Wei Zhang - Transport of Biochar Particles in Saturated Granular Media: Effects of Pyrolysis Temperature and Particle Size

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  Publication Details (including relevant citation   information): Wang, Dengjun, Zhang, Wei, Hao, Xiuzhen,   Zhou, Dongmei, Environ. Sci. Technol.,   2012, 47 (2), pp 821-828

  Abstract: Land application of biochar is   increasingly being considered for potential agronomic and   environmental benefits, e.g., enhancing carbon sequestration,   nutrient retention, water holding capacity, and crop   productivity; and reducing greenhouse gas emissions and   bioavailability of environmental contaminants. However, little is   known about the transport of biochar particles in the aqueous   environment, which represents a critical knowledge gap because   biochar particles can facilitate the transport of adsorbed   contaminants. In this study, column experiments were conducted to   investigate biochar particle transport and retention in   water-saturated quartz sand. Specific factors considered included   biochar feedstocks (wheat straw and pine needle), pyrolysis   temperature (350 and 550 °C), and particle size   (micrometer-particle (MP) and nanoparticle (NP)). Greater   mobility was observed for the biochars of lower pyrolysis   temperatures and smaller particle sizes. Extended   Derjaguin?Landau?Verwey?Overbeek (XDLVO) calculations that   considered measured zeta potentials and Lewis acid?base   interactions were used to better understand the influence of   pyrolysis temperature on biochars particle transport. Most   biochars exhibited attractive acid?base interactions that impeded   their transport, whereas the biochar with the greatest mobility   had repulsive acid?base interaction. Nonetheless, greater   retention of the MPs than that of the NPs was in contrast with   the XDLVO predictions. Straining and biochar surface charge   heterogeneity were found to enhance the retention of biochar MPs,   but played an insignificant role in the biochar NP retention.   Experimental breakthrough curves and retention profiles were   well-described using a two-site kinetic retention model that   accounted for depth-dependent retention at one site. Modeled   first-order retention coefficients on both sites 1 and 2   increased with increasing pyrolysis temperature and particle   size.

  Address (URL): http://dx.doi.org/10.1021/es303794d