Mineral surface reactivity: mechanisms and concepts

2021 ◽  
Author(s):  
Cornelius Fischer
Keyword(s):  
Reactive Transport ◽  
Large Scale ◽  
Fluid Transport ◽  
Crystal Surface ◽  
Solid Material ◽  
Surface Reactivity ◽  
Small Scale ◽  
Critical Surface ◽  
Mechanistic Understanding ◽  
Diagenetic Reactions

<p>Diagenetic reactions in sediments and sedimentary rocks are controlled by both fluid transport and surface reactivity. In this chapter, the major focus is on the effect of crystal surface reactivity and its variability. The “energetic landscape” of the solid material in contact with the fluid exerts control on reaction type, kinetics, and products. Critical surface processes include sorption, catalysis, dissolution, and precipitation. For diagenetic reactions, the sequence of processes and thus the potential inhibition of subsequent reactions due to surface modifications is of great interest. Consequently, the evolution of porosity and permeability is governed by the chronological sequence of surface reactions during the diagenetic history. This provides feedback to the fluid transport behaviour in the complex porous material. Because of this coupling, numerical approaches address the problem appropriately by the use of reactive transport codes. Pore scale treatment follows mechanisms at the scale of crystal surfaces that form the pore walls of the sedimentary rock. Such surface-chemical exercises require a parametrization that includes mechanistic understanding and connection to first-principles treatment. At larger scales, so-called continuum scale simulation treats fluid transport and fluid-solid reactions in a more generalized quantitative way. While such field-scale treatment is required and applied for multiple challenges, the small-scale mechanistic understanding is still a crucial part of geochemical research. The observed heterogeneity of surface reactivity requires specific upscaling strategies that are not yet reflected in large-scale analysis and predictions.</p>

scholarly journals Interaction between Crustal-Scale Darcy and Hydrofracture Fluid Transport: A Numerical Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tamara de Riese ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Numerical Model ◽  
Transport Mechanism ◽  
Large Scale ◽  
Fluid Transport ◽  
Numerical Study ◽  
Ballistic Transport ◽  
Accretionary Prism ◽  
Small Scale ◽  
Porous Flow

Crustal-scale fluid flow can be regarded as a bimodal transport mechanism. At low hydraulic head gradients, fluid flow through rock porosity is slow and can be described as diffusional. Structures such as hydraulic breccias and hydrothermal veins both form when fluid velocities and pressures are high, which can be achieved by localized fluid transport in space and time, via hydrofractures. Hydrofracture propagation and simultaneous fluid flow can be regarded as a “ballistic” transport mechanism, which is activated when transport by diffusion alone is insufficient to release the local fluid overpressure. The activation of a ballistic system locally reduces the driving force, through allowing the escape of fluid. We use a numerical model to investigate the properties of the two transport modes in general and the transition between them in particular. We developed a numerical model in order to study patterns that result from bimodal transport. When hydrofractures are activated due to low permeability relative to fluid flux, many hydrofractures form that do not extend through the whole system. These abundant hydrofractures follow a power-law size distribution. A Hurst factor of ~0.9 indicates that the system self-organizes. The abundant small-scale hydrofractures organize the formation of large-scale hydrofractures that ascend through the whole system and drain fluids in large bursts. As the relative contribution of porous flow increases, escaping fluid bursts become less frequent, but more regular in time and larger in volume. We propose that metamorphic rocks with abundant veins, such as in the Kodiak accretionary prism (Alaska) and Otago schists (New Zealand), represent regions with abundant hydrofractures near the fluid source, while hydrothermal breccias are formed by the large fluid bursts that can ascend the crust to shallower levels.

scholarly journals Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

2021 ◽  
Author(s):  
Torben Prill ◽  
Cornelius Fischer ◽  
Pavel Gavrilenko ◽  
Oleg Iliev
Keyword(s):  
Contaminated Soils ◽  
Reactive Transport ◽  
Transport Model ◽  
Crystal Surface ◽  
Reaction Rates ◽  
Surface Reactivity ◽  
Reservoir Rock ◽  
Intrinsic Variability ◽  
Multiple Systems ◽  
The Difference

AbstractCurrent reactive transport model (RTM) uses transport control as the sole arbiter of differences in reactivity. For the simulation of crystal dissolution, a constant reaction rate is assumed for the entire crystal surface as a function of chemical parameters. However, multiple dissolution experiments confirmed the existence of an intrinsic variability of reaction rates, spanning two to three orders of magnitude. Modeling this variance in the dissolution process is vital for predicting the dissolution of minerals in multiple systems. Novel approaches to solve this problem are currently under discussion. Critical applications include reactions in reservoir rocks, corrosion of materials, or contaminated soils. The goal of this study is to provide an algorithm for multi-rate dissolution of single crystals, to discuss its software implementation, and to present case studies illustrating the difference between the single rate and multi-rate dissolution models. This improved model approach is applied to a set of test cases in order to illustrate the difference between the new model and the standard approach. First, a Kossel crystal is utilized to illustrate the existence of critical rate modes of crystal faces, edges, and corners. A second system exemplifies the effect of multiple rate modes in a reservoir rock system during calcite cement dissolution in a sandstone. The results suggest that reported variations in average dissolution rates can be explained by the multi-rate model, depending on the geometric configurations of the crystal surfaces.

Small-Scale Science to Large-Scale Profession

2000 ◽  
Vol 45 (4) ◽  
pp. 396-398
Author(s):  
Roger Smith
Keyword(s):  
Large Scale ◽  
Small Scale

Development of Physics Learning Module Based on Guided Inquiry with Light Wave Material in Class XI of Senior High School

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Evi Rahmawati ◽  
Irnin Agustina Dwi Astuti ◽  
N Nurhayati
Keyword(s):  
Large Scale ◽  
Learning Strategy ◽  
Student Response ◽  
Average Score ◽  
Small Scale ◽  
Design Development ◽  
Teacher Response ◽  
Student Responses ◽  
Analysis Design ◽  
Scientific Skills

IPA Integrated is a place for students to study themselves and the surrounding environment applied in daily life. Integrated IPA Learning provides a direct experience to students through the use and development of scientific skills and attitudes. The importance of integrated IPA requires to pack learning well, integrated IPA integration with the preparation of modules combined with learning strategy can maximize the learning process in school. In SMP 209 Jakarta, the value of the integrated IPA is obtained from 34 students there are 10 students completed and 24 students are not complete because they get the value below the KKM of 68. This research is a development study with the development model of ADDIE (Analysis, Design, Development, Implementation, and Evaluation). The use of KPS-based integrated IPA modules (Science Process sSkills) on the theme of rainbow phenomenon obtained by media expert validation results with an average score of 84.38%, average material expert 82.18%, average linguist 75.37%. So the average of all aspects obtained by 80.55% is worth using and tested to students. The results of the teacher response obtained 88.69% value with excellent criteria. Student responses on a small scale acquired an average score of 85.19% with highly agreed criteria and on the large-scale student response gained a yield of 86.44% with very agreed criteria. So the module can be concluded receiving a good response by the teacher and students.

Planetary gentrification and urban (re)development

2019 ◽  
Vol 61 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Loretta Lees
Keyword(s):  
Low Income ◽  
Policy Making ◽  
Large Scale ◽  
Urban Redevelopment ◽  
Urban Transformation ◽  
Small Scale ◽  
Income Groups ◽  
Low Income Groups

Abstract Gentrification is no-longer, if it ever was, a small scale process of urban transformation. Gentrification globally is more often practised as large scale urban redevelopment. It is state-led or state-induced. The results are clear – the displacement and disenfranchisement of low income groups in favour of wealthier in-movers. So, why has gentrification come to dominate policy making worldwide and what can be done about it?

AGRICULTURAL PRODUCTION OF CA DONG PEOPLE IN RESETTLEMENT AREA OF TRANH RIVER HYDROPOWER NUMBER 2: CURRENT SITUATION AND IMPACT FACTORS

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Bùi Thị Bích Lan
Keyword(s):  
Social Relations ◽  
Agricultural Production ◽  
Large Scale ◽  
Transition Process ◽  
Impact Factors ◽  
Small Scale ◽  
Scale Production ◽  
Technical Application ◽  
Production Models ◽  
Role Of The State

In Vietnam, the construction of hydropower projects has contributed significantly in the cause of industrialization and modernization of the country. The place where hydropower projects are built is mostly inhabited by ethnic minorities - communities that rely primarily on land, a very important source of livelihood security. In the context of the lack of common productive land in resettlement areas, the orientation for agricultural production is to promote indigenous knowledge combined with increasing scientific and technical application; shifting from small-scale production practices to large-scale commodity production. However, the research results of this article show that many obstacles in the transition process are being posed such as limitations on natural resources, traditional production thinking or the suitability and effectiveness of scientific - technical application models. When agricultural production does not ensure food security, a number of implications for people’s lives are increasingly evident, such as poverty, preserving cultural identity, social relations and resource protection. Since then, it has set the role of the State in researching and building appropriate agricultural production models to exploit local strengths and ensure sustainability.

Managing the impacts of mining on Ghana’s water resources from a legal perspective

2018 ◽  
Vol 1 (3) ◽  
pp. 156-165 ◽  
Author(s):  
Nasirudeen Abdul Fatawu
Keyword(s):  
Surface Water ◽  
Water Resources ◽  
Environmental Protection Agency ◽  
Large Scale ◽  
Small Scale ◽  
Mining Activities ◽  
Protection Agency ◽  
Environmental Laws ◽  
Mining Areas ◽  
Legal Perspective

Recent floods in Ghana are largely blamed on mining activities. Not only are lives lost through these floods, farms andproperties are destroyed as a result. Water resources are diverted, polluted and impounded upon by both large-scale minersand small-scale miners. Although these activities are largely blamed on behavioural attitudes that need to be changed, thereare legal dimensions that should be addressed as well. Coincidentally, a great proportion of the water resources of Ghana arewithin these mining areas thus the continual pollution of these surface water sources is a serious threat to the environmentand the development of the country as a whole. The environmental laws need to be oriented properly with adequate sanctionsto tackle the impacts mining has on water resources. The Environmental Impact Assessment (EIA) procedure needs to bestreamlined and undertaken by the Environmental Protection Agency (EPA) and not the company itself.

RANCANG BANGUN PERANGKAT EKSPERIMENTASI PROSES PIROLISIS BIOMASA GELOMBANG MIKRO

2013 ◽  
Vol 14 (2) ◽  
Author(s):  
Noor Fachrizal
Keyword(s):  
Large Scale ◽  
Continuous Model ◽  
Biomass Energy ◽  
Scale Model ◽  
Small Scale ◽  
Laboratory Apparatus ◽  
Liquid Form ◽  
Large Scale Model ◽  
Bio Oil ◽  
Pyrolysis Of Biomass

Biomass such as agriculture waste and urban waste are enormous potency as energy resources instead of enviromental problem. organic waste can be converted into energy in the form of liquid fuel, solid, and syngas by using of pyrolysis technique. Pyrolysis process can yield higher liquid form when the process can be drifted into fast and flash response. It can be solved by using microwave heating method. This research is started from developing an experimentation laboratory apparatus of microwave-assisted pyrolysis of biomass energy conversion system, and conducting preliminary experiments for gaining the proof that this method can be established for driving the process properly and safely. Modifying commercial oven into laboratory apparatus has been done, it works safely, and initial experiments have been carried out, process yields bio-oil and charcoal shortly, several parameters are achieved. Some further experiments are still needed for more detail parameters. Theresults may be used to design small-scale continuous model of productionsystem, which then can be developed into large-scale model that applicable for comercial use.

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