Physicochemical property and colloidal stability of micron- and nano-particle biochar derived from a variety of feedstock sources

• Published in: The Science of the total environment 2019-04, Vol.661, p.685-695
• Main Authors: Song, Bingqing, Chen, Ming, Zhao, Ling, Qiu, Hao, Cao, Xinde
• Format: Article
• Language: English
• Subjects: Aggregation; Biomass; Characteristics; Charcoal - analysis; Charcoal - classification; Colloid; Colloids - analysis; Dynamic Light Scattering; Microscopy, Electron, Transmission; MP/NP biochar; Nanoparticles - analysis; Particle Size; Particulate Matter - analysis; Spectrometry, X-Ray Emission; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.01.193

The ever-increasing land application of biochar may raise the environmental issue of micronparticle (MP) and nanoparticle (NP) biochars for their high mobility or as a carrier to facilitate transport of contaminants in soil. In this study, a variety of biochars were produced from pyrolysis of nine biomass sources and then subjected to the extraction of MP and NP biochars. The diverse physicochemical properties and electrokinetic stability of MP and NP biochars were further investigated. MP and NP biochars accounted for 1.43–20.5% and 0.99–15.3% of bulk biochar and had colloidal particle diameters mainly smaller than 1 μm and 100 nm, respectively. The MP and NP biochars contained more O-containing functional groups and mineral components but less aromatic clusters than bulk biochar. The yield of MP/NP biochars derived from plant sources such as woods, herbs, and agricultural waste was positively linear to the ash content of their bulk biochars but this relationship wasn't applied to the municipal sourced biochar such as manure and sewage sludge. More condensed aromatic rings and functional groups were found in MP/NP biochar from plant biomass than municipal sourced biochar. However, the latter was rich with minerals like carbonates, phosphates, and silicates. Higher functional groups in the plant sourced MP/NP wheat straw biochar accounted for the extremely high stability to resist the whole range of ionic strength studied, while the municipal sourced MP/NP dairy manure biochar with less functional groups and more minerals were readily destabilized, with the Critical Coagulation Concentration (CCC) values of 75 mM and 100 mM, respectively. Overall, this study revealed the size-dependent characteristics of composition and structure as well as high colloidal stability of MPs and NPs which are helpful for prediction of their environmental fate and risk. [Display omitted] •Micron- and nano-particle biochars have more O-containing functional groups and minerals than bulk biochar.•Plant waste micron- and nano-particle biochars have more functional groups and aromatic rings than municipal waste biochars.•Municipal waste micron- and nano-particle biochars are rich with carbonates, phosphates, and aluminosilicate.•Colloidal stability of micron- and nano-particle biochars increases with reduced particle sizes and is affected by pH and IS.