Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
Environ Sci Technol. 2012 Oct 16;46(20):11104-11. doi: 10.1021/es302345e. Epub 2012 Sep 26.
This study investigated the sorption kinetics of a model solute (naphthalene) with a series of biochars prepared from a pine wood at 150-700 °C (referred as PW100-PW700) to probe the effect of the degree of carbonization of a biochar. The samples were characterized by the elemental compositions, thermal gravimetric analyses, Fourier transform IR spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller-N(2) surface areas (SA), and pore size distributions. Naphthalene exhibited a fast rate of sorption to PW150 owning a high oxygen content and a small SA, due supposedly to the solute partition into a swollen well-hydrated uncarbonized organic matter of PW150. The partial removal of polar-group contents in PW250/PW350, which increased the compactness of the partition medium, decreased the diffusion of the solute into the partition phase to result in a slow sorption rate. With PW500 and PW700 displaying low oxygen contents and high SA, the solute sorption rates were fast, attributed to the near exhaustion of a partition phase in the sample and to the fast solute adsorption on the carbonized biochar component. The results illustrate that the sorption rate of a solute with biochars is controlled largely by the solute's diffusivity in the biochar's partition phase, in which the medium compactness affects directly the solute diffusivity.
本研究考察了一系列由松木在 150-700°C 下制备的生物炭（简称 PW100-PW700）吸附模型溶质（萘）的吸附动力学，以探究生物炭碳化程度的影响。通过元素组成、热重分析、傅里叶变换红外光谱、扫描电子显微镜、Brunauer-Emmett-Teller-N2（N2）比表面积（SA）和孔径分布对样品进行了表征。由于 PW150 中含有高含量的氧和小的 SA，推测萘在溶胀的高度水合未碳化有机物中发生了溶质分配，从而快速吸附到 PW150 上。PW250/PW350 中极性基团含量的部分去除增加了分配介质的致密性，降低了溶质扩散到分配相的速度，导致吸附速率变慢。而 PW500 和 PW700 由于氧含量低、SA 高，溶质吸附速率较快，这归因于样品中分配相的接近耗尽以及碳化生物炭成分上的快速溶质吸附。结果表明，生物炭对溶质的吸附速率主要受溶质在生物炭分配相中的扩散性控制，其中介质的致密性直接影响溶质的扩散性。
