Molecular characteristics of organic matter obtained from biochar by carbon disulfide/acetone synergistic extraction

Abstract

Environmental context Novel insight into BEOMcc is provided by fractionation and FTICR MS. Sub-fractions of biochar were extracted due to the chemical properties of the organic solvents. BEOMcc has a carbon fixation effect, and so is likely beneficial to the growth of plants and microorganisms. Rationale Since carbon disulfide (CS2) has a strong penetrating ability and acetone (CH3COCH3) can dissolve tiny biochar particles, a mixture of these compounds may efficiently extract organic matter from biochar. The extraction efficacy and structural features of a mixture of CH3COCH3 and CS2 (1:1) were tested in this study. Π–Π interactions between CS2 and CH3COCH3 increase the solubility of organic matter in the extraction process. Methodology We used a mixture of CH3COCH3 and CS2 (1:1) to extract organic matter from soybean straw biochar (BEOMcc) and applied Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for analysis. Results We found that CS2/CH3COCH3 tended to extract refractory substances, and the resulting extract contained a higher number of heteroatoms than the CS2-extractable fraction (1.34 times). Discussion The H/C ratio of BEOMcc is lower than that of CS2- and CH3COCH3-extractable components. The aromatic component of BEOMcc accounts for 52.47%, which is higher than the contribution to CS2-extractable organic matter of approximately 49.9%. The polycyclic aromatic hydrocarbon component of BEOMcc is beneficial to improving soil stability. The organic matter fraction of BEOMcc has a lower H/C ratio. The C/N ratio of BEOMcc is lower than that of the CS2- and CH3COCH3-extractable components. This result reveals that BEOMcc may provide a significant environmental benefit. The polarity of BEOMcc is between that of CS2- and CH3COCH3-extractable components. Implications for future research In this study, the composition of BEOMcc was assessed at the molecular level, and the extraction method was continuously improved to provide more extraction options for the study of biochar–pollutant interactions. This method can be used to extract organic matter that is difficult to extract by conventional methods, which is more closely bound to the biochar framework. It can provide a technical basis for the in‐depth characterisation and utilisation of biochar organic matter.