Effect of dewatering conditioners on phosphorus removal efficiency of sludge biochar

Based on the best dehydration effect, this study compared the adsorption phosphorus effect of sludge biochar after sludge conditioning with FeCl₃, KMnO₄, and cationic polyacrylamide (CPAM). This provided insights into the effects of chemical conditioning during the sludge dewatering stage on the overall phosphate adsorption of the dewatered sludge biochar. The phosphorus adsorption mechanism of the dewatering sludge biochar was analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Under the optimal pyrolysis temperature (300°C), the phosphate adsorption capacity of FeCl₃-conditioned sludge biochar (SB-FeCl₃) was increased 77 times of the unconditioned sludge biochar. In different solution environments (e.g. pH and coexisting anions), Phosphate adsorption of SB-FeCl₃ was srtrongest when the pH of 9 and contained CO₃^2-. Through the analysis of surface elements and functional groups, it was explained that the phosphorus removal effect of SB-FeCl₃ comes from abundant active sites containing iron. Phosphorus release occurred in sludge biochar (SB) during the study. SB-FeCl₃ solved SB the release of phosphorus, and improved the adsorption capacity of phosphorus.