磁性石墨烯吸附水中Cr(Ⅵ)研究

Adsorption of Cr(Ⅵ) on Magnetic Graphene from Aqueous Solution

以氧化石墨和铁盐为原料,采用化学沉淀法制备出磁性石墨烯复合材料,运用静态吸附实验研究了吸附动力学、热力学、等温吸附模型以及不同因素如p H、温度、时间对Cr(Ⅵ)吸附的影响.结果表明,吸附动力学符合假二级动力学模型;与Freundlich模型相比,Langmuir模型更适合描述吸附过程.热力学参数为:ΔHθ=33.89 k J·mol-1,ΔSθ=120.15 J·(mol·K)-1,ΔGθ=-2.51 k J·mol-1(303 K),这表明吸附过程是吸热并且自发的.实验最佳p H值为2,升高温度和延长时间均有利于吸附的进行.初始Cr(Ⅵ)浓度为5 mg·L-1时,重复利用3次后吸附量由3.9 mg·g-1下降到2.1 mg·g-1.在磁铁存在的条件下吸附剂可轻易从溶液中分离出来,利用Na OH可使其再生,因此可作为去除Cr(Ⅵ)的良好吸附剂.

Chemical deposition method was applied to prepare magnetic graphene composites using graphite oxide and ferric salt( Fe Cl2·4H2O and Fe Cl3·6H2O) as starting materials. The static experiments were performed to study kinetics,thermodynamic,adsorption isotherm and effects of various parameters,such as p H,temperature and time on Cr( Ⅵ) adsorption. The results showed that adsorption kinetics followed the pseudo-second-order model. Compared with Freundlich isotherm,Langmuir isotherm could better describe the adsorption process. The parameters of thermodynamics were ΔHθ= 33. 89 k J·mol- 1,ΔSθ= 120. 15 J·( mol·K)- 1,ΔGθ=- 2. 51 k J·mol- 1( 303K),it demonstrated that the adsorption was a spontaneously endothermic process. It also indicated that the optimal p H was 2. Higher temperature and extension of time were in favor of adsorption. When used repeatedly for three times,the adsorption capacity decreased from 3. 9 mg·g- 1to 2. 1 mg·g- 1with an initial concentration of 5 mg·L- 1. By using a permanent magnet,the recycling process of adsorbent was easy to be operated and adsorbent could be regenerated by sodium hydrate solution.Hence,the composites is a promising adsorbent for efficient removal of Cr( Ⅵ) from wastewater.