MgFe-LDH@biochars for removing ammonia nitrogen and phosphorus from biogas slurry: Synthesis routes, composite performance, and adsorption mechanisms

Layered double hydroxide-biochar composites ([email protected]) have been developed for ammonia nitrogen (AN) and phosphorus (P) removal from wastewater. Improvement of [email protected] was limited due to the lack of comparative evaluation based on [email protected] characteristics and synthetic methods and information on the adsorption properties of [email protected] for N and P from natural wastewater. In this study, [email protected] were synthesized by three different co-precipitation procedures. The differences in physicochemical and morphological properties were compared. They were then employed to remove AN and P from biogas slurry. The adsorption performance of the three [email protected] was compared and evaluated. Different synthesis procedures can significantly affect the physicochemical and morphological characteristics of [email protected]. The [email protected] composite fabricated through a novel method (labeled '[email protected]') has the largest specific surface area, Mg and Fe content, and excellent magnetic response performance. Moreover, the composite has the best adsorption property of AN and P from biogas slurry (30.0% and 81.8%, respectively). The main reaction mechanisms include memory effect, ion exchange, and co-precipitation. Applying 2% [email protected] saturated with AN and P adsorption from biogas slurry as a fertilizer substitute can substantially improve soil fertility and increase plant production by 139.3%. These results indicate that the facile [email protected] synthesis method is an effective method to overcome the shortcomings of [email protected] in practical application, and provide a basis for further exploration of the potential application of biochar based fertilizers in agriculture.