Air oxidation coupling NH3 treatment of biomass derived hierarchical porous biochar for enhanced toluene removal

In this study, hierarchical porous biochar was prepared from poplar sawdust by air oxidation coupling with NH3 treatment for the removal of toluene. The results showed that the mesopore volume of the sample with air oxidation (PS-O-2) increased significantly to 0.263 cm(3)/g from the blank sample (PS, 0.053 cm(3)/g). This could be attributed to the selective removal of the lignin carbon by air oxidation to develop mesopores in biochar. Following further NH3 treatment (PS-O-2-NH3), the basic surface chemistry on biochar was improved due to increased basic N-containing groups and decreased acidic O-containing groups, together with the micropore volume also increased to 0.231 cm(3)/g from 0.186 cm(3)/g of PS-O-2. The formation mechanism of hierarchical porous structure of biochar was also discussed. The adsorption capacity of PS-O-2-NH3 for toluene reached 218.4 mg/g at the initial concentration of 820 mg/m(3), which was 383.2% higher than that of PS. The adsorption isotherm study indicated that the adsorption process of toluene was monolayered and the maximal adsorption capacity of PS-O-2-NH3 for toluene could reach as high as 476.2 mg/g. The results demonstrated that air oxidation coupling NH3 treatment is a highly effective method for the preparation of hierarchical porous biochar for enhancing toluene adsorption performance.

Automated summary

In this study, hierarchical porous biochar prepared from poplar sawdust by air oxidation coupling with NH3 treatment showed significantly enhanced mesopore and micropore volumes, improved basic surface chemistry, and increased adsorption capacity for toluene. The results indicated that the adsorption process of toluene was monolayered, and the maximum adsorption capacity of PS-O-2-NH3 for toluene could reach as high as 476.2 mg/g. The combination of air oxidation and NH3 treatment is a highly effective method for enhancing toluene adsorption performance of biochar.