Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA.
Material Science Lab, Integrated Microscopy Center, University of Memphis, Memphis, TN, 38152, USA.
Chemosphere. 2021 Apr;269:128409. doi: 10.1016/j.chemosphere.2020.128409. Epub 2020 Sep 28.
Biochar has become a popular research topic in sustainable chemistry for use both in agriculture and pollution abatement. To enhance aqueous Cr(VI), Pb(II) and Cd(II) removal efficiency, high surface area (535 m/g) byproduct Douglas fir biochar (DFBC) from commercial syn-gas production obtained by fast pyrolysis (900-1000 °C, 1-10 s), was subjected to a KOH activation. KOH-activated biochar (KOHBC) underwent a remarkable surface area increase to 1049 m/g and a three-fold increase in pore volume (BET analysis). Batch sorption studies on KOHBC verses pH revealed that the highest chromium, lead and cadmium removal capacities occurred at pH 2.0, 5.0 and 6.0, respectively. KOHBC exhibited much higher adsorption capacities than unactivated DFBC. Heavy metal loadings onto KOHBC were characterized by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Sorption of Cr(VI), Pb(II) and Cd(II) all followed pseudo-second order kinetics and the Langmuir adsorption model. The highest Langmuir adsorption capacities at the respective pH's of maximum adsorption were 140.0 mg g Pb(II), 127.2 mg g Cr(VI) and 29.0 mg g Cd(II). Metal ions spiked into natural and laboratory waste water systems exhibited high sorption capacities. Desorption studies carried out using 0.1 M HCl revealed that Pb(II) adsorption onto the KOHBC surface is reversible. Portions of Cd(II) and Cr(VI) adsorbed strongly onto KOHBC were unable to be desorbed by 0.1 M HCl and 0.1 M NaOH.
生物炭作为可持续化学领域的一个热门研究课题，在农业和污染治理方面都有应用。为了提高对水溶液中 Cr(VI)、Pb(II) 和 Cd(II) 的去除效率，我们使用商业合成气（通过快速热解 900-1000°C、1-10s 获得）生产过程中的副产物——高表面积（535m/g）的花旗松生物炭（DFBC）进行了 KOH 活化。KOH 活化后的生物炭（KOHBC）的表面积显著增加到 1049m/g，孔体积增加了三倍（BET 分析）。KOHBC 对 pH 值的批量吸附研究表明，铬、铅和镉的最大去除容量分别出现在 pH 值为 2.0、5.0 和 6.0 时。KOHBC 的吸附容量比未经活化的 DFBC 高得多。通过扫描电子显微镜、透射电子显微镜和 X 射线光电子能谱对 KOHBC 上的重金属负载进行了表征。Cr(VI)、Pb(II) 和 Cd(II) 的吸附均遵循准二级动力学和 Langmuir 吸附模型。在各自最大吸附 pH 值下，KOHBC 的最大 Langmuir 吸附容量分别为 140.0mg g Pb(II)、127.2mg g Cr(VI)和 29.0mg g Cd(II)。向天然和实验室废水体系中加入金属离子后，吸附容量很高。使用 0.1M HCl 进行的解吸研究表明，Pb(II)在 KOHBC 表面的吸附是可逆的。部分被强烈吸附在 KOHBC 上的 Cd(II)和 Cr(VI)无法被 0.1M HCl 和 0.1M NaOH 解吸。
