scholarly journals Direct currents stimulate carbonate mineralization for soil improvement under various chemical conditions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dimitrios Terzis ◽  
Patrick Hicher ◽  
Lyesse Laloui
Keyword(s):  
Electric Fields ◽  
Textural Properties ◽  
Soil Improvement ◽  
Transport Processes ◽  
Electric Currents ◽  
Electric System ◽  
Beneficial Effects ◽  
Treatment Conditions ◽  
Microbially Induced Carbonate Precipitation ◽  
Chemical Conditions

Abstract The present study integrates direct electric currents into traditional calcium carbonate mineralization to investigate electrochemical interactions and the subsequent crystalline growth of CaCO3 bonds in sand. A specific line of focus refers to the effect of three chemical reactive species involved in the stimulated geo-chemo-electric system, namely CaCl2, Ca(CH3COO)2 and Ca(CH3CH2(OH)COO)2. By altering treatment conditions and the applied electric field, we capture distinctive trends related to the: (i) overall reaction efficiencies and distribution of CaCO3 crystals is sand samples; (ii) promotion of CaCO3 mineralization due to DC (iii) crystallographic and textural properties of mineralized bonds. The study introduces the concept of EA-MICP which stands for Electrically Assisted Microbially Induced Carbonate Precipitation as a means of improving the efficiency of soil bio-cementation compared to traditional MICP-based works. Results reveal both the detrimental and highly beneficial effects that electric currents can hold in the complex, reactive and transport processes involved. An interesting observation refers to the “doped” morphology of CaCO3 crystals, which precipitate under electric fields, validated by crystallographic analyses and microstructural observations.

scholarly journals Benefits and drawbacks of applied direct currents for soil improvement via carbonate mineralization

2020 ◽  
Vol 195 ◽  
pp. 05007
Author(s):  
Dimitrios Terzis ◽  
Patrick Hicher ◽  
Lyesse Laloui
Keyword(s):  
Spatial Distribution ◽  
Electric Fields ◽  
Soil Improvement ◽  
Transport Processes ◽  
Particle Charge ◽  
Electric Currents ◽  
Electrically Assisted ◽  
New Vision ◽  
Chemical Conditions ◽  
Specific Line

The study presented herein adopts a new vision of the processes involved in carbonate mineralization induced by MICP from an electrochemical and crystal growth perspective. More precisely a specific line of focus refers to the species involved in the bio-chemical reactions and especially their net particle charge. By altering electro-chemical conditions via the application of direct electric currents, we observe distinctive trends related to: (i) overall reaction efficiency; (ii) carbonate mineralization/dissolution and (iii) spatial distribution of precipitates. The study introduces the concept of EA-MICP which stands for Electrically Assisted MICP as a means of improving the efficiency of soil bio-consolidation and overcoming various challenges which were previously reported in conventional MICP-based works. Results reveal both the detrimental and highly beneficial role that electric currents can hold in the complex, reactive and transport processes involved. An interesting finding is the “doped” morphology of calcite crystals, precipitated under electric fields, validated by microstructural observations.

A Case for Magneto Hydro Dynamics (MHD)

2001 ◽  
Author(s):  
Haim H. Bau
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Lorentz Force ◽  
Electric Fields ◽  
Biological Fluids ◽  
Fluid Volume ◽  
Chaotic Advection ◽  
Complex Flows ◽  
Electric Currents

Abstract In this paper, I review some of our work on the use of magneto hydrodynamics (MHD) for pumping, controlling, and stirring fluids in microdevices. In many applications, one operates with liquids that are at least slightly conductive such as biological fluids. By patterning electrodes inside flow conduits and subjecting these electrodes to potential differences, one can induce electric currents in the liquid. In the presence of a magnetic field, a Lorentz force is generated in a direction that is perpendicular to both the magnetic and electric fields. Since one has a great amount of freedom in patterning the electrodes, one can induce forces in various directions so as to generate complex flows including “guided” flows in virtual, wall-less channels. The magnetic flux generators can be either embedded in the device or be external. Despite their unfavorable scaling (the magnitude of the forces is proportional to the fluid volume), MHD offers many advantages such as the flexibility of applying forces in any desired direction and the ability to adjust the magnitude of the forces by adjusting either the electric and/or magnetic fields. We provide examples of (i) MHD pumps; (ii) controlled networks of conduits in which each conduit is equipped with a MHD actuator and by controlling the voltage applied to each actuator, one can direct the liquid to flow in any desired way without a need for valves; and (iii) MHD stirrers including stirrers that exhibit chaotic advection.

scholarly journals Biochemical Enhancement of Geotechnical Properties of Marginal Soils

2018 ◽  
Vol 203 ◽  
pp. 03010
Author(s):  
Murtala Hassan Mohammed ◽  
Ado Yusuf Abdulfatah
Keyword(s):  
Hydraulic Conductivity ◽  
Treatment Duration ◽  
Soil Improvement ◽  
Engineering Properties ◽  
Treatment Technique ◽  
Reagent Concentration ◽  
Soil Variables ◽  
Treatment Conditions ◽  
Metabolic Activities ◽  
Marginal Soil

Microbially-induced calcite precipitation (MICP) is a relatively new and sustainable soil improvement technique. This technique utilizes bio-activity of microorganism to precipitate calcite through metabolic activities of the organisms which decompose urea in to ammonium and carbon dioxide. The carbonate so produced combined with the supplied calcium to precipitate calcite. This calcite improves engineering properties of soil through the formation of coating and bonds between soil particles. Preliminary results have proved the feasibility of the isolated bacteria in MICP treatment technique to improve the engineering properties of marginal soil. The main objective of this study is to determine the preference conditions for effective MICP treatment in improving the soil engineering properties (Unconfined Compressive Strength, California Bearing Ratio and Hydraulic Conductivity) of a typical marginal soil. Variables such as; treatment duration (24, 48, and 72hours), reagent concentration (0.1, 0.25, 0.5, and 0.75M), and concentration of the isolates (1×105, 1×106, and 1×107cfu/ml) were considered in the MICP treatment. The results suggested that the preference treatment conditions were 72hours treatment duration, 0.75M reagent concentration, and 1×107cfu/ml concentration of the isolates. The corresponding alterations recorded were 94.86KN/m2 (295%) and 30.8% (92.5%) increment for CBR and UCS while 0.93X10-6m/s (78.95%) reduction was recorded for hydraulic conductivity. The calcite content showed a reasonably good comparison with the improvements in the soil engineering properties. The pH of effluents increased during MICP treatment indicating the presence of urease bio-activity.

scholarly journals Sulfonated Hydrothermal Carbons from Cellulose and Glucose as Catalysts for Glycerol Ketalization

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 804 ◽  
Author(s):  
Fernández ◽  
Fraile ◽  
García-Bordejé ◽  
Pires
Keyword(s):  
Catalytic Activity ◽  
Heterogeneous Catalysis ◽  
Flow Reactor ◽  
Chemical Properties ◽  
Textural Properties ◽  
Catalytic Synthesis ◽  
Physical Chemical ◽  
Treatment Conditions ◽  
First Results ◽  
Work Up

Solketal is one of the most used glycerol-derived solvents. Its production via heterogeneous catalysis is crucial for avoiding important product losses typically found in the aqueous work-up in homogeneous catalysis. In this work, we present a study of the catalytic synthesis of solketal using sulfonated hydrothermal carbons (SHTC). They were prepared from glucose and cellulose resulting in different textural properties depending on the hydrothermal treatment conditions. The sulfonated hydrothermal carbons were also coated on a graphite microfiber felt (SHTC@GF). Thus, up to nine different solids were tested, and their activity was compared with commercial acidic resins. The solids presented very different catalytic activity, which did not correlate with their physical-chemical properties indicating that other aspects likely influence the transport of reactants and products to the catalytic surface. Additionally, the SHTC prepared from cellulose showed better reusability in batch reaction tests. This work also presents the first results for the production of solketal in a flow reactor, which opens the way to the use of SHTC@GF for this kind of reactions.

Probiotics in colorectal cancer (CRC) with emphasis on mechanisms of action and current perspectives

2013 ◽  
Vol 62 (8) ◽  
pp. 1107-1123 ◽  
Author(s):  
Imen Kahouli ◽  
Catherine Tomaro-Duchesneau ◽  
Satya Prakash
Keyword(s):  
Colorectal Cancer ◽  
Early Stage ◽  
Tumour Progression ◽  
Great Promise ◽  
Anticancer Compounds ◽  
Beneficial Effects ◽  
Physico Chemical ◽  
Recent Developments ◽  
Chemical Conditions

Colorectal cancer (CRC) is the third most common form of cancer. Diverse therapies such as chemotherapy, immunotherapy and radiation have shown beneficial effects, but are limited because of their safety and toxicity. Probiotic formulations have shown great promise in CRC as preventive and early stage therapeutics. This review highlights the importance of a balanced intestinal microbiota and summarizes the recent developments in probiotics for treating CRC. Specifically, this report describes evidence of the role of probiotics in modulating the microbiota, in improving the physico-chemical conditions of the gut and in reducing oxidative stress. It also discusses the mechanisms of probiotics in inhibiting tumour progression, in producing anticancer compounds and in modulating the host immune response. Even though some of these effects were observed in several clinical trials, when probiotic formulations were used as a supplement to CRC therapies, the application of probiotics as biotherapeutics against CRC still needs further investigation.

The textural properties and microstructure of konjac glucomannan – tungsten gels induced by DC electric fields

2016 ◽  
Vol 212 ◽  
pp. 256-263 ◽  
Author(s):  
Lixia Wang ◽  
Yuanhong Zhuang ◽  
Jingliang Li ◽  
Jie Pang ◽  
Xiangyang Liu
Keyword(s):  
Electric Fields ◽  
Textural Properties ◽  
Konjac Glucomannan ◽  
Dc Electric Fields

The origin of fluctuations and cross-field transport in idealized magnetic confinement systems

1981 ◽  
Vol 300 (1456) ◽  
pp. 547-557 ◽  
Keyword(s):  
Electric Fields ◽  
High Frequency ◽  
Scaling Laws ◽  
Scaling Law ◽  
Low Frequency ◽  
Magnetic Confinement ◽  
Upper Bounds ◽  
Transport Processes ◽  
General View ◽  
Long Wavelength

The study of plasma fluctuations and confinement in idealized systems such as octupoles and levitrons has contributed to the understanding of cross-field transport processes. The linear theory of plasma instabilities that cause fluctuations is well developed and can predict growth rates γ and wavelengths θ x around lines of force. However, the theoretical prediction of cross-field transport coefficient D ± is restricted to quasilinear estimates of upper bounds (for example, D = 1 2 γ λ x 2 ) because of the complexity of the full nonlinear calculation. Such quasilinear estimates usually far exceed the measured values and are of limited worth. A general view of the results from octupole and levitron experiments shows that under collisional conditions ( λ ei / L < 0 ) the diffusion coefficient, D , scales in the same way as classical collisional diffusion ( D α n / T e 1 2 B 2 ). Agreement is closely approached in many cases, sometimes even in the presence of fluctuations. Under collisionless conditions ( D α n / T e 1 2 B 2 ), Bohm diffusion scaling ( D α T e / B ) is found in the few cases where the scaling law has been determined. This behaviour is consistent with the general scaling laws of Connor & Taylor (1977) but is not understood in detail. In addition there is evidence, both experimental and theoretical, that long-wavelength low-frequency electric fields (convection cells) can be generated nonlinearly from high-frequency fluctuations and can contribute to cross-field transport

The Coupling of Chemical and Transport Processes in Near-Field Modelling

1986 ◽  
Vol 84 ◽  
Author(s):  
S.M. Sharland ◽  
P.W. Tasker ◽  
C.J. Tweed
Keyword(s):  
Radioactive Waste ◽  
Chemical Equilibrium ◽  
Near Field ◽  
Transport Processes ◽  
Primary Interest ◽  
Field Modelling ◽  
Long Time ◽  
Waste Repository ◽  
Solid Phases ◽  
Chemical Conditions

AbstractNear-field modelling is concerned with the description of the migration, chemical and degradation processes that may occur within an engineered radioactive waste repository and its immediate environs. The object is to gain understanding of such processes in order to predict the long-time evolution of the repository and to assess the degree of containment provided by the proposed engineered construction. The conditions of primary interest to our programme concern the waste contained within a steel canister and buried in a concrete environment within a clay geology. The chemistry of the near-field is controlled in that it is the consequence of the choice of near-field components, but it may be extremely complex. Intrusion of external groundwater and degradation of the chosen materials will lead to variations in the chemistry in both space and time. It is vitally important to understand these changing chemical conditions since they determine the solubility and sorption of any released radionuclides. In this paper, we describe the computer program CHEQMATE (CHemical EQuilibrium with Migration And Transport Equations), which has many applications in modelling various changes in chemistry in the near-field. The program combines an ionic migration code with the geochemical program PHREEQE [1]. The program maintains local chemical equilibrium in the system as the transport processes evolve. The program includes automatic mineral accounting; solid phases are added or removed from the equilibrium as precipitation or dissolution occurs. We illustrate the use of the CHEQMATE program with an example of a coupled chemical and transport problem, particularly relevant to the near-field of a waste repository.

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