Abstract

MnO₂ was selected to modify the diatomite (Mn-D) to improve the adsorption capacity as a new adsorbent, which was employed to explore its adsorption capacity for Cr(VI) and As(III), respectively. Mn-D was characterized via SEM, BET, FTIR, XRD, TG and pH_zpc to investigate its morphology and structural properties. The structure and surface chemical properties of diatomite changed after coating with MnO₂, which improved the adsorption capacity for the metal ions. The various influencing factors, such as the pH, initial concentration, temperature and adsorbent dosage, were systematically studied. Based on these results, both the adsorption processes of Cr(VI) and As(III) were pH dependent, and the optimal pH for Cr(VI) and As(III) adsorption were 2 and 6, respectively. To further elucidate the mono/competitive adsorption process, different kinds of isotherm and kinetics models were applied to simulate the experimental data. In the single system, the Dubinin-Radushkevich isotherm model was more suitable than the other models to fit the adsorption process of Cr(VI) and As(III), indicating that the adsorption of Cr(VI) was dominated by a chemical process, while the adsorption of As(III) was physically dependent. The extended Langmuir and Freundlich multicomponents were employed to fit adsorption in the binary system. For Cr(VI), the pseudo-first-order model was better than the other models at describing the adsorption process, both in the single system and binary system. However, the kinetics data of As(III) well followed the pseudo-second-order model. In addition, the analysis of the thermodynamic study revealed that both the adsorption processes of Cr(VI) and As(III) were endothermic and spontaneous.

摘要

选择MnO ₂对硅藻土 (Mn-D) 进行改性以提高其作为新型吸附剂的吸附能力，并分别用于探索其对 Cr(VI) 和 As(III) 的吸附能力。通过SEM、BET、FTIR、XRD、TG和pH _zpc对Mn-D进行表征，研究其形貌和结构性质。_{MnO 2}包覆后硅藻土的结构和表面化学性质发生了变化，提高了对金属离子的吸附能力。系统研究了pH、初始浓度、温度和吸附剂用量等各种影响因素。基于这些结果，Cr(VI) 和 As(III) 的吸附过程都依赖于 pH 值，Cr(VI) 和 As(III) 吸附的最佳 pH 值分别为 2 和 6。为了进一步阐明单一/竞争吸附过程，应用不同种类的等温线和动力学模型来模拟实验数据。在单一体系中，Dubinin-Radushkevich 等温线模型比其他模型更适合拟合 Cr(VI) 和 As(III) 的吸附过程，表明 Cr(VI) 的吸附以化学过程为主，而 As(III) 的吸附是物理依赖的。扩展的 Langmuir 和 Freundlich 多组分用于拟合二元系统中的吸附。对于 Cr(VI)，伪一级模型在描述吸附过程方面优于其他模型，无论是单系统还是二元系统。然而，As(III) 的动力学数据很好地遵循了准二级模型。此外，热力学研究分析表明，Cr(VI) 和 As(III) 的吸附过程都是吸热和自发的。