Metal Oxalates Research Articles

Growth of Ni-Ga oxalate nanoparticles on 3D current collector as a supercapacitive electrode

Metal oxalate materials have been explored for electrochemical energy storage (EES) applications. Herein, Ni-incorporated gallium oxalate (Ni-Ga-C2O4) based binder-free electrode was fabricated through a facile process. The electrode gathers the benefit of Ni foam contributed as a conductive substrate and also acting as a Ni source with binder-free approach. The Ni-Ga-C2O4 crystalline phase formation was confirmed through X-ray diffraction spectroscopy (XRD). The morphological properties and elemnetal quantification were studied via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron spectroscopy (TEM). Importantly, electrochemical energy storage investigation revealed the Ni-Ga-C2O4 electrode exhibits battery behavior with capacity retention of 85.5 % and possessed the highest specific capacity of 319 C g−1 at 1 A g−1. Overall, the additional contribution of Ni during the synthesis has boosted the physicochemical properties and electrochemical energy storage performance of the Ni-Ga-C2O4 electrode.

Binder-free Ni-doped In/Mn oxalate electrode for next-generation supercapacitors

The worth of electrochemical energy storage systems is significantly influenced by the nature of the electrode material. In this work, metal oxalates have emerged as cost-effective and robust candidates for application in supercapacitors. In this context, a binder-free electrode composed of in-situ Ni-doped In/Mn oxalate was synthesized. The nickel foam served a dual function, acting both as a structural framework and as a source of nickel. X-ray diffraction (XRD) analysis verified the crystalline nature of the in-situ Ni-doped In/Mn oxalate. Morphological assessment using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the presence of a hybrid one-dimensional/two-dimensional morphology within the in-situ Ni-doped In/Mn oxalate. Electrochemical evaluations indicated that the in-situ Ni-doped In/Mn oxalate electrode exhibits characteristics akin to those of a battery, maintaining 88.8 % of its initial capacity. Furthermore, it demonstrated a superior specific capacity, amounting to 1238.3 F g−1 at a current density of 1 A g−1. The inclusion of nickel during the material's synthesis process is posited to significantly augment its overall electrochemical performance and properties.

Performance Changes of Lithium-Ion-Batteries due to Electrolyte-Introduced Metal Oxalate Contaminants

This work highlights how different metal oxalates (lithium, nickel, cobalt, manganese, aluminum, and copper) as possible contaminants from certain recycling technologies impact calendar and cyclic aging of NMC811 based LIBs. It also outlines the differences between their two aging modes. By comparing calendar and cyclic aging, differences become apparent: E.g., the presence of copper oxalate resulted in reduced calendar aging effects, while aluminum oxalate negatively affected calendar aging performance but cyclic aging less. Our method is also suitable for screening other materials, especially if one of the aging modes appears more important. By adding lithium oxalate to LIBs, overcharges strongly affected the SoH during cyclic aging. To optimize recycling performance by evaluating the impact of potential impurities, special attention should be given to particularly aluminum and, if economically viable, eliminated.

Fungal biomineralization of toxic metals accelerates organic pollutant removal

Fungal biomineralization plays an important role in the biogeochemical cycling of metals in the environment and has been extensively explored for bioremediation and element biorecovery. However, the cellular and metabolic responses of fungi in the presence of toxic metals during biomineralization and their impact on organic matter transformations are unclear. This is an important question because co-contamination by toxic metals and organic pollutants is a common phenomenon in the natural environment. In this research, the biomineralization process and oxidative stress response of the geoactive soil fungus Aspergillus niger were investigated in the presence of toxic metals (Co, Cu, Mn, and Fe) and the azo dye orange II (AO II). We have found that the co-existence of toxic metals and AO II not only enhanced the fungal biomineralization of toxic metals but also accelerated the removal of AO II. We hypothesize that the fungus and in situ mycogenic biominerals (toxic metal oxalates) constituted a quasi-bioreactor, where the biominerals removed organic pollutants by catalyzing reactive oxygen species (ROS) generation resulting from oxidative stress. We have therefore demonstrated that a fungal/biomineral system can successfully achieve the goal of toxic metal immobilization and organic pollutant decomposition. Such findings inform the potential development of fungal-biomineral hybrid systems for mixed pollutant bioremediation as well as provide further understanding of fungal organic-inorganic pollutant transformations in the environment and their importance in biogeochemical cycles.

Leaching of Nickel and Cobalt from a Mixed Nickel-Cobalt Hydroxide Precipitate Using Organic Acids

Nickel (Ni) and cobalt (Co) are strategic metals that have found applications in a wide range of metallurgical and industrial uses. In this study, the dissolution of a mixed nickel–cobalt hydroxide precipitate using organic acids (citric, oxalic, and malic acid) was investigated. Citric acid was found to be the best leaching agent yielding the following dissolution rates: 91.2% Ni, 86.8% Co, and 90.8% Mn. Oxalic acid resulted in low dissolution, which is likely due to the formation of insoluble metal oxalates. The impact of acid concentration, leaching time, and temperature on metal dissolution was systematically examined. The optimal dissolution conditions were identified as 0.5 M citric acid at 30 °C for 30 min, utilizing a 1/20 solid/liquid ratio and a stirring speed of 400 revolutions per minute (rpm). The attempt to use oxidants, such as potassium permanganate (KMnO4) and hydrogen peroxide (H2O2), to achieve selective dissolution in an organic acid environment was not successful, which was different from that in the sulfuric acid case. As for the leaching kinetics in the organic acids, it seems that the leaching of Ni correlates with the Shrinking Core Model, specifically regarding porous-layer diffusion control. Based on the experimental results, the activation energy for the leaching of Ni was estimated to be 3.1 kJ/mol.

57Fe-Mössbauer spectroscopic study of some double and triple metal oxalates

57Fe-Mössbauer spectra of double MM’(C2O4)2⋅4H2O (M = Fe, M’ = Mg, Co, Zn) and triple metal oxalates MM’M”(C2O4)3⋅6H2O (M = Fe, M’ = Mg, Mn, Co; M” = Zn) were recorded at room temperature and briefly discussed on the basis of their structural characteristics. No changes in the hyperfine interactions at the 57Fe site were detected because of the presence of the other metal ions.

Co-Precipitation of Metal Oxalates from Organic Leach Solution Derived from Spent Lithium-Ion Batteries (LIBs)

Recent studies in hydrometallurgy are focused on developing eco-friendly and selective leach agents such as organic acids. These agents can extract metal ions, which are usually separated through precipitation methods. When traditional methods are used, the separation is complex and time-consuming, and each metal cation is required to be isolated separately. Moreover, extracted metal salts are subsequently recombined in the regeneration of cathode materials. To simplify this, a novel simultaneous precipitation approach has been developed, allowing the separation of metal salts that can directly contribute to regenerating novel cathode materials, bypassing the need for separate isolation. This study aimed to recover cobalt, nickel, and manganese from the organic leach solution of spent lithium-ion batteries (LIBs) through co-precipitation of metal oxalates. The investigation includes the selection of organic acids and the best parameters for the leaching process, as well as testing different molar ratios of the metals M2+ (M = Co, Ni, Mn) to oxalic acid (1:3, 1:4.5, 1:6, and 1:7.5) to examine the effects of the precipitating agent on the recovery percentages of the metals. The findings indicate that 2 M citric acid and 4 vol% H2O2 is the optimal parameter in the leaching process. Meanwhile, in the co-precipitation process, an increase in the molar ratio leads to a corresponding rise in the resulting metal recoveries. At the ratio of 1:7.5, cobalt, nickel, and manganese were recovered to the extent of 99.26%, 98.93%, and 94.01%, respectively. Nevertheless, at the increased molar ratio, the co-extraction of lithium and aluminum was observed, resulting in reduced selectivity and decreased precipitate purity.

Solvent-free synthesis and optical properties of two open-framework metal oxalates with zeolitic ABW and diamondoid topologies

Two noncentrosymmetric open-framework metal oxalates with wide optical band gaps and moderate birefringences were prepared under solvent-free conditions.

Integrating 1D/2D nanostructure based on Ni–Co-oxalate for energy storage applications

The performance of an electrochemical energy storage device highly depends on the electrode material. Currently, metal oxalates are evolving as low-cost and stable electrode materials for batteries and supercapacitors. Herein, mixed metal oxalate (NixCo1-xC2O4/NF) based binder-free electrode was fabricated. The nickel foam contributed not only as a substrate but also as a nickel source. The NixCo1-xC2O4/NF confirmed the crystalline phase through X-ray diffraction spectroscopy (XRD). Scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) confirmed the integrated 1D/2D-like morphology of NixCo1-xC2O4/NF. The electrochemical results reveled the NixCo1-xC2O4/NF electrode exhibit battery behavior with capacity retention of 86.58 % and possessed the highest specific capacity of 470.012 C g−1 at 1 A g-1. Hence, the nickel inclusion during the synthesis has further enhanced the overall properties and performance of the NixCo1-xC2O4/NF electrode.

Enhancing electrochemical lithium-storage properties of hydrated iron oxalate (FeC2O4·2H2O) anode material by combining with dual-states copper

The application of iron oxalate (FeC2O4) as a new high-energy anode material for lithium-ion batteries is astricted by difficulty in obtaining 100 % anhydrous material and inhibitive role of crystal water on lithium storage. Herein, we fabricated the trepang-liked hydrated iron oxalate (FeC2O4·2 H2O) anode materials by combining with dual-states copper and investigated the special function of copper. Because of the differentiated distribution between C2O42- and oxalic acid complexes ([Fe(C2O4)x]-2(x-1) and [Cu(C2O4)x]-2(x-1)), the CuC2O4·xH2O nanosheets with compound state adsorb and imbed on surface of rod-like FeC2O4·2 H2O particles. Meanwhile, copper element with ion state can effectively doped into the crystal structure of FeC2O4·2 H2O, due to the similar three-dimensional crystal structure between transition metal oxalates. In virtue of the differentiated electrochemical behavior of crystal water for iron oxalate and copper oxalate, the copper derivatives (Cu, CuO, Cu2O et al.), formed by the reaction between CuC2O4·xH2O and Li+, exhibit high electrochemical activity and electrical conductivity, which can significantly enhance the lithium storage ability of dihydrate iron oxalate. Hence, hydrated iron oxalate combined with dual-states copper, suggests superior reversible capacity (∼550 mAh g-1 at 0.1 A g-1) and stable long-term cycling performance (∼520 mAh g-1 at 0.5 A g-1 after 200 cycles). This paper provides a novel opportunity to weaken the inhibitive role of crystal water on lithium storage and enhance the electrochemical properties of hydrous oxalate materials.

Tungsten oxide decorating-regulated iron-nickel oxide heterostructure as electrocatalyst for oxygen evolution reaction

The development of efficient and long-term stable electrocatalysts for oxygen evolution reaction (OER) is the key to harness hydrogen energy by water electrolysis. In this work, tungsten oxide decorated iron-nickel oxide heterostructure was grown on nickel skeleton by hydrothermal synthesis through simultaneously chemical etching reaction and decomposition of transition metal oxalate, forming porous WO3/Fe2O3-NiO/NF composite. The decoration of WO3 creates WO3/Fe2O3-NiO heterostructure interface with high-density heterometal-oxygen bridge sites, which can effectively modulate the intrinsic electronic structure of the catalyst and optimize the adsorption energy of the reaction intermediates, thus accelerate the OER through the adsorbate evolution mechanism. In addition, abundant oxygen vacancy (VO) sites induced by high valence W6+ further boost OER activity through the lattice oxygen-mediated mechanism. With the unique porous interfacial structure, the as-synthesized WO3/Fe2O3-NiO/NF exhibits remarkable OER electrocatalytic activity with low overpotential of 211 mV at OER current density of 100 mA cm-2, and high stability at 100 mA cm-2 with overpotential fluctuates within ± 2.8% range during the 100 h test. The as-proposed method is effective in lowering the overpotential of OER, and may be applicable for other electrochemical energy conversion applications.

Characterization of art materials and degradation processes in the exterior wall paintings of the main church of Rila Monastery, Bulgaria

The present study focused on the characterization of the art materials and the degradation processes in the exterior (exonarthex) mural paintings of the main church of the Nativity of the Virgin in Rila monastery, Bulgaria, which is believed to be the last large-scale example of Eastern Orthodox wall painting. For the first time the art materials used to create a unique and colourful polychrome decoration of the outer gallery and the possible degradation products, caused by atmospheric influence - permanent exposure to open air and moisture - were revealed by a multi-technique approach. The mineral pigments were identified by means of attenuated total reflectance Fourier transform infrared (ATR-FTIR), micro-Raman spectroscopy, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The natural yellow, red ochre, and green earth pigments, as well as some synthetic ones such as ultramarine and vermillion, were found in stable condition. Minium and emerald green pigments showed chemical transformations due to adverse environmental conditions which lead to chromatic changes of wall paintings. Black discolouration occurred due to the conversion of orange minium to black plattnerite (PbO2) and white discolouration – due to its transformation to white lead carbon oxide (PbCO3). The copper acetoarsenite (Cu(CH3COO)2.3Cu(AsO2)2) in the emerald green pigment showed partial transformation to arsen-containing mineral phases clinoclase and lindackerite, which fortunately did not affect much the colour appearance. Gypsum and calcium oxalate were found in the majority of the microsamples as decay products. Analysis of the binders by enzyme-linked immunosorbent assay (ELISA) implied the use of the Orthodox Church post-Byzantine egg-tempera technique. The registered Ca metal oxalates in accordance with ELISA results suggested binder chemical degradation induced by external factors. Most of the used painting materials are close to the those found in other Eastern Orthodox Byzantine and post-Byzantine monuments which indicates that the wall painting decoration of the main church of Rila monastery continues the post-Byzantine traditions. On the other hand, the study showed that the exonarthex wall paintings of the main charge of Rila monastery bear some new features as the religious artists supplemented the colourful scheme by emerald green as a new pigment and replaced smalt by the brighter synthetic ultramarine.

An oxalato-bridged dimetallic heptanuclear [K5IFe2III] complex anion with guanidinium as counter cation: Synthesis, crystal structure, Hirshfeld surface analysis and magnetism

An oxalato-bridged heterometallic heptanuclear [K5IFe2III] hybrid salt, (CH6N3)[K5(H2O)4Fe2(C2O4)6] (1) (CH6N3+ = guanidinium cation) has been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction, EPR and SQUID magnetometry. The asymmetric unit in 1 is composed of a dimetallic heptanuclear [K5(H2O)4Fe2(C2O4)6]− anionic complex and a guanidinium CH6N3+ cation insuring the charge compensation. Each Fe3+ center in the anionic complex is six-coordinate in a distorted octahedron defined by three chelating oxalato(2-) ligands. In contrast, the coordination numbers for K+ centers range from 7 to 9. The structural feature of focal interest in 1 is formation of an extended anionic network encapsulating guanidinium cations. This structure can be considered a sheet-MOF, where metal ions and oxalates (linkers) form infinite 2D units. The 3-D supramolecular architecture is stabilized by OH∙∙∙O and NH∙∙∙O hydrogen bonds linking polymeric oxalato-bridged anionic assemblies and organic cations. The thermal studies confirmed the anhydrous character of salt 1 and showed a three-step decomposition to yield a mixture of Fe2O3 and K2O as final residue. EPR spectrum of 1 is in accordance with the oxidation state + 3 of the iron center in an octahedral environment. Temperature-dependence susceptibility measurements investigated in the temperature range 2–300 K revealed weak antiferromagnetic coupling at low temperatures in salt 1. The distributions of different types of intermolecular interactions in the crystal structure were quantified by Hirshfeld surface analysis and their associated fingerprint plots.

Dual Modification of Stainless Steel by Small Molecule Oxalic Acid for Oxygen Evolution Reaction

A electrocatalyst with low cost and high performance is the key to achieve the industrial application of hydrogen energy. In this work, inexpensive commercial stainless steel is modified by a simple hydrothermal method. For the first time, surface corrosion modification and active substance loading are realized simultaneously with small-molecule oxalic acid. Compared with 304-type stainless steel mesh (SSM-304), the overpotential of the sample after two-step treatment (noted as OESSM) is largely decreased (125 mV), and exceptional stability (48 h) is achieved. In acidic hydrothermal corrosion, the metal on the surface of stainless steel is eroded into the solution. Then, the C2O42– recomplexes with the dissolved metal ions, and the oxalate is grown on the surface. The excellent catalytic activity and stability come from the unique framework structure of the metal oxalate crystals. Oxalic acid is widely available and with double carboxyl group in C2O42–. The electrons enriched in C═O can enhance the adsorption energy on the catalyst surface and induce the production of active catalytic sites *OOH. In addition, the oxalate crystal framework provides critical support for maintaining positive catalytic activity and stability. This work creates the possibility of realizing the large-scale application of stainless steel-based electrocatalysts in actual production.

Oxalate Crystallization under the Action of Brown Rot Fungi

Brown rot fungi belong to the wood-rotting fungi, which produce oxalic acid and actively decompose wood. We first found oxalates formed under the action of brown rot fungi in natural conditions on stone (Rogoselga adit, Karelia, Russia), proposed a model for their formation, and confirmed the hypothesis that frequent occurrence of metal oxalates in mines and adits may be associated with the activity of these fungi. We synthesized under the action of four species of brown-rot fungi (Serpula himantioides, Serpula lacrymans, Coniophora puteana, Antrodia xantha) on different mineral substrates analogs of all known biofilm oxalate minerals and oxalates of such toxic heavy metals as Pb, Cu, Mn. In addition, we compared the features of oxalate formation under the action of brown rot fungi and soil fungus Aspergillus niger, an active oxalic acid producer, widely used in model experiments and recommended for application in biotechnologies. It is shown that in contrast to A.niger, the contribution of the metabolic activity of brown rot fungi to oxalate crystallization exceeds the contribution of the underlying minerals. The prospects for the use of brown rot fungi such as Serpula himantioides, Coniophora puteana, and Antrodia xantha in modern environmentally friendly biotechnologies are justified.

How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) - a microspectroscopic study.

The extensive use of lanthanides in science, industry and high-technology products is accompanied by an anthropogenic input of rare earth elements into the environment. Knowledge of a metal's environmental fate is essential for reasonable risk assessment and remediation approaches. In the present study, Eu(III) was representatively used as a luminescent probe to study the chemical environment and to elucidate the molecular interactions of lanthanides with a suspension cell culture of Nicotiana tabacum BY-2. Biochemical methods were combined with luminescence spectroscopy, two-dimensional microspectroscopic mappings, and data deconvolution methods to resolve the bioassociation behavior and spatial distribution of Eu(III) in plant cells. BY-2 cells were found to gradually take up the metal after exposure to 100 μM Eu(III) without significant loss of viability. Time-resolved luminescence measurements were used to specify the occurrence of Eu(III) species as a function of time, revealing the transformation of an initial Eu(III) species into another after 24 h exposure. Chemical microscopy and subsequent iterative factor analysis reveal the presence of four distinct Eu(III) species located at different cellular compartments, e.g., the cell nucleus, nucleolus and cell walls, which could be assigned to intracellular binding motifs. In addition, a special type of bioaccumulation occurs through the formation of a Eu(III)-containing oxalate biomineral, which is already formed within the first 24 hours after metal exposure. Oxalate crystals were also obtained in analogous experiments with Gd and Sm. These results indicate that tobacco BY-2 cells induce the precipitation of metal oxalate biominerals for detoxification of lanthanides, although they also bind to other cellular ligands at the same time.

Synthesis, characterization, and biological activities of five new trivalent lanthanide complexes of hydrazine and 3,3’-thiodipropanoic acid

Some new hydrazine complexes of trivalent lanthanide 3,3’-thiodipropanoates of empirical formulae [M(N2H5)(tdp)2] and [Pr(N2H5)(tdp)2·H2O], where M = La, Ce, Sm and Nd, H2tdp = 3,3’-thiodipropanoic acid, have been prepared and characterized by elemental analysis, mass, FTIR, Raman and electronic spectral, powder X-ray diffraction, scanning electron microscopy (SEM) and simultaneous TG–DTA techniques. The presence of bidentate carboxylate anion and coordinated N2H5 in these complexes are confirmed by IR spectra. TGA/DTA results confirmed that all the rare earth metal complexes give the corresponding metal carbonate (heating up to 1000 °C) through a metal oxalate intermediate. SEM images of Pr2O3 residue obtained from its complex show nano-sized clusters, thus the complex may be used as a precursor for nano-Pr2O3 preparation. The synthesized complexes show good antimicrobial activity against six bacteria (Bacillus cereus, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa, Escherichia coli, and Serratia species) and four fungi (Candida albicans, Aspergillus niger, Aspergillus fumigatus, and Penicillium variance) as assessed by in vitro biological activity.

Achieving ultrastability and efficient lithium storage capacity with high-energy iron(II) oxalate anode materials by compositing Ge nano-conductive sites.

Transition metal oxalates (TMOxs, represented by iron oxalate) have attracted considerable interest in anode materials due to their excellent lithium storage properties and consistent cyclic performance. Although investigations into their electrochemical capabilities and lithium storage mechanisms are gradually deepening, the complex and varied electrochemical reactions in the initial cycle, poor inherent conductivity, and high irreversible capacity constrain their further development. Herein, to solve the above-mentioned problems, we controlled the hydrothermal synthesis conditions of iron oxalate with the assistance of organic solvents, which induced the growth of iron oxalate crystals with nano Ge metal as the core. The metal Ge space sites compounded to the stacked iron oxalate particles act as conductive nodes and metal frames, which enhances both the strength of iron oxalate samples and electronic conductivity and lithium-ion diffusion inside the electrode materials. This special structure enhances the electrochemical activity of iron oxalates and improves their lithium storage capability. The iron oxalate @ nano Ge metal composite (FCO@Ge-1) exhibits an excellent cycling performance and an appreciable reversible specific capacity (1090 mA h g-1 after 200 cycles at 1 A g-1). The obvious polarization and variation of the electrochemical reaction in the initial cycle of iron oxalate are reduced by compositing nano Ge metal. It is demonstrated that nano Ge metal can promote reversible capacity retention from 67.72% to 80.69% in the early cycles. The distinctive structure of iron oxalate @ nano Ge metal composite provides a fresh pathway to enhance oxalate electrochemical reversible lithium storage activity and develop high-energy electrode material by constructing composite space conductive sites.

Modified cobalt oxalate heterostructure catalyst P–FeOOH@CoC2O4/NF for a highly efficient oxygen evolution reaction

Oxygen evolution reaction (OER) has been recognized as the key role to determine the overall efficiency of hydrogen production by electrolysis of water. The development of green, low-cost and high stability electrocatalysts which can effectively reduce the reaction energy barrier is a key to promote the large-scale application of hydrogen energy. Herein, a modified transition metal oxalate loaded on nickel foam (NF), P–FeOOH@CoC2O4/NF heterostructure catalyst was synthesized by simple hydrothermal and electrodeposition methods. By constructing heterostructures and phosphorous doping, the morphology and electronic structure of CoC2O4 were optimized, thus, P–FeOOH@CoC2O4/NF shows excellent electrocatalytic performance, the overpotentials of 211/264/295 mV were needed to reach the current densities of 10/100/200 mA cm−2, with a low Tafel slope of 41.33 mV dec−1 and almost constant long-term stability. The results revealed that the construction of the heterostructure led to the superficial electrochemical reconstruction of the cobalt oxalate microrod, which effectually accelerated the transformation of the active species and primely realized the efficient alkaline water oxidation.

Complex Oxide Nanoparticle Synthesis: Where to Begin to Do It Right?

Synthesis of advanced ceramics requires a high degree of control over the particle size and stoichiometry of the material. When choosing a synthesis method for complex oxides it is important to begin with the correct precursors and solvents to achieve high purity nanoparticles. Here, we detail the selection process for precursors and solvents for liquid-phase precipitation synthesis. Data for metal nitrate, chloride, acetate, and oxalate precursors has been compiled to assist future synthesis. The role of hydration within the precursors is discussed as it affects the final stoichiometry of the material. Melting temperatures are also compiled for these compounds to assist in material selection. The solubility of the precursors in different solvents is examined to determine the correct solvent during synthesis. As an example, using the methodology presented here, two different materials are synthesized based on commonly available precursors. A catalyst based on a quaternary perovskite and an advanced ionic conductor based on a high entropy fluorite oxide are synthesized using precipitation methods and their characterization is detailed.