纳米MnO_(2)炭基复合材料的制备及吸附去除水中La(Ⅲ)离子性能研究

Nano-MnO_(2) carbon matrix composites:preparation and adsorption removal of La(Ⅲ)ions from water

稀土是一种珍贵的战略资源,但其开发冶炼过程会产生大量废水并造成严重的环境污染,因此如何高效吸附去除废水中稀土离子被大量研究。通过共沉淀法将纳米MnO_(2)负载至生物炭(Biochar, BC)表面,得到纳米MnO_(2)炭基复合材料(Nano-MnO_(2)Carbon Matrix Composites, MBC),并用于吸附去除废水中的La(Ⅲ)离子。研究通过表征分析材料的物理和化学结构变化,考察了应用环境条件对MBC吸附La(Ⅲ)离子性能的影响,在308 K、pH=6.0条件下,0.55 g/L MBC对20 mg/L La(Ⅲ)离子模拟废水进行吸附处理,24 h后吸附效率达到95.65%。吸附动力学、等温线和热力学研究显示,MBC对La(Ⅲ)离子的吸附过程符合拟一级动力学模型和Langmuir模型,为单分子层吸附,最大吸附质量比可达43.49 mg/g;通过D-R模型计算的Es为23.12 kJ/mol,表明吸附过程偏向于化学吸附,且是自发的吸热过程。MBC经5次循环后,吸附性能仍达到初始吸附质量比的79.18%,MBC作为炭基吸附剂用于吸附水中的La(Ⅲ)离子,展现出一定的应用前景。

In this study,nano-MnO_(2) is loaded onto the surface of biochar(BC)by the co-precipitation method to prepare nano-MnO_(2) carbon matrix composites(MBC),which are later applied to the adsorption and removal of La(Ⅲ)ions from wastewater.In experiments,characterization methods such as SEM,EDS,BET,XRD,FT-IR,and XPS show that the prepared MBC features a rich porous structure on the surface and a specific surface area of 149.63 m 2/g,both of which are conducive to the absorption of La(Ⅲ)ions.The significant change in the content of functional groups such as—OH,C—H,O—H,Mn—O promotes the ion exchange process and contributes to the adsorption of heavy metals by MBC.Adsorption kinetics,adsorption isotherm,and adsorption thermodynamics models are used to fit the experimental data.In a ddition,the single-factor variable method is adopted to explore the influence of application environmental conditions such as the pH value,reaction time,and initial mass concentration of La(Ⅲ)ions on the adsorption performance of MBC for La(Ⅲ)ions.According to the experiment results,the adsorption efficiency of 20 mg/L La(Ⅲ)ions from simulated wastewater reaches 95.65%after 24-hour-long adsorption at 308 K,pH=6.0 with the MBC dosage as 0.55 g/L.Besides,the adsorption process of La(Ⅲ)ions by MBC is consistent with the quasi-first-order kinetic model and the Langmuir model,indicating that the adsorption process is single molecule adsorption with a maximum adsorption capacity of 43.49 mg/g.Compared with the adsorption capacity of other adsorbents,the higher adsorption capacity of MBC proves its better adsorption capacity.The Es value calculated by the D-R model is 23.12 kJ/mol,meaning that the adsorption process is biased towards chemisorption and is a spontaneous endothermic process.After 5 cycles of adsorption-desorption,the adsorption performance of MBC remained at 79.18%of the initial value.To sum up,MBC is a promising carbon-based adsorbent and is expected to show great potential to remove La(Ⅲ)ions in water.