Catechol and Humic Acid Sorption onto a Range of Laboratory-Produced Black Carbons (Biochars)

Abstract

Although the major influence of black carbon (BC) on soil and sediment organic contaminant sorption is widely accepted, an understanding of the mechanisms and natural variation in pyrogenic carbon interaction with natural organic matter (NOM) is lacking. The sorption of a phenolic NOM monomer (catechol) and humic acids (HA) onto BC was examined using biochars made from oak, pine, and grass at 250, 400, and 650 degrees C. Catechol sorption equilibrium occurred after 14 d and was described by a diffusion kinetic model, while HA required only 1 d and followed pseudo-second-order kinetics. Catechol sorption capacity increased with increasing biochar combustion temperature, from pine < oak < grass and from coarse < fine particle size. At lower catechol concentrations, sorption affinity (Freundlich constant, K(f)) was directly related to micropore surface area (measured via CO(2) sorptometry) indicating the predominance of specific adsorption. In contrast, HA exhibited an order of magnitude less sorption (0.1% versus 1%, by weight) due to its exclusion from micropores. Greater sorption of both catechol and HA occurred on biochars with nanopores, i.e. biochars made at higher temperatures. These findings suggest that addition of BC to soil, via natural fires or biochar amendments, will sequester abundant native OM through sorption.

Effects of amendment of different biochars on soil carbon mineralisation and sequestration

“…Sobek et al (2009) showed that biochars could adsorb organic matter and protect it from being utilised. In this study, the lower soil mineralisation rates in the treatments with biochars produced at higher temperatures than at lower temperatures might be partly attributable to their higher surface areas with greater adsorption affinity for natural organic matter (Kasozi et al 2010).…”

Contrasting effects of biochar versus manure on soil microbial communities and enzyme activities in an Aridisol

“…Other researchers have suggested that biochar benefits microbial communities by enhancing the physical and chemical soil characteristics (Lehmann and Joseph 2009;Atkinson et al, 2010;Jindo et al, 2012), providing suitable habitats for microorganisms that protect them from predation (Pietikäinen et al, 2000), supplying labile C substrates for degradation (Thies and Rillig, 2009;Smith et al, 2010), enhancing the availability of macro-nutrients such as N and P (Atkinson et al, 2010;Lammirato et al, 2011), or sorbing compounds that would otherwise inhibit microbial growth (Kasozi et al,2010). To date, these mechanisms have been poorly studied and are mainly discussed in terms as possible explanations.…”

Effect of Biochars from Rice Husk, Bran, and Straw on Heavy Metal Uptake by Pot-Grown Wheat Seedling in a Historically Contaminated Soil

“…In addition to changing the mobility of metal(loid)s in soils, the blocking capacity of iron plaque, root-to-shoot translocation in the plant, and the accumulation of metal(loid)s in rice shoot were influenced by biochar amendments . Different types of biochars from various parent materials exhibit quite different properties (Kasozi et al 2010). However, it remains unknown to what extent different biochars can influence translocation and accumulation of metal(loid)s in wheat (an upland crop) grown in a historically contaminated soil containing multiple metals and As.…”

“…Different types of biochars from various parent materials exhibit quite different properties (Kasozi et al 2010). However, it remains unknown to what extent different biochars can influence translocation and accumulation of metal(loid)s in wheat (an upland crop) grown in a historically contaminated soil containing multiple metals and As.…”