Manganese Hydroxide Research Articles

Evaluation of ultra-filtration ceramic membrane plant for the treatment of drinking water from Ram group aquifers in south Jordan

Jordan is facing a severe shortage problem in drinking water resources which is becoming a top governmental priority to meet local water demands. Groundwaters are considered one of the main available resources. At Ram region south of Jordan, deep bedrock group Aquifers provide groundwater with elevated levels of radium isotopes of 226Ra and 228Ra that exceed health-based regulatory standards. The present study investigated the performance of the newly installed ultra-filtration ceramic membrane plant supported with hydrous manganese oxide process. The concentrations of Radium, 226Ra and 228Ra in treated water were 0.157 ± 0.061 Bq/l and 0.328 ± 0.187 Bq/l respectively. During more than 18 months of operation for 12 h daily, maximum removal efficiency achieved for 226Ra was 86.2% and for 228Ra was 92% with 99% of water recovery. The concentrations of 226Ra, 232Th and 40K were analysed in collected soil samples from the dumping area nearby the plant. The radium equivalent activities, external radiation hazard index (Hex) and the internal radiation hazard index (Hin) associated with the natural radionuclides were calculated. For contaminated soil with wastewater from the backwash operation, the radium equivalent value was 3221.6 Bq/kg and both values of Hex and Hin were greater than unity. Recommendations on mentoring and safety procedures were highlighted.

Laboratory and Pilot Plant Scale Study on the Removal of Radium, Manganese and Iron from Drinking Water Using Hydrous Manganese Oxide Slurry

Laboratory and Pilot Plant Scale Study on the Removal of Radium, Manganese and Iron from Drinking Water Using Hydrous Manganese Oxide Slurry

Interactions in MnCl2–Na2S–L-cysteine aqua system

MnS nanoparticles find potential applications in advanced materials like energy storage, photocatalysis, biomedicine, etc. With the development of nanotechnology, research on the synthesis and properties of nanoscale MnS is intensifying . In this work, MnS nanoparticles stabilized by L-cysteine were synthesized at ambient temperatures by co-precipitation technique under a control of pH in acidic and basic aqueous media. The synthesis of the MnS/L-cysteine nanoparticles using typical precursors MnCl 2 and Na 2 S has been performed in two series by increasing the crystal-forming ions concentration by the order of magnitude . Control samples of Mn(OH) 2 and MnS were prepared using the same concentration of Mn 2+ as in the MnS/L-cysteine nanoparticles case. The possibility of Mn(OH) 2 nanoparticles formation as a result of the S 2- and Mn 2+ -ions interaction is discussed. Optical properties of the MnS/L-cysteine nanoparticles colloid solutions and various binary combinations of the three-component system were analyzed using UV-visible absorbance and photoluminescence (with an excitation wavelength of 405 nm) spectrophotometry. The critical concentration of L-cysteine in the system that demonstrates stabilizing action was determined . The conditions for the formation of MnS nanoparticles stabilized by L-cysteine or L-serine molecules and the dependence of the size of the obtained MnS nanoparticles on the increase in the concentration of crystal-forming ions are discussed. The effect of intensification of photoluminescence in the synthesis of nanoparticles MnS/L-Cys in the alkaline conditions was revealed. It is assumed that the products of the system components interaction are manganese sulfide nanoparticles stabilized by the L-cysteine and manganese hydroxide capable of being oxidized by atmospheric oxygen. Keywords: nanoparticles, manganese (II) sulphide, synthesis, absorption spectra, photoluminescence.

Electrodeposition of binder-free polypyrrole on a three-dimensional flower-like nanosheet of manganese oxides containing pyrrole derivative for supercapacitor electrode

A series of nanocomposite electrodes for supercapacitors were manufactured using a two-step electrochemical synthesis of manganese oxides and polypyrrole (PPy). Under reductive conditions, an aqueous mixture of manganese nitrate and pyrrole monomer was used to develop flower-like 3D nanosheets of manganese hydroxide containing pyrrole derivative directly on a stainless-steel mesh. The nanosheets were calcined to manganese oxides, and then, PPy was deposited on the nanosheets under oxidative conditions as a polarity inversion process. The PPy changed its morphology from nanoparticles to films via aggregation as the deposition time increased. The electrochemical performance of obtained nanocomposites electrode was characterized using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The specific capacitance of the nanocomposites exhibited nearly 3 times higher specific capacitance (825 F/g) than the manganese oxides without PPy (270 F/g). This improvement could be attributed to the synergetic effects of two components. The nanocomposite electrode exhibited high stability (86% and 99.3% cycle stability and columbic efficiency, respectively, after 2000 cycles) and a high rate capability (376 F/g at 100 mV/s).

Минеральный состав руд, использовавшихся на укрепленном поселении бронзового века Устье-I (Южное Зауралье)

At the fortified settlement of the Bronze Age, Ustye-I (South Trans-Urals), metal products of copper, arsenic and tin bronzes, numerous fragments of metallurgical slags, as well as fragments of copper ores have been discovered. According to the results of early studies, pure copper predominates among metal items (53.4% of finds), but also a significant part contains an admixture of arsenic (25.4% of finds), tin (13.6% of finds) and both components simultaneously (7.6% of finds). Several alloying components of the samples are simultaneously found in slags: Pb (50% of cases), As (49% of cases), Zn (40% of cases), Bi (38% of cases), Sn (7% of cases), Ni (4% of cases), Sb (1% of cases). To identify the relationship between the incoming raw materials and the received metal, 15 ore samples were examined. The ores studied are ‘gravelly’ clasts with a size of 5 mm to several centimeters, and ‘sandy’ ores with a size of 2–3 mm. According to their mineral composition, ores are subdivided into malachite, azurite, and limonite. The main copper minerals are malachite and azurite; chrysocolla is found occasionally, chalcopyrite, cuprite are rarely found. Copper is bound to Fe- and Mn-hydroxides. We have identified copper slag fragments in ‘sandy’ ores. In all types of ores, natural alloying components are very rare and are represented by Pb and Zn. These elements can form their own minerals (mottramit, a mineral of the plumbogummite family) or act as an impurity to malachite (up to 0.62 wt% ZnO), azurite (up to 1.12 ZnO and up to 2.37 PbO), iron hydroxides (up to 2.66 ZnO and up to 2.02 PbO) or manganese hydroxides (up to 0.41 ZnO and up to 9.48 PbO). No As and Sn impurities were found. The presence of numerous fragments of brown iron ore at the settlement, the close location of copper mines indicates that the settlers were engaged in the extraction and processing of copper ore. The widespread occurrence of ores, consisting mainly of malachite and azurite, indicates that the ores were mined from the upper parts of the oxidation zone, and the metal smelted from these ores must correspond to pure copper. The distribution of Pb and Zn impurities indicates that some of the copper ores originate from the oxidation zones of pyrite ores or deposits of other formational types with a similar ore composition. The difference in the compositions of the ores found at the settlement and the compositions of slag and metal is associated with several sources of ores. The sources of copper ores could be mines located near the settlement. Arsenic-bearing ores could have come from mines in adjacent areas. Tin ores were brought in as a result of trans-regional exchange with the Central Asian region.

HMO-incorporated electrospun nanofiber recyclable membranes: Characterization and adsorptive performance for Pb(II) and As(V)

In the present work, hydrous manganese oxide (HMO) nanoparticles have been synthesized and successfully impregnated into polyacrylonitrile (PAN) nanofibers to obtain HMO-PAN composite electrospun nanofiber membranes (ENMs), via electrospinning technique. Characterization of the synthesized nanoparticles and composite ENMs using techniques high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray diffraction was performed. The adsorption viability of HMO-PAN composite ENMs as for removal of lead (Pb(II)) and arsenic (As(V)) from aqueous solution was evaluated using batch adsorption technique. HMO-PAN composite ENM preferably sequestrate As(V) and Pb(II) ions at pH 5.0 and 7.0, respectively. The maximum Langmuir adsorption capacity obtained for lead and arsenic was 194.4 mg/g and 95.7 mg/g, respectively at 318 K. During regeneration the material retained about 88% (for lead) and 83% (for arsenic) of adsorption capacity after five adsorption-desorption cycles indicating high potential for long-term application. Hence, the synthesized nanocomposite provides facile fabrication, excellent regeneration ability, and easy recovery without leaching, proving to be a promising adsorbent for uptake of Pb(II) and As(V) from aqueous solutions

Synthesis of MnSe @C yolk‐shell nanospheres via a water vapor‐assisted strategy for use as anode in sodium‐ion batteries

This study introduces a simple and eco-friendly synthetic strategy for yolk-shell nanospheres that consist of manganese selenide yolks and carbon shells (MnSe@C) by reacting manganese salt impregnated in the porous hollow carbon nanospheres (HCNS) with H2O vapor. First, manganese salt dissolved in ethanol was impregnated into the spacious pores of the HCNS by capillary force. Then, heat treatment of the powder in the presence of H2O triggered the nucleation and crystal growth of manganese hydroxide, resulting in the formation of HCNS whose central voids are filled with multiple nanoparticles. Subsequent selenization yielded yolk-shell nanospheres with MnSe@void@carbon configuration. MnSe@C was applied as the anode for sodium-ion batteries (SIBs), and the following electrochemical reaction was confirmed from various analytical techniques: MnSe +2Na+ + 2e− ↔ Mn + Na2Se. MnSe@C nanospheres exhibited stable cycle performance up to 1000 cycles at 0.5 A g−1, wherein a reversible capacity of 222 mA h g−1 was delivered in the 1000th cycle. Furthermore, MnSe@C nanospheres exhibited a fair rate performance (209 mA h g−1 at 2.0 A g−1).

Miniature microplasma carbon optical emission spectrometry for detection of dissolved oxygen in water

As one of the most important quality parameters of natural water, the quantification of dissolved oxygen (DO) attracts considerable attention in environmental analytical chemistry. In this work, an accurate and novel strategy based on selective oxidation reaction and miniature point discharge optical emission spectrometry (μPD-OES) is proposed for the simple, fast, and efficient quantitative analysis of DO in natural water samples. The DO present in the tested sample can easily oxidize an equivalent amount of manganese ions (Mn2+) to an insoluble precipitate of manganese hydroxide (Mn(OH)3) under alkaline conditions. The precipitate is able to convert oxalate to carbon dioxide (CO2) in the presence of H2SO4. Consequently, the determination of DO is accomplished via the detection of CO2 by μPD-OES at 193.0 nm. Under the optimum conditions, a limit of detection for DO detection was 0.016 mg L−1. Besides, a good precision of 3.8% was obtained for the determination of DO. Finally, the DO in tap water, river water, and lake water samples was successfully analyzed and the obtained results are in good agreement with those obtained by a Chinese national standard method (GB 7489-87), thus demonstrating that the proposed method retains a remarkable potential for the on-site analysis of DO in environmental surface water samples.

Multi-step purification of electrolytic manganese residue leachate using hydroxide sedimentation, struvite precipitation, chlorination and coagulation: Advanced removal of manganese, ammonium, and phosphate

Water pollution caused by the release of manganese (Mn2+) and ammonia nitrogen (NH4+-N) from electrolytic manganese residue (EMR) generated from industrial activities poses a serious threat to ecosystems and human health. In this study, an integrated process consisting sequentially of hydroxide sedimentation, struvite precipitation, breakpoint chlorination, and ferric chloride coagulation was optimized to remove Mn2+ and NH4+-N from EMR leachate, and to address the issue of residual orthophosphate caused by struvite precipitation. The precipitates were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analyses. Results show that Mn2+ ions and the resulting chemical oxygen demand (COD) were mainly removed using hydroxide precipitation at a sedimentation pH of 10.2, with poor-crystalline manganese hydroxide as the main precipitate. NH4+-N was primarily removed and recovered using struvite precipitation with well crystalline struvite as the main product, and then further eliminated using breakpoint chlorination. The residual orthophosphate introduced by struvite precipitation is successfully removed with ferric coagulation, and the effluent pH (7.5) is also lowered to discharge limits by means of hydrolysis of ferric coagulant. The concentration of COD, Mn2+, NH4+-N, and orthophosphate concentrations in the final effluent were 30.52 ± 9.38, 0.026 ± 0.013, 0.87 ± 0.01, and 0.06 ± 0.002 mg/L, respectively, meeting all local discharge standards. This combined process has robust pollutant removal efficiency, high resource recovery potential and few environmental constraints; thus, it is recommended as a potential solution for the treatment of Mn2+- and NH4+-N-rich acid mine drainage.

Минеральные ассоциации жил с кварцем типа «диаманты Донбасса» Селезневского угленосного района (cкладчатый Донбасс)

The authors have established quartz and quartz-carbonate veins, the formation of which is associated with a low-temperature hydrothermal system of methane-water composition within the Seleznevsky coal-bearing region of the Folded Donbass. The article considers the features of localization of hydrothermal mineralization containing quartz with inclusions of hydrocarbons, and its potential ore content. It is established that the vein bodies are localized mainly in the near-hinge parts of the third-order brachianticlines in the central and marginal parts of the Seleznevskaya syncline. These veins form systems associated with the fracturing of the inter-layer stratification or intersecting the layers. Interplastic veins are subdivided into plate-like massive and vein-like bodies with a druze texture. The veins of the second type contain quartz crystals with hydrocarbon inclusions, referred to as "diamonds of Donbass". They form a paragenetic association with dickite. In addition, calcite in the form of short-prismatic crystals is a typical associated mineral in the vein bodies among limestone strata. In the veins among the sandstone layers, the association with goethite, oxides and hydroxides of manganese is developed. Two morphological types of cinnabar were found in the vein bodies on the basis of HMS sampling, the largest number is confined to the brachianticlines of the marginal parts of the Seleznevskaya syncline. The analysis of the results indicates the prospects for identifying mercury mineralization with quartz-dickite-cinnabar type of mineralization.

Simultaneous Size- and Phase-Controlled Synthesis of Metal Oxide Nanocrystals through Esterification Reactions

Here, we report on the synthesis of metal oxide (manganese oxide) nanocrystals with simultaneous size- and phase-controlled manners through thermal decomposition of metal oleate. Bulk manganese oxide powders were applied as precursors, which react with oleic acid to yield manganese oleate at elevated temperature. In the presence of long-chain alkyl alcohols, these as-formed manganese oleates would react with alcohol to yield esters, which consequently leads to manganese hydroxide (oxide) (MnO or Mn3O4) nanocrystals. In this way, the size of manganese oxide nanocrystals can be tuned by different amounts of alkyl alcohols. Furthermore, the phase of manganese oxide nanocrystals can also be simultaneously controlled, where a small amount and large amount of alkyl alcohols lead to the formation of MnO and Mn3O4 phase, respectively. These high-quality manganese oxide nanocrystals are able to self-assemble into ordered nanocrystal superlattices.

Hydrometallurgical enrichment of polymetallic and ferromanganese ore

The article presents the results of theoretical and experimental studies of leaching of polymetallic manganese-containing and ferromanganese ore. Thermodynamic calculations and experimental studies on enrichment of manganese-containing raw materials made it possible to determine the main technological parameters of the extraction of manganese, iron and non-ferrous metals, and to develop technological schemes for enrichment of various types of manganese-containing raw materials. The studies were carried out for polymetallic and ferromanganese ores of the Kaigadat deposit, the Selezen deposit, the Sugul site, located in the Kemerovo Region – Kuzbass. Before carrying out laboratory studies, the authors have performed thermodynamic analysis of ore leaching, chemical and X-ray structural analyzes of the samples. Laboratory tests were carried out on a multichamber autoclave unit MKA-4-75 using calcium and iron chlorides as solvents. Since the introduction of a reducing agent into the charge during leaching significantly improves the conditions for dissolution of oxides and hydroxides of manganese in calcium chloride, a series of experiments was conducted with the use of charcoal in the charge. Thermodynamic calculations have shown that the leaching process is fully implemented in the temperature range from 323 to 673 K. The results of the experiments confirmed the theoretical research results. The obtained data allowed the authors to propose a technological scheme for hydrometallurgical enrichment of polymetallic and ferromanganese ores to produce high-quality concentrates. All processed products are suitable for use. The use of optimal technological parameters of enrichment allows 95–97 % of manganese, up to 80 % of nickel, up to 99 % of cobalt, and 96–98 % of iron to be extracted from polymetallic manganese-containing raw materials. As a result of the deposition of these elements, high-quality concentrates of manganese, nickel, iron, cobalt are obtained. According to the proposed technological scheme for ferromanganese raw materials with a high content of silicates, it is possible to obtain high-quality concentrates of manganese and iron, while the extraction of manganese is 90–92 %, and of iron – 86–90 %.

New strategy to enhance heavy metal ions removal from synthetic wastewater by mercapto-functionalized hydrous manganese oxide via adsorption and membrane separation.

The development of efficient materials and methods for the elimination of heavy metals contamination from water bodies is increasingly demanded as these toxic cations can acute diseases to humans or make serious threat to the environment. The aim of this research is to evaluate the effectiveness of the organosilane coupling agent for the modification of hydrous manganese oxide and the application of the functionalized nanoadsorbent for the removal of nickel and copper ions from synthetic wastewater samples. The synthesized thiol-functionalized hydrous manganese oxide was characterized in terms of their morphology, surface area, functional groups, surface elemental compositions, and the structural properties. In the adsorption process of Ni(II) and Cu(II), the effective parameters including the initial metal cation concentration (20-150 mg/L), operation temperature (298-318 K), and the contact time at the optimum pH were investigated. The uptake of Ni(II) and Cu(II) ions on the prepared adsorbents followed by the Freundlich isotherm model reveals the heterogeneous adsorption, with the adsorption capacities of 24.96 mg/g and 31.2 mg/g for the modified adsorbent and 23.92 mg/g and 29.6 mg/g for the virgin adsorbent, respectively. Based on the results, both the virgin and the functionalized adsorbents exhibited high affinity to copper ions than nickel in the single-component system. Kinetic experiments of both metal ions clarified that the experimental data was well predicted by pseudo-second-order model and the equilibrium was achieved after 10 min of contact time. Additionally, the incorporation of the as-prepared adsorbents in the electrospun nanofibers membrane matrix showed the promising potential for the removal of metal cations. The nickel and copper removal efficiency by the membranes containing 1.5 wt% of the modified adsorbent was 80% and 89%, respectively which implying that the modified adsorbent could be employed more efficiently in other treatment techniques for the removal of metallic pollutants. The modification of hydrous manganese oxide by the functional mercaptosilane increases the adsorption sites for trapping the metal ions and improves the adsorption capacity, making high capability for the removal of metal ions from the effluent.

Effect of various operating parameters towards PVDF/HMO mixed matrix membrane performance

The development of antifouling membranes to separate oil/water emulsions in various environmental approaches is urgently needed. This work reports on the development of a mixed matrix membrane (MMM) using polyvinylidene fluoride (PVDF) incorporated with self-synthesized hydrous manganese oxide (HMO). The filtration performance was compared to the pristine PVDF membrane in terms of flux and rejection efficiency. The membranes were characterized and evaluated under various operating parameters: different oil/water emulsion feed concentrations (50, 100, 500, and 1000 ppm), cycle stability, long-term membrane stability, and flux recovery ratio (FRR). When tested with a 1000 ppm oil/water emulsion feed concentration, the fabricated MMM exhibited higher flux performance of approximately eight folds compared to the pristine membrane, with the FRRs of 87% and 56%, respectively. After the eighth cycle, the performance of the MMM decreased gradually. However, the pristine membrane had completely collapsed at the end of the recyclability test. Furthermore, the modified PVDF/HMO MMM was physically stable for up to 6 h during the long-term stability study, indicating the potential of HMO in improving separation performance and the lifespan of MMM.

Arsenic-rich stalactites from abandoned mines: Mineralogy and biogeochemistry

Stalactites containing 0.13–294 g kg−1 As were collected from abandoned adits of the former Mikulov and Plavno mines (NW Czech Republic), and were then characterized by: X-ray diffraction, bulk chemical analysis, electron microprobe and Raman microspectrometry, chemical composition of the drip water, and analyses of the microbial communities. Several assemblages of mineral phases were identified: (i) straws of X-ray amorphous hydrous ferric arsenate (HFA) with younger kaňkite, (ii) pure HFA straws, (iii) straws composed of schwertmannite and HFA co-precipitates, and (iv) massive stalactites composed of X-ray amorphous hydrous ferric oxide (HFO) and HFA co-precipitates and minor hydrous manganese oxide (HMO). The chemistry of the drip water was closely linked to the solid phase composition of the stalactites. HFA- and schwertmannite-rich straws formed at pH < 4.4, while HFO-rich stalactites precipitated at a higher pH (>6.6). The concentrations of As and other trace elements (namely Pb and Zn) in the drip water is controlled by the solubility of HFA and/or sorption affinity of these elements to the schwertmannite, HFO, and HMO phases. Drying out of the HFA straws may lead to recrystallization and rearrangements of HFA, which result in formation of kaňkite and chemically anomalous HFA domains enriched in Ca, K, Mn, Pb, S, and Zn. Analyses of the stalactite's microbial communities revealed autotrophic oxidation of Fe, As, and S as the main factors driving formation of secondary minerals. Contrasting communities were found in similar mineral assemblages of stalactites, suggesting the high variability of microhabitats within each stalactite.

The geochemical behavior of trace metals and nutrients in submerged sediments of the Three Gorges Reservoir and a critical review on risk assessment methods.

Permanently submerged sediment samples (SS) were collected in the center stream of eleven tributaries of Changjiang (Yangtze River) and at eight confluence zones in the Three Gorges Reservoir (TGR) in May and December of 2017. The work showed that aqua regia digestion is a simpler, more reliable and robust method compared to total digestion with hydrofluoric acid (HF) for the determination of trace metals (TMs) in sediment for risk assessment purpose. Our study revealed a remarkable accumulation of TMs at the confluence zones and a trend of their gradual increase toward this zone. The presence of iron and manganese (oxy)hydroxides combined with hydrodynamic conditions created by the Three Gorges Dam (TGD) and its operation are believed to play a crucial role. This work also found that concentrations of [Formula: see text] in May sediment were significantly higher than those in December, which could have been caused by both the cyclic hydrodynamic conditions and the warmer water. TOC and TP were both very low in the sediment. Although TN was 2 times higher than the Lowest Effect Level suggested by the Ontario Ministry of Environment, it is uncertain if it reflects a natural background level or due to anthropogenic activities. A critical discussion is made by comparing the conclusions obtained when using different TMs risk assessment models. Necessary precautions are highly recommended when performing this exercise. In this study, no significant risk from either TMs or nutrients was identified.

Synthesis and Application of Titania Nanotubes and Hydrous Manganese Oxide in Heavy Metal Removal from Aqueous Solution: Characterization, Comparative Study, and Adsorption Kinetics

Titania nanotube (TNT) and hydrous manganese oxide (HMO) nanoparticles were synthesized via hydrothermal synthesis and chemical coprecipitation methods, respectively, to investigate their performance in separation of Cd2+ and Cu2+. Furthermore, field emission scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy analysis were used to examine the structural morphology, crystallinity, and composition of synthesized adsorbents and the calculated mean particle sizes of TNT and HMO nanoparticles were 26 and 7 nm, respectively, using the Scherrer equation. The applications of fabricated nanomaterials as an adsorbent for Cd2+ and Cu2+ decontamination were described via batch adsorption technique. The kinetic study of the adsorption process was performed at different initial concentrations of ions by two kinetic models: pseudo-first-order and pseudo-second-order models. Kinetic studies of the adsorption process revealed that the adsorption of Cd2+ and Cu2+ onto TNTs and HMOs is well described by pseudo-second-order kinetic model. According to the obtained equilibrium data for Cd2+ and Cu2+, the adsorption of metal ions was increased by increasing the initial concentrations of metal ions. It was further found that TNTs exhibited higher adsorption capacity for Cd2+ and Cu2+ than HMO nanoparticles so that at 200 mg/L of metal ion concentration, the maximum adsorption capacities of Cd2+ and Cu2+ were found as 49 and 47 mg/g, respectively, for sample TNT572 and 37 and 34 mg/g, respectively, for sample HMO1. However, the observed fast kinetics of adsorption revealed a high affinity between the heavy metal ions and the prepared nanostructured materials.

Clay minerals identification in rock varnish by XRD: A one-step reduction approach

Rock varnishes are known to be fine, dark, glossy submicron films found in deserts bare rock surfaces. The oxides and hydroxides of manganese and iron bind together the clay minerals present in the varnish layer. The processes of oxide-hydroxide accumulation at varnish sites are due to iron and manganese oxidizing bacteria which may require clay minerals for additional nutrition. Quantification and identification of clay minerals in this biofilm is needed to understand its formation. Past attempts to analyze the mineralogical composition of rock varnish have led to inconclusive results as varnish is a submicron thin layer composed of a complex mineral matrix. The elimination of non-crystalline cementing groups comprising of free iron oxides is a key step in the identification of many types of clay minerals, particularly in soil/sediment mineral studies.•The Fe-Mn oxide-hydroxide coatings, acting as cementing materials, can be easily removed using a one-step reduction method employing Na2S2O4 at 70 °C, leading to separation of clay minerals.•We have taken the lead from earlier reported Jackson (1958) method, wherein a combination of reagents was used such as sodium acetate, sodium citrate, hydrogen peroxide, sodium bicarbonate, and sodium dithionite for removing carbonate, organic carbon and Fe-Mn oxy-hydroxide coatings respectively from sediment grains to segregate individual grains from each other.•Our modification helps in the unveiling of clay minerals from a solid substrate and reports the X-ray diffraction peaks, which are elsewise hard to detect and therefore earlier studies are inconclusive.

Study on Speciation Chemical Analysis of Rare Earth Elements in Soil Based on Green Environmental Technology

The impact of rare earth elements on the soil environment is not only related to its total amount, but also more closely related to its chemical form. The green and environmentally friendly acid digestion and morphological continuous extraction methods were used to extract and analyze the total amount of rare earth elements and the forms of rare earth elements in the soil samples. Inductively coupled plasma mass spectrometry was used to determine the content of rare earth elements and the content of rare earth elements in the soil samples. Form content. The results show that the content of rare earth elements in the collected soil samples is 200-1418mg/kg, and the content of light rare earth elements is much higher than that of heavy rare earth elements; the recovery rate of the sum of the combined forms of rare earth elements relative to the total amount is 88.2% to 110%, indicating that the continuous extraction method is suitable for the analysis of rare earth elements in soil samples. The rare earth elements in soil samples mainly exist in the residue state, which is 33%-80%; the co-precipitation state of crystalline iron and manganese hydroxide is 10%-31%; the adsorption state of humus and amorphous oxide is 5.0%-18%; The exchange state and the carbonate combined state are 4.0% to 23%; the amorphous iron-manganese oxide co-precipitation state is less than 3%. The influence of the location of the sampling point and the nature of rare earth elements on the content of rare earth elements was analysed, and the influence of soil properties on the distribution of morphology was discussed.

Trace Element’s Speciation in the Water and Bottom Sediments of the Pirogovo Reservoir

The composition and speciation of trace elements were studied in surface and interstitial waters along with solid phase of bottom sediments to characterize the abiotic segment of the Pirogovo Reservoir. It was found that the concentrations of metals in surface waters did not exceed the MACs for fishery basins, excluding Zn and Cu (2–9 and up to 2 MACs, respectively). According to thermodynamic calculations, the predominant metal speciation in water is free ions (Sr, Ba, Zn, Ni, Co, and Cd), as well as fulvate and carbonate complexes of Cu and Pb, respectively. Interstitial waters showed a regular increase of the fraction of the sulfate complexes of trace elements in loamy sediments. The solid phase of the latter as well was characterized by low anomalous concentrations of Zn, Cd, Co, and Ni. According to the data of extraction, the metals were either fixed in bottom sediments within crystal structure of silicates or bound to oxides and hydroxides of iron and manganese, excluding Cd and Mn, which are characterized by a considerable role of their exchangeable and bound to carbonates fraction in the particulate matter.