Physicochemical property and colloidal stability of micron- and nano-particle biochar derived from a variety of feedstock sources
Graphical abstract
Introduction
Biochar is a carbonaceous material generated from the pyrolysis of biomass at relatively low temperatures (Lehmann, 2007; Tack et al., 2019). Characterized by condensed aromatic structures, high specific surface areas, high multiple porosity, and abundant functional groups, biochar has been proven to effectively serve as recalcitrant carbon pool for carbon sequestration (Zimmerman et al., 2011) and soil amendments for pollution remediation (Chen et al., 2008; Ahmad et al., 2014) or fertility promotion (Jeffery et al., 2011; Novak et al., 2009).
However, due to the highly heterogeneous properties stemming from different feedstock and production conditions, biochar may challenge to the ecological system (Lian and Xing, 2017). Once applied into soil, biochar can be lost from soils laterally to surface runoff and vertically to deeper soil or groundwater, even coupled to a common marine fate via fluvial and atmospheric transport (Qi et al., 2017; Schmidt and Noack, 2000). Especially, colloidal biochar and dissolved biochar with micron or even nanometer diameters have significant mobility in subsurface and downward migration of biochar in soils and aquifers (Qu et al., 2016). Distinguished from the bulk biochar, these fine fractions of biochar are very reactive component participating in earth's carbon-cycling and some terrestrial chemical processing (Major et al., 2010). Colloidal sized biochars are mainly formed by pore collapse and matrix fracture during biomass charring or by breakup due to grinding (Liu et al., 2018), and would release and subsequently transport by fluvial processes. Rapid mass loss of the carbon in biochar (<5%) were observed over an 8.5-year laboratory incubation by Kuzyakov et al. (2014), which might be attributed to the mineralized reactive component of biochar like colloidal biochars. Spokas et al. (2014) suggested that physical deterioration in natural environment like sorption of water and water vapor could stress the physical structure of biochar and led to the release of fine biochar particles. However, under field conditions, the release of these fine particles would vary with climatic conditions, soil hydrology, and surrounding solution chemistry (Spokas et al., 2014; Xu et al., 2017a), which make release and transport of micronparticle (MP) and nanoparticle (NP) biochar unpredictable.
Recently, an emerging attention has been turned to the potential environmental risks of MP and NP biochar (Chen et al., 2017; Wang et al., 2013a; Wang et al., 2013b; Joseph et al., 2014) resulting from not only transport in soil and groundwater, but also as a carrier to facilitate the transport and transformation of soil contaminants (Wang et al., 2013a; Zhang et al., 2010). Wang et al. (2013a) extracted MP and NP biochar from wheat straw and pine needle biochars with two pyrolysis temperatures (350 and 550 °C) by settling and filtration, and conducted column experiments to investigate the transport and retention of MP and NP biochar in water-saturated quartz sand. They reported greater mobility for the biochars of lower pyrolysis temperatures and smaller particle sizes. Chen et al., 2017, Chen et al., 2018 found that nano-size wood chip biochar had a great mobility in paddy soil and enhanced phosphorus transport in alkaline soils. However, fundamental studies on the physicochemical property and electrokinetic stability of MP and NP biochar are scarce.
Qian et al. (2016) investigated the structure and removal effect of Cr(VI) and Cd(II) of colloidal biochars derived from rice straw at 100–700 °C and found that lower temperature biochar colloids contain more carboxyl and hydroxyl which showed the higher reduction efficiency for Cr(IV). Liu et al. (2018) extracted and characterized the property of NP biochar from four biomass sources of agricultural waste polysized at 300–600 °C and further investigated colloidal processes of peanut shell NP biochar. These researches somewhat filled in the gap of fundamental study of structural and colloidal property of biochar fine particles and revealed the inherent connection between bulk biochar and the chemical features of the fraction of MP and NP biochar (Qu et al., 2016; Wang et al., 2013a; Qian et al., 2016). Yet, studies on the effect of feedstock on MP and NP biochar properties and colloidal behaviors are fairly limited. It has been widely reported that composition and chemical structure of bulk biochars were influenced by feedstock sources (Kloss et al., 2012; El-Naggar et al., 2018). Different biomass sources contained various amounts of cellulose, lignin, and minerals, and therefore resulted in various carbon contents, chemical structures and ash contents of biochars (Zhao et al., 2013; Han et al., 2018). For example, manure or sludge biochar always had high ash content and low carbon fraction while the opposite trend was observed for the crop residue biochar (Zhao et al., 2013; Sun et al., 2017). Inherent-minerals in biochar showed varied affinity to organic and inorganic containments, which further affected any particular application for pollution remediation (Xu et al., 2017b). Thus, systematical investigations on how MP and NP biochar vary from different feedstock sources and further influence their environmental behaviors.
The main objective of this study was to explore the difference in composition and conformation between MP or NP biochar and bulk biochar as a function of feedstock. The structure and property of MP and NP were examined by combined techniques, including elemental analysis, X-ray fluorescence spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The size distribution and morphology of MP and NP biochar were measured by dynamic light scattering and transmission electron microscope. The electrokinetic properties and colloid stability were also investigated through zeta potential measurements and aggregation kinetics.
Section snippets
Preparation of biochar and micron/nano-particle biochar
A total of 9 biochars were produced from five types of feedstock sources through a slow pyrolysis process. The five types of feedstock included woody biomass (pine wood and wood chips), herbaceous residues (barley grasses and wheat straws), agricultural wastes (peanuts shells and rice husks), animal manures (dairy manures and pig manures), and sewage sludge, which could be further divided into two categories with possible consistent property for each: the first three were referred to as the
Fractionation and yield of MP and NP biochar
Extracted suspensions of MP and NP biochars and their corresponding size distributions are shown in Fig. 1. The MP suspensions looked dark-brown while NP suspensions had light-brown colors (Fig. 1a and b). Generally, darker color indicated higher yield of MP/NP in biochars. So, MP biochars accounted for 1.43%–20.5%, while NP biochars were only between 0.99% and 15.3% (Table 1). Among all MP biochars, the barley grass (BG) MP biochar showed the darkest color, possessing the largest percentage of
Conclusion
This study investigated the composition and properties of micron- and nano-particle biochar and derived from a variety of feedstock sources. Although these fine particle biochars accounted for much less portion of the bulk biochar, they may raise environmental concern when large-scale applied in field. Compared with bulk biochars, the micron- and nano-particle biochars were abundant in mineral and in O-containing groups composition, high in alkalinity, and strong in dynamical stability,
Acknowledgments
This work was in part supported by the National Natural Science Foundation of China (No. 21537002, 21777095, 41701571), National Key R&D Program of China (No. 2018YFC1800600), and Shanghai Science and Technology Committee (No. 17DZ1202302).
References (57)
- et al.
Biochar as a sorbent for contaminant management in soil and water: a review
Chemosphere
(2014) - et al.
New approaches to measuring biochar density and porosity
Biomass Bioenergy
(2014) - et al.
Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar
Bioresour. Technol.
(2012) - et al.
Properties of dairy-manure-derived biochar pertinent to its potential use in remediation
Bioresour. Technol.
(2010) - et al.
Phosphoric acid-activated wood biochar for catalytic conversion of starch-rich food waste into glucose and 5-hydroxymethylfurfural
Bioresour. Technol.
(2018) - et al.
Transport and retention of biochar nanoparticles in a paddy soil under environmentally-relevant solution chemistry conditions
Environ. Pollut.
(2017) - et al.
Contrasting effects of biochar nanoparticles on the retention and transport of phosphorus in acidic and alkaline soils
Environ. Pollut.
(2018) - et al.
Influence of soil properties and feedstocks on biochar potential for carbon mineralization and improvement of infertile soils
Geoderma
(2018) - et al.
Characterization and quantification of biochar alkalinity
Chemosphere
(2017) - et al.
Oxidation resistance of biochars as a function of feedstock and pyrolysis condition
Sci. Total Environ.
(2018)
A quantitative review of the effects of biochar application to soils on crop productivity using meta-analysis
Agric. Ecosyst. Environ.
Influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochars derived from municipal sewage sludge
J. Hazard. Mater.
Biochar stability in soil: decomposition during eight years and transformation as assessed by compound-specific 14C analysis
Soil Biol. Biochem.
Effective removal of heavy metal by biochar colloids under different pyrolysis temperatures
Bioresour. Technol.
Chemical and structural properties of dissolved black carbon released from biochars
Carbon
Mechanisms of copper stabilization by mineral constituents in sewage sludge biochar
J. Clean. Prod.
Heteroaggregation of graphene oxide nanoparticles and kaolinite colloids
Sci. Total Environ.
Effect of biochar amendment on soil carbon balance and soil microbial activity
Soil Biol. Biochem.
Textural and chemical properties of swine-manure-derived biochar pertinent to its potential use as a soil amendment
Chemosphere
Facilitated transport of cu with hydroxyapatite nanoparticles in saturated sand: effects of solution ionic strength and composition
Water Res.
Indispensable role of biochar-inherent mineral constituents in its environmental applications: a review
Bioresour. Technol.
The heavy metal partition in size-fractions of the fine particles in agricultural soils contaminated by waste water and smelter dust
J. Hazard. Mater.
Heterogeneity of biochar properties as a function of feedstock sources and production temperatures
J. Hazard. Mater.
Effect of pyrolysis temperature on char structure and chemical speciation of alkali and alkaline earth metallic species in biochar
Fuel Process. Technol.
Positive and negative carbon mineralization priming effects among a variety of biochar-amended soils
Soil Biol. Biochem.
Do all carbonized charcoals have the same chemical structure? 2. A model of the chemical structure of carbonized charcoal
Ind. Eng. Chem. Res.
Dairy-manure derived biochar effectively sorbs lead and atrazine
Environ. Sci. Technol.
Interaction of fullerene (C-60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications
Environ. Sci. Technol.
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