Water purification provides a feasible way to relieve the pressure of water shortage and water pollution which we are facing and adsorption is one of the most effective ways to turn polluted water into clean water. Here, we prepared graphene-tannic acid hydrogel using graphene oxide and tannic acid, a natural green reducer and adsorbent, through one-step hydrothermal method. The composition, structure, and morphology of the compounds were systematically examined. The adsorption of dyes was mainly influenced by the morphology and chemical properties of gel. The addition of tannic acid, a molecule rich in oxygen containing functional groups, changed the surface chemistry of graphene sheets and microstructures of gels, which was beneficial for contaminate adsorption. Compared with reduced graphene oxide hydrogel, the graphene-tannic acid hydrogel showed an outstanding adsorption capacity for organic dye methylene blue, more than 500 mg/g at pH 10 and the maximum adsorption capacity was up to 714 mg/g. After adsorption, ethanol and inorganic acid solution can be used as desorption agent and there was no significant adsorption capacity loss after 5 cycles.

水净化为缓解我们面临的水资源短缺和水污染的压力提供了一种可行的方法，而吸附是将污水转化为纯净水的最有效方法之一。在这里，我们通过一步水热法，利用氧化石墨烯和单宁酸（一种天然的绿色还原剂和吸附剂）制备了石墨烯-单宁酸水凝胶。系统地检查了化合物的组成，结构和形态。染料的吸附主要受凝胶的形态和化学性质影响。单宁酸（一种富含含氧官能团的分子）的添加改变了石墨烯片的表面化学性质和凝胶的微观结构，这有利于污染吸附。与还原型氧化石墨烯水凝胶相比，石墨烯-单宁酸水凝胶对有机染料亚甲基蓝表现出出色的吸附能力，在pH 10时大于500 mg / g，最大吸附能力高达714 mg / g。吸附后，乙醇和无机酸溶液可用作解吸剂，经过5个循环后，吸附能力没有明显降低。