Impact of Deashing Treatment on Biochar Structural Properties and Potential Sorption Mechanisms of Phenanthrene

Abstract

Knowledge of the mineral effects of biochars on their sorption of hydrophobic organic contaminants (HOCs) is limited. Sorption of phenanthrene (PHE) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at two heating treatment temperatures (HTTs) (450 and 600 °C) and their corresponding deashed biochars was investigated. The decreased surface polarity and increased bulk polarity of biochars after deashing treatment indicated that abundant minerals of biochars benefit external exposure of polar groups associated organic matter (OM). Organic carbon (OC)-normalized distribution coefficients (K(oc)) of PHE by biochars generally increased after deashing, likely due to enhancement of favorable and hydrophobic sorption sites caused by mineral removal. Positive correlation between PHE log K(oc) by PLABs and bulk polarity combined with negative correlation between PHE log K(oc) values by ANIBs and surface polarity suggested PLABs and ANIBs have different sorption mechanisms, probably attributed to their large variation of ash content because minerals influenced OM spatial arrangement within biochars. Results of this work could help us better understand the impact of minerals, bulk/surface polarity, and sorption domain arrangement of biochars on their HOCs sorption and predict the fate of HOCs in soils after biochar application.

Sorption and degradation of carbaryl in soils amended with biochars: influence of biochar type and content

“…Additionally, the S BET of PBC700 was remarkably smaller than MBC700 and RBC700, which could be explained by its higher ash content and lower organic matter content. Sun et al (2013) found that the surface areas of biochars are positively related with their organic carbon contents and negatively correlated with their ash contents. The ash in the pig manure covered the organic surfaces and limited the developing of new pores with increasing pyrolyzing temperature.…”

Wood-Biochar-Supported Magnetite Nanoparticles for Remediation of PAH-Contaminated Estuary Sediment

“…(Figure 5a), with the highest degradation rate for the 6-ring, 5-ring, and 4-ring PAHs being 74%, 75%, and 84%, respectively (Figure 5b). This can probably be ascribed to the increase in the catalyst dose accelerating the decomposition of PS into SO 4 −• radicals because of the presence of the Fe 2+ /Fe 3+ species in a sufficient high amount and the interaction of with the π-electron-rich WB surface via π-π electron donor-acceptor interactions [18,30]. The degradation of the PAHs using the Fe 3 O 4 -WB/PS system was studied at pH values of 3.0-9.0.…”

“…Within this context, several mechanisms can occur on the biochar surface, including redox reactions and donor-acceptor complex formation, with many of these mechanisms being pH dependent [33]. Furthermore, with respect to the sorption properties of biochar, it has been shown that biochar has a strong affinity for PAHs [20,30]. Consequently, the …”

Biochar efficiency in pesticides sorption as a function of production variables—a review

“…), partial pressures (1 to 10 bar gauge), reaction vessels, pretreatments (e.g., drying, chemical activation), post-treatments (e.g., crushing, de-ashing, phosphoric acid activation) and handling are used (Chen et al 2011;Sun et al 2013;Taha et al 2014;Yargicoglu and Reddy 2014;Lehmann and Joseph 2015). Production conditions can be improved by varying these parameters to obtain desired end by-products.…”

“…The necessity of removing ash from the biochar when it is used as a sorbent is declared by Abe et al (1998). Sun et al (2013) reported that the de-ashed biochars exhibited higher affinity for phenanthrene mostly because of enhancement of hydrophobic sorption sites after removing the minerals. Rodríguez-Mirasol et al (1993) suggested a pretreatment method to remove the biomass minerals before pyrolysis by washing it with acid to prevent the biochar structural loss caused by high ash content.…”