Microwave- and acid-treated bentonite as adsorbents of methylene blue from a simulated dye wastewater

Batch adsorption tests for removal of methylene blue dye (MBD) from aqueous solutions onto bentonite was investigated using natural chemically treated (sulphuric acid) and physically treated (microwaved) bentonite. In batch sorption tests for MBD removal by the developed sorbents, the time needed to reach equilibrium was less than 30 min. The uptake of MBD by the microwave-treated bentonite was the highest, followed by the acid-treated and finally the untreated bentonite. The uptake of MBD increased with an increase in the dye concentration or the solution temperature. Three kinetic models were used for elucidation of the probable mechanisms of MBD uptake by the three sorbents. The rates of MBD uptake followed the pseudo second-order model with a high correlation. Intraparticle diffusion was involved in the sorption process but was not the rate-controlling factor. The Freundlich and Langmuir isotherm models were employed and well represented the experimental data.      

Laboratory and In Situ Tests for Long-Term Hydraulic Conductivity of a Cement-Bentonite Cutoff Wall

Slurry trench cutoff walls, constructed using self-hardening slag-cement-bentonite (Slag-CB), are the most common form of in-ground vertical contaminant barrier in the U.K., Europe, and Japan, and are increasingly being used in the United States. This paper presents a case study of the hydraulic conductivity evaluation of an 11-year-old Slag-CB wall material at a sulfate-contaminated site, using different in situ techniques and laboratory tests. The laboratory results suggest that the hydraulic conductivity of the samples, which vary in age from 4 weeks to 11 years, decreases with time for the first 3 years but then remains constant. The results indicate that the long-term performance of these containment walls is influenced by various parameters such as aging, the type/duration of contaminant exposure, mixing of surrounding soil during construction, and wall depth. Piezocone tests, packer tests, and self-boring permeameter tests were carried out in the field to determine the suitability of different in situ techniques and compare with the laboratory results. The hydraulic conductivity is affected by the type of in situ technique used and the geometric scale of the test section.     

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.     

Micro X-ray visualisation of the interaction of geosynthetic clay liner components after partial hydration

High-resolution X-ray tomography was used to observe a partially hydrated geosynthetic clay liner (GCL) specimen to gain a better understanding of the interaction of its compnents (i.e., geotextiles, fibres and bentonite) on partial hydration when deployed as part of a composite liner system. Detailed in-situ studies of hydration processes in GCLs has proven difficult despite more than two decades of effort. X-ray tomographs were collected at spatial resolutions of 12 and 7?μm to identify the different components within a GCL, as well as to examine in finer detail their interaction within the GCL after initial partial hydration. Tomograph projections provided an excellent aspect of the interaction of these components and some concepts, such as the presence of shearing features within the bentonite component, may require re-consideration based on evidence from X-ray tomography.     

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．     

The effect of sulphuric acid activation on the crystallinity,surface area,porosity, surface acidity,and bleaching power of a bentonite

The Hanç?l? (Keskin, Ankara, Turkey) bentonite was activated with H₂SO₄ by dry method at 97 °C for 6 h to obtain optimum parameters for imparting a maximum bleaching power towards soybean oil. The H₂SO₄ content in dry bentonite-acid mixture was changed between 0% and 70%. The natural and activated samples were examined by X-ray diffraction (XRD), N₂ adsorption–desorption, and n-butylamine adsorption (from the solution in cyclohexane). The specific surface area (S), specific micro–mesopore volume (V), mesopore size distribution (PSD), and surface acidity (n_m) of the samples were determined. The bleaching power (BP) of each sample for alkali-refined soybean oil was determined. The S, V, n_m, and BP increase after activation at various acid contents up to 40% H₂SO₄ without any considerable change in crystal structure of the smectite. The BP is controlled more by the PSD rather than other adsorptive properties of the bleaching earth. The optimum parameters for activation to obtain maximum bleaching power, are H₂SO₄% = 50–60, S = 250–230 m² g⁻¹, V = 0.46–0.47 cm³ g⁻¹, n_m = 9.0 × 10⁻⁴–8.4 × 10⁻⁴ mol g⁻¹ and PSD mainly distributed between 1.4 and 6.0 nm.     

乳液共聚法制备膨润土无机凝胶改性丙烯酸酯聚合物

将膨润土无机凝胶(SMP)制成水分散液,加入含有丙烯酸的可聚合性单体,通过乳液共聚法可以制得稳定的SMP改性丙烯酸酯聚合物乳液。它具有极好的抗电解质能力,并体现出了与乳液中直接掺混SMP明显不同的性质。含3%SMP改性的聚合物乳液,可以在保持聚合物弹性和柔韧性不变的前提下,将拉伸强度提高20%左右,但SMP的加入增大了聚合物材料的吸水性。     

膨润土/月桂酸/鳞片石墨定型储热材料的制备及性能

采用天然膨润土和月桂酸分别作为支撑基体和相变材料,通过真空浸渍法合成复合相变储热材料。结果表明,添加鳞片石墨不仅提高复合相变储热材料的导热特性,而且阻止相变材料从复合相变材料中泄露。制备的复合相变储热材料经历200次热循环实验后,仍具有较好的可靠性,具备在热能存储系统中应用的较大潜力。     

Factors affecting the down-slope erosion of bentonite in a GCL

Leaving a composite liner exposed for an extended period can sometimes lead to down-slope bentonite erosion from geosynthetic clay liners (GCLs). This laboratory study examines a number of factors that can affect the erosion of bentonite particles with an imposed flow of water for one particular geotextile-encased, needle-punched GCL. The factors examined include the effect of an initial wet/dry cycle, water chemistry, flow rate, slope, prior cation exchange, and the effect of no-drying phase in the test cycle. No erosion was observed unless the GCL had been hydrated and dried to create a wet/dry cycle. The most critical factor was found to be the water chemistry. No erosion was observed with tap water (39 ppm calcium) with up to 360 cycles and a flow of 3 L/hour. Tests simulating the evaporation and condensation of water below an exposed composite liner by imposing deionized water on the GCL surface developed erosion holes within 5–6 cycles.     

Production of desiccants from Turkish bentonites

Representative samples of three Turkish bentonites were investigated with the aim of producing moisture adsorbents, so-called desiccants, of commercial grade: 1) Ca-bentonite from Lalapaşa–Edirne region (LLP), 2) Na/Ca-bentonite from Çankırı region (CNK), and 3) Na-bentonite from Reşadiye–Tokat region (RSD). The samples were composed of smectite and small amounts of quartz, feldspar, calcite and opal-CT and minor amounts of zeolite and dolomite. The clay mineral contents of the raw samples were estimated at 75–80% for LLP, 50–55% for CNK and 75–80% for RSD.The bentonites were upgraded by mineral processing techniques and modified by addition of calcium chloride. The effect of particle size, heat treatment conditions such as drying temperature and drying time were examined. A maximum moisture adsorption capacity of 17.1% was obtained after heating at 150–200 °C for LLP Ca-bentonite. The mixed bentonite (CNK) achieved a maximum moisture adsorption capacity of 8.3% at 105 °C and the Na-type bentonite (RSD) exhibited the lowest adsorption capacity of 6.4% at 105 °C. In addition to the standard tests and parameters, chemical additives such as calcium chloride which is known as a hygroscopic material were mixed with the bentonites. Moisture adsorption capacities of the bentonites were raised to a level about 20% above required as standards. The results obtained in this study together with the standard specifications were compatible with the commercial counterparts.