Experimental study on the permeability and self-healing capacity of geosynthetic clay liners in heavy metal solutions

Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb²⁺) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb²⁺ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement.     

Modelling the FEBEX THM experiment using a state surface approach

Buffer materials being considered as engineered barriers in nuclear fuel waste (NFW) disposal systems possess a pronounced nonlinear behaviour in the unsaturated state. In order to simulate such non-linear responses,the authors adopted an incrementally nonlinear poro-elastic approach where the coefficients of the governing equations are assumed to be functions of suction and the void ratio. These functions are in turn developed from a state-surface equation obtained from suction-controlled oedometric tests. In this paper we show the derivation of the governing equations of the poro-elastic model. A finite element computer code, FRACON, was developed by the authors to numerically solve the above equations. We first use the code to simulate laboratory tests to characterize the swelling properties of a typical bentonite. That same bentonite was used in the FEBEX in-situ heater experiment, conducted at the Grimsel site, Switzerland. The FRACON code was also used to perform blind predictions of the FEBEX heater experiment. It is shown that the model correctly predicts drying of the bentonite near the heaters and re-saturation near the rock interface. The evolution of temperature and the heater thermal output were also reasonably well predicted by the model. The trends in the total stresses developed in the bentonite were correctly predicted; the absolute values however were underestimated probably due to the omission of pore pressure build-up in the rock mass.     

膨润土凝胶调剖剂XJF的研制及应用

介绍了调剖剂XJF的配方,讨论了影响调剖剂性能的配方因素(膨润土含量、HPAM溶液浓度、XJ用量及添加剂Fc的浓度),考察了封堵能力和应用范围,简介了在火烧山油田现场试验的结果。     

膨润土尾矿作PVC塑料填料的研究

研究了膨润土尾矿的比表面积、添加量及偶联剂表面改性处理对其作为PVC塑料填料时的力学性能和流变性能的影响。结果表明,膨润土尾矿作填料的PVC试样,拉伸强度优于重质CaCO_3,为填料的试样,冲击强度和流动性能则有所下降。钛酸酯作偶联剂有利于提高填充试样的冲击强度。但对拉伸强度无明显效果。膨润土尾矿的添加量约20份时,试样的力学性能最佳。     

膨润土及改性膨润土在造纸行业中的应用

膨润土特殊的构造使其具有离子交换性、吸水性、膨胀性、触变性、粘结性、吸附性等多重性质,其常用改性方法有活化法和添加改性剂法两种。概括了近期的文献资料,对膨润土和改性膨润土在造纸行业中的应用情况进行了综述,对今后的发展提出了建议。     

Charge reduction and regeneration in K+, Na+, Mg2+, Ni2+ and Co2+-exchanged Wyoming Bentonite

Controlled calcination of ion-exchanged Wyoming Bentonite in the presence and absence of ammonia leads to layer charge reductions. Detailed chemical analyses of both unexchangeable and exchangeable species lead to the conclusion that in no case is there migration of the original interlamellar cations into the octahedral region of the layers although, in terms of ionic radius alone, Mg²⁺, Ni²⁺ and, possibly Co²⁺, might be expected to do so. The production of unexchangeable Mg, Ni or Co, is identified as resulting from high temperature hydrolysis leading to hydroxide or oxide formation.     

Adsorption properties of tetradecyl- and hexadecyl trimethylammonium bentonites

This study concerns the adsorption properties of organo-bentonites obtained through the modification performed at 25%, 50% and 100% of the cation exchange capacity (CEC) using tetradecyl trimethylammonium bromide (TDTAB) and hexadecyl trimethylammonium bromide (HDTAB). According to the XRD measurements, TDTAB and HDTAB form bilayers between the silicate layers when the montmorillonite surface is modified by 100% CEC. At 25% and 50% CEC, a random interstratification of monolayer and bilayer structures is observed. The surface area of bentonite decreases upon modification. The adsorption properties of organo-bentonites were tested using phenol as a model pollutant. Batch kinetic and isotherm studies were conducted over the concentration range from 50 to 1000 ppm at pH of 5.5. The adsorption excess isotherms of bentonites show different regions. A considerable increase was observed in the adsorption efficiency of montmorillonite modified with HDTAB at 100% CEC.     

粉煤灰负载钒氧化物低温SCR催化剂脱硝性能研究

目前,我国电厂普遍采用SCR法高含尘工艺对烟气中的NOx进行脱硝,催化剂存在严重堵塞、中毒等问题,SCR法低含尘工艺越来越引起重视。为了制备SCR法低含尘工艺中的低温SCR脱硝催化剂,本文将钒氧化物负载在粉煤灰和膨润土混合制成的复合材料载体上,制成V2O5/FA-BT催化剂,同时分别用全自动比表面及孔隙度分析仪(Micromeritics Tristar 3 000)和扫描电子显微电镜(SEM)对催化剂的比表面积和表面形貌进行表征。结果表明:不同V2O5负载量的V2O5/FA-BT催化剂在低温下有很好的脱硝效果,其中以V2O5负载量(质量分数)为11%的V2O5/FA-BT脱硝效果最好,当反应温度为130℃时,脱硝率达到89%;对催化剂进行酸改,CH3COOH酸改的催化剂比表面积较大且脱硝效果最好。     

烷基季铵盐改性膨润土的膨胀性

用X射线衍射(XRD)、傅立叶红外光谱(FT-IR)和热重(TG)表征方法,考察了四甲基溴化铵(TMAB),四乙基溴化铵((Et)4NB),十二烷基三甲基溴化铵(DTAB),十六烷基三甲基溴化铵(CTAB)对膨润土膨胀性的影响。结果表明,不同季铵盐都已吸附到膨润土晶层间,短链季铵盐TMAB和(Et)4NB主要以单分子平躺在膨润土晶层之间,使膨润土的层间距比原土样降低,有很好的防膨作用。长链季铵盐DTAB和CTAB以假三层平卧、倾斜排列等方式排列,使膨润土的层间距比原土样增加,没有防膨作用。且膨润土对(Et)4NB和TMAB的吸附量低于DTAB和CTAB的。     

Comparing the impact of bentonite addition for both must clarification and wine fining on the chemical profile of wine from Chambave Muscat grapes

The impact of bentonite fining is generally studied on final wines, and few studies have evaluated it throughout the winemaking process. This work studied the fate of proteins and terpenols, the main targets of bentonite addition, during the processing of Chambave Muscat aromatic grapes. The experimental trials were performed in two vintages (2006 and 2007) and included the following processes: bentonite addition to must only (100 g hL^?1 in both vintages), fining of wine only (100 g hL^?1 in both vintages), double bentonite treatment on must and wine (200 and 150 g hL^?1 in 2006 and in 2007, respectively) and no treatment (control). The results demonstrated that the treatment allowing the best removal of protein was the addition of bentonite to must only. Moreover, a lower removal of free terpenols was observed in samples from double treatment compared with wines fined with bentonite only after alcoholic fermentation.