A facile and green strategy to synthesize N/P co-doped bio-char as VOCs adsorbent: Through efficient biogas slurry treatment and struvite transform

Controllable introduction of active sites on bio-char is certified as an available method to resolve a bottleneck issue of conversion of various green renewable bio-char into valuable materials. In this work, the bio-char was modified by air thermal oxidation after the formation of struvite via the facile impregnation in the biogas slurry. The structural and elemental properties of the surface of modified bio-char were analyzed by SEM, BET, XRD, and XPS. XPS analysis of the nitrogen and phosphorus valence states on the carbon surface shows that the N/P elements of struvite were synergically converted into N/P functional groups via air thermal oxidation. Then the modified bio-char was used as VOCs-acetone adsorber and the result shows that the acetone adsorption capacity was 4.8 times higher than that of bio-char. The density functional theory (DFT) proves that the binding force of C-O-P and acetone (-16.882 kcal) is stronger than that of C-P-O and acetone (−7.779 kcal). The results certified that air thermal oxidation coupling eutrophic element recycling is a promising approach for the preparation of N/P co-doped bio-char as value-add materials for improving acetone adsorption performance.