Oxyhydroxide Research Articles

Induced electro-Fenton triggers trace iron utilization for simultaneous organic phosphorous degradation and phosphate recovery

Phosphorus recovery from wastewater has the potential to alleviate both phosphorus scarcity and water pollution. Unlike mineral orthophosphate, organic phosphorus (OP) recovery typically requires multiple steps: oxidation to orthophosphate followed by separation. Electro-Fenton can synchronize these steps in a unified reactor. However, conventional anodic-Fenton (AF) that relies on the direct sacrificial Fe anode, often generates excessive iron sludge. This not only undermines the oxidative capacity but also changes the optimal pH conditions. Herein, we addressed these challenges by developing an induced electro-Fenton (I-EF) system that significantly reduces iron sludge by 94.0 %. The degradation of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC, 5.0 mg P/L) in I-EF reached 76.7 % in 60 min, which is much higher than that (46.0 %) in the conventional AF system. Following PBTC degradation to form PO43-, the I-EF system achieved 88 % PO43- recovery through adsorption onto iron hydroxides. The exceptional performance in simultaneous PBTC degradation and recovery can be attributed to multiple functions of minimal iron utilization in the I-EF system. First, trace iron release can prevent quenching of hydroxyl radicals (·OH) by excessive Fe2+. Second, the absence of strong iron hydrolysis can maintain a stable pH condition (3.0–3.2) for Fenton reaction and avoid PBTC removal through direct coagulation process. The feasibility of I-EF was also successfully demonstrated for other OP forms containing C-P and C-O-P bonds. The degradation efficiency of various OPs was closely related to their bond energy and complexation capacity with iron hydroxides. This study makes use of the I-EF system to innovatively accomplish the degradation of organic phosphorous and simultaneous phosphate recovery.

Determination of Surface Parameters of Iron(III) Hydroxide Sorbent

The surface layer parameters of iron(III) hydroxide were studied. The surface charge, the sorption of proton H+, hydroxyl OH– as a function of hydration time (TCT), the pH of the suspension solution and the sorbent concentration were presented. For this purpose, two methods were chosen: potentiometric mass titration (PMT) and potentiometric time titration (PTT). The concentrations suspensions used were 20, 40 and 60 g/L. The variations of surface charge with the time contact, Q = f(TCT) were examined for hydration time ranging from zero to 72 h. The isoelectric point (IEP) and point zero charge (PZC) were defined using the variations pH = f(TCT) resulting from protonation/deprotonating of surface sites >S–OH with derivative methods d(pH)/d(TCT) = f(pH) the values of PZC and IEP were found: PZC = 7.45 ± 0.1 and IEP = 7.65 ± 0.1.

INDIGO BLUE DEGRADATION: PROBABLE PRESENCE OF DYE ADSORBED BY IRON HYDROXIDE DURING FENTON PROCESS

A chemical method using FeSO4 and H2O2 was selected for indigo blue (IB) degradation in aqueous medium. The initial experiments demonstrated that high concentrations of hydrogen peroxide (H2O2) and iron sulfate heptahydrate (FeSO4.7H2O) were capable of total degradation of IB (approximately 100%). Controlled tests, varying the concentrations of both reagents, revealed that the mixture containing approximately 350 mg/L (v/v) of FeSO4.7H2O and 0.57% (v/v) of H2O2wasconsiderablyefficient in the degradation of IB (1,000 mg/L). The decay kinetics revealed rapid IB degradation and possible IB adsorption on iron (III) hydroxide precipitate [Fe(OH)3]↓. However, the adsorbed IB also subsequently, leaves the residue of [Fe(OH)3]↓, which suggests the occurrence of not only chemical degradation of IB but also its possible adsorption by Fe(OH)3 precipitate.

Bacterial oxidation in the hydrometallurgical process of copper extraction from copper-containing ore

Copper extraction technologies are constantly being improved including chemical oxidants. However, chemical oxidants slightly increase the extraction. Thus, this study aims to increase copper extraction using bacterial oxidation as oxidizing reagent. It also compares extraction results between standard leaching with sulfuric acid and Acidithiobacillus ferrooxidans with amino acids nutrient medium. Ore from Zhezkazgan deposit that contains chrysocolla, malachite and iron hydroxide was used as a sample. The ore was dug from a 6m depth. The initial sample was crushed, grinded, mixed, and reduced before preliminary biooxidation by bacterial culture of Acidithiobacillus ferrooxidans. A mineralogical study of ore was conducted to confirm the copper contains, other compounds and phase composition as well. Acidithiobacillus ferrooxidans were cultured within the nutrient medium of amino acid. This study chooses amino acid serine L, glycine, and asparagine to provide optimum bacterial cell of A. Ferrooxidants. Results showed that preliminary biooxidation by bacterial culture of A.Ferrooxidans increased copper extraction significantly. Further, Acidithiobacillus ferrooxidans that grow in the nutrient medium containing L-Serine have the highest effect on copper extraction.

Iron-Induced vacancy and electronic regulation of nickle phosphides for ampere-level alkaline water/seawater splitting

Rational design of non-precious metal catalysts can accelerate the oxygen evolution reaction (OER) kinetics. Herein, inspired by theoretical analysis, in-situ Fe-doped Ni2P/Ni12P5 with rich P vacancies (Fe-NiPx) is designed and constructed, in which the production of P vacancies is induced by Fe doping. Relevant characterizations confirm that the Fe doping and P vacancies can co-adjust the crystal and electronic structures, thereby optimizing the reconstruction behavior and improving the intrinsic activity of reconstructed-derived Ni(Fe)OOH. As a result, it exhibits excellent OER activity with overpotentials of 256 and 276 mV to achieve the current density of 100 mA cm−2 in 1 M KOH solutions and alkaline seawater, respectively. Furthermore, the Fe-NiPx electrode only requires 1.861 and 1.889 V to drive the 1.0 A cm−2 overall water and seawater splitting, respectively, and maintains stable output as high as 1000 h. Also, to demonstrate the great application potential, green energy-to-hydrogen systems are established. Electrochemical tests and theoretical calculations reveal that reconstructed-Fe-NiPx facilitates the OER kinetics under the adsorbate evolution mechanism (AEM) pathway, with optimized adsorption free energies of intermediates and reduced reaction energy barriers. This work provides new insights into efficient water and seawater splitting through in-situ heteroatom doping and vacancy engineering.

In Situ Self-Assembled 200nm-Depth Highly Active Layer Non-Precious Metals Catalyst for Industrial Water Electrolysis.

Nickel-based electrocatalysts are promising for industrial water electrolysis, but the dense hydroxyl oxide layer formed during the oxygen evolution reaction (OER) limits active sites accessibility and presents challenges in balancing structural stability with effective charge transfer. Based on this, an efficient in situ leaching strategy is proposed to construct grain boundary-rich catalyst structure with high charge transfer ability and a deep catalytic active layer reached >200-nm. Under OER conditions, stable sub-nano Ni3Al particles are embedded in Ni(Fe)OOH, originating from leaching out the unstable Ni2Al3 phase of the initial Ni2Al3/Ni3Al alloy doped with Fe. The structural evolutions are characterized using in situ Raman spectroscopy, transmission electron microscopy, and X-ray absorption spectroscopy. The catalyst exhibits exemplary performance, evidenced by a low overpotential of 212mV at 10mAcm-2, a minimal Tafel slope of 25.0mVdec-1. The catalyst maintains stable for >500h at 500mAcm-2 under industrial conditions. Furthermore, its performance in seawater electrolysis is notably superior, exhibiting an overpotential of 223mV at 10mAcm-2 and a Tafel slope of 37.5mVdec-1. The in situ high activity in the deep porous phase by leaching out unstable phases provides a new method for engineering high-performance industrial catalysts.

Impact of Bulk Nanobubble Water on a TiO2 Solid Surface: A Case Study for Medical Implants.

In the field of medical implants, enhancing the wettability of artificial surfaces is crucial for improving biocompatibility. This study investigates the potential of ozone nanobubble water, an aqueous solution known for its strong oxidizing and sterilizing properties, to modify the surface of titanium dental implants. By immersing the implants in ozone nanobubble water for ∼10 min, we observed a significant transformation of their surface characteristics. Implant surfaces that had become hydrophobic over time, likely due to organic contaminants, became superhydrophilic, exhibiting a contact angle near zero. Fresh implant material is initially hydrophilic but becomes hydrophobic within a few days of drying. In sharp contrast, the hydrophilicity induced by ozone nanobubble water treatment persisted for more than one month. This durability suggests not only the removal of organic matter through cleaning but also a substantial alteration in the surface properties of the implants. The generation of ozone nanobubble water involved releasing ozone microbubbles into an aqueous solution containing trace amounts of iron and manganese, resulting in spherical particles with an average diameter of ∼10 nm. These particles could be bulk nanobubbles, a stabilized gas body surrounded by a solid shell composed of iron hydroxide. Termed "nanoshells" in our previous study, these particles demonstrated exceptional dispersibility without the need for stabilizing agents such as surfactants or capping agents, attributed to their inherent high wettability. The sustained hydrophilicity of the implant surfaces might be attributed to the adherence of these hydrophilic nanoshells to the implant's surface. This study highlights the potential of ozone nanobubble water for long-term surface modification of dental implants, offering a promising avenue for enhancing implant biocompatibility.

Solvent effect on facile in situ precipitation of nickel–iron hydroxide for enhanced overall water splitting

Efficient and economical electrocatalysts are essential for addressing the high overpotential challenges of the oxygen evolution reaction (OER) in electrochemical water splitting. This study explores the synthesis of nickel–iron hydroxide (NiFeOH) catalysts via in situ precipitation, focusing on the impact of the solvent composition on the morphology and catalytic performance of the material. The volumetric ratio of H2O to ethanol in the solvent mixture was systematically varied, revealing that higher proportions of H2O promoted the formation of thicker and larger needle-like NiFeOH structures. In contrast with the common preference for thin needle-shaped morphologies, our findings reveal that these thicker structures exhibit superior electrocatalytic activity. This enhanced performance is attributed to the higher iron content and faster reaction kinetics promoted by the increased permittivity of water-rich environments. The optimized NiFeOH catalysts, particularly those with higher water content, exhibit excellent OER and hydrogen evolution reaction (HER) activities, achieving low overpotentials of 288 mV at 100 mA cm−2 for OER and 131 mV at 10 mA cm−2 for HER. Furthermore, long-term stability tests confirmed the robustness of the catalysts, with minimal morphological degradation and consistent performance in overall water splitting. This work highlights the significance of solvent effects in tailoring the morphology and catalytic properties of NiFeOH, providing valuable insights for the design of effective water-splitting electrocatalysts.

Soils of Tundra and Sub-Tundra Larch Open Woodland of Tit-Ary Island (Delta of the Lena): Genesis, Properties, and Distribution Trends

Physico-chemical properties and vertical distribution patterns of clay minerals were studied in the permafrost affected soils from the tundra and sub-tundra larch open woodland of Tit-Ary island. That unique complex is located in the delta of the Lena river, Republic of Sakha (Yakutia). Despite the small size of the island and the fact that permafrost is close to the surface, several variants of pedogenesis determine the soil diversity in this area. The soils are characterized by various degrees of gleyic and stagnic properties due to sandy or loamy texture and location in the landscapes (top of the hills as well as steep or gentle slope). Mineral association is the same in the studied profiles characterized by the predominance of two components – chlorite and illite. Iron hydroxide–lepidocrocite occurred on the boundary of permanently frozen ground in the profile within pronounced spodic features as well as smectitic clay indentified in the both horizon of this permafrost affected soil can be attributed as a result of modern pedogenesis.

Synthesis and catalytic study of manganese ferrites obtained by partial oxidation of ferrous hydroxide with permanganate

The main goal of present work was to show a new method of synthesis, of manganese ferrite (MnxFe3-xO4, x = 0.085 to x = 0.379) with variable composition of Fe(II), Fe(III) and Mn(II) ions by coprecipitation, with the application of KMnO4 and KNO3 as oxidizing agents, followed by the characterization and research of the catalytic properties of the prepared samples. The chemical analysis by Flame Atomic Absorption Spectroscopy (FAAS), X-Ray Fluorescence Spectroscopy (XRFS) and potentiometric titration, allows to calculate the elemental and ionic composition of the prepared ferrites. The use of KMnO4 enables not only the oxidation of iron(II) to iron(III) but also a source of manganese(II). The Mn substitution in MnxFe3-xO4 ferrite as well as higher gel dispersion, cause the exponential increase of the catalytic activity, which is more significant in smaller particles.

Elucidating the superwetting FeOOH-modified NiMoO4 electrodes for efficient alkaline oxygen evolution reaction: An in-situ spectroscopy study

Exploring the dynamic surface reconstruction of the pre-catalysts throughout the oxygen evolution reaction (OER) and analyzing the real active species are essential for water electrolysis. Here, we report FeOOH modified NiMoO4 nanowire arrays for efficient OER in alkaline. In-situ Raman, UV–vis and electrochemical impedance spectroscopies were employed to analyze the dynamic reconstruction process. Our results revealed that this process involves a fast dissolution of MoO42- and the synthesis of Ni(Fe)OOH species, which are determined as the genuine catalysts for the OER reaction. The reconstructed superwetting catalyst exhibited excellent catalytic activity, achieving an overpotential of 281.1 mV at 100 mA cm−2 and sustained operation for 1000 h. Density functional theory (DFT) simulations demonstrated that the reduced adsorption strength of OH* → O* step on Ni(Fe)OOH intermediates contributed to a lowered reaction energy barrier. Our work provides a simple method for modifying catalysts, accompanied by a comprehensive examination of the dynamic reconstruction process aimed at enhancing the kinetics of the pre-catalyst.

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction.

The catalysts were always undergoing continuous amorphization and dissolution of active structure in operating condition, hindering the compatibility between stability and activity for oxygen evolution reaction (OER). Herein, we propose the selective adsorption of leached NO3 - to strengthen the crystallinity and activity of surface reconstructed layer with amorphous and crystalline (a-c) heterojunction. Taking a-c Ni doped Fe2O(OH)3NO3 ⋅ H2O (Ni-FeNH) as a model precatalyst, we uncover that the leached NO3 - are readily adsorbs on the crystalline phase in the formed a-c Fe(Ni)OOH (Thank you for your reminding. In our paper, Fe(Ni)OOH was used to refer to a hetero-phase consisting of NiOOH and FeOOH) during OER, lowering the disorder degree and further activating Ni and Fe ion of the crystalline Fe(Ni)OOH on a-c heterojunctions. Accordingly, Ni-FeNH deliver a low overpotential of 303 mV and high durability of 500 hours at 500 mA cm-2 for OER. Particularly, constructing industrial water electrolysis equipment exhibits high stability of 100 hours under a high operating current of 8000 mA.

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction

AbstractThe catalysts were always undergoing continuous amorphization and dissolution of active structure in operating condition, hindering the compatibility between stability and activity for oxygen evolution reaction (OER). Herein, we propose the selective adsorption of leached NO3− to strengthen the crystallinity and activity of surface reconstructed layer with amorphous and crystalline (a‐c) heterojunction. Taking a‐c Ni doped Fe2O(OH)3NO3 ⋅ H2O (Ni−FeNH) as a model precatalyst, we uncover that the leached NO3− are readily adsorbs on the crystalline phase in the formed a‐c Fe(Ni)OOH (Thank you for your reminding. In our paper, Fe(Ni)OOH was used to refer to a hetero‐phase consisting of NiOOH and FeOOH) during OER, lowering the disorder degree and further activating Ni and Fe ion of the crystalline Fe(Ni)OOH on a‐c heterojunctions. Accordingly, Ni−FeNH deliver a low overpotential of 303 mV and high durability of 500 hours at 500 mA cm−2 for OER. Particularly, constructing industrial water electrolysis equipment exhibits high stability of 100 hours under a high operating current of 8000 mA.

SECONDARY MINERAL FORMATION IN PRODUCTIVE DEPOSITS OF THE PASHIYSKY HORIZON OF THE SOUTH TATAR ARCH (REPUBLIC OF BASHKORTOSTAN)

The article presents the results of studying the postsedimentary mineralization of productive terrigenous deposits of the Pashiysky horizon of the South Tatar arch. The authors' research was carried out on the basis of a large amount of core material from newly studied wells with the involvement of wells from the archival fund. The analytical work included the following methods: classical optical microscopy and scanning electron microscopy (SEM). Using these methods, the main types of secondary mineral formation, the form and nature of the allocation of authigenic minerals that form secondary cement were studied, and an assessment of the degree of their influence on the filtration-capacitive properties (FPP) was given. It is shown that sideritization is a fairly common phenomenon in the studied deposits, but it does not have a significant effect on the reduction of the reservoir properties of productive deposits. Detailed optical and mineralogical studies have shown that authigenic siderite in the studied rocks is presented in various forms (spherites, spherulites, oolites and granular grains) and is mostly found in silt varieties. In productive sandstones, an insignificant decrease in the reservoir properties can only be associated with expanding rims in siderite spherites. As shown by the study of the composition of these rims, they are composed mainly of ankerite, in places they contain mangano-siderite. In some samples of the Pashiysky horizon, partial replacement of siderite by iron hydroxides was observed; in isolated wells, thin layers of oolitic siderite-ferruginous rocks were encountered. It was shown that the main influence on the reduction of the filtration-capacity properties of the studied sediments is secondary silification and carbonatization. At the same time, secondary quartz is developed mainly in water-saturated sandstones and heterogeneous silt-sandstones, and, as a rule, is distributed mostly locally. Secondary silica is observed in the form of regeneration rims, xenomorphic grains and is deposited on the walls of pores and channels. A significant effect on the reduction of the porosity and permeability parameters of the productive sandstones of the Pashiysky horizon of the South Tatar arch is exerted by secondary crystalline calcite or dolomite island cement of the basal, basal-pore and poikillite type.

Further Results on the Effects of the Grinding Environment on the Flotation of Copper Sulphides

Grinding conditions affect the flotation of copper sulphide minerals as changes in the properties of the grinding media and their interactions with the sulphide minerals, and between sulphide minerals themselves, affect the chemical environment in the flotation pulp. Galvanic interactions between steel grinding media and sulphide minerals, and between sulphide minerals, can lower the pulp potential, decrease the dissolved oxygen concentration in the mineral slurry, and lead to the dissolution of iron and copper from the media and the minerals. As a result, the formation of hydrophilic iron hydroxides and their adsorption on the copper sulphide minerals can be deleterious to copper flotation while pyrite (when present) can be activated to flotation by dissolved copper lowering the grade of the copper concentrate. Electrochemically less active grinding media (e.g., chrome alloy balls rather than mild steel media) can have beneficial effects on flotation performance due to the lower oxidation of the grinding media and consequently the lower production of oxidised iron species in the pulp. Copper activation of pyrite can be decreased by chemical additions to the pulp. In this paper, relevant experimental data published in the last 15 years are discussed.

Morphogenetic varieties of iron oxyhydroxides in shimmering smokers-diffusers of the Rainbow hydrothermal field (36°13′ N, 33°54′ W, Mid-Atlantic Ridge): LA-ICP-MS data for the development of halmyrolysis theory

Research subject. Iron oxyhydroxides covering and replacing the chimneys of shimmering water smokers-diffusers of the Rainbow hydrothermal field (MAR). Aim. To identify features of the concentration and associations of chemical elements in varieties of iron oxyhydroxides to recognize patterns of geochemical differentiation under conditions of halmyrolysis of sulfide chimneys-diffusers. Materials and methods. Samples were collected during a dive to a depth of 2300 m using the manual manipulator of the Mir-2 manned vehicle (travel No. 50, research vessel Akademik Mstislav Keldysh, 2005). Varieties of iron ohyhydroxides were identified using electron microscopes (REMMA-202М with LZ-5 Link system, Tescan Vega 3 sbu with an Oxford Instruments X-act energy-dispersive analyzer, and Jeol Superprobe 733 with an EDA Oxford Instruments INCAx-sight) and a powder X-ray diffractometer (SHIMADZU XRD-6000, CuK-α radiation with monochromator). Further, a mass spectrometry with inductively coupled plasma and laser ablation (LA-ICP-MS) analysis was conducted at the South Urals Federal Scientific Center of Mineralogy and Geoecology, Ural Branch of the Russian Academy of Sciences. Results. Microlayered goethite aggregates containing admixtures of barite, calcite, aragonite, native sulfur, covellite, sphalerite, and an X-ray amophoric oxyhydroxide phase of iron cover the shimmering diffusers. Towards the inner parts of the chimney walls, they are replaced by pseudomorphs of lepidocrocite after pyrite and pyrrhotite, and then by radial and bacteriomorphic crustifications of lepidocrocite. The use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) showed that goethite varieties have the increased contents of Zn and Co associated with other elements of medium-temperature hydrothermal fluids (Cd, Mn, Ni, Ga, Sn, Pb and Sb) in the absence of significant concentrations of a high-temperature hydrothermal association (Se, Bi, Te). The role of elements of seawater association (Mg, Na, K, Sr, U, V, As, Mo, Ni, P, B, W, Cs, REE) decreases from the surface layered goethite aggregates to crustification varieties of lepidocrocite. Different scenarios of accumulation under conditions of sulfide halmyrolysis and precipitation on local reduction barriers are proposed for elements with different valences (U, V, Mo, As, Cr, Eu). It is assumed that some of the microelements (Sr, V, As, P, REE) found in goethite are products of sorption on iron hydroxides or are part of invisible Fe-Ca hydroxyphosphates. Conclusion. The influence of sulfide halmyrolysis on the differentiation of chemical elements has been revealed.

Sustainable chloramine-functionalized iron hydroxide nanofiber membrane for arsenic(Ⅲ) removal via oxidation-adsorption mechanism

Arsenic-contaminated groundwater is an intractable environmental problem worldwide, particularly As(III), which is not only highly toxic but also resistant to removal. In this study, sustainable chloramine-functionalized iron hydroxide cellulose nanofibrous membrane (Fe-CNFM-Cl) was prepared by electrostatic spinning followed by chemical grafting for As(III) decontamination. In situ engineered iron hydroxides were uniformly dispersed in cellulose nanofibers for As adsorption. The oxidative chlorine (+1) in the grafted chloramine could oxidize As(III) to readily removable As(V). Benefiting from oxidation-enhanced adsorption, Fe-CNFM-Cl was able to remove As(III) reliably. Using Fe-CNFM-Cl, As(III) levels were purified from 1418.73 μg L−1 to meet drinking water standards within 300 min. Additionally, Fe-CNFM-Cl exhibited high iron utilization with a normalized As adsorption capacity of 214.55 ± 15.52 mg g-iron−1. Fe-CNFM-Cl performed effectively over a broad pH range of 3–9. Common anions and humic acid hardly inhibit As(III) removal except at high concentrations of phosphate. During the removal of As(III), a portion of As(III) was oxidized to As(V) by activated chlorine. The adsorption and oxidation capacity of the used Fe-CNFM-Cl could be well recovered by desorption with NaOH solution followed by chlorination with NaClO solution. In addition, it could reliably purify the As(III) levels in natural groundwater to below 10 μg L−1. The study contributes a novel strategy for the development of multifunctional iron-based cellulose biocomposite sorbents for the effective removal of As(III) from water.

Evaluation of Ferric Ion Adsorption On The Surface Imprinting Adsorbent

<span lang="EN-AU">Rapidity in technological aspects encourages industrial sector to utilize and apply the latest technology to accelerate and optimize production in its field. Thus, waste from industry polluting various aspects of environment, such as water, gives rise to environmental impacts. Heavy metals, including iron, are one of the most common and dangerous pollutants often found in water environments. Therefore, consideration of methods for heavy metal separation from water becomes important. The adsorption method has been used for separating heavy metals because of its simplicity, thus effectively cuts energy consumption and costs in process. However, heavy metal characteristics in water can vary depending on the element. Consequently, understanding the heavy metal characteristics in water is important, hence capable of formulate appropriate and effective adsorption systems. This study, Fe(III)-IIPs was applied to adsorb and separate iron from water through repeated adsorption with parameter improvements. The pH parameter plays an important role, with ion competition happens at pH <2 and the formation of iron hydroxide species at pH >4.5, which results in adsorption inhibition. The modeling of adsorption kinetic equation was found that the adsorption system carries chemisorption characteristics, with adsorption capacity of 11.15 mg/g and reaction rate constant of 19 min<sup>-1</sup>.</span>

Antimony resistant bacteria isolated from Budúcnosť adit (Pezinok-Kolársky vrch deposit) in western Slovakia

Potentially toxic elements (PTE), such as antimony (Sb), are dangerous putative contaminants for ground and surface waters around abandoned mines and ore deposits in Slovakia. Nearby mines antimony is commonly coprecipitated in ochre sediments precipitated from Fe-rich drainage waters and, therefore, these sites function as natural scavengers of this metalloid. Bacteria are well known to contribute to the process of redox state maintenance, biosorption and bioaccumulation of antimony and, consequently, to antimony precipitation or release from iron oxides complexes. Here we isolated 48 bacterial strains from circumneutral hydrous ferric oxides (HFO) rich iron ochres accumulated in the waters running from tailing pounds nearby Budúcnosť mine, Pezinok, Slovakia and polluted with high, but fluctuating, concentrations of antimony (130 μg/l Sb in water and 2317 mg/kg Sb in iron ochre in average). The isolated strains were V1-V9 16S rRNA sequenced and the resulting taxonomic affiliations of isolated strains were compared with taxonomy assignments obtained by V4 16S rRNA next generation sequencing approach, including two independent NGS analysis pipelines and different taxonomy classifiers ((IDTAXA (RDP, GTDB, SILVA, CONTAX), MEGAN (NCBI), RDP a SILVAngs). A Sb resistant subgroup of isolated strains (Pseudomonas A60B, Pseudomonas A59, Pseudomonas A28, Aeromonas A21, Aeromonas A13, Aeromonas A60A, Acinetobacter A14, Buttiauxella A58, Shewanella A20A a Yersinia A68), well growing at high Sb concentration (300 mg/l Sb), was tested for an ability of the strains to retain Sb from cultivation media. Based on ICP-MS measurements of the dried biomasses we concluded that all the strains can retain antimony from growth media to some extent, with strains Shewanella A20A, Buttiauxella A58, Yersinia A68 and Aeromonas A60A being the most effective.

Synthesis, characterization and study of Sb(Ⅲ) adsorption from aqueous solution by iron-aluminum pillared attapulgite

In this study, a simple, environmentally friendly and inexpensive adsorbent for Sb(III) in aqueous solution was prepared by the copolymerization method using attapulgite as the matrix, FeCl3 and AlCl3 as the metal sources. The morphology and structure of iron-aluminum pillared attapulgite were analyzed through various characterization methods. The conditions and influencing factors of iron-aluminum pillared attapulgite preparation and Sb(III) adsorption were studied. The saturated adsorption capacity of Sb(III) could reach 60.44 mg·g−1 for 180 min at pH 7 and 298 K. The adsorption process is conformed to Langmuir isothermal model and pseudo-second-order kinetic model, and the thermodynamic investigation suggested a spontaneous and endothermic adsorption process. It was revealed by X-ray photoelectron spectroscopy analysis and Zeta potential analysis that Sb(III) was first electrostatically adsorbed by the adsorbent, part of Sb(III) was oxidized to Sb(V) by Fe(III) and then antimony was complexed with iron and aluminum hydroxides to form surface complexes. In addition, a small amount of antimony migrated through intra-particle diffusion into the internal micropores and reacted with hydroxyl groups. Most coexisting components under the chosen conditions had no influence on Sb(III) adsorption, and PO43−, AsO33−, C6H8O7 and H2C2O4 had a negligible effect. However, the adsorption capacity of over 90 % without interference showed that the material has a strong selectivity for Sb(III) adsorption. The findings of the desorption experiment showed that the adsorption product has a considerable degree of desorption at increased hydrochloric acid concentrations. It may be concluded that the adsorption product is more stable in the overall polluted water environment since the actual acidity of the polluted water environment is significantly lower than the desorption experiment acidity. Overall, iron-aluminum pillared attapulgite has great potential for application in removing Sb(III).