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铁改性杭锦土吸附剂对水中砷的去除研究
蔡金水1, 康得军2, 杨天学1, 龚天成1, 陈其晓2, 赵颖1, 吕伟3
1.中国环境科学研究院;2.福州大学土木工程学院;3.北京中环博宏环境资源科技有限公司
摘要:
为提高天然杭锦土对水溶液中砷的吸附性能,采用氯化铁(FeCl3?6H2O)浸渍天然粘土矿物杭锦土(HJ),制备表面负载铁氧化物的铁改性杭锦土除砷吸附剂(FHJ)。通过比表面积(BET)和扫描电镜(SEM)分析技术对材料进行表征以观察其微观形貌特点,通过X射线光电子能谱分析(XPS)和傅里叶红外光谱(FTIR)技术测定材料组成及化学基团,以初步探究材料吸附除砷机理。通过批实验考察材料投加量、溶液pH、共存离子以及腐殖酸浓度对FHJ除砷效能的影响。结果表明:①当铁负载比在0%~50wt%范围内时,FHJ 对溶液中As(Ⅴ)吸附容量随着铁负载比的增加而增加,最佳铁负载比为33wt%,此时铁与杭锦土的理论质量比为1:3。②BET分析结果表明经铁改性后,杭锦土比表面积显著增加,由71.14 m2/g增至158.50 m2/g;SEM分析显示经改性后杭锦土表面形貌发生明显变化,结合mapping图表明铁被有效负载到杭锦土表面。③批实验结果表明砷去除率随着FHJ投加量的增加而升高;溶液pH对砷的去除率有较大的影响,pH的降低有利于FHJ对砷酸盐的吸附。④FHJ除砷性能受溶液中共存离子CO32-、SiO32-影响较大,但受Cl-、SO42-、NO3-以及腐殖酸影响程度比较小。⑤吸附动力学过程符合准二级动力学模型,Freundlich等温吸附模型可更好描述FHJ吸附除砷行为(R2=0.999)。⑥XPS分析结果显示铁氧化物主要以FeOOH和Fe2O3的形态负载于杭锦土表面,FTIR 表明FeOOH的羟基基团同As(Ⅴ)发生吸附作用。在FHJ除砷过程中,化学吸附是主要的吸附除砷机理。研究显示,铁改性杭锦土除砷效果良好,具有一定的应用潜力。
关键词:  杭锦土  改性  吸附  除砷  机理
DOI:
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基金项目:中央级公益性科研院所基本科研业务专项 零价铁除磷过程中铁氧化物生成与磷去除的耦合机制研究
Study on Removal of Arsenic from Water by Iron Modified Hangjin Clay Adsorbent
KANG Dejun,YANG Tianxue,et al
Abstract:
In order to enhance the adsorption performance of natural Hangjin Clay for arsenic in aqueous solution, Ferric chloride(FeCl3·6H2O) is used to impregnate the natural clay mineral Hangjin clay (HJ) to prepare an iron-modified Hangjin clay adsorbent (FHJ) with surface-loaded iron oxides. The adsorbent is characterized by specific surface area (BET), scanning electron microscopy (SEM) to observe its microscopic morphology and characterized by X-ray photoelectron spectroscopy (XPS), and Fourier infrared spectroscopy (FTIR) in order to determine the composition and chemical groups and to explore the mechanism of arsenic removal. The effects of adsorbent dosage, solution pH, co-existing ions and humic acid on the arsenic removal efficiency of FHJ are investigated through batch experiments. The results show that:① the adsorption capacity of As (Ⅴ) in the solution increases with the increase of the iron loading ratio when the iron loading ratio is in the range of 0%-50wt%. The optimal iron loading ratio is 33wt%, the theoretical mass ratio of iron to Hangjin clay under which condition is 1:3. ②BET analysis results show that the specific surface area of Hangjin clay is significantly increased from 71.14 m2/g to 158.50 m2/g after iron modification. SEM analysis manifests that the surface morphology of Hangjin clay changed obviously after modification, and the mapping map showes that iron is loaded on the surface of Hangjin clay effectively. ③The batch experimental results show that the arsenic removal rate increases with the increase of the amount of FHJ dosage, while the pH of the solution showes a great effect on the removal rate of arsenic, and the decrease of solution pH is favorable for the adsorption of arsenate by FHJ. ④The arsenic removal performance is greatly affected by CO32- and SiO32-, but less affected by Cl-, SO42-, NO3- and humic acid. ⑤The adsorption kinetics process complies with the quasi-second-order kinetic model and the Freundlich isothermal adsorption model describes the behavior of FHJ adsorbing arsenic better (R2=0.999). ⑥XPS analysis results indicate that iron oxides are mainly supported on the surface of Hangjin clay in the form of FeOOH and Fe2O3. FTIR demonstrates that the hydroxyl group of FeOOH adsorbs with As(Ⅴ). Chemisorption is the main mechanism during the process of arsenic removal by FHJ. Research suggests that iron-modified Hangjin clay exhibits excellent arsenic removal effect and showes certain application potential.
Key words:  hangjin clay, modification, adsorption, arsenic removal, mechanism