Physico-chemical variation in bentonite by sulfuric acid activation

The physico-chemical behavior of Iranian typical bentonite was characterized during the activation process by sulfuric acid. The main variations were studied by evaluating specific surface area, chemical and mineralogical composition, thermal gravimetric curves, Fourier transform infrared spectrometry pattern, and morphology of starting and activated samples. The effects of acid concentration, particle size distribution, activation temperature and time on specific surface area were discussed. It was found that the above parameters have significant role in the activation process. The optimum condition was also obtained for the activation of typical bentonite.     

Synthesis of nano crystalline zeolite Y from bentonite

Zeolite Y was synthesized from bentonite via the hydrothermal method. The effects of various parameters on the synthesis were investigated. The samples were characterized by XRD, XRF, IR, DTG and wet chemical analysis. The results show that crystallization temperature, aging time and concentration of sodium hydroxide play important roles in the formation of the zeolite. P zeolite was the competitive phase and present in most of the products. However, under optimized conditions, such as crystallization temperature (97 °C), aging time (20 h), concentration of NaOH (3N), pure zeolite Y with high crystallinity was synthesized. The results showed that optimization of the process results in a commercial route to synthesis zeolite Y from bentonite.

改性膨润土在胶粉聚苯颗粒外墙外保温系统中的应用

改性膨润土用于胶粉聚苯颗粒外墙外保温系统可提高该系统中各材料的相容性、粘结性及系统防水性,文章通过研究膨润土在外墙外保温体系中的使用,确定其最佳使用方法。     

Effect of Operating Parameters on the Effectiveness of Electric Field-Enhanced Separations

The purpose of this work is to summarize our latest research results about constant-current electroosmotic dewatering (EOD). The Terzaghi-Voigt combined model is used for the analysis of EOD of various solid-liquid systems by considering the creep deformation of the material. Bentonite clay, KC-flock, zinc oxide, and some of their mixtures are used as experimental materials. It is assumed that the electroosmotic pressure gradient E _pg and modified consolidation coefficient C _e of the materials are constant. The relation between the ratio of creep deformation to total deformation B and the modified consolidation coefficient C _e is determined and compared with previous observations for the case of mechanical expression. The effectiveness of dewatering is described depending on operating parameters such as preconsolidation pressure, material composition, electric current density, and total solid volume per unit cross-sectional area. The model is verified by comparing the calculations with experimental data.     

Wall friction measurement and compaction characteristics of bentonite powders

This paper presents a new method (referred to as direct method) for measuring wall friction during powder compaction and ejection. The accuracy for wall friction force measurement by both new and conventional methods (referred to as indirect method) were first studied according to the theory of error propagation. The error sources for compact density measurement in both methods were also examined. Based on the accuracy in the measurement of wall friction force and compact density, the direct method is compared favorably to the indirect method. Two bentonites, Black Hills bentonite and Zhi-Hsing bentonite which were considered as the candidate buffer materials for the geological disposal of high-level radioactive wastes were adopted to conduct a series of compaction and ejection tests. The compaction characteristics of bentonite blocks were expressed in terms of compressibility curve, wall friction ratio and friction index. The Gurnham's equation was used to describe the compressibility curve. The effects of the aspect ratio of block on the friction ratio and friction index are discussed from both experimental and theoretical point of views. Ejection profiles of the compacted bentonite blocks during ejection phase were presented. The proposed measuring method is validated by comparing the readings of ejection force recorded by both upper load cell and ring-type load cell.     

Methane Hydrate Formation and Dissociation in the presence of Bentonite Clay Suspension

The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure‐temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius‐Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater.     

Modeling of leaching from cementitious materials used in underground environment

The purpose of this research is to evaluate the long-term durability of engineered barrier materials used in underground radioactive waste disposal facilities. Radioactive waste repositories are constructed in crystalline rocks, sedimentary rocks, or clay, which are natural barrier materials, using bentonite and/or cementitious materials as additional engineered barriers in those natural barriers. These engineered barriers are required to inhibit leakage of radionuclides for a long period of more than 1000 or 10,000 years. This necessitates the actual evaluation of long-term durability and quantitative evaluation of the interactions of each of these barrier materials. Cementitious materials are considered to come in contact with underground water or bentonite and release alkali components, which may degrade their performance. Furthermore, there is apprehension that the properties of bentonite may be altered due to the effect of alkaline components included in cementitious materials. In view of the above, the estimation of changes with time of various components that leach out of cementitious materials is considered to be important for evaluating the long-term performance of engineered barriers.The authors firstly carried out leaching experiments considering temperature effects to construct a solubility equilibrium model of cement hydrate. Next, leaching of calcium from concrete was modeled using this solubility model and an advection–diffusion model. Furthermore, the degradation due to leaching of actual structures, from 34 to 104 years old, was studied, and it was observed that a degradation of 100 mm maximum occurs over a period of 100 years. The calculated results of the proposed model showed very good agreement with the results of studies on actual structures. Finally, the effects of various factors on the degradation rate were evaluated numerically using this model. In addition, a simple evaluation of the degradation of bentonite was also performed.     

Adsorption of p-chlorophenol from aqueous solutions on bentonite and perlite

The adsorption of p-chlorophenol (p-CP) from aqueous solutions on bentonite and perlite was studied. These materials are available in large quantities in Bulgaria. Model solutions of various concentrations (1–50 mg dm⁻³) were shaken with certain amounts of adsorbent to determine the adsorption capacity of p-CP on bentonite and perlite as well. The influence of several individual variables (initial adsorbate concentration, adsorbent mass) on the rate of uptake of the studied compound on the adsorbent was determined by carrying out experiments at different contact times using the batch adsorber vessel designed according to the standard tank configuration. Rapid adsorption was observed 20–30 min after the beginning for every experiment. After that, the concentration of p-CP in the liquid phase remained constant. The adsorption equilibrium of p-CP on bentonite and perlite was described by the Langmuir and the Freundlich models. A higher adsorption capacity was observed for bentonite (10.63 mg g⁻¹) compared to that for perlite (5.84 mg g⁻¹).     

交联粘土矿物的吸附特性研究(Ⅲ)——改性膨润土对水中酚吸附性能研究

探讨经Ａｌ（ＯＨ）０．５＋２．５，Ｈ２ＳＯ４处理的膨润土对废水中酚吸附性能和处理效率，结果表明：最高去除率为７３．８８％．处理水再经活性炭吸附处理，总去除率达９９．８％，酚含量可降至０．５ｍｇ／ＬＨ２Ｏ，达到国家排放标准．     

(土般)土中石英含量的红外光谱定量分析

本文介绍了一种用红外光谱测定搬土中石英含量的方法,讨论了制样时研磨对分析结果的影响。