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Adsorption of Cr(VI) ion on tannic acid/graphene oxide composite aerogel: kinetics, equilibrium, and thermodynamics studies
Biomass Conversion and Biorefinery ( IF 3.5 ) Pub Date : 2020-07-24 , DOI: 10.1007/s13399-020-00899-4
Chen Cheng , Mengying Jia , Linlin Cui , Yue Li , Lanshu Xu , Xiaojuan Jin

A novel tannic acid–reduced graphene oxide (TAG) composite absorbent was prepared by using a simple one-step method. The prepared TAG was characterized by various analytical techniques including FTIR, Brunauer–Emmett–Teller (BET), scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Tannic acid (TA) not only can prevent graphene sheets from agglomerating by suppressing the hydrophobic stacking interactions but also can introduce a large number of phenol hydroxyls. The adsorption studies indicate that the TAG composite showed an excellent uptake capacity (179.22 mg/g) for Cr(VI) under the optimized conditions (viz., adsorbent dosages of 0.75 g/L, solution pH of 2.5, contact time of 360 min, and temperature of 60 °C), which is higher than that of most graphene oxide– and TA-based adsorbents. The BET specific surface area of TAG was calculated to be 118.3 m2/g; the pore diameter of Tannin acid-reduced graphene hydrogel (TAGH) was mainly 3–6 nm, with pore size peak at 5.0 nm. The kinetics of Cr(VI) adsorption on TAG followed the pseudo-second-order model. The isotherm studies confirmed that the Cr(VI) chemically adsorbed on TAG in a monolayer fashion, which was attributed to the electrostatic interaction between chromium ions and oxygen negative ions. The process of Cr(VI) adsorption was found to be thermodynamically spontaneous and endothermic.



中文翻译:

单宁酸/氧化石墨烯复合气凝胶上Cr(VI)离子的吸附:动力学,平衡和热力学研究

一种简单的一步法制备了一种新颖的单宁酸还原氧化石墨烯(TAG)复合吸收剂。制备的TAG具有多种分析技术的特征,包括FTIR,Brunauer-Emmett-Teller(BET),扫描电子显微镜,X射线衍射和X射线光电子能谱。单宁酸(TA)不仅可以通过抑制疏水性堆叠相互作用来防止石墨烯片聚结,而且可以引入大量的酚羟基。吸附研究表明,在最佳条件下(即吸附剂剂量为0.75 g / L,溶液pH为2.5,接触时间为360分钟),TAG复合材料对Cr(VI)表现出优异的吸收能力(179.22 mg / g)。 ,温度为60°C),高于大多数氧化石墨烯和TA基吸附剂的温度。2 /克;单宁酸还原石墨烯水凝胶(TAGH)的孔径主要为3–6 nm,孔径峰值为5.0 nm。TAG上Cr(VI)的吸附动力学遵循伪二级模型。等温线研究证实,Cr(VI)以单层方式化学吸附在TAG上,这归因于铬离子和氧负离子之间的静电相互作用。发现Cr(VI)的吸附过程是热力学自发的并且是吸热的。

更新日期:2020-07-24
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