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

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• 作者：Dengjun Wang ; Wei Zhang ; Xiuzhen Hao ; Dongmei Zhou
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：January 15, 2013
• 年：2013
• 卷：47
• 期：2
• 页码：821-828
• 全文大小：344K
• 年卷期：v.47,no.2(January 15, 2013)
• ISSN：1520-5851

文摘

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 掳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鈥揕andau鈥揤erwey鈥揙verbeek (XDLVO) calculations that considered measured zeta potentials and Lewis acid鈥揵ase interactions were used to better understand the influence of pyrolysis temperature on biochars particle transport. Most biochars exhibited attractive acid鈥揵ase interactions that impeded their transport, whereas the biochar with the greatest mobility had repulsive acid鈥揵ase 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.