Biochar production using biogas residue and their adsorption of ammonium nitrogen and chemical oxygen demand in wastewater

Modified biochars prepared from straw, pig manure, and chicken manure biogas residues were used to adsorb and remove ammonium nitrogen (NH4+-N) and chemical oxygen demand (COD) in wastewater. The results showed that at 400-600 degrees C, the adsorption performance of the biogas residue biochars increased with pyrolysis temperature, reaching the maximum at 550 degrees C. Biochar from chicken manure biogas residue exhibited strong NH4+-N (20.3%) and COD (28.1%) adsorption capacity. Through FeCl3 modification, the Fe content on the surface of the biochar increased, and the adsorption data of the modified biochar conformed well to the pseudo-second-order kinetics and Langmuir model, and the reaction was dominated by chemical adsorption. The fitting calculation revealed that the FeCl3-modified biochar from chicken manure biogas residue showed maximum NH4+-N (55.29 mg/g) and COD (186.24 mg/g) absorption capacity. These results indicated that modified biochar from biogas residue could have potential application for the treatment and recycling of biogas slurry.

Automated summary

Modified biochars prepared from biogas residues showed increased adsorption capacity for NH4+-N and COD, with the chicken manure biogas residue biochar exhibiting the highest absorption rates. FeCl3 modification further enhanced the adsorption properties, indicating potential applications for biogas slurry treatment and recycling.