Hydrogen adsorption on natural and sulphuric acid treated sepiolite and bentonite

In this study, hydrogen (H₂) adsorption on sepiolite and bentonite and those of acid treated forms were studied at 77 K using volumetric apparatus up to 100 kPa. Both clay minerals were treated with 100 ml of 0.5, 1.0, 2.0 and 4.0 M H₂SO₄ solutions at 80 °C for 5 h. Differences in the structures of the sepiolite and bentonite samples before and after the acid treatments were determined by XRD, XRF, TG, DTA and N₂ adsorption methods. The level of H₂ adsorption of original and acid treated sepiolite samples (1.332–2.252 mmol/g) was higher than those of the bentonite samples (0.341–1.003 mmol/g). The variation in the H₂ adsorption capacities during the acid treatment was also discussed.     

钒钛铁精矿润磨试验研究

针对川威集团自产的钒钛铁精矿,在钒钛铁精矿、膨润土理化性能测定结果基础上,进行了钒钛铁精矿的润磨、成球试验研究,探究了该钒钛铁精矿较佳的润磨工艺参数。      

基于聚吡咯合成的多孔碳材料的CO2吸附性能

采用氢氧化钾做活化剂,聚吡咯做碳前驱体,高温化学活化法制备掺杂氮元素的多孔碳材料。在273K一个大气压下,二氧化碳吸附量可达182．36cm2g-1（8．14mmolg-1）,二氧化碳相对于氮气的选择性吸附系数为47：1,吸附量之比约为13：1。     

天然及改性膨润土在磷污染水体净化中的应用

膨润土应用于磷污染水体净化处理的研究越来越受到关注,天然膨润土对含磷废水虽有一定的处理效果,但仍需进一步改性提高其对磷的吸附性能。膨润土的改性方法主要包括物理改性和化学改性,物理改性的核心工艺是采用加热的方法,按照导热方式可分为焙烧和微波加热;化学改性主要可以归结为钠化、酸改性、柱撑、有机改性等。物理改性工艺相对简单,化学改性效率高且在实际生产中应用较多,但目前仅仅凭借单因素改性作用尚难以满足环境应用领域对膨润土物化性能的要求。因此,深入系统地研究膨润土的基本性能,揭示膨润土吸附磷污染水体的净化机理,提出进一步提高膨润土材料净化性能的改性工艺,将有利于进一步扩大其应用领域。     

Slug Test Analysis in Vertical Cutoff Walls with Consideration of Filter Cake

In constructing a vertical cutoff wall, bentonite-water slurry is frequently used to maintain the stability of sidewalls during excavation before backfilling the trench with less permeable materials to complete the cutoff wall construction. This procedure leads to a thin but relatively impermeable layer, called a filter cake, on the excavation surface. The aim of this paper is to examine the effect of a filter cake on evaluating hydraulic conductivity of the cutoff wall backfill through a slug test analysis with the aid of the verified numerical program, Slug_3D. As an upper bound solution for evaluation of the hydraulic conductivity of the cutoff wall backfill, no-flux boundary conditions for the boundaries of cutoff walls are imposed to consider the effect of filter cakes. The type-curve method and modified line-fitting method are employed to reanalyze the case of EMCON/OWT, Inc., as an example. The previous analysis, without consideration of a filter cake, is compared with the current results that consider the filter cake to reveal the necessity of considering the effect of a filter cake in the slug test analysis. The comparison shows that the hydraulic conductivity of the cutoff wall backfill will be underestimated in a slug test analysis if the filter cake is not properly considered.     

Shear strength and failure mechanism of needle-punched geosynthetic clay liner

The internal shear strength of a geosynthetic clay liner (GCL) within composite liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct shear tests with five normal stress levels (250–1000 kPa) and eight displacement rates (1–200 mm/min) were conducted. The shear stress to horizontal displacement relationships exhibit well-defined peak shear strengths and significant post-peak strength reductions. The monitoring results of the thickness change indicate that the degree of volumetric contraction is related to the reorientation of fibers and dissipation of pore water pressure. Furthermore, the peak and residual shear strengths both depend on the displacement rate because of the rate-dependent tensile stiffness of needle-punched fibers and shear strength of the soil/geosynthetic interface. Through additional tests and lateral comparison, it was discovered that the shear behavior of sodium bentonite, degree of hydration, and pore water pressures all affect the shear mechanisms of the NP GCL. In particular, the failure mode transfers from fiber pullout to fiber rupture with the increase in water content as the hydrated bentonite particles facilitate the stretching of needle-punched fibers.     

Curing Characteristics,Morphological, Tensile and Thermal Properties of Bentonite-Filled Ethylene-Propylene-Diene Monomer (EPDM) Composites

Bentonite (Bt) with irregular shape and surface morphology was used as a new type of filler in EPDM. EPDM/Bt composites were prepared using a laboratory size two-roll mill by adding 0 to 70 phr Bt. The effects of Bt loading on curing characteristics, morphology, tensile and thermal properties of EPDM/Bt composite were studied. Scorch and curing time were decreased with 0 to 30 phr loading and increased subsequently at 50 and 70 phr. Tensile strength and elongation at break (E_b) were increased with increasing Bt loading from 0 to 50 phr and decreased at 70 phr, whereas the tensile modulus (M100%) shows an increasing trend with increasing Bt loading. Thermogravimetric analysis shows the enhancements of thermal properties with increasing Bt loading. Morphological studies of tensile fracture surfaces of EPDM/Bt composite proves good interaction between Bt particles and EPDM at 50 phr and formation of Bt agglomerates at 70 phr.     

膨润土的铝酸脂表面改性研究

为提高无机膨润土与有机塑料的相容性,强化两者的复合效果,研究了铝酸脂对膨润土的偶联改性行为。以沉降体积和粘度为评价指标,考察了单次物料用量、改性温度、改性剂用量及改性时间等对膨润土改性效果的影响,并利用红外光谱分析探讨了铝酸脂对膨润土的改性机理。结果表明：铝酸脂偶联剂对膨润土的改性效果明显,较佳改性条件为改性温度110 ℃,改性剂用量3.0%,改性时间30 min;铝酸脂偶联剂对膨润土的改性同时存在化学吸附和物理包覆作用。     

活化膨润土吸附Pb~(2+)离子的研究

研究了热活化及酸活化的膨润土对重金属 Pb2 +离子的吸附。结果表明 ,活化膨润土对Pb2 +离子具有较强的吸附性能 ,p H值是影响吸附的主要因素 ,较高温度热活化的膨润土具有最大的吸附容量 ,基本符合 Langmuir吸附等温线 ,离子交换和表面络合反应是主要吸附形式     

膨润土对Zn(Ⅱ)和Cd(Ⅱ)离子的吸附作用研究

在静态条件下 ,研究了膨润土对重金属离子 (如 Zn2 +、Cd2 + )的吸附与交换。结果表明 ,膨润土对重金属离子具有较强的吸附性能 ,p H值是影响吸附的主要因素 ,离子交换和表面络合反应是主要吸附形式。