Submicron Pores Research Articles

A novel feathery nanoporous magnesium synthesized by ethanol vapor assisted physical vapor deposition

Nanoporous magnesium exhibits outstanding performance in hydrogen absorption and desorption, rendering it a promising candidate for hydrogen storage applications. Nevertheless, there is limited discussion on the preparation method and growth mechanism of nano-porous magnesium. In this paper, a novel nanoporous magnesium material characterized by a feathery morphology was successfully synthesized at 823 K for 2 h under a vacuum pressure of 3 Pa, assisted by ethanol vapor through the physical vapor deposition method. The ethanol vapor was identified as the crucial factor in the synthesis of the feathery nanoporous magnesium. A vacancy-assisted formation mechanism is proposed to elucidate the creation of feathery nanoporous magnesium, whereby the ethanol vapor occupies specific positions within the magnesium vapor, resulting in the formation of nano and submicron pores.

Evaluation of movable fluid and controlling factors in lacustrine gravity-flow tight sandstone reservoirs: Implications for predicting reservoir quality

Lacustrine gravity-flow tight sandstone reservoirs are rich in petroleum resources, and the presence of movable fluids is essential for the efficient recovery of tight oil. However, characterizing the properties of movable fluids and predicting their content are challenging due to the limited data available on these fluids. To address this research gap, it is imperative to conduct a comprehensive study on the distribution patterns and controlling factors of movable fluids within the lacustrine gravity-flow tight sandstone reservoirs of the Chang-7 Member in the Heshui region of the Ordos Basin. The study utilized a range of analytical techniques, such as thin section analysis, scanning electron microscopy (SEM), high-pressure mercury injection (HPMI), constant-rate mercury injection (CRMI), and nuclear magnetic resonance (NMR). We identified three distinct lithofacies and three types of pore-throat spaces within these lacustrine gravity-flow sandstones. The highest amount of movable fluid was observed in the submicron pore throats, followed by nanopore throats, while the micron pore throats exhibited the lowest amount. Our analysis indicates that petrophysical parameters, mineral composition, and pore throat structures collectively influence the content of movable fluids. Specifically, quartz and feldspar content are positively correlated with the movable fluid content, while clay and carbonate cement content are negatively correlated. Fine sandstones with massive bedding typically have a high content of movable fluids, which is associated with elevated quartz and feldspar content. In contrast, very fine sandstones to siltstones with parallel or ripple beddings have a very low content of movable fluids, characterized by high levels of carbonate and clay cementation. The study also suggests that the lower limit of the pore throat radius of movable fluid is about 0.03 μm. These findings offer novel insights for evaluating and predicting high-quality lacustrine gravity-flow tight sandstone reservoirs, enabling more effective exploration and development strategies.

Morphology evolution and mechanism of massive three-level hierarchically porous silver fabricated by vapor phase dealloying

In this study, the Gasar process and vapor phase dealloying (VPD) method were combined to fabricate a massive three-level hierarchical porous silver (MTHPS), which composed of interconnected micron-sized, submicron-sized, and nanoporous structures. The key aspect of this study lies in the preparation of a hypoeutectic Gasar Mg91.6Ag8.4 alloy with the regular micron-scale pore structure as the dealloying precursor, improving the size of the hierarchical porous metal. Under high vacuum conditions, by adjusting the dealloying time and temperature, MTHPS samples with various morphologies were obtained. After dealloying, the MTHPS exhibited Gasar pores (diameter 376 ± 86 μm), submicron pores (diameter 465 ± 125 nm), and a continuous ligament/channel structure (pore size less than 70 ± 40 nm). The coarsening index was 3.6258, and the activation energy was measured to be 0.95 eV, indicating that the formation and coarsening of the pores during VPD are attributed to surface diffusion. The calculated evaporated mass of the precursor alloy after dealloying was very close to the experimental value (±0.004 g), indicating that the evaporation of Mg occurred simultaneously in both solid and liquid phases during the VPD process. This study elucidates the phase transformation characteristics, structural control, and diffusion mechanisms of MTHPS prepared by VPD, providing valuable insights for further research and applications of MTHPS.

Adsorption and retention of fracturing fluid and its impact on gas transport in tight sandstone with different clay minerals

To elucidate the adsorption characteristics and retention mechanisms of fracturing fluids in diverse clay minerals, we conducted on-line nuclear magnetic resonance (NMR) and atomic force microscopy (AFM) experiments. The depth and extent of solid phase damage are determined by the ratio between the size of fine fractions in fracturing fluid residue and the pore-throat size in experiments. Poor physical properties (K < 0.5 mD) result in a more preferential flow pathway effect during flowback, and the stepwise incremental pressure differential proves to be more effective for the discharge of fracturing fluid in submicron pore throats. The permeability is significantly influenced by the differential distribution of retained fracturing fluid, as supported by direct experimental evidence. The presence of good physical properties (K > 0.5 mD) combined with a scattered distribution of retained fracturing fluid is associated with high gas phase recovery permeability, whereas a continuous sheet-like distribution results in low recovery permeability. The expansive surface area and presence of filamentous illite minerals facilitate the multiple winding and adsorption of fracturing fluids, demonstrating strong hydrogen-bonding, multi-layering and multiple adsorption properties. The geological characteristics of the main gas formations exhibit significant variation, and the severity of damage caused by fracturing fluids occurs in diverse sequences. To address this issue, a differentiated strategy for optimizing fracturing fluids has been proposed.

Fabrication of low conductivity and high strength MgO-MgAl2O4 aggregates with sub-micron pore structure

Lightweight MgO-MgAl2O4 refractory aggregates were fabricated by using fine MgO and spherical Al(OH)3 powders as starting materials. The evolutions of microstructure and pores and their effects on the properties of the specimens were investigated. During heating process, MgO crystallites diffused into the formed Al2O3 pseudomorph, producing sub-micron intra-particle pores in both MgAl2O4 cores and MgO matrix. Besides, larger inter-particle pores between the MgAl2O4 cores and MgO matrix were occurred, attributing to the Kirkendall effect resulting from in-situ spinalization. As MgO content increased from 50 wt% to 80 wt%, due to reduction of the number of the porous MgAl2O4 cores, the inter-particle pores caused by Kirkendall effect decreased sharply in both number and size, while no obvious changes occurred in the intra-particle pores as the porous MgO matrix amount increased simultaneously. The decrease of large inter-particle pores caused obvious improvement in strength but slight increase in thermal conductivity. With a further increase of MgO to 90 wt%, as the number of the porous MgAl2O4 cores reduced further and the MgO matrix densification improved obviously, intra-particle pores and thermal insulation performance reduced significantly. The specimen with 80 wt% MgO showed the best performance, with a median pore diameter of 0.26 μm, apparent porosity of 36.0 %, flexural strength of 23.9 MPa, and thermal conductivity of 2.1 W/(m·K) at 500 °C.

Agglomerate Engineering to Boost PEM Water Electrolyzer Performance

AbstractDensely packed IrOx‐ionomer agglomerates play a crucial role in the high mass transport resistance inside the anode catalyst layer (ACL), which in turn greatly affects the electrolysis performance at high current density. Therefore, agglomerate engineering for PEMWE is proposed in this work to enhance the oxygen transport process inside ACLs. Using self‐assembling nanotechnology, tightly packed primary aggregates are avoided and introduce the interconnected submicron pores and nanocavities into the catalyst‐ionomer agglomerate, confirmed by synchrotron radiation‐based nano‐CT, TEM, and BET. Such agglomerate engineering results in the enhancement of both dissolved oxygen and oxygen bubble transport inside the ACL confirmed by RDE tests and in‐situ bubble visualization. As a result, the mass transport overpotential is significantly reduced from 330 to 30 mV at 5 A cm−2 in PEMWE, optimized Ohmic resistance and catalyst utilization are also observed. Finally, high operating current density is achieved, i.e., 5 A cm−2 @2.04 V with Nafion 115 membrane and 7 A cm−2 @ 2.07 V with Nafion 212 membrane, under a low catalyst loading of 0.72 mgIr cm−2. This study proves the importance and feasibility of agglomerate engineering in further elevating the performance of PEMWE.

Experimental and numerical simulation study on enhanced oil recovery by N2-Assisted water huff-n-puff in a tight oil reservoir

The water huff-n-puff (WHP) method is widely used for improving oil recovery in tight reservoirs. However, the poor flow conductivity and low sweep efficiency of the matrix restrict the oil recovery performance of this method. Herein, N2-assisted water huff-n-puff (NAWHP) was proposed to improve oil recovery under reservoir conditions. First, the feasibility of NAWHP for tight reservoirs was investigated by comparing the enhanced oil recovery (EOR) performance with that of WHP and N2 huff-n-puff (NHP). The core flooding experimental results revealed that NAWHP facilitated oil recovery improvement, outperforming the existing practice of water or N2 huff-n-puff injection. Thereafter, with the aid of nuclear magnetic resonance (NMR) technology, the application of NAWHP could significantly enhance oil recovery in fractured tight cores, which mainly increased oil recovery from micro- and nanopores in the matrix. Specifically, for submicron pores and micropores, after three cycles of NAWHP, the recovery efficiency increased by 21.35% and 36.19%, respectively, while the recovery only increased by 14.34% and 24.8%, respectively, during WHP. For nanopores and micro/nanopores, the use of WHP increased the total oil recovery by only 4.71%, while the use of NAWHP increased the total oil recovery threefold. Finally, a series of numerical simulations were conducted to explore the effects of different parameters on oil recovery by NAWHP. The results illustrated that a high N2–water ratio (NWR) positively affected the overall oil recovery, but the higher the NWR was, the more difficult to extract the oil below the injection layer. By injecting 13,000 m3 of N2, the maximum swept volume was achieved for the matrix, and water filled the major fractures after injecting 11,000 m3, effectively accomplishing this task. Increasing the soaking time positively influenced oil recovery, N2 diffusion within the matrix led to an even distribution over 50 days, and water imbibition caused a significant increase in the oil saturation in hydraulic fractures within 30 days. The application of NAWHP increased the number of huff-n-puff cycles of water from a maximum of 3–5.

3D Printing of High-Porosity Membranes with Submicron Pores for Microfluidics

3D Printing of High-Porosity Membranes with Submicron Pores for Microfluidics

Impact of Lime Saturation Factor on Alite-Ye'Elimite Cement Synthesis and Hydration.

Alite(C3S)-Ye'elimite(C4A3$) cement is a high cementitious material that incorporates a precise proportion of ye'elimite into the ordinary Portland cement. The synthesis and hydration behavior of Alite-Ye'elimite clinker with different lime saturation factors were investigated. The clinkers were synthesized using a secondary thermal treatment process, and their compositions were characterized. The hydrated pastes were analyzed for their hydration products, pore structure, mechanical strength, and microstructure. The clinkers and hydration products were characterized using XRD, TG-DSC, SEM, and MIP analysis. The results showed that the Alite-Ye'elimite cement clinker with a lime saturation factor (KH) of 0.93, prepared through secondary heat treatment, contained 64.88% C3S and 2.06% C4A3$. At this composition, the Alite-Ye'elimite cement clinker demonstrated the highest 28-day strength. The addition of SO3 to the clinkers decreased the content of tricalcium aluminate (C3A) and the ratio of Alite/Belite (C3S/C2S), resulting in a preference for belite formation. The pore structure of the hydrated pastes was also investigated, revealing a distribution of pore sizes ranging from 0.01 to 10 μm, with two peaks on each differential distribution curve corresponding to micron and sub-micron pores. The pore volume decreased from 0.22 ± 0.03 to 0.15 ± 0.18 cm3 g-1, and the main peak of pore distribution shifted towards smaller sizes with increasing hydration time.

Solvent Cavitation during Ambient Pressure Drying of Silica Aerogels.

Ambient-pressure drying of silica gels stands out as an economical and accessible process for producing monolithic silica aerogels. Gels experience significant deformations during drying due to the capillary pressure generated at the liquid-vapor interface in submicron pores. Proper control of the gel properties and the drying rate is essential to enable reversible drying shrinkage without mechanical failure. Recent in operando microcomputed X-ray tomography (μCT) imaging revealed the kinetics of the phase composition during drying and spring-back. However, to fully explain the underlying mechanisms, spatial resolution is required. Here we show evidence of evaporation by hexane cavitation during the ambient-pressure drying of silylated silica gels by spatially resolved quantitative analysis of μCT data supported by wide-angle X-ray scattering measurements. Cavitation consists of the rupture of the pore liquid put under tension by capillary pressure, creating vapor bubbles within the gels. We found the presence of a homogeneously distributed vapor-air phase in the gels well ahead of the maximum shrinkage. The onset of this vapor/air phase corresponded to a pore volume shrinkage of ca. 50 vol % that was attributed to a critical stiffening of the silica skeleton enabling cavitation. Our results provide new aspects of the relation between the shape changes of silica gels during drying and the evaporation mechanisms. We conclude that stress release by cavitation may be at the origin of the resistance of the silica skeleton to drying stresses. This opens the path toward producing larger monolithic silica aerogels by fine-tuning the drying conditions to exploit cavitation.

Design and preparation of a massive trimodal porous silver by the combinational process of Gasar and dealloying

This study introduces a combined way of Gasar and dealloying process for fabricating massive three-level hierarchically porous silver (MTHPS). The key contributions of this research lie in improving the dimension of obtained hierarchical porous metals. The thickness of the de-alloyed precursor can be skillfully characterized by the inter-pore spacing l in Gasar porous metals utilizing Gasar process. By effectively adjusting the phase in as-cast Mg82.43Ag17.57 and the corrosion solution, the MTHPS samples with different morphologies are obtained. After dealloying the as-cast Gasar porous Mg82.43Ag17.57, hierarchical porous Ag which consists of lotus-type macropores (a diameter of 376 ± 86 μm), honeycomb submicron pores (a diameter of 360 ± 78 nm), and continuous ligament/channel structures (with pore diameters less than 56 ± 23.9 nm) were obtained. The Mg4Ag phase was observed in the T4-treated Gasar porous Mg82.43Ag17.57, which contributes to the formation of a novel tertiary porous structure. In addition, the catalytic performance of MTHPS for formaldehyde was evaluated in an alkaline environment, and the results showed that three-level porous silver with small pore size and well-continuous ligament/channel structured nanopores exhibited excellent electrocatalytic properties.

Microstructure and phase evolution of Fe-20Ni-20W foams during high-temperature redox cycling

Freeze-cast Fe-20Ni-20 W (at%) foams suitable for high-temperature redox cycling show excellent microstructural stability and regenerative porosity formation, but they exhibit slower reduction kinetics as compared to previously studied Fe-25 W foams. The Fe-20Ni-20 W lamellar foams, after initial hydrogen reduction, consist of a two-phase mixture of µ-Fe7W6 and γ-Fe(Ni,W), with significant microporosity due to the sintering inhibition of W. During oxidation by steam at 800 °C, these phases are oxidized to a three-phase mixture of (Fe,Ni)WO4, Fe3O4, and γ-Ni(Fe); upon subsequent reduction by H2, the foams return to their initial composition. The chemical vapor transport reduction of FeWO4 results in the formation of submicron pores during each reduction half-cycle which accelerate subsequent reaction and limit sintering in the reduced state. The reduction of mixed oxide is relatively sluggish, which is likely due to the increased stability of the (Fe,Ni)WO4 phase brought on by the substitution of Ni in Fe sites in FeWO4.

Effect of submicron pore sized waste coffee emesis biochar on glass–epoxy composite thermal interface material

Effect of submicron pore sized waste coffee emesis biochar on glass–epoxy composite thermal interface material

Microstructural and microchemical analysis of zircon in a syenite lithic fragment from Ulleung Island volcano, South Korea

Abstract Background The intricate textural patterns commonly observed in metamorphosed and recrystallized zircon (ZrSiO4) underscore the crucial necessity of understanding the underlying mechanisms governing their formation to ensure accurate interpretation of the chemical and isotope data they contain. This study employed a combination of microanalytical techniques, including electron backscattered diffraction (EBSD) analysis, electron microprobe (EMP) mapping, and scanning electron microscope (SEM) imaging, to investigate the processes of formation and modification of zircon in a late Pleistocene (~ 35 ka) syenite enclosed within the Nari Tephra Formation on Ulleung Island in South Korea. Findings Under cathodoluminescence (CL), zircons within the syenite reveal dark, featureless, or oscillatory-zoned cores containing numerous inclusions of britholite. These cores are partially or entirely replaced by inward-penetrating bright-CL domains that exhibit minimal inclusion presence. Despite these changes, the external morphologies of the zircons remain largely unchanged, and the faded oscillatory zoning is preserved in the replaced regions. EMP mapping discloses amoebiform micro-domains with high Y, U, and Th concentrations within the dark-CL cores, while the bright-CL domains are relatively deficient in these trace elements. Microstructural analysis of the zircons using EBSD mapping indicates no significant misorientation between the dark-CL cores and the bright-CL rims. Deformation-related low-angle boundaries by lattice distortion are clearly observed in certain grains, cutting across the discrete SEM and EMP domains, and often aligned along submicron pore trails. Conclusions Microstructural and microchemical analyses carried out in this study establish that the zircons within the Ulleung syenite have undergone subsolidus recrystallization, a process likely influenced by the presence of fresh melts or fluids. This recrystallization process could be attributed to either coupled dissolution and reprecipitation or thermoactivated particle and defect volume diffusion due to inherent lattice strain. The subsequent deformation observed in the zircons might be a result of increased stress within the magma system after the recrystallization.

Determination of the porosity characteristics by pycnometric methods

Data on pore size distribution in solids are obtained by pycnometric density-based methods for measuring the pore structure of materials. The results of measuring open porosity by weighing a dry sample followed by evacuation and saturation with distilled water at atmospheric pressure, impregnation with water under pressure using a hydrostat and mercury porosimetry are presented. The samples of porous nickel obtained using powder technology by sintering of the compacts from mixtures of nickel nanopowder with powder ammonium bicarbonate NH4HCO3 (a blowing agent), the volume fractions of which were 80 and 20%, respectively, were studied. A powder blowing agent with a particle size of 63 – 125, 140 – 200, and 250 – 315 μm was used. A theoretical estimation of the pore size available for the penetration of the impregnating liquid was carried out for three methods used for the determination of open porosity. It is shown that upon water saturation after evacuation the liquid can penetrate only into pores larger than 3 μm. Moreover, in porous structures with a large fraction of submicron pores, the actual values of the open porosity are significantly underestimated when using the method of saturation with distilled water after evacuation. The higher the fraction of fine pores in the material, the lower the open porosity value. The difference between the open porosity values determined by methods of water impregnation using a hydrostat and mercury porosimetry was negligible. It has been established that among three considered methods for measuring open porosity, only the method of saturation with distilled water after evacuation cannot be used in analysis of structures with submicron pores. The results obtained can be used to develop porous functional materials and products with a given porosity structure.

Leveraging Expertise in Thermal Catalysis to Understand Plasma Catalysis.

Best practices in testing heterogeneous catalysts are translated to plasma-catalytic experiments. Independent determination of plasma-catalytic and plasma-chemical contributions is essential. Non-porous catalyst particles are preferred because active sites inside sub-micron pores cannot contribute. Temperature variation is needed to determine kinetics, despite the complexity of thermal effects in plasma. Rigorous checks on catalyst deactivation and mass balance are needed. Plasma enhanced reversed reactions should be minimized by keeping conversion low and far from thermodynamic equilibrium, preventing underestimation of the rate of forward reaction. In contrast, plasma-catalytic studies often aim at conversions surpassing thermodynamic equilibrium, not obtaining any information on kinetics. Calculation of catalyst activity per active sites (turn-over-frequency) requires also appropriate characterization to determine the number of active sites. The relationship between kinetics and thermodynamics for plasma-catalysis is discussed using endothermic decomposition of CO2 and exothermic synthesis of ammonia from N2 and H2 as examples. Assuming Langmuir-Hinshelwood and Eley-Rideal mechanisms, the effect of excitation of reactant molecules on activation barriers and surface coverages are discussed, influencing reaction rates. The consequences of reversed reactions are considered. Plasma-catalysis with catalysts applied for thermal catalysis at much higher temperature should be avoided, as adsorbed species are bonded too strongly resulting in low rates.

Low temperature regulated reverse interfacial polymerization for fabricating thin film composite membranes based on nanofibrous substrates

In this study, a novel thin film nanofibrous composite (TFNC) nanofiltration (NF) membranes comprised of polyacrylonitrile (PAN) nanofibrous supporting layer and polyamide (PA) compact separating layer was constructed by low-temperature-controlled reverse interfacial polymerization (LTIP-R) at − 5 °C. The strategy for lowering the temperature of organic phase solution played a crucial role in forming a dense and thin PA layer on the PAN nanofibrous substrate with submicron pores. The results revealed that the reduced evaporation rate of organic phase at low temperature was contributed to maintaining a complete and uniform interface for the following reverse IP process, effectively overcoming shortcomings of surface incompleteness and easy infiltration of PA barrier layer. Owing to the reduced thickness and the enhanced wholeness of the PA separating layer via LTIP-R, the optimized TFNC membranes exhibited NF performance with great rejection of divalent salt ions (98.2%) and an improved permeation (13.3 L‧m−2‧h−1‧bar−1). This work would provide an efficient and facile method to fabricate high performance NF membranes for practical applications.

Advancing Breathability of Respiratory Nanofilter by Optimizing Pore Structure and Alignment in Nanofiber Networks.

Respiratory masks are the primary and most effective means of protecting individuals from airborne hazards such as droplets and particulate matter during public engagements. However, conventional electrostatically charged melt-blown microfiber masks typically require thick and dense membranes to achieve high filtration efficiency, which in turn cause a significant pressure drop and reduce breathability. In this study, we have developed a multielectrospinning system to address this issue by manipulating the pore structure of nanofiber networks, including the use of uniaxially aligned nanofibers created via an electric-field-guided electrospinning apparatus. In contrast to the common randomly collected microfiber membranes, partially aligned dual-nanofiber membranes, which are fabricated via electrospinning of a random 150 nm nanofiber base layer and a uniaxially aligned 450 nm nanofiber spacer layer on a roll-to-roll collector, offer an efficient way to modulate nanofiber membrane pore structures. Notably, the dual-nanofiber configuration with submicron pore structure exhibits increased fiber density and decreased volume density, resulting in an enhanced filtration efficiency of over 97% and a 50% reduction in pressure drop. This leads to the highest quality factor of 0.0781. Moreover, the submicron pore structure within the nanofiber networks introduces an additional sieving filtration mechanism, ensuring superior filtration efficiency under highly humid conditions and even after washing with a 70% ethanol solution. The nanofiber mask provides a sustainable solution for safeguarding the human respiratory system, as it effectively filters and inactivates human coronaviruses while utilizing 130 times fewer polymeric materials than melt-blown filters. This reusability of our filters and their minimum usage of polymeric materials would significantly reduce plastic waste for a sustainable global society.

Thermal insulating and mechanical properties of high entropy pyrochlore oxide ceramic with hierarchical porous structures

High entropy pyrochlore oxide ceramics with hierarchical porous structures were prepared by coprecipitation, freeze-casting, and press-less sintering methods. In the fabrication process, a Ca2+-crosslinked alginate network was utilized to control the growth of ice crystals, resulting in uniformly dispersed micro-scale circular pores. The submicron pores were formed in the high entropy oxide ceramic during the press-less sintering method. The XRD was employed to explore the phase of the high entropy pyrochlore oxide ceramic. The porous structures of high-entropy ceramic were analyzed through the discussion of microstructure and pore size distribution. The tests show that the prepared series of ceramics with high porosity have optional compressive strength and thermal insulation properties. The high entropy oxide ceramic (La0.2Y0.2Gd0.2Sm0.2Nd0.2)2Zr2O7 with hierarchical porous structures possess moderate density (0.4 g/cm3) and low thermal conductivity (0.04 W m−1 K−1). The excellent comprehensive performance makes the porous high entropy oxide ceramic could be applied as a thermal insulating material.

First principal observation documenting the three-dimensional uptake of cadmium and spatial distribution of cadmium hydroxyapatite mineral in bone char

The 3-D matrix scale ion-exchange mechanism was explored for high-capacity cadmium (Cd) removal using bone chars (BC) chunks (1–2 mm) made at 500 °C (500BC) and 700 °C (700BC) in aqueous solutions. The Cd incorporation into the carbonated hydroxyapatite (CHAp) mineral of BC was examined using a set of synchrotron-based techniques. The Cd removal from solution and incorporation into mineral lattice were higher in 500BC than 700BC, and the diffusion depth was modulated by the initial Cd concentration and charring temperature. A higher carbonate level of BC, more pre-leached Ca sites, and external phosphorus input enhanced Cd removal. The 500BC showed a higher CO32-/PO43- ratio and specific surface area (SSA) than the 700BC, providing more vacant sites by dissolution of Ca2+. In situ observations revealed the refilling of sub-micron pore space in the mineral matrix because of Cd incorporation.The X-ray nanodiffraction (XND) analyses revealed that Cd was mainly removed from water by incorporation into the mineral lattice of 500BC via ion exchange, rather than surface sorption and precipitation, and the mineral phase was transformed from hydroxyapatite (HAp) to cadmium hydroxyapatite (Cd-HAp). The Rietveld's refinement of X-ray diffraction (XRD) data resolved up to 91% of the crystal displacement of Ca2+ by Cd2+. The specific phase and stoichiometry of the new Cd-HAp mineral was dependent on the level of ion exchange. This mechanistic study confirmed that 3-D ion exchange was the most important path for heavy metal removal from aqueous solution and immobilization in BC mineral matrix, and put forward a novel and sustainable remediation strategy for Cd removal in wastewater and soil clean-up.