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.

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。