巯基改性坡缕石的制备、表征及其对镉的吸附作用
Preparation and Characterization of Sulfhydryl Modified Palygorskite and Their Application for Adsorption of Cadmium
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摘要: 通过高速剪切凝胶法制备巯基改性坡缕石材料,并将其用于从水溶液中吸附Cd2+,以研究吸附机制并评估其在修复镉污染水和土壤中的应用潜力。通过X射线衍射(XRD)、BET孔结构分析、傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)以及X射线电子能谱(XPS)对吸附前后的样品进行表征,探讨其吸附机制。结果表明,天然坡缕石和巯基改性坡缕石均能有效吸附水溶液中的Cd2+,改性坡缕石吸附效果优于天然坡缕石。拟二级动力学模型更适合描述Cd2+在坡缕石和巯基改性坡缕石上的吸附量的动态变化过程,改性坡缕石约90min达到吸附平衡,相比于天然坡缕石能更加迅速。Freundlich等温线能够更好地描述吸附数据,在试验条件下,巯基改性坡缕石的饱和吸附容量为44.41 mg/g,明显高于天然坡缕石的饱和吸附容量33.65 mg/g。结合XRD衍射峰分析、FTIR官能团振动模式分析以及XPS关键元素结合能分析结果等,天然坡缕石主要是通过表面羟基与Cd2+形成表面络合来吸附镉,而巯基改性坡缕石还提供了大量巯基官能团作为吸附位点,通过表面的羟基和巯基与Cd2+发生络合反应形成络合沉淀。该研究将为镉污染土壤的钝化治理提供重要的基础数据和技术支撑。Abstract: In order to study the adsorption mechanism of Cd2+ from aqueous solution and evaluate its potential application in remediation of cadmium contaminated water and soil, a sulfhydryl modified palygorskite material was prepared by high-speed shear gel method. X-ray diffraction (XRD), BET pore structure analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray electron spectroscopy (XPS) were used to characterize the samples before and after adsorption, and to explore the adsorption mechanism. The results showed that both natural and sulfhydryl modified palygorskite could effectively adsorb Cd2+ in aqueous solution, and the adsorption effect of modified palygorskite was better than that of natural palygorskite. The pseudo second order kinetics model is more suitable to describe the dynamic change process of Cd2+ adsorption on palygorskite and sulfhydryl modified palygorskite. The modified palygorskite reaches the adsorption equilibrium in about 90 minutes, which is faster than natural palygorskite. Freundlich isotherm can better describe the adsorption data. Under the experimental conditions, the saturated adsorption capacity of sulfhydryl modified palygorskite is 44.41 mg/g, which is significantly higher than that of natural palygorskite (33.65 mg/g).Combined with XRD diffraction peak analysis, FTIR functional group vibration mode analysis and XPS key element binding energy analysis results, natural palygorskite mainly adsorbs cadmium by surface hydroxyl group and Cd2+ forming surface complexation, and sulfhydryl modified palygorskite also provides a large number of sulfhydryl functional groups as adsorption sites. Complex precipitation is formed by complexing Cd2+ with hydroxyl and sulfhydryl groups on the surface. This study will provide important basic data and technical support for the passivation treatment of cadmium contaminated soil.
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Key words:
- palygorskite /
- cadmium /
- adsorption /
- hydroxyl group /
- sulfhydryl group
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