Hydraulic Conductivity and Compressibility of Soil-Bentonite Backfill Amended with Activated Carbon

Flexible-wall permeability tests and rigid-wall consolidation/permeability tests were performed to evaluate the hydraulic conductivity and compressibility of a model soil-bentonite (SB) backfill amended with granular activated carbon (GAC) or powdered activated carbon (PAC). The tests were performed as part of an assessment of enhanced SB backfill with improved attenuation capacity for greater longevity of barrier containment performance. Backfill specimens containing fine sand, 5.8% sodium bentonite, and GAC or PAC (0, 2, 5, and 10% by dry weight) were prepared to target slumps of 125±12.5?mm. Hydraulic conductivity (k) and compressibility of backfill test specimens were measured in consolidometers as a function of effective stress, σ′ (24 ? σ′ ? 1,532?kPa), whereas flexible-wall k was measured for backfill specimens consolidated to σ′ = 34.5?kPa. The results indicate that addition of GAC has little impact on the hydraulic and consolidation properties of the backfill, whereas addition of PAC causes a decrease in k and consolidation coefficient (cv) and a slight increase in compression index (Cc). Differences in behavior between GAC-amended backfills and PAC-amended backfills are attributed primarily to differences in GAC and PAC particle size.     

膨润土对Cd2+的吸附作用及影响因素

研究了盐亭钙基膨润土的理化性质及其对Cd^2 的吸附作用。实验研究结果表明，该膨润土对重金属离子Cd^2 有较好的吸附作用，吸附作用受溶液pH值影响明显。膨润土对重金属离子的吸附主要通过离子交换作用进行，增加膨润土吸附剂添加量或加大溶液中Cd^2 浓度，均有利于提高膨润土对Cd^2 的吸附总量。膨润土对Cd^2 的吸附模式符合Frendlish方程。     

在微波场中合成矿物无机凝胶

以天然矿物为原料,添加其他化学试剂在微波场中合成了矿物无机凝胶,反应时间由常规的6~8h减至45m in,反应温度由230~310℃减至90~95℃。经XRD、DTA、IR和化学成分分析,均表明其特征与天然矿物无机凝胶具有很好的吻合性。     

新疆夏子街膨润土的柱撑化改性及吸附性能研究

以新疆夏子街钠基膨润土为原料,制备了无机柱撑膨润土和无机—有机柱撑膨润土,考察了溶剂及配比等对柱撑膨润土的影响。无机柱撑膨润土的合成条件为[OH-]/[Al3+]=2.2,Al3+/土=15mmol/g。膨润土应用于城市污水的吸附研究结果表明:膨润土原矿对废水中COD去除率为38.5%,无机柱撑膨润土在最优吸附条件下对废水中COD去除率达到91.85%,无机—有机柱撑膨润土在最优吸附条件下对废水中COD去除率达到97.12%。     

Utilisation of waste clay from boron production as a landfill liner material

The objective of this study was to investigate the potential utilisation of waste clay from boron production in sanitary landfills. The waste clay (CW) was mixed with bentonite (B) and waste tyre (TW) at different ratios. Results show that, any of the CW-TW mixtures were not acceptable to use in landfills because of insufficient bearing capacity values. On the other hand, CW and 2B/98CW mixtures have sufficient values from the point of experimental tests. As a conclusion, it has been concluded that CW can be used as a liner material for landfills without an addition.     

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).     

Investigating the mechanism of downslope bentonite erosion in GCL liners using X-Ray CT

Exposed composite GMB-GCL liners are at risk of downslope bentonite erosion caused by the release of low ionic strength condensed water onto the top surface of the GCL following daily solar heating. This paper investigates the use of X-ray computed tomography (X-ray CT) to quantify the thinning of the bentonite layer and the application of X-ray diffraction techniques (XRD) to investigate the changes in clay chemistry (if any) of the bentonite from the virgin GCL to the eroded bentonite. The effect of specimen size and scanning orientation was investigated resulting in a revised testing procedure in which the CT scanning orientation was changed from horizontal to vertical to permit a longer test specimen which was also sealed at the bottom edge to minimise the edge boundary condition. The X-ray CT results provide highly visual evidence that a) bentonite thinning immediately under the upper cover geotextile is the initial location of erosion, and b) the bentonite core erodes at a significantly higher rate when not covered by a geotextile than when covered by a geotextile. These observations indicate that the upper geotextile of the GCL plays a significant role in controlling the rate of bentonite erosion. Finally, a comparison of the virgin and runoff bentonite properties was conducted to investigate potential changes in swell index, X-ray diffraction results, and concentration of Na and Ca cations. The runoff bentonite was observed to had a significantly higher swell index (40?ml/2?g) than the virgin bentonite (28?ml/2?g) and lower Na and Ca concentrations. This finding is consistent with the observation from XRD analyses of the runoff bentonite which illustrate that the clay fraction of the bentonite is preferentially eroded by the application of DI water.     

Bentonite deposits of Northern Patagonia

Some Argentine North Patagonia bentonite deposits have been characterised by chemical and differential thermal analysis (DTA), X-ray diffraction and Isoelectric Point (IEP), Cation Exchange capacity (CEC) and specific surface area (S) determinations.Samples with high degree of tetrahedral isomorphic substitution, and consequently high interlayer cation charge compensation, would be used as organic pollutant adsorbent when the adsorption was a cation exchange mechanism.     

Elemental sulfur fertilizers and their use on crops and pastures

This paper reviews the use of elemental sulfur (S°) as a fertiliser and its efficacy in different pastoral and cropping situations. The effect of S° particle size on rate of oxidation is critical to the effectiveness of S° fertilisers. Emphasis is therefore centred on the issue of how particle size of S° affects the rate of oxidation in different environments and cropping systems, and the size of S° in different S° fertiliser products. Rate constants of S° oxidation offer the opportunity to generalise particle size relationships needed in S° fertilisers for different crops in different environments, or alternatively, to calculate the agronomic effectiveness of different S° fertilisers available on the market. Conversely they offer a technique to set specifications as to S° particle size requirements, which together with dispersion rate specifications provide the basis for the design of S° fertilisers for specified crops and environments.     

新型活化工艺制备超轻硅钙保温材料的研究

针对目前国内硅钙材料生产中原材料单一、产品性能差等问题，以膨润土为硅质原料，采用新型活化工艺，成功研制出超轻量(表现密度＜170kg/m^3)、低成本的硅钙产品，同时也改善了硅钙产品的保温性能。