插层法制备膨润土-有机复合高性能吸水材料的试验研究

研究了膨润土插层聚合制备吸水材料的过程中各因素对膨润土-有机复合高性能吸水材料吸水性能的影响，探索低成本、工艺简单的方法制备出高性能吸水材料，通过XRD、SEM对材料进行了表征，该高性能吸水材料的推广将使有助于新疆优势矿产资源得以利用，可以推动当地的经济发展。     

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.     

Catalytic oxidation of aromatic VOCs with Cr or Pd-impregnated Al-pillared bentonite: Byproduct formation and deactivation studies

The catalytic behavior of chromium and palladium-impregnated Al-pillared bentonite for the oxidation of aromatic VOCs, i.e. chlorobenzene or xylene, was investigated. The Cr-impregnated bentonite showed high activity for the total oxidation of cholorobenzene and xylene but the materials were completely deactivated during the reaction at 600 °C. Atomic absorption, XPS, XRD and TG analyses suggested three main causes for the deactivation, i.e. the loss of Cr due to the formation of volatile CrO₂Cl₂, a strong decrease on the surface area due to the collapse of the pillars and the formation of coke. For the Pd supported pillared bentonite, the impregnation procedure completely destroyed the Al-pillars but produced a very active and stable catalyst to oxidize aromatic contaminants. However, in the case of chlorobenzene almost 20% yield of the hazardous hexachlorobenzene was obtained likely by an oxychlorination process.     

Coupled Thermohydromechanical Modeling of the Full-Scale In Situ Test “Prototype Repository”

The Prototype Repository project represents a full-scale in situ test of the Swedish concept for high level radioactive waste disposal in deep geological repositories, being conducted at the underground ?sp? Hard Rock Laboratory and managed by SKB (Swedish Agency for Radioactive Waste Disposal). Instead of canisters with radioactive material, heaters installed in cylindrical containers surrounded by compacted bentonite have been used in the test. A large number of thermohydromechanical parameters for materials used in the test were carefully determined based on the latest laboratory experiments and site investigation. After comparison among six simulation models, some valuable conclusions are made about the interaction effects of six deposition holes and the effects of thermohydrogas–mechanical coupling. A three-dimensional coupled thermohydraulic model was selected for the prediction of temperature, whereas an axisymmetric two-dimensional coupled thermohydromechanical model was selected for the prediction of relative humidity and stresses for the system of heater–bentonite–near rock. Selected results of temperature, relative humidity, and total stress are presented and discussed, and the agreement between the compared variables highlights the ability of the developed models to reproduce the complex coupled processes involved in the test.     

Preparation and properties of polyacrylate/bentonite superabsorbent hybrid via intercalated polymerization

Polyacrylate intercalated bentonite superabsorbent hybrid had been prepared by means of solution polymerization with intercalating, polymerizing and crosslinking reaction. The partially neutralized acrylic acid (NaA) was intercalated, polymerized and crosslinked to bentonite. The initiator was potassium persulfate and the crosslinking agent was sugar. The structure of the polyacrylate/hybrid was determined by FT-IR and XRD. The results showed that bentonite was intercalated by polyacrylate. The layers' spacing of bentonite was enlarged. The various factors, such as the degree of neutralization, the consumption of monomer, the amount of initiator and crosslinking agent and the amount of bentonite, which affected the resin's water absorbency, were studied through orthogonal experiments. The optimum conditions showed that the ratio (wt) of bentonite to monomer was 1/2, the degree of neutralization was 75% (mol), the initiator content was 3%, and the crosslinker content was 5%. The cost of the superabsorbent has decreased by 30%, whereas its water absorbency was about 120 g/g for water, and 30-36 g/g for saline solution.     

Diffusion with micro-sorption in bentonite: evaluation by molecular dynamics and homogenization analysis

We here give a numerical analysis method of a diffusion problem including sorption chemistry for bentonite clay. Bentonite predominantly consists of the microscopic smectitic clay minerals (mainly montmorillonite and beidellite). Physico-chemical properties of smectite clays such as diffusivity of chemical species and adsorptivity on surface of clay mineral are characterized by crystalline structure of hydrated smectite minerals. To obtain the microscopic properties of the hydrated smectite, the molecular behavior is analyzed by a molecular dynamic (MD) simulation. We understand at least two types of adsorption are formed on the smectite surface; outer sphere complex and inner sphere complex. The inner sphere complex occurs on the edge sites of clay minerals. The amount of mono-layer of cations on the edge surface is considered as the adsorptivity of smectite in the microscopic level. A multiscale homogenization analysis (HA) is applied to extend the microscopic characteristics of the hydrated smectite to the macroscopic behavior. The diffusion and adsorption of a radioactive specie, cesium (Cs), is introduced by this analysis. The calculated results appear to be acceptable.     

膨润土负载壳聚糖吸附镍离子研究

将壳聚糖负载在膨润土上,得到一种复合吸附剂,并利用其进行含Ni2 废水吸附试验,当吸附剂质量为0．5 g,在最佳条件下对初始质量浓度为10 mg／L的含Ni2 废水去除率达到99％左右。傅立叶变换红外光谱研究表明,吸附过程中Ni2 取代了膨润土中的金属离子,其中含有的少量壳聚糖也参与了反应,反应位置为氨基。     

Enhanced pesticide adsorption by thermally modified bentonites

Wyoming bentonite was calcined at 350–550° for 1, 3, and 12 h, dispersed in water and freeze-dried. Calcination at 350–450°C for 12 h decreased the specific surface area strongly. At higher calcination temperatures, the surface area became similar to the value of the uncalcined bentonite (24 m²/g). The micropore (diameter <2 nm) volume of the calcined samples was very small (<0.2 μl). In contrast, the mesopore (diameter 2–50 nm) volume increased sharply when the bentonite was calcined at >450°C. The total specific surface area mainly comprised the mesopore surface area. The Wyoming bentonite used in these experiments adsorbed considerable amounts of metolachlor from aqueous solutions, and the adsorption was enhanced by calcinating the bentonite. The metolachlor molecules, very likely, interact with aluminum ions or oligomeric hydroxoaluminum cations enriched on the edges of the silicate layers as a consequence of the thermal attack to the edges. A pronounced adsorption–desorption hysteresis is advantageous for using these bentonites in slow-release pesticide formulations.     

酸化改性膨润土对柴油中硫化物的吸附性能研究

按一定比例混合酸(硫酸/盐酸)对膨润土进行了酸化改性,考察了改性膨润土对柴油中含硫化合物的吸附性能,试验结果表明:酸化处理后,膨润土对柴油中硫化物的吸附能力显著提高。当H2SO4/HCl比例为25%/30%、吸附时间为60min、吸附剂/柴油比为1∶6时,吸附效果较好。其中,先酸化再经热处理后的膨润土脱硫率最高,可达44.01%。     

粘土矿物对废水中Cu~(2+)、Cd~(2+)、Cr~(3+)的吸附实验研究

采用膨润土和高岭土对重金属的吸附性能进行了实验研究。结果表明:pH对吸附效果有明显影响,当pH值增大时,膨润土和高岭土对重金属的吸附量也随之增大。初始浓度相同的情况下,蒙脱石对重金属的吸附大于高岭土,而且都是随初始浓度的增加而增大。蒙脱石和高岭土对三种不同的重金属离子的吸附能力的强弱都是Cr>Cu>Cd,用Langmuir吸附方程式对吸附等温线进行拟合,相关系数达到0.98以上。