scholarly journals Experimental Study on the Fine-Grained Uranium Tailings Reinforced by MICP

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Rong Gui ◽  
Yu-xiang Pan ◽  
De-xin Ding ◽  
Yong Liu ◽  
Zhi-jun Zhang
Keyword(s):  
Discharge Rate ◽  
Physiological Activity ◽  
Friction Angle ◽  
Solution Concentration ◽  
High Concentration ◽  
Sand Column ◽  
Sporosarcina Pasteurii ◽  
Fine Grained ◽  
And Migration ◽  
Uranium Tailings

Sporosarcina Pasteurii was chosen for the experiment to study the effect and mechanism of fine-grained uranium tailings reinforced by MICP. The biochemical characteristics of strains and microbial immobilization in uranium tailings were analyzed. The results showed that the CaCO3 production rate is positively correlated with the physiological activity of Sporosarcina Pasteurii and the concentration of calcium sources, and the higher the solution concentration of CaCl2, the lower the discharge rate of bacterial liquid from the sand column, but high concentration of CaCl2 solution will affect the uniform distribution and migration of bacteria in the uranium tailings. After 16 days, the direct shear was used to test the reinforcement effects of fine-grained uranium tailings by MICP. The cohesive force and the internal friction angle of fine-grained uranium tailings were increased by 140.1% and 46.7%. The production amount of CaCO3 is 138.89 kg/m3. The results showed that the MICP-reinforced technology can effectively improve the shear strength of the uranium tailings, and the experiment provides a new method for the reinforcement of the fine-grained uranium tailings dam.

scholarly journals Effect of Different Mineralization Modes on Strengthening Calcareous Sand under Simulated Seawater Conditions

2021 ◽  
Vol 13 (15) ◽  
pp. 8265
Author(s):  
Shiyu Liu ◽  
Bowen Dong ◽  
Jin Yu ◽  
Yanyan Cai ◽  
Xingqian Peng ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Construction Projects ◽  
Construction Material ◽  
X Ray Diffraction ◽  
Calcareous Sand ◽  
Sand Column ◽  
Sporosarcina Pasteurii ◽  
Phosphate Mineralization ◽  
Filling Water ◽  
Simulated Seawater

Calcareous sand, as a blow-fill or construction material, is widely used in island and reef construction projects in marine environments after treatment. When microorganism-induced mineralization is used to strengthen calcareous sand, salinity and other conditions in the marine environment will adversely affect microorganisms or their mineralization process. For this reason, the two environmental conditions created by deionized water and simulated seawater were introduced to explore their effects on the growth and urease activity of Sporosarcina pasteurii. Then, the changes in the permeability and mechanical strength of calcareous sand under different mineralization methods were compared by one-dimensional sand column tests. Finally, the reinforcement mechanism was compared and analyzed based on the results of scanning electron microscopy and X-ray diffraction tests. The results show that Sporosarcina pasteurii can induce carbonate and phosphate precipitation and mineralization to strengthen calcareous sand in simulated seawater. The mineralized products greatly reduce the permeability of calcareous sand and significantly improve the mechanical strength by wrapping calcareous sand particles, filling water seepage channels and cementing adjacent particles. The reinforcement effect of carbonate mineralization is better than that of phosphate mineralization, but phosphate mineralization has less impact on the environment during the treatment process.

scholarly journals Tuned S-Scheme Cu2S_TiO2_WO3 Heterostructure Photocatalyst toward S-Metolachlor (S-MCh) Herbicide Removal

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2231
Author(s):  
Alexandru Enesca ◽  
Luminita Isac
Keyword(s):  
Sol Gel ◽  
Annealing Treatment ◽  
Atomic Ratio ◽  
High Concentration ◽  
Step Procedure ◽  
Constant Rate ◽  
Efficient Charge ◽  
Crystallite Sizes ◽  
Oxygen Excess ◽  
And Migration

A dual S-scheme Cu2S_TiO2_WO3 heterostructure was constructed by sol–gel method using a two-step procedure. Due to the synthesis parameters and annealing treatment the heterostructure is characterized by sulfur deficit and oxygen excess allowing the passivation of oxygen vacancies. The photocatalytic activity was evaluated under UV and UV–Vis irradiation scenarios using S-MCh as reference pollutant. The heterostructure is composed on orthorhombic Cu2S, anatase TiO2 and monoclinic WO3 with crystallite sizes varying from 65.2 Å for Cu2S to 97.1 Å for WO3. The heterostructure exhibit a dense morphology with pellets and particle-like morphology closely combined in a relatively compact assembly. The surface elemental composition indicate that the heterostructure maintain a similar atomic ratio as established during the synthesis with a slight sulfur deficit due to the annealing treatments. The results indicate that the three-component heterostructure have higher photocatalytic efficiency (61%) comparing with two-component heterostructure or bare components. Moreover, Cu2S_TiO2_WO3 exhibit a superior constant rate (0.114 s−1) due to the high concentration of photogenerated charge carriers, efficient charge separation and migration.

Preparation of Silicalite-1 Membranes on α-Al2O3 Tubes and its Concentration Performance of Low Ethanol/water Mixtures

2012 ◽  
Vol 608-609 ◽  
pp. 1337-1341
Author(s):  
Hong Liang Chen ◽  
Ji Song Yang ◽  
Yan Wang ◽  
Hui Ying Li ◽  
Xin Xin Li ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solution Concentration ◽  
High Concentration ◽  
Separation Selectivity ◽  
Naoh Solution

Silicalite-1 membranes were successfully synthesized on α-Al2O3 tubes by in-situ hydrothermal synthesis after filling the tubes with water and glycerol mixtures, and all the membranes show high concentration performance towards ethanol/water mixtures after pretreating tubes with different NaOH solution. The results show that the flux enhances with the enhancement of NaOH solution concentration, but the separation selectivity decreases with the enhancement of NaOH solution concentration. After pretreating the α-Al2O3 tubes with different NaOH solution, the weight of all the α-Al2O3 tube decreases, but the Si/Al ratio increases, which shows that suitable pretreatment of α-Al2O3 is useful for improving the hydrophobicity of silicalite-1 membranes.

Chemical Durability of High Burnup Lwr-Spent Fuel in Concentrated Salt Solutions

1993 ◽  
Vol 333 ◽  
Author(s):  
A. Loida ◽  
B. Grambow ◽  
P. Dressier ◽  
K. Friese ◽  
H. Geckeis ◽  
...  
Keyword(s):  
Surface Area ◽  
Volume Ratio ◽  
Sample Surface ◽  
Solution Concentration ◽  
Reaction Rates ◽  
Spent Fuel ◽  
Intrinsic Dissolution ◽  
Fine Grained ◽  
High Burnup ◽  
Saturation Effects

ABSTRACTHigh-burnup (<50 MWd/kgU) spent fuel samples of various sizes were exposed to NaCl solutions under static, anaerobic and reducing conditions. The accumulated corrosion time was about 200 days. Gas phase and leach solutions were analyzed. By dissolving mm sized fragments in large volumes of solution, saturation effects were avoided and upper limits for intrinsic dissolution rates of about 5-20 mg/(m2d) were measured. Surface area normalized reaction rates were significantly lower when using fine grained fuel powder (estimated sample surface area to solution volume ratio S/V ca. 3000 m-1), indicating saturation effects. The maximum concentrations of Pu and Am in the tests are close to reported solubility limited concentrations in pure 5m NaCl solutions in the absence of radiolysis effects. The presence of iron effectively reduces the solution concentration of all measured radionuclides (except Cs).

A REVIEW OF THE HYDROCARBON HABITAT OF THE EASTERN AND CENTRAL BARROW — DAMPIER SUB-BASIN, WESTERN AUSTRALIA

1985 ◽  
Vol 25 (1) ◽  
pp. 154 ◽  
Author(s):  
E. Kopsen ◽  
G. McGann
Keyword(s):  
Coarse Grained ◽  
Hydrocarbon Source Rock ◽  
Mixed Composition ◽  
Fine Grained ◽  
Third Phase ◽  
Dynamic Charging ◽  
Rich Liquid ◽  
Northern Carnarvon Basin ◽  
And Migration ◽  
Carnarvon Basin

The most completely known section of the Barrow- Dampier Sub-basin in the northern Carnarvon Basin of the Northwest Shelf comprises three depositional super- cycles spanning the Triassic to the Tertiary. Each cycle is made up of an initial transgressive section of mainly fine-grained clastics overlain by a thick, extensive, off- lapping sequence of coarse-grained deposits. The transgressive sedimentary package typically contains a coarse basal unit overlain by a thick, argillaceous unit, whereas the progradational package changes character in each cycle, representing increasingly open marine conditions as the depocentre and its palaeogeography evolved. Continental siliciciastics at the end of the Triassic Supercycle contrast with the marine-marginal marine siliciciastics at the end of the Jurassic-Neocomian Supercycle and the prograding Tertiary carbonate wedge of the youngest cycle. Each of these gross sequences has a distinctive seismic signature upon which are superimposed stratigraphic features reflecting basin evolution from a broad intra-continental depocentre to a mature, passive continental margin basin.In the area east of Barrow Island, potential hydrocarbon source rock quality and richness varies between each cycle but potential source beds frequently occur at similar levels within each supercycle. The Dingo Claystone within the Jurassic-Neocomian depositional package contains by far the thickest and most extensive potential sources in the area and is likely to be the source for most of the hydrocarbon liquids discovered to date in the northern Carnarvon Basin (with the probable exclusion of the majority of the Rankin Platform condensates).The occurrence of oils of mixed composition and considerable variability beneath the Muderong Shale regional seal in areas of low thermal maturity suggests that many of the hydrocarbon liquids have undergone considerable vertical migration and have also a complex genesis. Furthermore, saturate-rich liquid hydrocarbons overprinting an older biodegraded oil are recognised in a number of wells along the basin margin hingeline. The likely migration and entrapment model for the majority of hydrocarbons discovered to date in the area under review involves dynamic charging of reservoirs, mainly during the Tertiary. Two main pulses of generation and migration are recognised in the eastern portion of the sub -basin, and a third phase is probably occuring at present-day, west of Barrow Island.

Sediment contamination by heavy metals in a lock-regulated section of the River Neckar

1995 ◽  
Vol 46 (1) ◽  
pp. 101 ◽  
Author(s):  
U Kern ◽  
B Westrich
Keyword(s):  
Heavy Metals ◽  
Principal Component ◽  
Coarse Grained ◽  
Acid Neutralizing Capacity ◽  
High Concentration ◽  
Fine Grained ◽  
Neutralizing Capacity ◽  
Sediment Fraction ◽  
Sediment Layers ◽  
Different Sources

For a lock-regulated reach of the River Neckar at Lauffen, Germany, results from sediment core analysis are presented. It is observed that sediment layers with a high concentration of heavy metals, especially cadmium, are covered by younger, less polluted sediment layers. A principal component analysis separated the parameters measured into three groups: heavy metals from human activities (Cd, Cr, Ni, Pb, Zn), metals from natural sources (Co, Fe, Mn), and inorganic carbon. Within the fine-grained sediment fraction containing particles smaller than 20 μm, a higher concentration of anthropogenic trace metals was found in fine-grained samples than in coarse-grained samples, whereas Co, Fe and Mn showed the opposite tendency. Obviously, this is due to two different sources of fine-grained material: sewage flocs and natural erosion particles. Acid-producing capacity (APC) and acid-neutralizing capacity (ANC) are calculated for both pore water and particulate matter of the sediment. At a depth of 20 cm, APC and ANC are controlled by the sediment matrix. ANC, which is due to calcium carbonate, is 20 times higher than APC, which is predominantly due to reduced sulfur components. Therefore, oxidation of sediment of the River Neckar does not lead to acidification.

scholarly journals Experimental Investigation of Water–Sand Mixed Fluid Initiation and Migration in Porous Skeleton during Water and Sand Inrush

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18 ◽  
Author(s):  
Xin Yang ◽  
Yong J. Liu ◽  
Ming Xue ◽  
Tian H. Yang ◽  
Bin Yang
Keyword(s):  
Structural Instability ◽  
Sand Particle ◽  
Incipient Motion ◽  
High Concentration ◽  
Sand Mixture ◽  
Porous Skeleton ◽  
Key Factor ◽  
Motion Characteristics ◽  
And Migration ◽  
Mixed Fluid

Water–sand inrush is one of the most serious disasters for mining in China. The evaluation of the occurrence and development of a high-concentration water and sand mixed fluid is an important issue for mining in China. In this study, contraposing to the 3 phases of water–sand inrush, three kinds of experiments are designed for the investigation of initiation, development, and occurrence of the disaster. A new sand–water transport testing system is setup to perform the tests. The results show that there are two key points in the disaster: (1) sand particle incipient motion and (2) porous skeleton structural instability. The incipient motion of sand grains is accompanied with the phenomena of volumetric dilatation and granular fluidization. The critical velocity of the incipient motion of the water–sand mixed fluid is significantly affected by the particle size and external stress. The interaction between water and sand grains is the key factor affecting the motion characteristics of water–sand mixture. When the hydraulic conditions exceed the threshold, the water and sand grains are mutually promoted, and the aquifer skeleton becomes unstable. Furthermore, during the water–sand inrush, the curves of volumetric flow rates of sand and water, respectively, for different samples manifest as two distinct waveforms.

Study on Corrosion Resistant Performance of Sulfoaluminate Cement

2013 ◽  
Vol 710 ◽  
pp. 362-366
Author(s):  
Hao Yu ◽  
Jian Meng Li ◽  
Huang Xin
Keyword(s):  
Salt Solution ◽  
Saline Soil ◽  
Salt Lake ◽  
Solution Concentration ◽  
Cementitious Materials ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
High Concentration ◽  
Underground Engineering ◽  
High Durability

In the salt lake areas in China, the ordinary cement concrete can be corroded by the salt in the saline soil seriously, and the application of ordinary portland cement concrete in this area is impeded. Therfore, some new cementitious materials which has high durability should be searched in order to be used in the underground engineering in saline soil areas. In this study, the sulfoaluminate cement is immersed into the salt solution that has high concentration Mg2+, Cl-, SO42-, and the complex solution of them. The corrosion resistance performance of sulfoaluminate cement against high concentration salt solution is tested. The results indicate that Sulfoaluminate cement has perfect durability against sulfate corrosion whose concentration is in the scope of this test. Sulfoaluminate cement can not be corroded by MgCl2 solution when MgCl2 solution concentration is lower than degree 3; but when the concentration of MgCl2 solution reaches degree 4, MgCl2 solution could corrode the sulfoaluminate cement seriously. The corrosion of the specimens immersed in MgCl2 solution whose concentration is degree 4 is caused by the composite action of Mg2+ and Cl-.

Seasonal vertical distribution and diel migration of zooplankton in a temperate stratified lake

Biologia ◽  
2011 ◽  
Vol 66 (2) ◽  
Author(s):  
Evangelia Doulka ◽  
George Kehayias
Keyword(s):  
Vertical Distribution ◽  
Zooplankton Community ◽  
Abiotic Factor ◽  
High Concentration ◽  
Diel Migration ◽  
Four Seasons ◽  
Diel Vertical Migrations ◽  
Vertical Segregation ◽  
And Migration ◽  
The Vertical Distribution

AbstractThe investigation of the vertical distribution of the zooplankton community in the temperate Lake Trichonis during four seasons in 2005, showed the existence of vertical segregation among species, ontogenetic stages and sexes within and between the major groups. In each season, the two or three more abundant rotifer species distributed at separate depth layers, while this feature was maintained during the entire 24 h period, since no diel vertical migrations (DVM) were performed. In contrast, the crustacean community, comprised mainly by the calanoid copepod Eudiaptomus drieschi and the cladoceran Diaphanosoma orghidani, showed various patterns of DVM, being more pronounced in spring and summer. Females of E. drieschi distributed deeper than males, while the copepod nauplii were found mainly in the surface layer in all four seasons. Temperature was the most important abiotic factor affecting directly and indirectly the vertical distribution and migration of various species. During stratification, the metalimnion was the most productive layer in Lake Trichonis, having maximum values of dissolved oxygen and low transparency due to high concentration of organic matter and phytoplankton. The DVM patterns of the crustaceans indicate that the metalimnion acts probably as a daylight refuge against predation by Atherina boyeri, which is the dominant planktivorous fish in the lake.

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