ESTIMASI NILAI POROSITAS DAN PERMEABILITAS UNTUK CITRA SAMPEL SANDSTONE NGRAYONG MENGGUNAKAN METODE ADAPTIVE

Penelitian ini bertujuan untuk mengestimasi nilai porositas dan permeabilitas sampel sandstone Ngrayong dengan metode Adaptive. Metode Adaptive merupakan salah satu metode Digital Rock Physics (DRP). DRP merupakan metode citra digital yang digunakan sebagai salah satu metode untuk memvisualisasikan batuan menjadi citra digital. Metode ini dapat digunakan untuk menentukan besaran-besaran fisis dari suatu sampel batuan secara lebih efektif dan efisien. Metode Adaptive memiliki tiga pendekatan yaitu Adaptive Median-C, Adaptive Mean-C, Adaptive mean of minimum and maximum. Ketiga pendekatan tersebut memperoleh hasil dari porositas menggunakan metode DRP kemudian akan dibandingkan dengan hasil perhitungan porositas yang dilakukan di laboratorium menggunakan metode porositas Helium. Estimasi nilai porositas menggunakan metode Adaptive yang mendekati dengan hasil perolehan nilai porositas Helium adalah menggunakan metode Adaptive Median-C. Hasil estimasi nilai porositasnya adalah 26,8%. Sedangkan hasil nilai porositas Helium mencapai 29%. Hasil estimasi nilai porositas dari pendekatan metode Adaptive yang lain, nilainya lebih dari 30%. Estimasi nilai permeabilitas pada sampel Ngrayong dengan ukuran resolusi citra digital 200x200x200 piksel dan menggunakan iterasi 30.000 adalah 14,6175 mD

4D microvelocimetry reveals multiphase flow field perturbations in porous media

Many environmental and industrial processes depend on how fluids displace each other in porous materials. However, the flow dynamics that govern this process are still poorly understood, hampered by the lack of methods to measure flows in optically opaque, microscopic geometries. We introduce a 4D microvelocimetry method based on high-resolution X-ray computed tomography with fast imaging rates (up to 4 Hz). We use this to measure flow fields during unsteady-state drainage, injecting a viscous fluid into rock and filter samples. This provides experimental insight into the nonequilibrium energy dynamics of this process. We show that fluid displacements convert surface energy into kinetic energy. The latter corresponds to velocity perturbations in the pore-scale flow field behind the invading fluid front, reaching local velocities more than 40 times faster than the constant pump rate. The characteristic length scale of these perturbations exceeds the characteristic pore size by more than an order of magnitude. These flow field observations suggest that nonlocal dynamic effects may be long-ranged even at low capillary numbers, impacting the local viscous-capillary force balance and the representative elementary volume. Furthermore, the velocity perturbations can enhance unsaturated dispersive mixing and colloid transport and yet, are not accounted for in current models. Overall, this work shows that 4D X-ray velocimetry opens the way to solve long-standing fundamental questions regarding flow and transport in porous materials, underlying models of, e.g., groundwater pollution remediation and subsurface storage of CO2 and hydrogen

The Effect of Macroscopic Particle Features on Mineral Dissolution

Mineral dissolution is a dynamic process in which kinetics depend on the reactive surface area, orientation, and geometry of the dissolving mineral grain. Dissolution rate is, thus, not represented by a single value, but rather, by a spectrum that is affected by the reactivity of different types of surface features. Such dissolution rate spectra are usually obtained by very detailed studies of perfectly cleaved surfaces by atomic force microscopy or in situ studies, such as flow-through experiments. This study visualizes dissolution progress by repeated X-ray computed tomography scans of a single particle. This allows studying the influence of larger particle features, such as corners and edges, at the interception of macroscopic faces of particles, as well as the influence of those macroscopic features on the dissolution rate spectra. As a suitable case study, the dissolution of a monomineralic galena (PbS) particle in ethaline is studied. The observed changes in particle geometry are evaluated using a newly developed empirical model in order to break down the rate spectra as a function of the particle geometry. Results illustrate that dissolution rates are exponentially correlated with the distance to crystal corners and edges. The reactivity map generated from these exponential relations shows a linear trendline with the dissolution rates over the entire surface of the studied galena particle. The empirical reactivity map developed here opens the possibility of predicting the dissolution rate of particulate materials based on computed tomography and the optimal geometrical properties of the particles that maximize the dissolution, e.g., size and shape

Segmented Galena Dissolution Data

Raw CT data which are used to calculate the dissolution rates spectra and to generate reactivity map.Funded by European Union's Horizon 2020 Research and Innovation Program under Grant Agreement 81574

The Effect of Macroscopic Particle Features on Mineral Dissolution

Mineral dissolution is a dynamic process in which kinetics depend on the reactive surface area, orientation, and geometry of the dissolving mineral grain. Dissolution rate is, thus, not represented by a single value, but rather, by a spectrum that is affected by the reactivity of different types of surface features. Such dissolution rate spectra are usually obtained by very detailed studies of perfectly cleaved surfaces by atomic force microscopy or in situ studies, such as flow-through experiments. This study visualizes dissolution progress by repeated X-ray computed tomography scans of a single particle. This allows studying the influence of larger particle features, such as corners and edges, at the interception of macroscopic faces of particles, as well as the influence of those macroscopic features on the dissolution rate spectra. As a suitable case study, the dissolution of a monomineralic galena (PbS) particle in ethaline is studied. The observed changes in particle geometry are evaluated using a newly developed empirical model in order to break down the rate spectra as a function of the particle geometry. Results illustrate that dissolution rates are exponentially correlated with the distance to crystal corners and edges. The reactivity map generated from these exponential relations shows a linear trendline with the dissolution rates over the entire surface of the studied galena particle. The empirical reactivity map developed here opens the possibility of predicting the dissolution rate of particulate materials based on computed tomography and the optimal geometrical properties of the particles that maximize the dissolution, e.g., size and shape

Reactivity Map Code

Matlab code to generate reactivity map of the galena particleFunded by European Union's Horizon 2020 Research and Innovation Program under Grant Agreement 81574

Data: A particle-based approach to predict the success and selectivity of leaching processes

Raw CT data which are used to calculate the dissolution rates and particles data which are used for the leaching simulation https://doi.org/10.1016/j.hydromet.2022.105869Funded by European Union's Horizon 2020 Research and Innovation Program under Grant Agreement 81574

A particle-based approach to predict the success and selectivity of leaching processes using ethaline - Comparison of simulated and experimental results

Publisher Copyright: © 2022 The AuthorsEncouraged by the need for ecologically and economically sustainable technologies for the recovery of metals from complex raw materials, ionometallurgical leaching using deep eutectic solvents is emerging as a promising alternative to conventional hydro- and pyrometallurgical process routes. Current approaches of studying leaching processes do not provide a mineral-based understanding of the leaching process – thus limiting the opportunities for process optimization. This study addresses this shortcoming by combining laboratory-based X-ray computed tomography (CT) and scanning electron microscopy-based image analysis. The latter method provides precise information on the mineralogy and texture of the leach feed material, whereas CT is used to observe the progress of the leaching process through time. Leaching of Au[sbnd]Ag bearing sulfide flotation concentrate by the deep eutectic solvent ethaline with iodine as oxidizing agent is used as a relevant case study. Results show that time-lapse CT provides an accurate estimation of the dissolution rate of pyrite, chalcopyrite, galena, telluride minerals and gold. Dissolution rates were used to simulate the metal recoveries from the sulfide concentrate as a function of leaching time. Simulation results are within 5% variation of metal recoveries obtained by batch leaching experiments. The developed workflow can be easily transferred to other ore types or mineral concentrates; results may be used to study and optimize industrial leaching processes.This work was part of the ION4RAW project that received funding from the European Union's Horizon 2020 research and innovation program under grant agreement 815748 .Peer reviewe

Hawaiian beaches as natural analogues for long-term rates and impacts of Coastal Enhanced Silicate Weathering

Silicate weathering is the primary natural sink for atmospheric carbon dioxide (CO2) on geological time scales and Coastal Enhanced Silicate Weathering (CESW) aims to accelerate this process as a Carbon Dioxide Removal (CDR) technology for climate stabilization. However, the CO2 sequestration efficiency and environmental impacts of CESW remain largely unknown as dedicated field studies are lacking and long-term conditions are not yet investigated. However, some natural coastal environments can function as suitable analogues of CESW. Papakōlea Beach in Hawai’i is the world’s largest and best example of such a natural coastal analogue, comprising ∼90 wt % of olivine, a fast weathering Mg-silicate. As time is the critical factor, these beaches are extremely rare because olivine undergoes rapid dissolution in marine settings. It hence provides an opportunity to study the long-term rate and impact of olivine weathering, as envisioned in CESW applications. In summer 2022, field investigations were conducted on Papakōlea beach (olivine sand) and the nearby Richardson Bay (carbonate sands). Sediment incubation were done to investigate the dissolution kinetics under natural conditions, the fate of weathering products from olivine dissolution, and to explore the influence of olivine dissolution on biogeochemical cycling and ecology. Our findings reveal alkalinity release from the incubated olivine sand of Papakōlea beach, as well as the calcium carbonate equivalent from Richardson Bay. The alkalinity released during chemical weathering of silicate minerals results in supplementary transfer of atmospheric CO2 to the coastal ocean, with long-term storage in the form of bicarbonate (HCO3-) thereafter. The increase of alkalinity concentrations correlates with the production of dissolved inorganic carbon, indicating atmospheric CO2 uptake. To characterize the olivine dissolution and reflect surface alteration process on the grain scale, the study included non-destructive scans via electron microscopy (SEM) and high-resolution x-ray diffraction (XRD) of weathered minerals