Long-term performance of cement-bentonite containment wall

The paper presents hydraulic conductivity, unconfined compression strength (UCS) and triaxial test results of an 11 year old slag-cement-bentonite (CB) cut-off wall material and identifies factors affecting their long-term performance. The laboratory tests were performed on three types of CB samples ranging from contaminated block field samples to uncontaminated laboratory cast samples. The results showed that hydraulic conductivity reduces till 3 years and UCS increases till 90 days, but there after it remains constant till 11 years of age. The mean hydraulic conductivity and UCS values of block field samples are inferior and have large variability than laboratory cured samples. Such variations are mainly because of heterogeneity caused by aggressive environment and impurities within the specimen. Consolidated undrained triaxial test found that under an effective confining pressure of less than 200 kPa, tension failure occurred since the minor principal stress dropped to zero value at failure. The research outcome is useful for understanding future liability of CB wall and improving their design. © 2009 IOS Press.

Relating monolithic and granular leaching from contaminated soil treated with different cementitious binders.

This work employed a clayey, silty, sandy gravel contaminated with a mixture of metals (Cd, Cu, Pb, Ni and Zn) and diesel. The contaminated soil was treated with 5 and 10% dosages of different cementitious binders. The binders include Portland cement, cement-fly ash, cement-slag and lime-slag mixtures. Monolithic leaching from the treated soils was evaluated over a 64-day period alongside granular leachability of 49- and 84-day old samples. Surface wash-off was the predominant leaching mechanism for monolithic samples. In this condition, with data from different binders and curing ages combined, granular leachability as a function of monolithic leaching generally followed degrees 4 and 6 polynomial functions. The only exception was for Cu, which followed the multistage dose-response model. The relationship between both leaching tests varied with the type of metal, curing age/residence time of monolithic samples in the leachant, and binder formulation. The results provide useful design information on the relationship between leachability of metals from monolithic forms of S/S treated soils and the ultimate leachability in the eventual breakdown of the stabilized/solidified soil.

Initial investigation into the use of GGBS-MgO in soil stabilisation

Portland cement (PC) is the most widely used binder for ground improvement. However, there are significant environmental impacts associated with its production in terms of high energy consumption and CO2 emissions. Hence, the use of industrial by-products materials or new low-carbon footprint alternative cements has been encouraged. Ground granulated blastfurnace slag (GGBS), a by-product of the steel industry, has been successfully used for such an application, usually activated with an alkali such as lime or PC. In this study the use of MgO as a novel activator for GGBS in ground improvement of soft soils is addressed and its performance was compared to the above two conventional activators as well as PC alone. The GGBS:activator ratio used in this study was 9:1. A range of tests was performed at three curing periods (7, 28 and 90 days), including unconfined compressive strength (UCS), permeability and microstructure analysis. The results show that the MgO performed as the most efficient activator yielding the highest strength and the lowest permeability indicating a very high stabilisation efficiency of the system. © 2012 American Society of Civil Engineers.

Properties of two model soils stabilized with different blends and contents of GGBS, MgO, lime, and PC

This paper addresses the use of ground granulated blast furnace slag (GGBS) and reactive magnesia (MgO) blends for soil stabilization, comparing them with GGBS-lime blends and Portland cement (PC) for enhanced technical performance. A range of tests were conducted to investigate the properties of stabilized soils, including unconfined compressive strength (UCS), permeability, and microstructural analyses by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of GGBS:MgO ratio, binder content, soil type, and curing period were addressed. The UCS results revealed that GGBS-MgO was more efficient than GGBS-lime as a binder for soil stabilization, with an optimum MgO content in the range of 5-20% of the blends content, varying with binder content and curing age. The 28-day UCS values of the optimum GGBS-MgO mixes were up to almost four times higher than that of corresponding PC mixes. The microstructural analyses showed the hydrotalcite was produced during the GGBS hydration activated by MgO, although the main hydration products of the GGBS-MgO stabilized soils were similar to those of PC. © 2014 American Society of Civil Engineers.

Comparisons of operating envelopes for contaminated soil stabilised/solidified with different cementitious binders

This work initiated the development of operating envelopes for stabilised/solidified contaminated soils. The operating envelopes define the range of operating variables for acceptable performance of the treated soils. The study employed a soil spiked with 3,000 mg/kg each of Cd, Cu, Pb, Ni and Zn, and 10,000 mg/kg of diesel. The binders used for treatment involved Portland cement (CEMI), pulverised fuel ash (PFA), ground granulated blast furnace slag (GGBS) and hydrated lime (hlime). The specific binder formulations were CEMI, CEMI/PFA = 1:4, CEMI/GGBS = 1:9 and hlime/GGBS = 1:4. The water contents employed ranged from 13 % to 21 % (dry weight), while binder dosages ranged from 5 % to 20 % (w/w). We monitored the stabilised/solidified soils for up to 84 days using different performance tests. The tests include unconfined compressive strength (UCS), hydraulic conductivity, acid neutralisation capacity (ANC) and pH-dependent leachability of contaminants. The water content range resulted in adequate workability of the mixes but had no significant effect on leachability of contaminants. We produced design charts, representing operating envelopes, from the results generated. The charts establish relationships between water content, binder dosage and UCS; and binder dosage, leachant pH and leachability of contaminants. The work also highlights the strengths and weaknesses of the different binder formulations. © 2013 Springer-Verlag Berlin Heidelberg.

Differentiate performance of eight filter media in vertical flow constructed wetland: Removal of organic matter, nitrogen and phosphorus

A comparative study was conducted to reveal the differentiate effects of eight different filter media including gravel, zeolites, anthracite, shale, vermiculite, ceramic filter media, blast furnace steel slag and round ceramsite. The study mainly related to the eight different filter media's removal performances of organic matter, nitrogen and phosphorus in the vertical flow constructed wetland simulated system, which treating wastewater at hydraulic loading rate of 1000-2500 mm/d. The results indicated that the removal effects were closely related to the physical and chemical properties of medium materials. Anthracite-filled system had the highest removal rate for the total organic carbon (TOC), up to 70%, and the removal rates of other systems ranged from 20% to 30%. As for the five-day biochemical oxygen demand (BOD5), anthracite-filled and steel slag-filled systems had the highest removal rates, also up to 70%, as well as other systems all exceeded 50%. At the same time, for the total nitrogen (TN) and NH4(+)-N, the zeolites-filled and ceramic-filled systems had the best performances with the removal rates of more than 70%, the other way round, the removal rates of other systems were only about 20%. The distinguishable effects were also observed in removal performances of total phosphorus (TP) and total dissoluble phosphorus (TDP). The removal rates of TP and TDP in steel slag-filled systems were more than 90%, a much higher value, followed by that of the anthracite-filled system, more than 60%, but those of other systems being the less. Our study provided a potential mechanism to optimize the filter media design for the vertical flow constructed wetlands.

Properties and microstructure of GGBS-magnesia pastes

Reactive magnesia (MgO) was used as an alkali activator for ground granulated blast-furnace slag (GGBS) and its activating efficiency was investigated compared with hydrated lime. GGBS-MgO and GGBS-hydrated lime paste samples with different compositions and different water to solid ratios were prepared and cured for different periods. A range of tests was conducted to investigate the properties and microstructure of the pastes, including compressive strength, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray and thermogravimetric analysis. The results showed that the reactive MgO acts as an effective alkali activator of GGBS, achieving higher 28-day compressive strength than that of the corresponding GGBS-hydrated lime system. The extensive microstructural investigation indicated that the main hydration product of reactive MgO-activated GGBS and hydrated lime-activated GGBS systems was hydrated calcium silicate, but there was much more hydrotalcite present in the former, which contributed to its superior 28-day compressive strength.

INFLUENCE OF LINEAR ALKYLBENZENE SULFONATE (LAS) AS ORGANIC COSOLVENT ON LEACHING BEHAVIOR OF PCDD/FS FROM FLY-ASH AND SOIL

The leaching of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was measured in soil and standard fly ash column eluted with pure water and linear alkylbenzene sulfonate (LAS)- water. The data obtained were used to evaluate the leachability of PCDD/Fs from waste dump like incineration residual slag and fly ash deposition. The leaching rate was shown to be increased significantly by using LAS water. The leachate contents of PCDD/Fs were above their known water solubility. Concentration of PCDD/Fs in the leachates as well as the relative leaching (calculated on the fly ash content) increased with increasing chlorinating degree and decreasing water solubility. LAS above the critical micelle concentration (CMC) probably enhances PCDD/Fs solubility.

The Deposition and Burning Characteristics During Slagging Co-Firing Coal and Wood: Modeling and Numerical Simulation

Numerical analysis was used to study the deposition and burning characteristics of combining co-combustion with slagging combustion technologies in this paper. The pyrolysis and burning kinetic models of different fuels were implanted into the WBSF-PCC2 (wall burning and slag flow in pulverized co-combustion) computation code, and then the slagging and co-combustion characteristicsespecially the wall burning mechanism of different solid fuels and their effects on the whole burning behavior in the cylindrical combustor at different mixing ratios under the condition of keeping the heat input samewere simulated numerically. The results showed that adding wood powder at 25% mass fraction can increase the temperature at the initial stage of combustion, which is helpful to utilize the front space of the combustor. Adding wood powder at a 25% mass fraction can increase the reaction rate at the initial combustion stage; also, the coal ignitability is improved, and the burnout efficiency is enhanced by about 5% of suspension and deposition particles, which is helpful for coal particles to burn entirely and for combustion devices to minimize their dimensions or sizes. The results also showed that adding wood powder at a proper ratio is helpful to keep the combustion stability, not only because of the enhancement for the burning characteristics, but also because the running slag layer structure can be changed more continuously, which is very important for avoiding the abnormal slag accumulation in the slagging combustor. The theoretic analysis in this paper proves that unification of co-combustion and slagging combustion technologies is feasible, though more comprehensive and rigorous research is needed.

利用城乡废弃资源提高土壤保水保肥功能

以生活炉渣、建筑废料、生物秸秆等城乡废弃资源为原料,制备一种面向节水农业的环保新产品———土壤扩蓄增容肥.实验结果表明:在棉花苗期,6种土壤扩蓄增容肥配方的节水效果较土对照高300倍,干物质积累增加4.77%~50.00%.6种配方的皮棉产量均比对照高,增产幅度为4.70%~14.25%,纤维物理性状有所改善.产量高低顺序依次是,玉米秸秆>小麦秸秆>生活炉渣>秸秆木炭>建筑废料>煤矸石>CK.利用城乡废弃资源生产的扩蓄增容剂,不仅能改良土壤物理和化学性状,更是棉花增产、优质、节水、降低生产成本的关键技术措施之一,具有显著的生态效益、社会效益和经济效益.

Rare earth complexes with Ge-132 and their catalytic hydrolysis to phosphatide bond of mononucleotide

The complexes of a series of rare earths with Ge-132 have been prepared. The carboxyl anions of Ge-132 molecule were coordinated to rare earth ion with chelate style. In the complexes molecule, the GeO3/2 group of Ge-132 were hydrolyzed to become -Ge(OH)(3) group, and later does:not coordinate with rare earth ions. All of the complexes possess similar properties. In aqueous solution of pH 6 and 50 degrees C, these complexes can obviously selectively catalytically hydrolize the phosphatide bond of 5'-AMP and 5'-dAMP into phosphatic acid and riboside.

ELECTROCHEMICAL MECHANISM FOR FULLERENE FORMATION IN PLASMA ARCS

During the synthesis of fullerenes by dc plasma arcs, it has been found that the anodic graphite rod consistently burns up, while the cathodic graphite rod grows slag at its end. Further investigations revealed that the anodic and cathodic graphite rods p

转炉钢渣对海洋生态环境影响及碳的生物利用探索研究

利用“铁肥”方法增加海洋初级生产力、吸收大气中的CO2、降低温室效应是目前国际上的一个研究热点。为此，本文利用炼钢企业产生的废料转炉钢渣，系统研究了其对海洋微藻生长的影响， 同时研究了转炉钢渣对海水水质及海洋生物的影响，探讨了其作为“铁肥”材料的可行性。 本文首先研究了转炉钢渣对海水水质的影响，包括金属、营养盐、pH、COD及浊度等理化参数。研究发现，在天然海水中加入转炉钢渣后营养盐均有不同程度的溶出；实验条件下，在天然海水和人工海水中加入钢渣，金属大部份被吸附，个别金属溶出，但基本都达到了一、二类海水标准，而pH明显增高，大多超过了海水水质三、四级（6.88.8）的范围，COD低于一类海水水质标准。实验结果显示，钢渣粒度越小、浓度越大，水质浊度越大，但钢渣的比重一般较大，在水体中可以较快的沉降，所以在实际应用过程中不会对水体的透明度造成不良影响。 研究了转炉钢渣对典型海洋底栖生物（紫贻贝）、海洋游泳生物（日本对虾和中国对虾幼虾）的影响。在实验浓度范围内，钢渣对紫贻贝的急性毒性作用基本可以忽略，但紫贻贝的生长率和摄食率随钢渣浓度的增加有所下降，血细胞个数有所下降，但形态没有显著变化，对紫贻贝的免疫功能没有太大影响。钢渣对日本对虾幼虾的半致死浓度为1.62g/L，对中国对虾幼虾的半致死浓度要高于日本对虾，说明在实验条件下中国对虾幼虾的适应能力高于日本对虾幼虾。 另外，重点考察了转炉钢渣对海洋浮游植物－赤潮异弯藻和中肋骨条藻生长的影响，发现加入钢渣以后，相对于对照组微藻生物量显著增加。当钢渣浓度为124248mg/L时赤潮异弯藻的生物量达到最大，当钢渣浓度达到61124mg/L时，中肋骨条藻的生物量最大；钢渣对两种微藻生长的影响规律是相同的，但是影响程度因不同藻种而有所不同，其中对中肋骨条藻的促进作用更加显著，可能与钢渣中能溶出较大量的硅酸盐有关。在室内实验的基础上，初步估算了通过钢渣对微藻生长的促进作用，近海每平方公里海域对二氧化碳吸收的增加量。

Flocculation and removal of the brown tide organism, Aureococcus anophagefferens (Chrysophyceae), using clays

Previous attempts to remove the brown tide organism, Aureococcus anophagefferens, through flocculation with clays have been unsuccessful, in spite of adopting concentrations and dispersal protocols that yielded excellent cell removal efficiency (RE>90%) with other species, so a study was planned to improve cell removal. Four modifications in clay preparation and dispersal were explored: 1) varying the salinity of the clay suspension; 2) mixing of the clay-cell suspension after clay addition; 3) varying of concentration of the initial clay stock; 4) pulsed loading of the clay slurry. The effect of salinity was dependent on the clay mineral type: phosphatic clay (IMC-P2) had a higher RE than kaolinite (H-DP) when seawater was used to disperse the clay, but H-DP removed cells more efficiently when suspended in distilled water prior to application. Mixing after dispersal approximately doubled RE for both clays compared to when the slurry was layered over the culture surface. Lowering the concentration of clay stock and pulsing the clay loading increased RE, regardless of mineral type. However, this increase was more apparent for clays dispersed in seawater than in distilled water. In general, application procedures that decrease the rate of self-aggregation among the clay particles and increase the collision frequency between clay particles and A. anophagefferens achieve higher cell removal efficiency. These empirical studies demonstrated that clays might be an important control option for the brown tide organism, given the proper attention to preparation, dispersal methods, environmental impacts, and the hydrodynamic properties of the system being treated. Implications for the treatment of brown tides in the field are discussed.