode is very promising for practical application in wastewater treatment, especially for dyes and other recalcitrant organic compounds to improve its biodegradability.