Natural Allophane Research Articles

Nitrate adsorption characteristics of synthesized allophanes with various chemical compositions

AbstractAllophane-related aluminium silicates with various chemical compositions were synthesized using a hydrothermal reaction with inorganic reagents as starting solutions. The X-ray diffraction traces of the synthesized allophanes showed broad reflections centred at 0.34 and 0.23 nm, which were attributed to the imogolite-like structure of the allophanes. Energy-dispersive X-ray measurements confirmed that the Al-rich materials were synthesized as targeted. The specific surface area of the synthesized allophanes was 313–500 m2 g–1, which is greater than that of a natural allophane (248 m2 g–1). The amount of nitrate adsorbed on the synthesized allophanes tended to increase as the Al content increased. The maximum amount of nitrate adsorbed was 2.07 mmol g–1 at pH ~2, which was comparable to that of a common anion-exchange material. A possible adsorption mechanism for nitrate at lower pH levels is the weak NO3– interaction of the positively charged surface of Al-OH2+ sites.

Aggregation and charging of natural allophane particles in the presence of oxyanions

Allophane is a typical clay mineral in young volcanic ash soil with special and complex structures and properties. The aggregation-dispersion and charging behaviors of natural allophane may have implications on sustainable agriculture and environment. Oxyanions, such as phosphate and arsenate, may also be related to many environmental resource problems. To investigate the aggregation and charging behaviors of allophane in the presence of oxyanions, the stability ratio (W) and electrophoretic mobility (EPM) of allophane were measured. The results of EPM, W and the values of CCCs show ion specific effect, which is not explicitly considered by the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory. However, the relationship between critical coagulation ionic strength (CCIS) and surface charge density from EPM based on DLVO theory with the Debye-Huckel (DH) approximation is in good agreement with the experimental CCIS. This agreement indicates that the DLVO forces controlled by ionic strength and electrokinetic charge are the driving forces in the aggregation process of natural allophane particles in the presence of oxyanions.

The aggregation and charging of natural clay allophane: Critical coagulation ionic strength in the presence of multivalent counter-ions

Allophane is an amorphous aluminosilicate clay mineral which is typically found in young volcanic ash soils. The aggregation-dispersion and charging behaviors of allophane may affect the usability and protection of the volcanic ash soils and surrounding environment. To understand the aggregation-dispersion and charging of natural allophane, dynamic and electrophoretic light scattering experiments were carried out at pH 5 as a function of potassium salt concentration and counter-ion (Cl - , SO 4 2- , Fe(CN) 6 3- , and Fe(CN) 6 4- ) valence. The temporal increase of particle hydrodynamic diameters and electrophoretic mobilities (EPM) were measured, and the stability ratio, critical coagulation concentration (CCC), critical coagulation ionic strength (CCIS), zeta potential, and surface charge density were further obtained. The experimental results of stability ratio and EPM of allophane particles were affected by the counter-ion valence, and the CCCs strongly depended on the counter-ion valence. The behavior was well described by the well-known empirical Schulze-Hardy rule. The allophane particles showed a low surface charge density in the presence of multivalent counter-ions. Thus, Derjaguin-Landau and Verwey-Overbeek (DLVO) theory with the Debye-Huckel (DH) approximation was applied to consider the CCIS. The experimental relationship between CCIS and surface charge density was well explained by DLVO theory by taking account of particle size. We conclude that, in the presence of multivalent counter-ions, the DLVO theory with DH approximation has a good applicability to the aggregation-dispersion of natural clay allophane particles. • Counter-ion valence affects the aggregation and charging of allophane particles. • Tetravalent counter-ion induces charge reversal and re-stabilization of allophane. • Critical coagulation ionic strength vs. surface chare follows DLVO theory. • DLVO theory has a good applicability to the aggregation and dispersion of allophane.

Use of Allophane as Face Mask Filter for Coronaviruses (Sars-Cov-2)

The traditional mouth cover masks can be made by hand. But with the arrival of the Coronavirus pandemic, these masks have special requirements and we will have to use these until at least 2022. Therefore, the current technological problem is what must be the appropriate filter nanomaterial (cuprum, zinc, zeolite or Allophane) to absorb and/or destroy coronaviruses. In addition, the preparation of this specific purpose mask must be certified, easy to manufacture and inexpensive. Taking these requirements into account, there is a suitable nanomaterial called Allophane, which has active centers of silicon and aluminum (Si / Al), which rapidly absorb micro droplets and nanodrops of water [3, 5] nm. Coronaviruses are microscopically embedded in water droplets. To build an absorbent filter that also destroys coronaviruses, we can use some organic surfactant in optimal proportions and that works cooperatively with Allophane. The physicochemical properties of natural Allophane were studied. For the characterization, analytical techniques were used: Fourier transform infrared spectroscopy (FTIR), BET surface area, X-ray diffraction (XRD), Chemisorption and Atomic Force Microscopy (AFM). In addition, the Navier Stokes 3D equations were studied, which allow us studying molecular dynamics contributing substantively to chemical kinetics describing the process of absorption of water and decomposition of water + coronavirus.

Natural and Activated Allophane Catalytic Activity Based on the Microactivity Test in Astm Norm 3907/D3907M-2019

The optimal conditions of the catalytic activation of allophane were evaluated for possible use as a catalyst within a fluidized bed catalytic cracking unit (FCC). The physicochemical properties of natural allophane and activated allophane were studied by using an alkaline activating agent, followed by a hydrothermal treatment. For the characterization, analytical techniques were used: Fourier transform infrared spectroscopy, particle size, (BET) surface area, thermogravimetry (TGA), X-ray diffraction (XRD), chemisorption, X-ray fluorescence (XRF), atomic force microscopy (AFM), and chromatography. The catalytic evaluation was determined by the (MAT) micro activity test equipment constructed according to ASTM D-3907/D3907M-2019. In addition, the Navier–Stokes 3D equations (nonlinear partial derivatives) were studied, which allow studying molecular dynamics contributing substantively to chemical kinetics describing the process of decomposition of crude oil in thermal cracking, determining the maximum temperature at which it retains its properties through the action of heat.

APLIKASI ALOFAN DALAM TANAH ANDISOL SEBAGAI ADSORBEN UNTUK MENURUNKAN BAKTERI Coliform LIMBAH CAIR DOMESTIK

Research on allophane has been done as an adsorbent to decrease MPN Coliform in domestic wastewater. The purpose of this study was to look for natural adsorbent materials that can be used to decrease MPN Coliform. Natural allophane was identified from andisol soil by pH analysis of NaF, FTIR, XRD, and SAA. The result of the analysis showed that there was allophane on andisol soil with pH 11,73. The diameter of empty space or alloy pores of 5 nm with a hole/pore size of 0.5 nm. Testing of MPN Coliform is done by method of Most Probable Number (MPN) variety 5: 5: 5. Based on the result of the research, allophane adsorbent can decrease MPN Coliform by 60.9%.

Stable Solidification of Silica-based Ammonium Molybdophosphate in Ceramic Matrices and Its Cesium-leaching Properties

A pressing/sintering method was used for the stable solidification of spent cesium adsorbent by adding natural allophane and mordenite. The stable Cs4Al4Si20O48 crystalline phase was recrystallized by the reaction of Cs2O, Al2O3, and SiO2 above 1000 °C, and the Cs immobilization ratio of approximately 100% was maintained. The solidified products exhibited excellent leaching resistance in distilled water and 0.1 M NaCl. The leaching rate of Cs at 90 °C was in the order of H2O ≈ 0.1 M NaCl ≪ 0.1 M HNO3 < 0.1 M NaOH.

Kinetics, adsorption and desorption of Cd(II) and Cu(II) on natural allophane: Effect of iron oxide coating

Volcanic soils are a potential source of abundant and low-cost adsorbent materials. Allophane and iron oxides are the main inorganic constituents of Andisols, soils derived from volcanic-ashes abundant in the central and southern continental Chilean territory. The present study aimed to elucidate the effect of free iron oxides on the adsorption of Cd(II) and Cu(II) from aqueous media on natural allophane (NA). Allophane samples consisted of natural allophane, obtained from a Chilean Andisol series, with (NA-FeOx) and without (NA) an iron oxide coating. Material characterisation showed that NA-FeOx was formed by nanometric (100–500nm) sized spheres coated with an iron oxide layer that most likely consisted of a ferrihydrite-like mineral. On the other hand, NA consisted of aggregates (with particles as big as 1.0μm) mostly constituted by allophane. The specific surface area of NA-FeOx and NA were ca. 150 and 17m2g−1, respectively, and presented variable surface charge with an isoelectric point of 10.3. and 5.4. From the kinetic studies, equilibrium adsorption was achieved within 60min and was almost independent of the presence of the iron oxides. Among the kinetic models evaluated, the pseudo-second order model presented a better correlation with the experimental data. The adsorption studies revealed that NA has a greater adsorption capacity of both Cd+2 and Cu+2 compared to NA-FeOx. Langmuir and Freundlich adsorption models fit the experimental data well, suggesting that the adsorption process is a combination of physical and chemical phenomena. The Freundlich constant (adsorption coefficient, KF) values obtained confirmed the superior affinity of NA active surface sites compared to NA-FeOx. Desorption studies demonstrated that the majority of adsorbed cations were retained by the adsorbent, indicating irreversible chemical adsorption on specific active sites of the adsorbents.

Stable solidification of silica-based ammonium molybdophosphate by allophane: Application to treatment of radioactive cesium in secondary solid wastes generated from fukushima

Silica-based ammonium molybdophosphate (AMP/SiO2) is an absorbent material that can effectively remove Cs from radioactive-contaminated wastewater (RCW) generated by Fukushima nuclide accident. Pressing/sintering method was used for final disposal of secondary waste (spent absorbent) to achieve the volume reduction of AMP–Cs/SiO2 (AMP/SiO2 saturation adsorption of Cs) and stable solidification of Cs by adding natural allophane. The structure of AMP–Cs completely collapsed at approximately 700°C, and most Mo and P species in AMP sublimed. The optimal sintering temperature was estimated as 900°C. The stable crystalline phase of Cs4Al4Si20O48 was recrystallized by the reaction of Cs2O, Al2O3, and SiO2, and the immobilization ratio of Cs was approximately 100%. The leachability of Cs from the sintered product in distilled water was approximately 0.41%. The high immobilization and low leachability of Cs were attributed to the excellent solidification properties of the sintered products of AMP–Cs/SiO2–allophane.

New opportunities for drug delivery carrier of natural allophane nanoparticles on human lung cancer A549 cells

The complexation of allophane nanoparticles with cisplatin, cis-dichlorodiammineplatinum (II) (CDDP) to deliver platinum prodrug into cancer cells was investigated. Using human lung carcinoma (A549) cells, profound studies including cellular uptake (endocytosis) analysis of allophane nanoparticle, cell cycle arrest abilities and apoptosis induction profiles were discussed in detail. As well as the features against A549 cells to emerge a promising strategy to enhance their anti-cancer activity and to mitigate side-effects were discussed.

The anti-inflammatory activity of natural allophane

This paper presents evidence of the novel anti-inflammatory properties of natural allophane collected from New Zealand, Japan, and Ecuador. Allophanes were assessed by (i) the mouse-ear edema method using 12-O-tetradecanoylphorbol-13-acetate (TPA) as inflammatory agent; and (ii) the myeloperoxidase (MPO) enzymatic-activity method. After 4h, applying 1mgear−1 allophane conveyed edema inhibition (EI; p≤0.01) in up to 39%, while MPO content inhibition (CI) values surpassed 60%. Pearson's correlation analysis between EI and MPO data showed that edema was mediated by the migration of neutrophils at t=4h (p<0.05), but not at t=24h. The lack of variation in cellular migration with time was explained because of a reaction of zero-order kinetics. EPR spectra for allophanes showing higher anti-inflammatory activity denoted a broad signal centered at g=2, and an intense spin–spin interaction, typical of a low-spin, octahedral Fe3+ environment (S=1/2); and overlapping signals typical for Ni, with octahedral coordination, explained either by oxidation states +1 (Ni1+), +3 (Ni3+), or bulk Ni2+ ions.

Single-stranded DNA adsorption characteristics by hollow spherule allophane nano-particles: pH dependence and computer simulation

Clay mineral surfaces have been important for the prebiotic organization and protection of nucleic acids. The morphological observation to provide insight into the adsorption structure and characteristics of single-stranded DNA (ss-DNA) by natural allophane particles was presented. The molecular orbital (MO) computer simulation has been used to probe the interaction of ss-DNA and/or adenosine 5′-monophosphate and allophane with active sites. Our simulations predicted that the strand undergoes some extent of the elongation, which induces the alteration of the conformation of the phosphate backbone, base–base distance and excluded volume correlation among bases. This work demonstrates the ss-DNA adsorption by the allophane particles with novel insights into the morphological features and detailed molecular level information. The overall results support a general adsorption mechanism for the ss-DNA/allophane complexation.

XAFS Study of Fe-Substituted Allophane and Imogolite

AbstractThe nano-aluminosilicate mineral allophane is common in soils formed from parent materials containing volcanic ash and often contains Fe. Due to its lack of long-range order, the structure of allophane is still not completely understood. In the present study, Fe K-edge X-ray absorption fine structure (XAFS) was used to examine Fe-containing natural and synthetic allophane and imogolite samples. Results indicated that Fe substitutes for octahedrally coordinated Al in allophane, and that Fe exhibits a clustered distribution within the octahedral sheet. Iron adsorbed on allophane surfaces is characterized by spectral features distinct from those of isomorphically substituted Fe and of ferrihydrite. Fe adsorbed on the allophane surfaces probably exists as small polynuclear complexes exhibiting Fe-Fe edge sharing, similar to poorly crystalline Fe oxyhydroxides. The XAFS spectra of natural allophane and imogolite indicate that the Fe in the minerals is a combination of isomorphically substituted and surface-adsorbed Fe. In the synthetic Fe-substituted allophanes, the Fe XAFS spectra did not vary with the Al:Si ratio. Theoretical fits of the extended XAFS (EXAFS) spectra suggest that local atomic structure around octahedral Fe in allophanes is more similar to Fe in a smectite-like structure than to a published theoretical nanoball structure.

DNA adsorption characteristics of hollow spherule allophane nano-particles

To understand the propensity of natural allophane to adsorb the DNA molecules, the adsorption characteristics were assessed against natural allophane (AK70), using single-stranded DNA (ss-DNA) and adenosine 5′-monophosphate (5′-AMP) as a reference molecule. The adsorption capacity of ss-DNA on AK70 exhibited one order of magnitude lower value as compared with that of 5′-AMP. The adsorption capacity of ss-DNA decreased with increasing pH due to the interaction generated between phosphate groups of ss-DNA and functional Al–OH groups on the wall perforations through deprotonating, associated with higher energy barrier for the adsorption of ss-DNA. The adsorption morphologies consisting of the individual ss-DNA with mono-layer coverage of the clustered allophane particle were observed successfully through transmission electron microscopy analysis.

Preparation and characterization of DNA/allophane composite hydrogels

The preparation and characterization of the composite hydrogels based on double-stranded deoxyribonucleic acid (DNA) and natural allophane (AK70) were reported. To understand the propensity of the natural allophane to adsorb the DNA molecules, using zeta potential measurement, Fourier transform infrared spectroscopy (FTIR) and electrophoresis analyses assessed the adsorption characteristics. The freeze-dried DNA/AK70 hydrogels were demonstrated that the DNA bundle structure with a width of ∼2μm and a length of ∼15–20μm was wrapped around the clustered allophane particles as revealed by FE-SEM/EDX analysis. The incorporation of AK70 in hydrogels induced the increase in the enthalpy of the helix-coil transition of DNA duplex due to the restricted molecular motions of the DNA duplex facilitated by the interaction between the phosphate groups of DNA and the protonated +(OH2)Al(OH2) groups on the wall perforations of the allophane.

Patterned Deposition of Allophane Nanoparticles on Silicon Substrates

AbstractIn order to obtain nanopatterned surfaces, natural allophane particles originating from Japanese soils were immobilized as single particles on Si wafer substrates.When derived from aqueous suspensions, only a few nanoparticles were deposited and detected on the surface due to the weak adsorption of allophanes on the substrate. The amount of immobilized allophane was increased significantly, however, by using an organic solvent in combination with a micelle-based technique to suspend the allophane particles. The micelles were formed from a tailored, aliphatic diblock copolymer that was dissolved in toluene and contained several allophane particles. A cleaned silica chip was used as a substrate on which a monolayer of micelles was immobilized equidistant from each other by dip coating. To remove the polymer from the substrate and to produce free, single allophane nanoparticles, ultraviolet (UV) irradiation was used. After UV treatment, single allophane particles formed ring-shaped deposition patterns with a high surface density. Transmission electron microscopy (TEM) was used to verify the presence of single allophane nanoparticles in the Japanese samples which came from natural sources. The single allophane particles as well as the allophane-containing di-block copolymer micelles, both immobilized on Si substrates and TEM sample grids, were imaged by atomic force microscopy and TEM. In this way, the diameters of the single allophane particles, as well as the distances between the immobilized micelles and the particles and their topography on the substrates, were determined.

Synthesis and adsorption characteristics of hollow spherical allophane nano-particles

We synthesized three allophanes from precursors by a hydrothermal reaction at 100 °C for 48 h. The precursors were formed from the solutions of Na 4SiO 4 and AlCl 3⋅ 6H 2O at different Si/Al molar ratios (0.5, 0.75, 1.0). The nanostructure of the synthetic allophanes was compared with that of a natural allophane from New Zealand by using X-ray diffractometry, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetry/differential thermal analysis, 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), field emission electron microscopy, and pore-size distribution based on the Cranston–Inkley method. The propensity of the allophanes to adsorb adenine and adenosine-5′-monophosphate (5′-AMP) was assessed by batch experiments. The adsorption data were fitted by the Freundlich equation and the adsorption parameters were discussed in relation to the properties of the natural and synthetic allophanes. The adsorption capacity ( K f) of the natural allophane for 5′-AMP was three times that for adenine. The average K f value of the three synthetic allophanes for 5′-AMP was more than twice that of the natural allophane, possibly due to the higher purity of the synthetic allophanes.

Surface Complexation Modeling of the Acid/Base Chemistry of Natural Allophane

Surface Complexation Modeling of the Acid/Base Chemistry of Natural Allophane

B21 Fenton-like Reaction on Degradation of Organic Dye by Natural Allophane

B21 Fenton-like Reaction on Degradation of Organic Dye by Natural Allophane

Effect of Tris-HCl Buffer on DNA Adsorption by a Variety of Soil Constituents

We investigated the effect of tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer (pH 7.0) as a bulk solution on the adsorption of DNA by gibbsite, goethite, montmorillonite, kaolinite, synthetic and natural allophanes, two humic acids and two andosols. The natural allophane, gibbsite, kaolinite and an andosol adsorbed significantly more DNA in a 0.1 M Tris-HCl buffer than in a 0.1 M NaCl solution (t-test, P<0.005). In contrast, montmorillonite adsorbed significantly less DNA in the Tris-HCl than NaCl solution (P<0.05). Care should be taken when using Tris-HCl in studies on the adsorption of extracellular DNA molecules by soil particles.