Sorption of Metal Ions on Clay Minerals

The mechanism of Co uptake from aqueous solution onto hectorite (a magnesian smectite) and its impact on the stability of this clay mineral were investigated as a function of Co concentration (TotCo = 20 to 200 μM, 0.3 M NaNO(3)) and ionic strength (0.3 and 0.01 M NaNO(3), TotCo = 100 μM) by combining kinetics measurements and Co K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The morphology of the sorbent phase was characterized by atomic force microscopy (AFM) and consists of lath-type particles bounded by large basal planes and layer edges. At low ionic strength (0.01 M NaNO(3)), important Co uptake occurred within the first 5 min of reaction, consistent with Co adsorption on exchange sites of hectorite basal planes. Thereafter, the sorption rate dramatically decreased. In contrast, at high ionic strength (0.3 M NaNO(3)), Co uptake rate was much slower within the first 5 min and afterward higher than at 0.01 M NaNO(3), consistent with Co adsorption on specific surface sites located on the edges of hectorite. Time-dependent isotherms for Co uptake at high ionic strength indicated the existence of several sorption mechanisms having distinct equilibration times. The dissolution of hectorite was monitored before and after Co addition. A congruent dissolution regime was observed prior to Co addition. Just after Co addition, an excess release of Mg relatively to congruent dissolution rates occurred at both high and low ionic strengths. At high ionic strength, this excess release nearly equaled the amount of sorbed Co. The dissolution rate of hectorite then decreased at longer Co sorption times. EXAFS spectra of hectorite reacted with Co at high and low ionic strengths and for reaction times longer than 6 h, exhibited similar features, suggesting that the local structural environments of Co atoms are similar. Spectral simulations revealed the occurrence of approximately 2 Mg and approximately 2 Si neighboring cations at interatomic distances characteristic of edge-sharing linkages between Co and Mg octahedra and corner-sharing linkages between Co octahedra and Si tetrahedra, respectively. This local structure is characteristic of inner sphere mononuclear surface complexes at layer edges of hectorite platelets. The occurrence of these complexes even at low ionic strength apparently conflicts with kinetics results, as exchangeable divalent cations are known to form outer sphere surface complexes. To clarify this issue, the amount of Co adsorbed on exchange sites was calculated from the solute Co concentration, assuming that cation exchange was always at equilibrium. These calculations showed that sorbed Co was transferred within 48 h from exchange sites to edge sorption sites. Copyright 1999 Academic Press.     

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 1. Isoproturon

The adsorption of isoproturon and two model compounds, N,N-dimethylurea and4-isopropylaniline, on clay minerals (bentonite,montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has been studied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressure liquid chromatography (HPLC) and X-ray diffraction (XRD).N,N-dimethylurea interacted with bentonite and montmorillonite by the coordination of the carbonyl group, directly or indirectly through water molecules, with exchangeable cations. Adsorption on humic acid was due to hydrogen bonding with the active sites of the adsorbent. The amino group ofN,N-dimethylurea appears tobe relatively inactive during adsorption. The mechanisms involved in the adsorption of 4-isopropylaniline were hydrogen bonding and protonation. No adsorption of 4-isopropylaniline was observed on kaolinite. The investigation of isoproturon suggested that both the carbonyl and amino groups of isoproturon were involved in interactions with the active sites of the adsorbents. Both the clay minerals and organic matter of soil contribute to the adsorption of organic compounds on soil but the clay minerals bentonite and montmorillonite play a major role in their adsorption on soil.     

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds,2-chloropyrimidine and 3-chloropyridine on clay minerals(bentonite, montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has beenstudied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressureliquid chromatography (HPLC) and X-ray diffraction (XRD).3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbedthrough hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition tohydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed.In the adsorption of 2-chloropyrimidine on bentonite and montmorillonitean ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine wasobserved on the kaolinite clay mineral.Both the clay minerals and organic matter of soil contribute tothe adsorption of organic compounds on soil but the clay minerals bentonite and montmorilloniteplay a major role in their adsorption on soil.     

Mechanochemical Adsorption of Phenol by Tot Swelling Clay Minerals

The mechanochemical adsorption of phenol by laponite, saponite, montmorillonite, beidellite and vermiculite was studied by IR and X-ray spectroscopy. Mixtures containing phenol and clay in the ratio of 6:10 were manually ground by a mortar and pestle for 1,3,5 and 10 min and the ground mixtures were investigated. Depending on the basicity of the clay mineral and the time of grinding, two different associations between interlay er cations, water and phenol were identified. In these associations phenol can act either as a proton acceptor or donor (Configurations I and II, respectively). The phenol is more acidic than water and in most cases phenol acts as a proton donor. With montmorillonite and beidellite phenol acts as a proton acceptor. In this association the aromatic ring forms π bonds with atoms of the oxygen planes of the tetrahedral sheets which donate electrons to the anti-bonding π orbitals of the phenol.     

Water on the Surfaces of Clay Minerals: Orientation,Diffusion and Proton Exchange

Abstract

The surface of clay minerals such as montmorillonite and vermiculite offersan unique environment for the study of water molecules arrangement and of their interaction with cations since     

The Sorption of Radionuclides on Clay Minerals—the Components of Engineering Safety Barriers

Moscow University Chemistry Bulletin - The sorption properties of various clay minerals and materials based on them in relation to Cs(I), Sr(II), U(VI), Eu(III), and Pu(IV,V,VI) are compared. To...     

粘土矿物对低浓度镧、钕的吸附性研究

采用振荡平衡法,对高岭土、膨润土、凹凸棒石等3种不同类型的粘土矿物进行低浓度稀土元素镧、钕的吸附试验;通过ICP测定培养溶液的平衡浓度和吸附量,绘制各自的等温吸附曲线并拟合吸附热力学方程.得出 Langmuir方程能较好地描述低浓度条件下3种粘土矿物对稀土元素(La,Nd)的等温吸附过程;发现3种粘土矿物对稀土元素(La,Nd)的吸附性能大小排序为:膨润土＞凹凸棒石＞高岭土,吸附性能表现的差异性主要由粘土矿物自身的晶层结构决定.     

Effect of Phosphate on the Adsorption of Glyphosate on Soils,Clay Minerals and Oxides

The effect of phosphate (ortho-phosphate) on the adsorption of the widely used glyphosate herbicide was evaluated with three typical Danish agricultural soils as well as pure oxides (goethite, FeOOH and gibbsite, Al(OH) 3 ) and silicates (illite and montmorillonite), which are considered the most important glyphosate and phosphate adsorbents in soils. Batch experiments where made in order to find out how phosphate affects adsorption of glyphosate and how glyphosate affects adsorbed phosphate. Solution glyphosate was quantified by liquid scintillation counting of 14 C-taggered herbicide and the concentration of phosphate by the molybdenum blue method. All experiments showed competition between phosphate and glyphosate for adsorption sites but the various adsorbents exhibited great variation in affinity for glyphosate and phosphate. Thus, gibbsite and, in particular goethite strongly prefer phosphate, whereas the competition on the silicates is more equal. The current studies showed that the competition in soils is almost equal, but still phosphate affects the sorption of glyphosate in soil. The amount of glyphosate and phosphate adsorbed by the various kinds of adsorbents was found to decrease in the order: oxides > silicates > soils. For the soils tested aluminium oxides, and to a lesser extent iron oxides seem the most important components in determining a soil's ability to adsorb phosphate and glyphosate, whereas the clay content and clay type seem of minor or little importance for adsorption of these species.     

Some Remarks on the Methodology of Thermal Analysis of Clay Minerals

The influence of certain experimental conditions on the courses of the thermal curves (DTA and DTG) of selected clay minerals was studied. The thickness of the sample layer, the sample mass, the type of sample holder and the parameters of the air atmosphere were varied in thermal analyses of 13 samples of clay minerals. Comparison of the results obtained on different clay samples analysed under different experimental conditions may serve as the basis for the improvement of the thermal analysis methodology applied for the study of clay minerals. This revised version was published online in July 2006 with corrections to the Cover Date.     

粘土矿物的结构特征及其应用研究

阐述了贮量巨大、用途广泛的粘土矿物，其充分开发应用的关键，在于根据其结构特征，并通过适当的物理、化学方法加以改造、以适应各种不同工业应用的要求。并以我们对粘土矿物进行活化、改性、层间插入及其工业应用产品开发的初步研究成果，阐明利用粘土硅酸盐多层次结构的可变性，开拓新的应用性能的可能性及粘土矿物充分开发应用的途径。     

The Transformation of Clay Minerals in Triassic Mudstone of North Shaanxi Province During Burial Metamorphism

According to the analysis of X-ray diffraction and the investigation under electron microscope (SEM, TEM) of clay minerals, the transformation of clay minerals in Triassic mudstone during burial metamorphism has been studied in detail. Berthierine, the mixed layer of illite and chlorite, and the changeable texture from berthierine to chlorite have been first discovered in the paper; and then it is considered that the transformation of clay minerals during burial metamorphism is shown in the following reaction: Smectite+ Kaolinite + K~+ = lllite + Chlorite + Quartz. The metamorphic temperature of the above reaction is about 160—220℃, according to the calculation of oxygen isotope geothermometry of illite and quartz. The study of crystallinity and polytype of illite and chlorite shows that the different indexes have varied in regular way, and have certain functional relationship between them.     

Clay,Zeolite and Oxide Minerals: Natural Catalytic Materials for the Ozonation of Organic Pollutants

Ozone has been successfully employed in water treatment due to its ability to oxidize a wide variety of refractory compounds. In order to increase the process efficiency and optimize its economy, the implementation of heterogeneous catalysts has been encouraged. In this context, the use of cheap and widely available natural materials is a promising option that would promote the utilization of ozone in a cost-effective water treatment process. This review describes the use of natural clays, zeolites and oxides as supports or active catalysts in the ozonation process, with emphasis on the structural characteristics and modifications performed in the raw natural materials; the catalytic oxidation mechanism; effect of the operating parameters and degradation efficiency outcomes. According to the information compiled, more research in realistic scenarios is needed (i.e., real wastewater matrix or continuous operation in pilot scale) in order to transfer this technology to the treatment of real wastewater streams.     

甲基对硫磷和西维因在粘土矿物表面的吸附解吸特性

研究了甲基对硫磷和西维因在蒙脱石、高岭石和针铁矿表面的吸附 解吸特征。结果表明,Langmuir方程能较好的描述甲基对硫磷和西维因在３种矿物表面的等温吸附过程,且蒙脱石对农药的最大吸附量大于高岭石和针铁矿。用动力学方程对2种农药的吸附过程进行拟合,Elovich方程、双常数方程和一级动力学方程均得到较好的结果,其中Elovich方程为最佳模型,相关系数（R²）在0.93～0.98之间,说明该吸附为非均相扩散过程。3种矿物对甲基对硫磷和西维因的吸附强度均为蒙脱石＞高岭石＞针铁矿。     

Efficient Nonlinear Optical Properties of Dyes Confined in Interlayer Nanospaces of Clay Minerals

Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation. In some cases, extension of the π‐electron system as a consequence of improved molecular planarity, obtained by the intercalation of a dye into the 2‐dimensional interlayer space of an inorganic layered material, is also observed as a factor that enhances NLO responses of chromophores at the molecular level. This review focuses on recent progress in the strategies for controlling the molecular orientation of NLO‐phores by employing clay minerals, which are one of the typical inorganic layered materials. In addition, development of a means for fabricating composites that satisfy the properties of an optical material, such as a sufficient size and thickness, a flat surface, and low light‐scattering characteristics is required to utilize the superior NLO properties observed for clay/dye hybrid materials for practical applications. A novel means for obtaining such a hybrid material is also outlined.     

恶臭假单胞菌与土壤矿物的界面反应及其对甲基对硫磷降解影响

研究了恶臭假单胞菌在蒙脱石、高岭石和针铁矿表面的吸附特征,探讨了细菌在不同粘粒矿物存在下的生长代谢活性,及对甲基对硫磷的降解动力学.结果表明, 三种矿物对细菌的吸附强度为针铁矿>高岭石>蒙脱石.当甲基对硫磷浓度较低时(10 mg/L), 游离菌的降解能力始终比固定菌强;在高浓度(20～40 mg/L)下, 固定菌对农药的降解能力起初(前9 h)高于游离菌, 随后渐渐低于游离菌.不同矿物固定的细菌, 其降解能力为蒙脱石>高岭石>针铁矿.蒙脱石对细菌的亲和力最弱, 但它对细菌的代谢活性有促进作用, 有利于农药的生物降解; 而针铁矿与细菌的结合强度最大, 细菌活性受到抑制, 不利于农药的降解.     

浅谈重金属元素在土壤中的迁移及黏土矿物对其修复作用

重金属元素在土壤中的存在形式有多种,且迁移能力各不相同,而影响重金属元素形态的因素是土壤p H、土壤植物根际环境,重金属元素迁移的过程还受到土壤类型、含水量以及土壤中有机和无机配体的影响。黏土矿物具有良好的吸附作用,它主要是通过离子交换、配合反应和共沉淀反应来修复土壤中的重金属污染。     

Sorption of Metal Ions on Clay Minerals: II. Mechanism of Co Sorption on Hectorite at High and Low Ionic Strength and Impact on the Sorbent Stability

The mechanism of Co uptake from aqueous solution onto hectorite (a magnesian smectite) and its impact on the stability of this clay mineral were investigated as a function of Co concentration (TotCo = 20 to 200 μM, 0.3 M NaNO₃) and ionic strength (0.3 and 0.01 M NaNO₃, TotCo = 100 μM) by combining kinetics measurements and Co K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The morphology of the sorbent phase was characterized by atomic force microscopy (AFM) and consists of lath-type particles bounded by large basal planes and layer edges.At low ionic strength (0.01 M NaNO₃), important Co uptake occurred within the first 5 min of reaction, consistent with Co adsorption on exchange sites of hectorite basal planes. Thereafter, the sorption rate dramatically decreased. In contrast, at high ionic strength (0.3 M NaNO₃), Co uptake rate was much slower within the first 5 min and afterward higher than at 0.01 M NaNO₃, consistent with Co adsorption on specific surface sites located on the edges of hectorite. Time-dependent isotherms for Co uptake at high ionic strength indicated the existence of several sorption mechanisms having distinct equilibration times. The dissolution of hectorite was monitored before and after Co addition. A congruent dissolution regime was observed prior to Co addition. Just after Co addition, an excess release of Mg relatively to congruent dissolution rates occurred at both high and low ionic strengths. At high ionic strength, this excess release nearly equaled the amount of sorbed Co. The dissolution rate of hectorite then decreased at longer Co sorption times.EXAFS spectra of hectorite reacted with Co at high and low ionic strengths and for reaction times longer than 6 h, exhibited similar features, suggesting that the local structural environments of Co atoms are similar. Spectral simulations revealed the occurrence of 2 Mg and 2 Si neighboring cations at interatomic distances characteristic of edge-sharing linkages between Co and Mg octahedra and corner-sharing linkages between Co octahedra and Si tetrahedra, respectively. This local structure is characteristic of inner sphere mononuclear surface complexes at layer edges of hectorite platelets. The occurrence of these complexes even at low ionic strength apparently conflicts with kinetics results, as exchangeable divalent cations are known to form outer sphere surface complexes. To clarify this issue, the amount of Co adsorbed on exchange sites was calculated from the solute Co concentration, assuming that cation exchange was always at equilibrium. These calculations showed that sorbed Co was transferred within 48 h from exchange sites to edge sorption sites.     

Minerals of Moscow

By the example of the territory of Moscow, possibilities of studying large cities as independent topomineralogical objects are shown. A cadastre of minerals, their varieties, and mineral formations, consisting of more than 100 names, has been collected for Moscow for the first time on the basis of different sources (publications, geological funds, and museums). Distribution of important discoveries of minerals on the territory of the city is demonstrated in detail and their characteristics are given.