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.     

DTAC有机改性云南砚山膨润土的工艺研究

以经过钠化改性的砚山膨润土为原料,用十二烷基三甲基氯化铵(DTAC)进行有机改性,应用单因素及正交实验,研究了制备季铵型有机膨润土的最佳工艺条件,并用XRD和IR对合成的有机膨润土进行了结构表征。     

镁铝交联膨润土吸附处理结晶紫废水的研究

以镁铝双金属离子低聚物为交联剂,制备了复合联膨润土,用于处理含结晶紫染料的废水。通过改变废水溶液pH值、吸附剂用量和搅拌处理时间等因素研究了镁铝交联膨润土对结晶紫的吸附特性和处理效果。研究表明,镁铝交联膨润土对阳离子染料结晶紫废水的脱色率较好,可以达到99%以上。此外,还对镁铝交联膨润土与膨润土原土的处理效果进行了比较。结果表明,用镁铝交联剂对膨润土进行改性后吸附能力显著增强,脱色率在98%以上。由于膨润土的储量大、价格低,是一类很有发展前景的优质廉价吸附剂。     

Dye removal using some surface modi?ed silicate minerals简

The objective of this work is to study the efficiency of some surface modified phyllosilicate minerals (bentonite and glauconite) in the removal of dyes from textile waste water. It is found that complete dye removal was achieved by using 10–25 g modified glauconite from solutions having a dye concentration of 10–50 mg/L. Adsorption data were modeled using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Adsorption capacities and optimum adsorption isotherms were predicted by linear regression method. The analysis of experimental isotherms showed that Langmuir isotherm reasonably fit the experimental data in the studied concentration range for the adsorption of dye onto glauconite mineral surface where Freundlich isotherm fit the experimental data for the adsorption of dye onto bentonite mineral surface.     

Design and validation of the THMC China-Mock-Up test on buffer material for HLW disposal

According to the preliminary concept of the high-level radioactive waste （HLW） repository in China, a large-scale mock-up facility, named China-Mock-Up was constructed in the laboratory of Beijing Research Institute of Uranium Geology （BRIUG）. A heater, which simulates a container of radioactive waste, is placed inside the compacted Gaomiaozi （GMZ）-Na-bentonite blocks and pellets. Water inflow through the barrier from its outer surface is used to simulate the intake of groundwater. The numbers of water injection pipes, injection pressure and the insulation layer were determined based on the nu- merical modeling simulations. The current experimental data of the facility are herein analyzed. The experiment is intended to evaluate the thermo-hydro-mechano-chemical （THMC） processes occurring in the compacted bentonite-buffer during the early stage of HLW disposal and to provide a reliable database for numerical modeling and further investigation of engineered barrier system （EBS）, and the design of HLW repository.     

热改性膨润土对甲基橙废水的吸附

研究了热改性膨润土对甲基橙的吸附性能。结果表明改性的方法能够明显地改善膨润土在水中的沉降性与过滤性,大大地提高了膨润土对甲基橙的吸附能力。在pH等于7及常温条件下,当经300℃煅烧2h的热改性膨润土的用量为12g／L时,对浓度为248mg／L的甲基橙的吸附量和去除率分别为22．12mg／g、98．58％;对浓度为41．0mg／L的甲基橙的去除率达97．4％。     

Construction of Barrettes for High‐Rise Foundations

Barrettes are huge concrete piers, basically rectangular. The cross‐sectional areas of barrettes have often been more than 75 sq ft (7?m2) and they have been used for depths exceeding 260 ft (80?m) facilitating heavy vertical loads of the order of 3,000 tons∕barrette to be transmitted to the bearing layer. Barrettes are used also as Moscovite wall for deep basements of high‐rise buildings to resist both vertical and lateral loads. The fact that a single barrette can replace a group of conventional piles results in a more compact, economical, and reliable foundation system. The installation technique of barrettes follows closely the method of constructing diaphragm wall using bentonite slurry, reinforcing cage, and tremie concreting with careful quality control. Although there are certain reservations for using barrettes instead of conventional piles and diaphragm walls, the inherent advantages and the confidence gained by experience have been responsible for their increased usage, especially as heavy load‐bearing elements for high‐rise foundations and basements.     

黄原胶/AMPS/膨润土制备油田堵水剂的研究

通过水溶液法制备了一种黄原胶/2-丙烯酰胺基-2-甲基丙磺酸（AMPS）/膨润土三元复合型油田堵水剂,考察了2-丙烯酰胺基-2-甲基丙磺酸、膨润土、交联剂以及引发剂质量分数等因素对堵水剂吸水率的影响,测试了不同温度下堵水剂的吸水倍率和保水值,研究了堵水剂对不同质量分数NaCl溶液的吸水性能。结果表明,最佳的制备工艺：膨润土的质量分数为15%,AMPS的质量分数为3%,交联剂的的质量分数为2%,引发剂的质量分数为2.5%,在60℃的温度下反应4h,在最佳工艺下,环境温度20℃时,堵水剂的吸去离子水的倍率最高达到1 677g/g,吸质量分数0.9%NaCl溶液的倍率为165g/g;环境温度80℃的高温下仍保持着1 590g/g的吸水倍率,12h后仍能保水20%以上,具有良好的热稳定性和耐盐性。     

Adsorption of malachite green onto bentonite: Equilibrium and kinetic studies and process design

The adsorption of malachite green onto bentonite in a batch adsorber has been studied. The effects of contact time, initial pH and initial dye concentration on the malachite green adsorption by the bentonite have been studied. Malachite green removal was seen to increase with increasing contact time until equilibrium and initial dye concentration, and the adsorption capacity of bentonite was independent of initial pH in the range 3–11. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of malachite green onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equations. Adsorption of malachite green onto bentonite followed the Langmuir isotherm. The thermodynamic parameters, such as ΔH, ΔS and ΔG, were also determined and evaluated. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.     

Microstructure and anisotropic swelling behaviour of compacted bentonite/sand mixture

Pre-compacted elements(disks,torus) of bentonite/sand mixture are candidate materials for sealing plugs of radioactive waste disposal.Choice of this material is mainly based on its swelling capacity allowing all gaps in the system to be sealed,and on its low permeability.When emplaced in the gallery,these elements will start to absorb water from the host rock and swell.Thereby,a swelling pressure will develop in the radial direction against the host rock and in the axial direction against the support structure.In this work,the swelling pressure of a small scale compacted disk of bentonite and sand was experimentally studied in both radial and axial directions.Different swelling kinetics were identified for different dry densities and along different directions.As a rule,the swelling pressure starts increasing quickly,reaches a peak value,decreases a little and finally stabilises.FOr some dry densities,higher peaks were observed in the radial direction than in the axial direction.The presence of peaks is related to the microstructure change and to the collapse of macropores.In parallel to the mechanical tests,microstructure investigation at the sample scale was conducted using microfocus X-ray computed tomography(μCT).Image observation showed a denser structure in the centre and a looser one in the border,which was also confirmed by image analysis.This structure heterogeneity in the radial direction and the occurrence of macro-pores close to the radial boundary of the sample can explain the large peaks observed in the radial swelling pressure evolution.Another interesting result is the higher anisotropy found at lower bentonite dry densities,which was also analysed by means of μCT observation of a sample at low bentonite dry density after the end of test It was found that the macro-pores,especially those between sand grains,were not filled by swelled bentonite,which preserved the anisotropic microstructure caused by uniaxial compression due to the absence of microstructure collapse.