Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA.
Material Science Lab, Integrated Microscopy Center, University of Memphis, Memphis, TN 38152, USA.
J Environ Manage. 2021 Oct 15;296:113186. doi: 10.1016/j.jenvman.2021.113186. Epub 2021 Jul 10.
Biochar adsorbents can remove environmental pollutants and the remediation of Cr(VI) and nitrate are considered. Cr(VI) is a proven carcinogen causing serious health issues in humans and nitrate induced eutrophication causes negative effect on aquatic systems around the world. Douglas fir biochar (DFBC), synthesized by fast pyrolysis during syn gas production, was treated with aniline. Then, a polyaniline biochar (PANIBC) composite containing 47 wt% PANI was prepared by precipitating PANI on DFBC surfaces by oxidative chemical polymerization of aniline in 2M HCl. PANIBC exhibited a point of zero charge (PZC) of 3.0 and 8.2 m/g BET (N) surface area. This modified biochar was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) morphology and surface elements, and oxidation states by X-ray photoelectron spectroscopy (XPS). PANIBC exhibited positive surface charge below pH 3, making it an outstanding adsorbent, for Cr(VI) removal. Cr(VI) and nitrate removal mechanisms are presented based on XPS analysis. DFBC and PANIBC Cr(VI) and nitrate adsorption data were fitted to Langmuir and Freundlich isotherm models with maximum Langmuir adsorption capacities of 150 mg/g and 72 mg/g, respectively. Cr(VI) and nitrate removal at pH 2 and 6 were evaluated by reducing the amount of PANI (9 wt%) dispersed on to DFBC. Adsorption capacities verses temperature studies revealed that both Cr(VI) and nitrate adsorption are endothermic and thermodynamically favored. Regeneration studies were conducted on both DFBC and PANIBC using 0.1M NaOH and PANIBC exhibited excellent sorption capacities for Cr(VI) and nitrate in lake water samples and in the presence of competitive ions.
生物炭吸附剂可以去除环境污染物，并且被认为可以修复六价铬（Cr(VI)）和硝酸盐。六价铬已被证明是一种致癌物质，会对人类健康造成严重问题，而硝酸盐引起的富营养化对全球水系统造成负面影响。由合成气生产过程中的快速热解合成的花旗松生物炭（DFBC）用苯胺处理。然后，通过在 2M HCl 中苯胺的氧化化学聚合，将苯胺沉淀在 DFBC 表面上，制备出含有 47wt%PANI 的聚苯胺生物炭（PANIBC）复合材料。PANIBC 的零电荷点（PZC）为 3.0 和 8.2m/g BET（N）表面积。通过热重分析（TGA）、扫描电子显微镜（SEM）形貌和表面元素以及 X 射线光电子能谱（XPS）的氧化态对改性生物炭进行了表征。PANIBC 在 pH 值低于 3 时表现出正表面电荷，使其成为一种出色的 Cr(VI)去除吸附剂。根据 XPS 分析提出了 Cr(VI)和硝酸盐去除机制。DFBC 和 PANIBC 的 Cr(VI)和硝酸盐吸附数据拟合到 Langmuir 和 Freundlich 等温线模型，最大 Langmuir 吸附容量分别为 150mg/g 和 72mg/g。通过减少分散在 DFBC 上的 PANI（9wt%）的量，在 pH 值为 2 和 6 时评估了 Cr(VI)和硝酸盐的去除。吸附容量与温度的研究表明，Cr(VI)和硝酸盐的吸附都是吸热的，并且热力学上是有利的。对 DFBC 和 PANIBC 进行了再生研究，使用 0.1M NaOH，PANIBC 在湖水样品和存在竞争离子的情况下对 Cr(VI)和硝酸盐表现出优异的吸附能力。
