School of Environment, Tsinghua University, Beijing 100084, China.
School of Environment, Tsinghua University, Beijing 100084, China.
Bioresour Technol. 2015 Aug;190:388-94. doi: 10.1016/j.biortech.2015.04.115. Epub 2015 May 6.
In this work, static equilibrium experiments were conducted to distinguish the adsorption performance between the two valence states of chromium on biochar derived from municipal sludge. The removal capacity of Cr(VI) is lower than 7mg/g at the initial chromium concentration range of 50-200mg/L, whereas that of Cr(III) higher than 20mg/g. It indicates that Cr(III) is much easier to be stabilized than Cr(VI). No significant changes in the biochar surface functional groups are observed before and after the adsorption equilibrium, demonstrating the poor contribution of organic matter in chromium adsorption. The main mechanism of heavy metal adsorption by biochar involves (1) surface precipitation through pH increase caused by biochar buffer ability, and (2) exchange between cations in solution (Cd(2+)) and in biochar matrix (e.g. Ca(2+) and Mg(2+)). The reduction of Cr(VI) to Cr(III) is necessary to improve removal efficiency of chromium.
在这项工作中，进行了静态平衡实验，以区分来自城市污泥的生物炭上两种价态的铬的吸附性能。在初始铬浓度范围为 50-200mg/L 时，Cr(VI)的去除容量低于 7mg/g，而 Cr(III)的去除容量高于 20mg/g。这表明 Cr(III)比 Cr(VI)更容易稳定。吸附平衡前后，生物炭表面官能团没有明显变化，表明有机物对铬吸附的贡献较差。生物炭吸附重金属的主要机制包括：(1) 通过生物炭缓冲能力引起的 pH 值增加导致的表面沉淀，以及 (2) 溶液中阳离子（Cd(2+)）与生物炭基质中阳离子（如 Ca(2+)和 Mg(2+)）之间的交换。还原 Cr(VI)为 Cr(III)是提高铬去除效率所必需的。
