Rapid Removal of Phenothiazine Pollutants by Novel Catalytic Composites Derived from Sewage Sludge: Decolorization and Degradation Mechanism

Phenothiazines are new synthetic pollutants that have attracted attention in the present years. In order to remove such novel pollutants, in this paper, novel catalytic composites loaded with iron metals (SFCs) were prepared by high-temperature pyrolysis of sewage sludge for the degradation of novel pollutants of phenothiazines, represented by methylene blue (MB). It was found that among the five SFCs prepared, SFC700, prepared at a pyrolysis temperature of 700 °C, had the best pore structure, the largest specific surface area (452.3 m 2 g −1 ), the richest functional groups (such as carboxyl, hydroxyl, and C = O bonds, etc.), the most Fe 3 O 4 content, which exhibited the best performance. SFC700 composites could remove 99.9% of MB within 60 min, and the optimal initial pH was 11. SFC700 had a certain decolorization stability, and the degradation rate could still be maintained at about 90%. It was presumed that SFC700 played the dual role of adsorption and catalysis.