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

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 degrees C), and specifically analyzed their different advantages in environmental applications. In terms of all the PBCs and DBCs. PBC of 900 degrees C and the corresponding DBC have the highest degree of graphitization that is recalcitrant in environment, they are be for carbon sequestration. PBC of 300 degrees 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 degrees C have the greatest releasable PO43- content (0.418-0.441 mg/g), and PBCs of 700-900 degrees C have highest pH (9.28-9.59) and mineral elements content (1158-12.64 mg/g), they are potential provision of P. and acid soil amendments with potential provision of mineral elements, respectively. DBCs of 300-400 degrees 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 degrees C have the highest surface area (SA) (351 m(2)/g), the most developed porosity, and the highest releasable NI4+ 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. (C) 2018 Elsevier B.V. All rights reserved.