Surface chemistry variations among a series of laboratory-produced biochars
Surface chemistry variations among a series of laboratory-produced biochars
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DOI：
10.1016/j.geoderma.2011.04.021
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发表时间：
2011-07-15
期刊：
影响因子：
6.1
通讯作者：
Harris, W.
中科院分区：
文献类型：
--
作者：
Mukherjee, A.;Zimmerman, A. R.;Harris, W.
虽然添加热解碳（用作土壤改良剂时称为“生物炭”）将提高土壤肥力和碳固存的想法已获得广泛关注，但对其化学和物理特性以及最适合确定这些特性的方法的了解仍然滞后。需要此类信息来优化生物炭的特性，以实现特定目的，例如营养保留、pH 值改善或污染物修复。检查了一系列生物炭类型的许多表面特性，以更好地了解这些特性与生物炭生产条件以及彼此之间的关系。在由橡树 (Quercus lobata)、松树 (Pious taeda) 和草 (Tripsacum floridanum) 制成的生物炭中，在空气中 250 摄氏度以及 N-2 下 400 和 650 摄氏度下，随着挥发性物质 (VM) 的降低，微孔表面积（通过 CO2 吸光法测量）随着生产温度的增加而增加，表明 VM 从孔隙填充物中释放出来。使用 K+ 交换测定，400 和 650 摄氏度的炭的 CEC 约为 10 cmol(c) kg(-1)，并且没有显示任何 pH 依赖性，而 250 摄氏度的生物炭 CEC 具有 pH 依赖性，在 pH 7 时升至 70 cmol(c) kg(-1)。生物炭颗粒表面电荷的测量表明，在中性 pH 和等电点pH 2-3。然而，胶体或溶解的生物炭成分的负电性是其 4-5 倍。总酸官能团浓度范围为4.4-8.1 mmol g(-1)（通过Boehm滴定法测定），随着生产温度的升高而降低，且与VM含量直接相关。总之，这些发现表明生物炭的 VM 成分具有酸性、负电荷，因此具有络合能力。然而，并非所有酸性官能团都交换阳离子，因为阳离子交换位点 (CEC) 的数量比生物炭表面上存在的酸性官能团的数量少约 10 倍，并且随生物质类型而变化。这些发现表明，较低温度的生物炭将更好地用于增加土壤 CEC，而高温生物炭将提高土壤 pH 值。尽管没有测量生物炭中的阴离子交换容量，但它们可以通过二价阳离子桥接吸附磷酸盐和硝酸盐。 (C) 2011 Elsevier B.V. 保留所有权利。
While the idea that adding pyrogenic carbon (referred to as 'biochar' when used as a soil amendment) will enhance soil fertility and carbon sequestration has gained widespread attention, understanding of its chemical and physical characteristics and the methods most appropriate to determine them have lagged behind. This type of information is needed to optimize the properties of biochar for specific purposes such as nutrient retention, pH amelioration or contaminant remediation. A number of surface properties of a range of biochar types were examined to better understand how these properties were related to biochar production conditions, as well as to each other. Among biochars made from oak (Quercus lobata), pine (Pious taeda) and grass (Tripsacum floridanum) at 250 degrees C in air and 400 and 650 degrees C under N-2, micropore surface area (measured by CO2 sorptometry) increased with production temperature as volatile matter (VM) decreased, indicating that VM was released from pore-infillings. The CEC, determined using K+ exchange, was about 10 cmol(c) kg(-1) for 400 and 650 degrees C chars and did not show any pH dependency, whereas 250 degrees C biochar CECs were pH-dependant and rose to as much as 70 cmol(c) kg(-1) at pH 7. Measurements of surface charge on biochar particles indicated a zeta potential of -9 to -4 mV at neutral pH and an iso-electric point of pH 2-3. However, a colloidal or dissolved biochar component was 4-5 times more electronegative. Total acid functional group concentration ranged 4.4-8.1 mmol g(-1) (measured by Boehm titration), decreased with production temperature, and was directly related to VM content. Together, these findings suggest that the VM component of biochar carries its acidity, negative charge, and thus, complexation ability. However, not all acid functional groups exchanged cations as the number of cation exchanging sites (CEC) was about 10 times less than the number of acid functional groups present on biochar surfaces and varied with biomass type. These findings suggest that lower temperature biochars will be better used to increase soil CEC while high temperature biochars will raise soil pH. Although no anion exchange capacity was measured in the biochars, they may sorb phosphate and nitrate by divalent cation bridging. (C) 2011 Elsevier B.V. All rights reserved.