Thermogravimetric characterization of tyrosine and catechol adsorbed on montmorillonite

Thermogravimetric analysis is suggested as an essential methodology for studying the interaction between montmorillonite-type clays and organic molecules such as amino acids and phenolic compounds. In this work, two commercial clays, a bentonite and a montmorillonite commercially called K10, were separately put in contact with solutions of catechol and tyrosine. After the contact with the organic molecules, the powders were characterized by X-ray diffraction, infrared spectroscopy, nitrogen adsorption at 77?K, scanning electron microscopy, and thermogravimetric analysis. The thermal stability of the organic molecules on the particles’ surface depended mainly on the type of the montmorillonite clay used. This characteristic can be associated with the adsorption strength. The results show the importance of the thermogravimetric analysis for choosing the appropriate clay to be used in environmental studies or in the elaboration of industrial materials.     

吸附粒子浮选法回收碘的研究

以钠质膨润土为吸附载体、以ＣＴＭＡＢ为捕收剂,进行了碘的浮选回收研究。在弱酸性条件下浮选,碘的回收率＞９９％,残余液碘的浓度仅为２．２～２．８ｍｇ／Ｌ．     

Arsenic (V) removal from aqueous solutions using natural clay ceramic monoliths

Abstract

An adsorbent material arranged in a ceramic monolith (CM) obtained by extrusion technique using natural bentonite and alumina (as raw materials) is presented. Ceramic and raw materials were characterized by X-ray fluorescence, thermal analysis, X-ray diffraction, and textural analysis (with N₂ adsorption–desorption at 77?K and Hg intrusion–extrusion porosimetry) to determine their chemical and physical properties. Then, As (V) adsorption capacity of the CM at different pH (3–9) using arsenic aqueous solution (with 2000?µg As (V) L^?1) was evaluated. Additionally, studies of kinetics and equilibrium of As (V) adsorption on CM were performed. It was found that: (i) the As (V) removal capacity is favored at acidic pH, reaching an average value of 15?µg As (V) per gram of CM; (ii) from kinetic studies, As (V) adsorption on CM occur in two stages, the first of them reaching a lower As uptake in a short time period, followed by an slow second stage with a subsequent higher As uptake, which continued for a longer time period, reaching equilibrium conditions in approximately 24?h; and (iii) the As (V) adsorption isotherm is a type-Langmuir, indicating that the CM present an homo quantity of fixed sites to adsorb the As (V).     

富铁膨润土的脱色性能研究

对矿产粗制富铁膨润土进行了金属元素分析。通过对矿产粗制膨润土进行研磨、筛分取小于160目的细微颗粒进行酸处理以脱除膨润土中的金属杂质(主要是铁)。经水洗、过滤并用硫氰化钾检验处理效果、干燥、焙烧等步骤最终以焙烧产品的色泽确定对产品的脱色效率。考察了酸种类、浓度、处理温度和时间以及焙烧温度对脱色效果的影响。结果表明,在膨润土脱色过程中,在室温下,8mol/L的浓硝酸,酸处理16h,焙烧温度为550℃,焙烧时间为2h,在该条件下制备的产品颜色由原始的棕红色脱变为乳白色,白度值由43.0提高到81.6。     

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。     

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.     

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。