Large particle size boosting the engineering application potential of functional biochar in ammonia nitrogen and phosphorus removal from biogas slurry

The practical engineering application of biochar has been hindered by limitations in the fabrication process and parameters used. This study aimed to overcome these limitations by preparing layered double hydroxides (LDH)-anchored biochar using larger particle size biomass. We analyzed the physicochemical properties of the functional biochar and conducted adsorption studies on wastewater-biogas slurry. Based on elemental analysis and static adsorption experiments, the biochar fabricated from powdered biomass had higher activator utilization and maximum adsorption capacity than biochar from larger particle size biomass. However, based on BET analysis and results from adsorption kinetics studies, the biochar derived from larger particle biomass exhibited outstanding surface properties and exceptional adsorption efficiency. Notably, in dynamic adsorption experiments, the LDH-anchored biochar derived from larger particle size biomass performed exceptionally well in a fixed bed column at high liquid flow rates (15 mL min−1). Based on the fitting results of mass transfer kinetics, we observed that the adsorption capacity of ammonia nitrogen remained relatively constant, while phosphorus adsorption increased at high flow rates compared to low flow rates. Scale-up design results showed that the biochar fixed bed column could handle a large volume (108 m3) of biogas slurry per day, recovering significant amounts of ammonia nitrogen (188.6 kg) and phosphorus (1.2 kg). These findings highlight the potential of functional biochar derived from larger particle size biomass for engineering applications in wastewater treatment.