Characteristics of wood-derived biochars produced at different temperatures before and after deashing: Their different potential advantages in environmental applications.

Abstract Ash in biochar has great influence on the characteristics of biochars. This study systematically compared the differences in physico-chemical properties between pristine biochars (PBCs) and deashed biochars (DBCs) produced at different temperatures (300–900 °C), and specifically analyzed their different advantages in environmental applications. In terms of all the PBCs and DBCs, PBC of 900 °C and the corresponding DBC have the highest degree of graphitization that is recalcitrant in environment, they are benefit for carbon sequestration. PBC of 300 °C and the corresponding DBC have the highest content of O-containing functional groups and aliphaticity that is labile in environment, they are potential carbon source for the growth of soil organisms. PBCs of 300–400 °C have the greatest releasable PO 4 3− content (0.418–0.441 mg/g), and PBCs of 700–900 °C have highest pH (9.28–9.59) and mineral elements content (11.58–12.64 mg/g), they are potential provision of P, and acid soil amendments with potential provision of mineral elements, respectively. DBCs of 300–400 °C possess less competitive cations including Ca, Mg, Al, Fe, and Zn (1.49–2.01 mg/g) and highest content of O-containing functional groups, they are good sorbents for heavy metals, meanwhile these DBCs have the lowest pH (4.49–4.70) that are potential amendments for alkaline soil. Moreover, DBCs of 900 °C have the highest surface area (SA) (351 m2/g), the most developed porosity, and the highest releasable NH 4 + content (0.052 mg/g), they are good sorbents for hydrophobic organic pollutants and potential provision of N. This study gives an effective guidance for selecting the suitable biochars-design (deashing or non-deashing) according to their applications in environment. Graphical abstract Unlabelled Image Highlights • Difference of properties between PBCs and DBCs is related to pyrolysis temperature. • Deashing decrease pH, bulk metal content and releasable PO 4 3− of biochars • Deashing increase SA and releasable NH 4 + of biochars produced at high temperature. • PBCs are benefit for provision of nutrient element. • DBCs are benefit for sorption of pollutants. [ABSTRACT FROM AUTHOR]