| EDTA-nSiO2纳米颗粒对Cd2+的吸附 |
| 摘要点击 3154 全文点击 1350 投稿时间：2016-03-01 修订日期：2016-04-13 |
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| 中文关键词 EDTA nSiO2纳米颗粒 改性 Cd2+ 吸附 |
| 英文关键词 EDTA nSiO2 nanoparticle modification Cd2+ adsorption |
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| 中文摘要 |
| nSiO2纳米颗粒是一种广泛应用的工程纳米材料，为增加其对水溶液中Cd2+的吸附性能，采用接枝改性的方法制备出乙二胺四乙酸（EDTA）改性nSiO2纳米颗粒（EDTA-nSiO2），并用透射电镜、氮气吸附-解吸、红外光谱和差热分析等手段对其进行了结构表征，同时以其为吸附剂，通过批处理实验法探讨了体系pH、吸附时间、温度、离子强度等因素对Cd2+吸附的影响，并结合X射线能谱（XPS）分析对其吸附机制进行了分析.结果表明，以EDTA为改性剂，可以成功制备出稳定性良好的EDTA-nSiO2纳米颗粒，其对Cd2+的吸附受体系pH控制；nSiO2对Cd2+的吸附量较小，EDTA改性可增加nSiO2对Cd2+的吸附作用，随着pH的升高，Cd2+的吸附效果逐渐增强，在pH大于4.0后逐渐趋于稳定.EDTA-nSiO2对Cd2+的吸附速率较快，可在1 h内达到吸附平衡.EDTA-nSiO2对Cd2+的吸附为吸热的自发过程，吸附等温线可用Langmuir模型描述.NaCl浓度增加会导致Cd2+的吸附量下降，当体系NaCl浓度从0增加到 100 mmol·L-1，Cd2+的最大吸附量从0.433 mmol·g-1降低至0.294 mmol·g-1.0.1 mol·L-1 HCl是较为合适的吸附剂再生液，Cd2+洗脱率约94.36%.结合pH、温度、离子强度、再生和XPS分析结果，可以推测出EDTA-nSiO2对Cd2+的吸附是包含有简单的物理吸附和离子交换过程，并以化学络合为主的吸附过程.EDTA-nSiO2 是一种对水体Cd2+具有较好吸附能力的工程纳米材料吸附剂. |
| 英文摘要 |
| Silicate nanoparticles(nSiO2) are a kind of widely used engineering material. In order to improve the Cd2+ adsorption ability, the EDTA-modified nSiO2 nanoparticles were prepared by grafting method and characterized by TEM, N2 adsorption-desorption, FTIR, and TGA. The effects of solution pH, contact time, temperature and ionic strength were examined. The adsorption mechanism was further investigated by XPS. The results showed that the EDTA-nSiO2 nanoparticles possessed excellent stability, and were successfully prepared. Cd2+ adsorption was mainly controlled by solution pH. The raw nSiO2 had limited Cd2+ adsorption ability, while the EDTA-modified nSiO2 particles had significantly improved adsorption performance. At high pH, the Cd2+ adsorption rate increased and kept balance above pH 4.0. The Cd2+ adsorption was an endothermic spontaneous process which could be finished within 1 h. Langmuir model could be used to describe the adsorption isotherm. The temperature ranged from 293-313 K during the process, while the maximum adsorption was observed at higher temperature. Higher ionic strength could inhibit the Cd2+ adsorption. The Cd2+ adsorption decreased from 0.433 to 0.294 mmol·g-1, when NaCl concentration varied from 0 to 100 mmol·L-1. The desorption of Cd2+ from the EDTA-nSiO2 nanoparticles was carried out with distilled water, 0.1 mol·L-1 NaCl and 0.1 mol·L-1 HCl. The maximum Cd2+ desorption of 94.36% was obtained at 0.1 mol·L-1 HCl. Based on the results of thermodynamics, pH, ionic strength, and XPS analysis, it could be concluded that Cd2+ adsorption was a multiple process dominated by chemical chelating reaction, physical adsorption and ion exchange. This study indicated that the EDTA-nSiO2 is an effective engineering nanomaterial that could be used in Cd2+ adsorption. |
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