Pyrite activated peroxymonosulfate combined with as a physical–chemical conditioner modified biochar to improve sludge dewaterability: analysis of sludge floc structure and dewatering mechanism

In this study, we proposed an advanced oxidation process of pyrite (FeS(2)) and peroxymonosulfate (PMS) and prepared a modified polyaluminum chloride biochar (P-BC). The motivation is to use the combination of FeS(2) + PMS + P-BC to improve waste activated sludge (WAS) dewaterability. The method to improve the sludge dewatering effect with the combination of FeS(2) + PMS + P-BC is as follows: in the first step, pour 0.75 g/g TSS FeS(2) and 0.6 g/g TSS PMS into the sludge, and stir for 15 min. Then, add P-BC and stir for 5 min; complete the entire WAS processing process. The vacuum filtration test was used to evaluate the dehydration effect. The water content (Wc) and specific resistance to filtration (SRF) of the raw sludge can be reduced from the original values of 92% and 2.36 × 10(13) m/kg to 67% and 9.89 × 10(11) m/kg, respectively. The results showed that the combination of FeS(2) + PMS + P-BC can effectively improve the sludge dewatering effect through oxidation. A laser particle size analyzer is used to observe changes in sludge particle size. The median diameter of sludge particles increased from 55.37 to 64.56 μm. A zeta analyzer to is used observe changes in sludge zeta potential. The zeta potential of sludge particles increased from − 15.8 to 0.4 mV. In the analysis of extracellular polymeric substances (EPS) of sludge, it was found that protein (PN) and polysaccharide (PS) in EPS decreased significantly. To further analyze the phenomenon of PN and PS drop, excitation-emission-matrix spectra (3D-EEM) was used. To observe the changes of sludge functional group, X-ray photoelectron spectroscopy was used. It was found that FeS(2) + PMS + P-BC can destroy the functional groups of sludge, such as O–H, C–C, and O═C—NH– related to proteins and polysaccharides. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11356-022-21074-4.