Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture/Tianjin Key Laboratory of Agro-environment and Safe-product, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China.
School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China.
Chemosphere. 2019 Feb;217:686-694. doi: 10.1016/j.chemosphere.2018.11.040. Epub 2018 Nov 5.
In this study, novel biochar supported nano-scale zero-valent iron (biochar-CMC-nZVI) stabilized by carboxymethyl cellulose (CMC) was developed and used for the removal of hexavalent chromium (Cr(VI) from aqueous solution. With the stabilization of CMC, nZVI particles (about 80 nm) were effectively dispersed onto the surface of biochar, which inhibited the aggregation of nZVI and resulted in the smaller particle size of nZVI on the surface of biochar. The results showed that the specific surface area of the composite was 11.1 m/g, lower than that of pristine biochar. The basic element composition was C, O, and Fe with a large number of oxygen-containing functional groups (-COOH, OH, and OCO) observed on the surface. Cr(VI) was reduced to Cr(III) by the composite material, mainly due to the reduction of nZVI on the biochar surface. Upon reaction with Cr(VI), CrFe(OH) and FeCrO were deposited on the surface of biochar-CMC-nZVI composite. Electrostatic attraction, reduction, and surface complexation were the dominant removal mechanisms. The results showed that the 100 mg/L Cr(VI) could be removed completely by biochar-CMC-nZVI within 18 h, at a dosage of 1.25 g/L and an initial pH of 5.6. Cr(VI) removal by biochar-CMC-nZVI was favored by lower pH. The pseudo-second-order kinetic model and the Langmuir isothermal adsorption model fitted well with the sorption kinetic and isotherm data, indicated Cr(VI) adsorption mechanism was a chemisorption based multi-layer adsorption. The present study demonstrated the promise of biochar-CMC-nZVI composite as a low-cost, "green", and effective sorbent for removal of Cr(VI) in the environment.
在这项研究中，开发了一种新型的生物炭负载纳米零价铁（CMC-生物炭-nZVI），并用羧甲基纤维素（CMC）进行稳定，用于从水溶液中去除六价铬（Cr(VI)。通过 CMC 的稳定，nZVI 颗粒（约 80nm）有效地分散在生物炭表面，抑制了 nZVI 的聚集，导致 nZVI 在生物炭表面的粒径更小。结果表明，复合材料的比表面积为 11.1m/g，低于原始生物炭。基本元素组成为 C、O 和 Fe，表面观察到大量含氧官能团（-COOH、OH 和 OCO）。Cr(VI)被复合材料还原为 Cr(III)，主要是由于生物炭表面 nZVI 的还原。与 Cr(VI)反应后，CrFe(OH)和 FeCrO 沉积在生物炭-CMC-nZVI 复合材料表面。静电吸引、还原和表面络合是主要的去除机制。结果表明，在 1.25g/L 用量和初始 pH 值为 5.6 的条件下，100mg/L 的 Cr(VI)可在 18h 内完全被生物炭-CMC-nZVI 去除。Cr(VI)的去除受较低 pH 值的影响。准二级动力学模型和 Langmuir 等温吸附模型很好地拟合了吸附动力学和等温线数据，表明 Cr(VI)的吸附机制是基于化学吸附的多层吸附。本研究表明，生物炭-CMC-nZVI 复合材料作为一种低成本、“绿色”、有效的环境中 Cr(VI)去除剂具有广阔的应用前景。
