title: Functional Groups Determine Biochar Properties (pH and EC) as Studied by Two-Dimensional (13)C NMR Correlation Spectroscopy.
abstract: While the properties of biochar are closely related to its functional groups, it is unclear under what conditions biochar develops its properties. In this study, two-dimensional (2D) (13)C nuclear magnetic resonance (NMR) correlation spectroscopy was for the first time applied to investigate the development of functional groups and establish their relationship with biochar properties. The results showed that the agricultural biomass carbonized to biochars was a dehydroxylation/dehydrogenation and aromatization process, mainly involving the cleavage of O-alkylated carbons and anomeric O-C-O carbons in addition to the production of fused-ring aromatic structures and aromatic C-O groups. With increasing charring temperature, the mass cleavage of O-alkylated groups and anomeric O-C-O carbons occurred prior to the production of fused-ring aromatic structures. The regression analysis between functional groups and biochar properties (pH and electrical conductivity) further demonstrated that the pH and electrical conductivity of rice straw derived biochars were mainly determined by fused-ring aromatic structures and anomeric O-C-O carbons, but the pH of rice bran derived biochars was determined by both fused-ring aromatic structures and aliphatic O-alkylated (HCOH) carbons. In summary, this work suggests a novel tool for characterising the development of functional groups in biochars.
authors.affiliation: Agricultural Ministry Key Lab of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, Nanjing, PR China ; College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, PR China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Li
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.forename: Dongqing
authors.initials: D
authors.lastname: Zhang
authors.forename: Xinlan
authors.initials: X
authors.lastname: Mei
authors.forename: Wei
authors.initials: W
authors.lastname: Ran
authors.forename: Yangchun
authors.initials: Y
authors.lastname: Xu
authors.forename: Guanghui
authors.initials: G
authors.lastname: Yu
mesh_terms: D000383:Agriculture; D018533:Biomass; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D002606:Charcoal / Q000737:chemistry*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D012275:Oryza / Q000737:chemistry*; D013696:Temperature
chemical_list: C540010:biochar; D002606:Charcoal