Pyrolysis Temperature-Dependent Changes in the Characteristics of Biochar-Borne Dissolved Organic Matter and Its Copper Binding Properties

Abstract

The dissolved organic matter (DOM) samples from biochars produced from Jerusalem artichoke stalks by pyrolysis at 300, 500, and 700 °C were characterized using a combination of spectroscopic techniques. Additionally, the binding affinities (long K) and the complexation capacities (C) of the DOM samples with Cu(II) were calculated to assess their Cu binding properties. The biochar-borne DOM contained mainly humic-like components (C1-C3) with a small amount of a protein-like component (C4). As the charring temperature increased, the concentrations of released DOM decreased. The low temperature biochar-borne DOM was found to have more carboxyl groups than its high temperature counterparts, and thus it had larger C values. In contrast, the high temperature biochar-borne DOM had larger long K values. Low temperature biochars, if applied in a large quantity, would alter copper mobility in the environment because of their high DOM contents and large copper binding capacities.

Limited Cu(II) binding to biochar DOM: Evidence from C K-edge NEXAFS and EEM-PARAFAC combined with two-dimensional correlation analysis

“…With a rise in pyrolysis temperature, DOM released from RSC biochars quickly decreased from 2.73 ± 0.19 g C/kg in RSC300 to 0.19 ± 0.001 in RSC500 and 0.13 ± 0.02 g C/kg in RSC700 (Table 1). This trend was also observed for biochars produced from other lignocellulose-rich feedstocks, such as Jerusalem artichoke stalks (Wei et al, 2019a), rice straws (Xiao et al, 2014), and wetland plant litters (Wu et al, 2019). DOM content in biochar was primarily affected by pyrolysis temperature and feedstock.…”

“…DOM in the biochar actually was consisted of both original components in the feedstock and pyrolysis products, such as humicand protein-like substances, which have been identified by a variety of spectroscopic and mass spectrometric techniques (Li et al, 2017;Qu et al, 2016;Smith et al, 2016;Uchimiya et al, 2013). Numerous studies have indicated that the chemical compositions of DOM varied greatly from the feedstocks and pyrolysis temperatures of biochar, as well as the extraction protocols (Lee et al, 2018;Wei et al, 2019a;Wu et al, 2018). Among these parameters, pyrolysis temperature was usually a vital determinant of the DOM characteristics (Liu et al, 2019;Wu et al, 2019).…”

“…Similarly, Wu et al (2019) found that the proportion of humic-like substances clearly increased with the increasing pyrolysis temperature, while the proportion of fulvic-like substances exhibited an opposite trend. Recently, advanced synchrotron-based spectroscopic techniques, such as carbon (C) K-edge near-edge X-ray absorption fine structure spectroscopy (NEXAFS), have been used to further probe the in-situ chemical state and functional groups of biochars (Singh et al, 2014;Wei et al, 2019b) and their released DOM (Wei et al, 2019a). This highly sensitive and non-destructive technique is particularly suitable for the analysis of DOM extracted from high-temperature biochar because of the scarcity of the DOM.…”

“…This highly sensitive and non-destructive technique is particularly suitable for the analysis of DOM extracted from high-temperature biochar because of the scarcity of the DOM. Wei et al (2019a) investigated the molecular structure of DOM from halophyte derived biochars by the C K-edge NEXAFS, and the functional groups identified included hydroxyl, carboxyl, phenyl, ether, amine, and alkyl. Further, the carboxyl group gradually decreased with the increasing pyrolysis temperature.…”

Evaluation of the lipid fraction of pyrochars organic matter in the aspect of negative effects on soil

“…The second factor, which strongly affects both the qualitative and quantitative composition of PAHs, and the lipid component of product, is the pyrolysis process [8]. The main danger to humans is the carcinogenic, immunotoxic, teratogenic properties of PAHs.…”