Porous Sand Research Articles

Kinetic Formation Process of Carbon Dioxide Hydrate in Porous Sands under 274.15–280.15 K Reaction Temperature and 20–70% Initial Water Saturation

Kinetic Formation Process of Carbon Dioxide Hydrate in Porous Sands under 274.15–280.15 K Reaction Temperature and 20–70% Initial Water Saturation

Comprehensive study on copper adsorption using an innovative graphene carbonate sand composite adsorbent: Batch, fixed-bed columns, and CFD modeling insights

This study focused on an innovative graphene carbonate sand composite adsorbent, synthesized from carbonated porous sand and sucrose as raw materials, for the removal of copper ions via the adsorption process. The characteristics of this adsorbent are determined through comprehensive experiments and numerical simulations in batch and fixed-bed column conditions, which has not been extensively explored. Extensive experimentation demonstrated a remarkable 100 % removal efficiency under optimal conditions, which included a copper ion concentration of 3 g/L, a contact time of 10 h, and an adsorbent dosage of 35 g/L. The adsorption kinetics and isotherm results exhibited that the Elovich model (R² = 0.998) and the Langmuir model (R² = 0.996 for linear with qm=123.91 mg g-1, and R² = 0.993 for nonlinear fitting) more effectively described the adsorption of copper onto the adsorbent. In the fixed-bed column studies, among the well-known analytical models, the Log-Gompertz model showed better compatibility (R2 = 0.97∼0.99) between breakthrough curves with experimental results for various copper inlet concentrations. Also, numerical results obtained using computational fluid dynamics and mass transfer simulations with the linear driving force model were successfully validated by experimental results, particularly in the initial and transition zones of the breakthrough curve.

Design Optimal Riser Size for Reducing Shrinkage Defect in 1100 Aluminum Alloy Sand Casting Process

This research aims to design a sprue system for aluminum castings in sand pores for a basic form prototype in metal casting, which is a one-piece pattern with a parting line. There are several types of liquid metal gating systems available. In the design, variables were specified regarding the height of the sprue, the cross-sectional area of the sprue, the cross-sectional area of the reservoir, the cross-sectional area of the runner, and the cross-sectional area of the gating. The riser size was used as a comparison variable. Following study and design, an experiment was conducted to cast the actual casting and to analyze the behavior simulation using Cast-Designer to determine a solution. In the simulation, the following results were found: the time taken to add liquid metal; the flow behavior of liquid metal; the metal hardening time; and the formation of shrinkage cavities in the casting. Based on the results of casting experiments and behavioral simulations, it was demonstrated that the large riser significantly reduced the shrinkage of the actual casting.

Effect of particle size, water saturation, inorganic salt and methane on the phase equilibrium of CO2 hydrates in sediments

Understanding the thermal stability of gas hydrate in complex marine geological environment is of importance to hydrate-based carbon sequestration. In this work, the factors affecting the equilibrium of CO2 hydrate in ocean sediments, including quartz sands, inorganic salts and gas impurities were quantitatively measured in a temperature range from 273 to 283 K and a phase equilibrium model of hydrate was established. To reveal the distribution in pore structure, the micro-morphologies of hydrate-bearing sediments were measured by cryo-SEM. Results showed that reduction of initial water saturation, addition of NaCl and CH4 were found to have inhibitory effect on CO2 hydrate equilibrium. Initial water saturation reduced the equilibrium temperature by the capillary pressure, but only 0.3–0.7 K temperature depression was observed as the water saturation reduced to 5 %. About 5.7 K in the average temperature depression was found by the addition of 10 wt% NaCl and 24 mol% CH4. NaCl and CH4 influenced the hydrate equilibrium by changing the water activity and chemical potential of hydrate water lattice. SEM images showed that the hydrate formed in pores of quartz sand had porous surface and coated the sand particles like a layer of cells which are 5–20 μm in diameter, suggesting the hydrate layer exists between the liquid and gas phase. Based on the van der Waals-Platteeuw model, a hydrate equilibrium model was developed. The model provided a good prediction of the hydrate equilibrium in the presence of quartz sand, NaCl and CH4 with an averaged deviation of ±4.2 %, which had the potential to be applicated in more complexed ocean sedimentary environment.

Performance enhancement of cement mortar with superabsorbent polymer composite internally embedded with porous ceramsite sand

Superabsorbent polymer (SAP), which can act as water reservoir, was an internal curing (IC) agent with great potential to reduce the shrinkage and cracking of cement-based materials. However, the volume shrinkage of SAP after water release will lead to the formation of additional voids, which will lead to a clear reduction of mechanical properties. In present work, a novel SAP composite with a rigid skeleton (IP-PS) was synthesized by embedding in-situ polymerized SAP hydrogel into the pores of porous ceramic (PS). The results demonstrated that the compressive strength of IP-PS0.054 was above 10 % higher than that of SAP0.054 in the early and late stages, the compressive strength of IP-PS0.054 at 28 days reached 97.71 % of that of the control group, which was predominantly ascribed to the support provided by the embedded skeleton. The development of self-desiccation was also notably delayed by the incorporation of IP-PS, as evidenced by the approximately 12 % reduction compared to SAP0.054 and 47 % reduction compared to Control group in 7-day autogenous shrinkage, which was on account of the enhanced water storage and durable IC capacity of IP-PS. Furthermore, the impermeability of cement-based materials was also improved by the in-situ polymerized hydrogel modification.

Characterizing coastal aquifer heterogeneity from a single piezometer head chronicle

We propose a new method for identifying the hydraulic properties of coastal aquifers based on their response to continental and marine influences observed from isolated piezometers displaying both tidal and seasonal fluctuations. From a single piezometer, a first approximation of hydraulic conductivity and porosity can be derived analytically from the mean hydraulic head and its tidal fluctuations. If this approximation also allows a correct simulation of seasonal head variations, the aquifer can be modelled as homogeneous. Otherwise, the seasonal head variations provide constraints on the heterogeneity of hydraulic properties. This new method is applied to a coastal aquifer in Normandy, formed by a relatively flat, kilometer-wide coastal strip of Quaternary sands followed by a foothill of higher Brioverian shales. Hydraulic head variations monitored daily for 8 years in a piezometer located in the Quaternary sand formation enable us to constrain their hydraulic conductivity (5–20 m.d−1) and porosity (7–10 %) within restricted ranges. They also suggest the existence of a significantly more porous formation (15–30 %) upstream of the observation piezometer, which could consist of more porous sands or fractured shales. In the case of limited surface–subsurface interactions, the identification method relies on a step-by-step combination of analytical solutions and simplified 1D numerical models. When more important surface–subsurface interactions are involved, a spatialized 2D model is used, that allows the analysis of seepage areas. Based on this case study, we gradually introduce 1D and 2D approaches, and discuss their applicability. We finally illustrate one major application of this approach by analyzing the interest of aquifer properties investigation on groundwater-induced flooding vulnerability.

Analysis of the Effects of Partially Hydrolyzed Polyamide on Oil Reservoir Rocks

The exploitation of heavy oil fields has recently gained momentum due to increased investment in new oil and gas fields and especially due to environmental legislative constraints. That is why in this article I have described the possibility of using partially hydrolyzed polyacrylamide in the exploitation of heavy crude oil deposits, by injecting it into reservoir rocks followed by injection of reservoir water. The role of this polymer is to provide lubrication of the crude oil and water flow channels and especially to block (by reverse osmosis) the large pore communication channels in order to limit pressure leaks in uncontrollable areas. In the study we created two polymers that were used in order to increase the flow rate and decrease the viscosity and the freezing point (additives that are easy to procure and especially with spectacular results in the treatment of stills and without affecting the stability and quality of the final products refinery). We also studied the flow of the polymer through carbonate reservoir rocks, managing to obtain a numerical model that provides data on the rock resistance factor to the flow of partially fluidized polyacrylamide. The adsorption on the surface of the rocks determined the reduction of the mobility of the polymer but also the modification of the gel structure by the modification (crossing) of the polymer (of the polymer chains) which led to clogging (blocking of the pores) and increasing the possibility of fluid flow. In the laboratory we determined the adsorption of silicon for a solution of polyacrylamide of 0.05% partially hydrolyzed concentration in water, it increases from the value of 0.01 mg/m2 to 0.05 mg/m2 when the concentration in NaCl increases from 0 .5% to 10% in are we showed that adsorption increases for pH values ​​lower than 7, and it is stated that for a porous sand medium with a permeability of 140 mD, replacing saline water with 20 g/l NaCl, a presence of the polymer with a concentration of 400 ppm was observed in the effluent, and this value being approximately stabilized after 5 injected pore volumes.

Penanganan Rembesan dan Perkuatan Tanah Menggunakan Metode Insitu Test (Pressure Meter Test) Studi Kasus : Proyek Bendungan Margatiga

The bearing capacity of the soil is the support of the foundation, where the foundation transmits the loads derived from the weight of the building itself and the loads acting on the building to the surrounding soil. The purpose of this paper is to determine the handling of seepage and soil reinforcement needed in the case study of the Margatiga Dam Project, East Lampung. Based on the results of geological investigations, the Margatiga Dam is composed of a quarter-aged rock layer with a fragment composition of fine sand - gravel, with a soft - hard hardness level and the need for foundation repair. Based on the lithological conditions of the Margatiga Dam Extraction Gate foundation and the Spillway building which are composed of relatively deep and quite porous alluvial sand deposits, this causes the curtain grouting results to be ineffective, therefore it is necessary to change the seepage control design from the Grouting Curtain to the boundary wall. Based on the simulation check in Plaxis Software for Seepage and Excavation Staging, processing was carried out using Secant Pile and Soldier Pile with a depth of 30 meters with a stretch of 140 m and overlapping with Curtain Grouting of Embankment Dam on the left side and 5 m right side. Field PMT results showed that the maximum stress of the rock layer under the spillway foundation was 0.016 MPa and 0.630 MPa.

Experimental study on a combined sand barrier: Integration of porous mesh plate and novel porous sand-fixing bricks

Wind and sand disasters frequently impact the newly constructed railroad along the Hongyi line in Qinghai Province's Qaidam Basin. The existing wind and sand prevention measures, primarily comprising polyethylene (PE) nets, have shown limited effectiveness. To this end, this study introduces an innovative combined sand barrier: A new type of porous sand fixing bricks (PSBs) are made from local aeolian sand, arranged in a square grid like low vertical sand barrier, and combined with a high vertical porous mesh plate (PMP) to form a combined sand barrier. Wind tunnel experiments were conducted to optimize the combined sand barrier's structure. The results indicate that incorporating porous sand-fixing brick sand barrier (PSBSB) on the leeward side of the PMP substantially impacts the near-surface flow field and plays a crucial role in decreasing wind velocity while enhancing sand control. The PSBSB with five rows of PSBs, positioned 18H from the PMP's leeward side, maximizes windproof and sand control efficiencies. Notably, the PSBs exhibit excellent self-stability under wind load, eliminating the need for additional fixing measures. This combined sand barrier presents a replicable, cost-effective solution for wind-blown sand disaster prevention in aeolian sand regions like the Hongyi line, promising advancements in sand barrier technology.

Manganese‐Rich Sandstones as an Indicator of Ancient Oxic Lake Water Conditions in Gale Crater, Mars

AbstractManganese has been observed on Mars by the NASA Curiosity rover in a variety of contexts and is an important indicator of redox processes in hydrologic systems on Earth. Within the Murray formation, an ancient primarily fine‐grained lacustrine sedimentary deposit in Gale crater, Mars, have observed up to 45× enrichment in manganese and up to 1.5× enrichment in iron within coarser grained bedrock targets compared to the mean Murray sediment composition. This enrichment in manganese coincides with the transition between two stratigraphic units within the Murray: Sutton Island, interpreted as a lake margin environment, and Blunts Point, interpreted as a lake environment. On Earth, lacustrine environments are common locations of manganese precipitation due to highly oxidizing conditions in the lakes. Here, we explore three mechanisms for ferromanganese oxide precipitation at this location: authigenic precipitation from lake water along a lake shore, authigenic precipitation from reduced groundwater discharging through porous sands along a lake shore, and early diagenetic precipitation from groundwater through porous sands. All three scenarios require highly oxidizing conditions and we discuss oxidants that may be responsible for the oxidation and precipitation of manganese oxides. This work has important implications for the habitability of Mars to microbes that could have used Mn redox reactions, owing to its multiple redox states, as an energy source for metabolism.

A statistical model for estimating porosity based on various parameters of flow through porous media

ABSTRACT Flow through porous media is a process with a momentous impact on the environment. Hydraulic conductivity, which depends on the particle size, shape, and porosity of the media, has applications in different fields of science, e.g., groundwater, seepage, and soil stability. Precise estimation of porosity leads to accurate computation of the hydraulic conductivity of porous media. The present study investigates the effect of particle size on the porosity of porous media, i.e., crushed quartzite, river gravel, marble chips, and sand. The influence of the wall effect on packing and porosity of porous media based on the diameter ratio, i.e., the ratio of permeameter-to-particle size (Dp/dg) has also been investigated. The hydraulic conductivity and the porosity of porous media are observed to increase with an increase in the particle size. The study postulates a dependable relation between hydraulic conductivity and porosity. The experimentally obtained and the model-generated porosity values for crushed quartzite, river gravel, marble chips, and sand range between 0.38–0.42 and 0.37–0.43, respectively. Experimental data have been used to derive a statistical model based on the diameter ratio (5.08 ≤ (Dp/dg) ≤ 254) for estimating the porosity of media. The validation of the statistical model using experimental data establishes the efficacy of the developed model.

Experimental and Theoretical Analysis of the Thermostatic Drying Process in Wetted Porous Sand Beds with Different Pore Sizes

The drying kinetics of porous media are crucial for controlling the drying process, which is a vital component in many processes. A mathematical model of the drying process in a granular bed was developed using Whitaker’s model, and its accuracy was verified through experimental results. The results indicated that the three stages of porous media drying are closely linked to the heat flow to the media and the latent heat of evaporation required by the liquid water inside it. Moreover, as the influence of gravity weakens and the capillary force strengthens, specifically due to the gradual decrease in the pore size of the bed, significant differences in the drying kinetics of the bed are observed, particularly in the third stage of drying, which is most affected. The onset of saturation in the third stage of bed drying varies with the pore size of the particles, with smaller pore sizes exhibiting an earlier onset. Additionally, the temperature change in this stage demonstrates the occurrence of secondary warming as the pore size decreases.

A bounding surface model of methane hydrate-bearing carbonate sand-silt mixtures

The geological environment of marine methane hydrate-bearing sediments (MHBS) is highly complex. Mastering the mechanical behavior of MHBS is crucial for analyzing geomechanical hazards and evaluating its stability. The marine sediment in the South China Sea (SCS) contains a significant amount of porous foraminifera shells, which serve as the primary storage space for natural gas hydrates and differ significantly from other sea areas. In the laboratory, porous carbonate sand (CS) and cohesion-less silt were utilized to prepare host sand of methane hydrate. In this paper, based on the analysis of experimental data, a bounding surface model was proposed to describe the mechanical behavior of artificial MHBS. The effect of methane hydrates on the elastic strain, normal consolidation and critical state of host sand is discussed, and corresponding equations for the model parameters are established, taking into consideration the cementing mechanism of hydrates. These equations are defined as functions of hydrate saturation, carbonate sand content (CSC), and initial void ratio. The increase in hydrate saturation significantly reduces the compressibility of the host sand and improves its strength. The proposed model is applied to predict the results of isotropic consolidation and drained triaxial tests on MHBS, demonstrating satisfactory performance.

MODELING AND SIMULATIONS OF WET POROUS MEDIUM CONVECTIVE DRYING

In the convective drying of a wet porous medium by hot air, the medium surface exposed to the air fluid may experience three stages, namely the fully wet, partly wet, and fully dry stages. At the fully wet stage, the medium surface is fully covered by a water film, with the convective moisture transfer taking place all over the medium surface; at the partly wet stage, the medium surface is partly covered by water film, with the convective moisture transfer occurring only at the wet surface where free water is present. In this research, a theoretical model is presented to simulate the convective drying of a wet porous medium, and experiments on hot-air convective drying of a wet porous sand layer are carried out to investigate the sand-layer temperature and water content variations during the drying, in which the sand layer thickness is 4 mm, the initial water-film thickness is 0.4 mm, and the hot-air temperatures are 45, 60, and 75°C, respectively. Inverse calculations are conducted to get some insight into the water-film coverage function based on the experimental data, which are necessary for quantitatively evaluating the effective moisture transfer surface area when calculating the convective moisture transfer at the partly wet stage. By combining the coverage function with the wet porous medium drying model, a comprehensive model is obtained. Calculations are implemented to simulate the convective drying of the wet porous sand layer, and the effects of the two constants included in that function on the wet sand-layer drying characteristics are discussed. The calculation results are compared with the experimental data; they agree very well, supporting the effectiveness of the current model in simulating the sand-layer convective drying process.

FORMATION AND DISSOCIATION OF CO2 HYDRATES WITHIN A NATURAL BASALTIC-BASED POROUS MEDIUM FROM ICELANDIC MARGINS

Carbon dioxide hydrates were formed and dissociated in a lab-scale apparatus, filled with demineralized water and porous sediments. Two different porous media were tested; the first consists of glass beads, commonly used to reproduce marine environments during lab-scale hydrate formation experiments. Natural basaltic sand, typical of the Icelandic margins, was chosen as second sediment. The role played by the two sediments was analyzed during both the hydrate formation and dissociation processes and the results were compared with each other. In particular, the pressure-temperature values measured during the dissociation phase were compared with the phase boundary equilibrium conditions for pure carbon dioxide hydrates, carried out in the absence of any porous sediment, collected from the scientific literature. The presence of porous sand favored the preservation of hydrates during the dissociation phase; in detail, hydrates melted at pressures 1.1 bar higher (on average) in the presence of glass beads, and 1.0 bar higher with the basaltic sand. The formation was more abundant in the presence of glass beads: 0.227-0.232 mol of hydrates were produced, against 0.141-0.21 mol achieved when the basaltic sediment was used.

Study of Moulding Sands to Create Three-Layer Magnesium Concrete

Abstract The article is devoted to the problem of creating energy-efficient building materials for enclosing structures. The aim of the research is to develop a recipe and a method for moulding sands placing to create heat-insulating concrete of a multilayer structure. The three-layer magnesium concrete containing layers of different densities is an object of a scientific research. Compositions of moulding sands for concrete’s central and surface layers have been developed and studied. Materials specially developed were used as raw materials for moulding sands; they are as follows: composite magnesial binder and porous filler obtained by low-temperature firing of a granular mixture based on sodium liquid glass and thermal energy waste (fly ash from thermal power plants, aluminosilicate microsphere). Possibility of regulating moulding sand’s properties for concrete’s central layer by varying the content and fractional composition of porous granules has been shown. There has been proposed the moulding sand for surface layers of three-layer magnesium concrete containing crushed porous sand. The related composition of moulding sands favours with adhesion of concrete’s different layers. Various technological methods for producing magnesium concrete of a complex structure have been studied. The research reveals technological and operational characteristics of three-layer magnesium concrete obtained by horizontal and vertical deposition of moulding sands.

Performance Evaluation of Various Filter Media for Multi-Functional Purposes to Urban Constructed Wetlands

The escalating demand for innovative solutions is driven by the challenges posed by water quality degradation and the pervasive impacts of climate change. As such, this study evaluated the performance of filter media to mitigate these challenges through multi-functional applications in urban constructed wetlands (UCWs). Column testing of organic filter media, including biochar (BC), woodchip (WC), anthracite (AT), and activated carbon (AC), as well as inorganic filter media, such as ceramic balls (CB), basalt (BS), and porous sand (PS), with synthetic stormwater runoff influent was conducted to assess their performance through water quality parameters and Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) analysis for carbon storage potential. Among the media tested, AC exhibited high pollutant removal efficiencies amounting to 84%, 54%, 56%, and 44% for total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), respectively. For inorganic media, PS had the highest TSS and TN removal, whereas BS exhibited the highest COD and TP removal. Overall performance rating revealed that AC and BS, despite their efficient pollutant removal, are associated with higher costs, resulting in a lower ranking compared to AT and PS. SEM-EDX analysis identified PS and AC as standout media for potential carbon storage, attributed to their extensive surface areas and pore structures providing abundant adsorption sites. The results from this study highlighted the potential applications of various filter media in UCW designs with the aim of achieving carbon neutrality and sustainable urban development.

Heterogeneous distribution of lightweight porous ceramic sands in a high strength cement grout

Material heterogeneity may occur to cement grouts especially when lightweight fine inclusions are used, however, the quantitative assessment still remains a challenging task. In this work, a lightweight ceramic sand (LCS) was adopted to partially replace a quartz sand (QS) for fabricating two grouts, namely LCS-GM and O-GM. The impacts of LCS on the flowability, expansion and compressive strength were first measured in laboratory tests. To approach the real construction conditions, the grouting materials were cast in 6-meter-long tubes, and the compressive strength and microstructure of the specimens at different depths were measured. X-ray computed tomography (XCT) was employed to nondestructively quantify the structure and distribution of the pores and LCS particles. Results demonstrated that the partial replacement of QS with LCS can decrease compressive strength, reduce expansion, but increase flowability. Both density and compressive strength increased linearly with depth. The long-tube casting entrapped more air voids for O-GM. Less air voids and LCS particles were detected for a deeper LCS-GM specimen. Tight interactions between the cement matrix and LCS particles were observed. The regimes of water release and air void accommodation by the porous LCS particles may account for the experimental observations. The findings provide a reliable way to fabricate lightweight and high strength grouting materials and deepen the understandings of material heterogeneity in cement-based materials.

Investigating the transport and colloidal behavior of Fe3O4 nanoparticles in aqueous and porous media under varying solution chemistry parameters.

The possible adverse effects of engineered iron oxide nanoparticles, especially magnetite (Fe3O4 NP), on human health and the environment, have raised concerns about their transport and behavior in soil and water systems. Accumulating these NPs in the environment can substantially affect soil and water quality and the well-being of aquatic and terrestrial organisms. Therefore, it is essential to examine the factors that affect Fe3O4 NP transportation and behavior in soil and water systems to determine their possible environmental fate. In this work, experiments were conducted in aqueous and porous media using an environmentally relevant range of pH (5, 7, 9), ionic strength (IS) (10, 50, 100 mM), and humic acid (HA) (0.1, 1, 10 mg L-1) concentrations. Fe3O4 NPs exhibited severe colloidal instability at pH 7 (⁓ = pHPZC) and showed an improvement in apparent colloidal stability at pH 5 and 9 in aquatic and terrestrial environments. HA in the background solutions promoted the overall transport of Fe3O4 NPs by enhancing the colloidal stability. The increased ionic strength in aqueous media hindered the transport by electron double-layer compression and electrostatic repulsion; however, in porous media, the transport was hindered by ionic compression. Furthermore, the transport behavior of Fe3O4 NPs was investigated in different natural waters such as rivers, lakes, taps, and groundwater. The interaction energy pattern in aquatic systems was estimated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. This study showed the effects of various physical-chemical conditions on Fe3O4 NP transport in aqueous and porous (sand) media.

Bio-cementation of coral sand using microbial-induced calcite precipitation with sodium alginate

Coral sand with microbial-induced calcite precipitation (MICP) is a promising material for practical engineering. This study attempts to improve the precipitation efficiency by using a modified bio-cement method based on MICP and sodium alginate (SA). It was found that adding an appropriate amount of SA in the bacterial solution could greatly improve the ability of immobilising bacteria, thus achieving an effective precipitation of calcium carbonate on the aggregate surfaces. As the SA content increased, the weight increment and unconfined compressive strength of each sample after MICP cementation initially increased and then decreased. Three main failure modes were observed, i.e., the particle unbroken failure, stepped failure, and steep drop failure. Owing to the macro pores of coral sand, the specific loss of calcium carbonate crystals produced by MICP had a significant effect on the cementation performance, while prolonging the single soaking time could favourably reduce the crystal loss. The calcium carbonate crystals occupied part of the pores between sand aggregates, but did not change the compression strength of a single aggregate significantly.