共查询到19条相似文献，搜索用时 125 毫秒
1.
在模拟的氧化、酸性土壤条件下，用制备的低聚合羟基铁离子-蒙脱石复合体对磷酸根、铬酸根离子的竞争吸附进行实验研究发现：磷酸根离子和铬酸根离子的不同用量、不同添加顺序对竞争吸附的影响。并与蒙脱石和含水氧化铁对磷酸根离子、铬酸根离子的竞争吸附行为进行了对比。研究表明：在实验条件下，磷酸根离子、铬酸根离子在低聚合羟基铁离子蒙脱石复合体表面存在弱的竞争吸附现象。由于低聚合羟基铁离子蒙脱石复合体具有对磷酸根稍强的亲和性，在竞争吸附中，磷酸根离子处于稍有利的位置。 相似文献
2.
聚合羟基铁铝蒙脱石复合体对磷的吸附行为及其动力学 总被引：2，自引：0，他引：2
在一定条件下利用钠基化蒙脱石合成了聚合羟基铝-蒙脱石复合体(HyA1-Mt)、2个不同铁含量的聚合羟基铁-蒙脱石复合体(HyFe-Mt)和3个不同Fe:Al摩尔比的聚合羟基铁铝-蒙脱石复合体(HyFeAl-Mt),研究了酸性和弱酸性条件下(pH=3.0～6.5)以上蒙脱石复合体对磷的吸附行为和动力学特征。结果表明,HyFeAl-Mt对磷的吸附容量大于HyA1-Mt和HyFe-Mt复合体,且随着Fe:Al摩尔比的增大,对磷的吸附容量依次增加。随pH升高,蒙脱石复合体对磷的吸附量容量变小。但随Fe:Al摩尔比增大,HyFeAl-Mt复合体零电荷点(pHZPC)升高,pH对磷的吸附的影响越来越小,HyFe-Mt对磷的吸附几乎不受pH的影响。随Fe:A1摩尔比的增大,HyFeAl-Mt对磷的吸附能力增强,铁含量是磷吸附量的重要控制因素。磷在各蒙脱石复合体上的吸附实验数据可很好地用Langmuir吸附等温方程拟合。磷在各蒙脱石复合体上的吸附动力学过程可分为快速和慢速两个过程,快速过程中的动力学受铁含量影响明显。动力学数据可同时用准二级动力学方程和Elovich方程拟合。 相似文献
3.
低聚合羟基铁离子-蒙脱石复合体吸附磷和氟的实验研究 总被引：4，自引：1，他引：4
将提纯的钙蒙脱石与羟基铁离子溶液作用，制备了低聚合羟基铁-蒙脱石复合体。在实际土壤的酸度(pH=4～8)和温度(t=34～50℃)条件下，进行了低聚合羟基铁-蒙脱石复合体吸附P和F的实验，探讨了复合体的P和F吸附能力与pH值、温度、吸附时间、P和F的初始浓度、离子强度间的关系，并与蒙脱石和含水氧化铁的P和F吸附行为进行了对比。研究表明，在实验条件下，低聚合羟基铁-蒙脱石复合体对磷具有明显的亲合力，对氟的亲合力较低，只略高于蒙脱石原样。低聚合羟基铁-蒙脱石复合体对P和F的吸附，特别是对磷的吸附行为对该元素在土壤中的迁移过程有重要影响，成果对土壤学和环境学研究有参考价值。 相似文献
4.
低聚合羟基铁离子-蒙脱石复合体吸附砷的实验研究 总被引：15，自引：2，他引：15
将提纯的钙蒙脱石与羟基铁离子溶液作用，制备了低聚合羟基铁－蒙脱石复合体，用化学分析，电子探针分析，粉晶X射线衍射分析，差热分析和穆斯堡尔谱分析等手段。对蒙脱石原样，低聚合羟基铁－蒙脱石复合体和相同条件下制备的铁的含水氧化物进行了表征。在实际土壤的酸度（pH=4-7)和温度（18－40℃）条件下，进行了低聚合羟基铁－蒙脱石复合体吸附有害元素砷的实验，探讨了复合体的砷吸附能力与pH值，温度，吸附时间，砷初始浓度，离子强度间的关系，并与蒙脱石和铁的含水氧化物的砷吸附行为进行了对比，研究表明，在实验条件下，低聚合羟基铁－蒙脱石复合体对砷具有明显的亲合力，低聚合羟基铁－蒙脱石复合体吸附砷的过程有可能是地表岩石和土壤中重要的地球化学过程，是影响砷地地表，特别是土壤中迁移，富集的重要因素。 相似文献
5.
在一定条件下,利用钠基化蒙脱石(Na-Mt)合成聚合羟基铁铝-蒙脱石复合体(HyFeAl-Mt),M3+/Mt比为10mmol/g,Fe3+/Al3+摩尔比分别为0.1、0.2和0.5。研究了酸性和弱酸性条件下低分子有机酸(以柠檬酸、草酸和苹果酸为代表)及其添加顺序对HyFeAl-Mt复合体吸附磷的影响。结果表明,低分子有机酸对HyFeAl-Mt复合体吸附磷有抑制作用,且随着低分子有机酸浓度的增加愈加明显,酸性条件下的抑制作用比弱酸性条件下明显;低分子有机酸羧基个数越多、分子结构越大,对HyFeAl-Mt对吸附磷的影响越大;酸性环境中低分子有机酸与磷共存时,磷吸附曲线较好地符合Freundlich方程,且其对磷在HyFeAl-Mt0.2上的最大吸附量影响较小;磷与低分子有机酸的添加顺序不同也影响HyFeAl-Mt复合体对磷的吸附。 相似文献
6.
低聚合羟基铁离子-蛭石复合体吸附铬的实验研究 总被引：3，自引：0，他引：3
将提纯的镁型蛭石与羟基铁离子溶液作用,制备低聚合羟基铁一蛭石复合体。用化学分析、电子探针分析、粉晶X射线衍射分析、差热分析等手段对蛭石原样、低聚合羟基铁一蛭石复合体进行表征。在模拟实际土壤酸度（pH=4～7）和温度（20℃～40℃）条件下,进行低聚合羟基铁蛭石复合体吸附有害元素铬的实验,探讨复合体的铬吸附能力与pH值、温度、吸附时间、铬初始质量浓度、离子强度间的关系,并与蛭石的铬吸附行为进行对比。研究表明,在实验条件下,低聚合羟基铁一蛭石复合体对铬具有明显的亲和力,低聚合羟基铁蛭石复合体吸附铬的过程有可能是地表岩石和土壤中重要的地球化学过程,是影响铬在地表,特别是土壤中迁移、富集的重要因素． 相似文献
7.
Cu2+和Cd2+在蒙脱石-胡敏酸复合体上的吸附及其竞争 总被引：1，自引：0，他引：1
土壤和水体中的腐殖酸常常与粘土矿物紧密结合成为特殊的复合体.这种粘土矿物-腐殖酸复合体对重金属的吸附作用既有别于粘土矿物,更有别于腐殖酸.以蒙脱石和胡敏酸分别作为粘土矿物和腐殖酸的代表,通过一系列实验研究了Cu2+、Cd2+在单一体系和共存体系条件下在蒙脱石-胡敏酸复合体上的吸附作用,同时探讨了二者的竞争特点.实验结果表明,在单一体系条件下,蒙脱石-胡敏酸复合体对Cu2+的吸附量始终明显大于Cd2+,且二者的吸附量均随其初始浓度的增大而呈线性增大;而在Cu2+和Cd2+共存体系条件下,Cu2+的吸附量始终略大于Cd2+的吸附量,即复合体对Cu2+的吸附有较好的选择性.在吸附过程中,复合体中的蒙脱石与Cd2+和Cu2+的阳离子交换作用处于主导地位.无论是在单一体系还是在共存体系中,Cd2+优先替换电价相同而半径略大的Ca2+,而Cu2+则优先替换半径相近、电价低的Na+.因此,Cd2+的存在使Cu2+在复合体上的吸附量明显地减小,而Cu2+的存在对Cd2+的吸附几乎没有影响.这些实验结果将有助于深入探讨重金属离子在土壤、水体等环境中的迁移-固定行为. 相似文献
8.
实验表明蒙脱石吸附氟的能力与溶液的PH值呈显著的负相关关系：在较低PH值条件下，蒙脱石的吸氟量较大，具有显著的降氟作用；而对中性—碱性溶液来说，蒙脱石对氟的吸附能力则大大降低，基本不具吸氟能力。蒙脱石的吸氟量还与其用量及含氟溶液的浓度有关。吸附原因一方面是由于体系PH值降低，导致其表面带正电荷而吸附F^-；另一方面，随着NaF浓度升高，蒙脱石的双电层变薄，体系ξ电势减少，发生絮凝作用，并携带F^-沉淀下来。另外，F^-与OH^-的离子交换作用也是酸性条件下蒙脱石吸氟的一个重要原因。 相似文献
9.
铬酸根离子在羟基铁离子一蒙脱石体系中的吸附行为研究 总被引：2，自引：0，他引：2
采矿，电镀，制革等行业废物排放及含Cr矿物风化可造成一些地区土壤和地下水的Cr污染，Cr主要以三价和六价形式存在，其中Cr(Ⅵ）有强的迁移能力，对动植物均有很强的毒害性。研究了在氧化，酸性条件下，土壤及土壤溶液中的蒙脱石和羟基铁离子共存时对铬酸根离子（主要以HCrO4^2-)和CrO4^2-等Cr(Ⅵ）形式存在）的吸附行为，进行了蒙脱石，羟基铁离子，Cr(Ⅵ）离子添加顺序不同的3个系列的实验，重点研究了Cr的初始质量浓度，溶液pH值，环境温度，吸附时间，溶液离子强度对3个系列Cr吸附行为的影响，并与羟基铁离子体系进行了对比。结果表明，蒙脱石－羟基铁离子体系的Cr吸附能力明显强于蒙脱石而低于羟基铁离子，其Cr吸附率随Cr初始质量浓度，温度的升高和吸附时间的延长而降低，随离子强度的升高而升高，而pH值对不同系列的Cr吸附率有不尽相同的影响。 相似文献
10.
基于当前发生的抗生素污染环境严峻问题,本文开展高活性粘土矿物蒙脱石吸附水中盐酸四环素(TC)的实验研究。采用批处理吸附实验方法,着重考查溶液初始TC浓度、初始pH值、电解质的阳离子类型及其浓度等对蒙脱石吸附性能的影响。结果显示,蒙脱石对TC的吸附行为可用Freundlich吸附等温线进行描述,并表现出显著的非线性特征;Langmuir方程确定其最大吸附量为625 mg/g;在较强酸性介质条件下(pH=2～4)蒙脱石对TC的吸附能力最强,其次为弱酸性-弱碱性环境(pH=5～9);不同阳离子类型也能显著影响蒙脱石对TC的吸附,表现为阳离子价态越高,对TC吸附的影响程度越明显。蒙脱石可被认为是一种TC的高效吸附剂,应用于盐酸四环素污染废水的处理过程。 相似文献
11.
Removal of chromate from wastewater using amine-based-surfactant-modified clinoptilolite 总被引：1，自引：1，他引：0
P. Guzel Y. A. Aydın N. Deveci Aksoy 《International Journal of Environmental Science and Technology》2016,13(5):1277-1288
This study presents the results of chromate adsorption upon organically modified clinoptilolite obtained by the treatment of Bigadic clinoptilolite with surfactants in primary amine structure, namely 1-dodecylamine, 1-hexadecylamine and oleylamine. Natural and organo-clinoptilolites were characterized by X-ray diffraction, thermal gravimetry and Fourier transform infrared spectrometry which proved the integration of amine groups followed by the order oleylamine > 1-hexadecylamine > 1-dodecylamine. Organo-clinoptilolites were tested for their efficacy in chromate removal under base case conditions which implied 100 ppm initial concentration, pH 4.0, 10 g l?1 adsorbent dose and at 298 K. Results showed that amine loading induced chromate removal reaching up to 90 % for oleylamine-modified clinoptilolite. Experimentation was continued to determine the effects of pH, adsorbent dosage and initial concentration on chromate adsorption. Accordingly, maximum removal of 94.0 % was attained with 14 g l?1 of oleylamine-modified clinoptilolite, from Cr(VI) solution of 100 ppm initially at pH 3.0. Langmuir isotherm described the adsorption of chromate on oleylamine-modified clinoptilolite with 96.4 % consistency. Maximum theoretical uptake capacity was calculated as 6.72 mg g?1. Kinetic data were consistent with pseudo-second-order model with the controlling steps being film and pore diffusions. 相似文献
12.
The adsorption behavior of chromate on two variable charge soils (Oxisol and Ultisol) was investigated through batch experiments
at different ionic strengths and pH values. The adsorption of chromate on the variable charge soils was found to be strongly
dependent on the pH of the soil solutions. A characteristic pH was observed, which corresponds to the intersection of the
chromate adsorption—pH curves at different ionic strengths. The characteristic pH values are 5.50 for Oxisol and 5.04 for
Ultisol, close to the point of zero salt effect (PZSE) of these soils. The zeta potentials measured for these soils provide
the evidences to support the interpretation of the effect of ionic strength on the adsorption of chromate on these variable
charge soils. The adsorption behavior of chromate was interpreted by a schematic representation of chromate distribution at
increasing ionic strength. The chromate desorption–pH curves were also found to intersect at pH of 5.15 and 4.89 for the Oxisol
and Ultisol, respectively. It is considered that chromate adsorption by the variable charge soils was mainly determined by
the electrostatic potential on the adsorption plane, which was controlled by the ionic strength of the soil solutions. 相似文献
13.
Thomas J. Reich 《Geochimica et cosmochimica acta》2011,75(22):7006-7017
Adsorption of Cr(VI) on γ-alumina was investigated as a function of ionic strength (0.001, 0.01 and 0.1 M NaNO3), pH (4-10), Cr(VI) concentration (10−4 or 10−5 M with 5 g/L solid) and pCO2 (0, atmospheric, 2.5%). Cr(VI) sorption is significant at low pH and decreases with increasing pH, with 50% of the Cr(VI) adsorbed between pH ∼6.5 and 8. Adsorption varies little with ionic strength or pCO2 under most of the studied conditions. However, at low pH under high ionic strength and especially at high ionic strength and high pCO2, Cr(VI) sorption on γ-alumina is suppressed. The adsorption edge data were used to parameterize constant capacitance (CCM), diffuse double layer (DLM) and triple layer (TLM) surface complexation models. None of the models entirely captures the full range of observed adsorption dependence on ionic strength and sorbate/sorbent ratio. The best fits to the full dataset are produced by the CCM, mostly because it has ionic-strength dependent stability constants. The more sophisticated TLM, which requires the most fitting parameters, does not produce better fits than the simpler CCM or DLM approaches for the conditions tested in this study. 相似文献
14.
Sajjad Hussain Saima Gul Sabir Khan Habib ur Rehman 《Arabian Journal of Geosciences》2013,6(11):4547-4556
In the present study, the retention capacity of carbonaceous material obtained from the diesel engine exhaust mufflers for Cr(VI) removal has been investigated. The physicochemical properties such as density, pH of aqueous slurry, pH at point of zero charge, ash content, moisture content, volatile matter, surface area, scanning electron microscopy and electron dispersive spectroscopy of the carbonaceous material were determined. The capacity of adsorbent for removal of Cr(VI) from aqueous solution was observed under different experimental condition like contact time, initial concentration of metal ions, pH and temperatures on the adsorption capacity of the adsorbent. Maximum adsorption of Cr(VI) ions was found at low pH. The adsorption process was found to follow second-order kinetics. The rate constant was evaluated at different temperatures along with other thermodynamic parameters like activation energy, Gibbs free energy change, enthalpy change and entropy change. Both Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium of carbonaceous material at different temperatures. Langmuir isotherm shows better fit than Freundlich isotherm at given conditions. The result shows that low-cost carbonaceous material from diesel engine exhaust mufflers can be efficiently used for wastewater treatment containing Cr(VI) ions. 相似文献
15.
The problem associated with multi-metals contaminated soils has generated increasingly more attention. Thus, it is necessary within the field to study the mutual influence of environmental factors on competitive adsorption. The majority of studies carried out to date have concentrated on the variation of adsorption capacity or the removal efficiency, with only a single factor changed (including pH, ionic strength, and metal concentration). However, the interaction effect among various environmental factors was ignored in these studies. The purpose of this study was mainly aimed toward the investigation of the interaction of two influential factors, as well as the influential degree of each factor (such as the initial pH, ionic strength, initial metal concentration, and the competitive metal concentration) on competitive adsorption using the response surface method. These results demonstrated that the influential degree of each factor studied on the competitive adsorption of Zn2+ and Cd2+ followed the trend of having the initial concentration of the target metal?>?initial pH?>?concentration of competitive metal?>?ionic strength. When the metal concentration was held constant, we found that the competitive adsorption of Zn2+ initially increased, followed by a decrease with increasing initial pH. However, this was found to change minimally with increasing ionic strength. When the initial pH or ionic strength was held constant, the competitive ability was observed to increase with increasing Zn2+ concentration. However, with increasing Zn2+ or Cd2+ concentrations, the variation degree of the competitive adsorption was found to become smaller. These results provide novel information toward a better understanding of the effect of multifactors on the competitive adsorption of Zn2+ and Cd2+. 相似文献
16.
The effects of elevated pH, ionic strength, and temperature on sediments in the vadose zone are of primary importance in modeling contaminant transport and understanding the environmental impact of tank leakage at nuclear waste storage facilities like those of the Hanford site. This study was designed to investigate biotite dissolution under simulated high level waste (HLW) conditions and its impact on Cr(VI) reduction and immobilization. Biotite dissolution increased with NaOH concentrations in the range of 0.1 to 2 mol L-1. There was a corresponding release of K, Fe, Si, and Al to solution, with Si and Al showing a complex pattern due to the formation of secondary zeolite minerals. Dissolved Fe concentrations were an order of magnitude lower than the other elements, possibly due to the formation of green rust and Fe(OH)2. The reduction of Cr(VI) to Cr(III) also increased with increased NaOH concentration. A homogeneous reduction of chromate by Fe(II)aq released through biotite dissolution was probably the primary pathway responsible for this reaction. Greater ionic strengths increased biotite dissolution and consequently increased Fe(II)aq release and Cr(VI) removal. The results indicated that HLW would cause phyllosilicate dissolution and the formation of secondary precipitates that would have a major impact on radionuclide and contaminant transport in the vadose zone at the Hanford site. 相似文献
17.
P. K. Pandey Ph.D. S. K. Sharma Ph.D. S. S. Sambi Ph.D. 《International Journal of Environmental Science and Technology》2010,7(2):395-404
This study aims to report Batch adsorption study of hexavalent chromium, Cr (VI) on zeoliteNaX. Kinetics of Cr (VI) adsorption and adsorption isotherms were determined by varying operating parameters such as pH, initial concentration, temperature and contact time. ZeoliteNaX was found to remove Cr (VI) in acidic solutions down to ppm level at pH of about 4. Removal rate of Cr (VI) was found to decrease as pH rises above 4.0. Langmuir, Freundlich, Temkin and Redlich-Peterson models were applied to adsorption equilibrium data to find the best amongst these models. Langmuir model with R2 = 0.9711 best fits the adsorption data. The kinetics of adsorption was found to follow the first order reversible reaction. The separation parameter, RL values of less than 1.0 i.e., 0.7369, 0.5834 and 0.4828 corresponding to initial concentrations of 10, 20 and 30 mg/L, respectively indicated that adsorption of Cr (VI) on zeoliteNaX is favoured. The estimated values of thermodynamic parameters such as heat of adsorption and standard gibbs free energy confirmed the exothermic nature of adsorption of Cr (VI) on zeoliteNaX. 相似文献
18.
The adsorption behaviors of Cr(VI) on laterite from Guizhou Province were studied in this paper, and the adsorption mechanism
was discussed as well. Results showed that different mineral compositions in the laterite would cause differences in the capacity
of laterite to absorb Cr(VI). Gibbsite, iron oxide minerals and non-crystalloids are the main contributors to enhancing the
capacity of laterite to absorb Cr(VI). The pH of the solution is an important factor affecting the adsorption of Cr(VI) on
laterite. Acidic environment (pH=2–5) is favorable to the adsorption of Cr(VI). The amount of adsorbed Cr(VI) decreases with
increasing pH of the solution. With increasing initial concentrations of Cr(VI), the amount of adsorbed Cr(VI) increases first,
and then decreases. The optimal adsorption concentration of Cr(VI) on laterite is 250 μg/mL. The adsorption of Cr(VI) on laterite
is a rapid process, about 80% Cr(VI) will be adsorbed within 2 hours. And the adsorption of Cr(VI) on kaolinite is a slow
process. 相似文献
19.
M. Aliabadi M.Sc. K. Morshedzadeh B.Sc. H. Soheyli B. Sc. 《International Journal of Environmental Science and Technology》2006,3(3):321-325
The batch removal of Cr(VI) from aqueous solution using lignocellulosic solid wastes such as sawdust and pine leaves under different experimental conditions was investigated in this study. The influence of pH, temperature, contact time, initial concentration of Cr(VI) and particle size on the chromium removal was investigated. Adsorption of Cr(VI) is highly pH-dependent and the results indicate that the optimum pH for the removal is 2. The capacity of chromium adsorption at equilibrium by these natural wastes increased with absorbent concentration. Temperature in the range of 20–60 °C showed a restricted effect on the adsorption capacity of pine leaves, but had a considerable effect on the adsorption capacity of sawdust. The capacity of chromium adsorption at the equilibrium increased with the decrease in particle sizes. The suitability of adsorbents was tested with Langmuir and Freundlich isotherms and their constants were evaluated. Results indicated that the Freundlich model gave a better fit to the experimental data in comparison with the Langmuir equation. The study showed that lignocellulosic solid wastes such as sawdust and pine leaves can be used as effective adsorbents for removal of Cr(VI) from wastewater. 相似文献