Fraction Of Mn Research Articles

Speciation the heavy metals; Fe, Mn, Cu, Zn, Ni, Cd and Pb in the Sediment of Lake Burullus (Ramsar site), Egypt

This study was carried out to investigate the speciation and distribution of the heavy metals; Fe, Mn, Cu, Zn, Ni, Cd and Pb in the sediments of Lake Burullus, Egypt. The mean metal concentrations of the sediments followed the order of Fe >Mn> Zn > Cu > Ni >Pb> Cd. The evaluated contamination with these metals was revealed moderate to strong ecological risk. According to applying index of the potential ecological risk index (RI), risk assessment code (RAC) and modified risk assessment code (mRAC); the risk levels showed the following order Cd = Pb>Mn> Ni > Zn > Cu > Fe. Considering the metals speciation, high levels were found in the residual fraction for Fe, Cu, Zn and Ni; while were in Fe-Mn hydroxide fraction for Cd and Pb, and in carbonate fraction for Mn. All metals showed enrichment during summer at stations of the southeastern parts of the lake due to the heavy discharge of contaminants from shakhloba, kotichener and Hoksa drains. Therefore, monitoring of contaminants discharge and determination of heavy metal and other pollutants in the water and sediments and its fractionation at Lake Burullus should be introduced for future and management strategies.

Spectrophotometric determination of manganese in acidified matrices from (pore)waters and from sequential leaching of sediments

Manganese (Mn) is a major redox reactive element in marine sediments and it plays an important role in the biogeochemical cycles of carbon, nitrogen, phosphorus, or trace metals. Mn cycle in marine sediments is characterized by an alternation of oxidation and reduction processes depending on physicochemical and biological conditions: assessing the quantification and the speciation of Mn is thus an essential issue to understand redox reaction-transport processes in sedimentary deposits. Solid Mn phases can be determined through chemical extractions techniques that permits selective leaching of operationally defined Mn fractions. Mn oxides and oxyhydroxides are extracted with an ascorbate leaching solution, while the whole Mn (oxyhydr-)oxides and Mn associated to carbonates is extracted with HCl.An existing spectrophotometric method allows to quantify Mn dissolved in (sea) water. We present here a modified version, which permits to measure Mn in acidified matrices, including ascorbate and HCl solutions. A metallic substitution occurs between a Cd-TCPP complex and Mn at pH 7.5–8.0, with imidazole as catalyst. We propose here to use a NaHCO3 solution to dilute the samples in order to be in the necessary pH range to perform the metal substitution. Using this method, Mn(II,III) concentrations were determined in standard solutions with a precision of 3% within a concentration range of 0.5–80 μM. The procedure was successfully applied to determine Mn in acidified pore waters and in ascorbate and HCl sequential extractions from muddy sediments of the Bay of Biscay. Spectrophotometric results agreed closely with results from atomic absorption spectrometry, validating the proposed method.

Distribution of desferrioxamine-B-extractable soluble manganese(III) and particulate MnO2 in the St. Lawrence Estuary, Canada

Soluble organically-complexed manganese(III) (Mn(III)-L) is an intermediate species in the manganese cycle. The reactivity of the complex(es) depends on the abundance and nature of the ligand(s), as well as its physicochemical environment. Currently, the strength of Mn(III)-L complexes is assessed by their ability to react either directly with a porphyrin complex, using the kinetics of its competitive ligand exchange reactions, or after being reduced to manganese(II). We present a new three-step technique that quantifies part of the Mn(III)-L pool which may represent a bioavailable and reactive fraction of the complexes. This technique relies on 1) ligand exchange of the dissolved complexes in a filtered field sample with the siderophore desferrioxamine-B (DFOB), 2) chromatographic separation and concentration of manganese(III)-DFOB from the aqueous matrix, and 3) quantification of the naturally ligated manganese(III) that was outcompeted by DFOB (Mn(III)-LDFOB) at low concentrations by flow injection UV-Vis spectrophotometry. The formation of an extractable Mn(III)-LDFOB complex provides an operationally-defined benchmark by which to assess biological interactions and better understand the cycling of manganese(III) in the environment. The technique, with a detection limit of 0.09 nM, was applied to water samples collected in the St. Lawrence Estuary (SLE) and adjacent Saguenay Fjord in Canada. Mn(III)-LDFOB was ubiquitous at our study sites, but its concentration was low relative to total dissolved manganese (dMnT) and particulate MnO2. Spatial variations of the dMnT speciation within the Saguenay Fjord suggest that Mn(III)-L forms from the reduction of MnO2. Likewise, variations of the dMnT speciation along a dissolved oxygen gradient in the SLE leads us to believe that Mn(III)-LDFOB likely represents a fraction of the total Mn(III)-L that cycles more readily in estuarine and marine systems.

Distribution and Phytoavailability of Potentially Toxic Metals in Different Fe/Mg Mine Tailings.

The environmental risk of potentially toxic metals in tailing soils is of universal concern. We conducted a 3-month pot experiment to research the distribution and variations of potentially toxic metals (PTMs), and the translocation and accumulation capability of these metals (Cr, Ni, Mn, Cu, Zu) in natural plants for three Fe/Mg tailing soils (serpentine-type, olivine-type and magnetite-type) with growth of a grass plant-Imperata cylindrica. We used comparative analysis, regression analysis and correlation analysis to process relevant experimental data. Results showed the rhizosphere tailing soils decreased from 3.70% to 16.8%, compared to the bulk soils, after growth of Imperata cylindrica, and the acid soluble fraction of Mn, Cu and Zn increased significantly. Cu and Zn were more bioavailable than other PTMs, especially for serpentine-type tailing soils. Linear regression analysis indicated that non-residual fractions showed different effects on metal concentrations of Imperata cylindrica. The non-residual metal fractions of serpentine-type and olivine-type tailing soils showed better correlations with metal concentrations in grass plants than those of magnetite-type tailing soils. We found that the chemical compositions of tailing soils showed remarkable effects on Ni and Mn compared with other elements, especially Mg and Al. Overall, the grass plant can alter the metal distribution, enhance metal bioavailability and promote land use of Fe/Mg tailing soils.

Soil manganese dynamics and its uptake in wheat (Triticum aestivum) influenced by chloride and manganese application

Manganese (Mn) is one of the essential micro-nutrients having an important contribution in paddy (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping systems. Wheat is an important cereal crop of Haryana State and is highly susceptible to Mn deficiency. During submerged paddy, solubility of Mn increases appreciably because of its reduction and continuous leaching from upper to lower soil layers which in turn results in its deficiency in the succeeding winter season crops especially wheat. Often, Mn fertilization under salinity stress is of main concern to be investigate, especially in arid and semi-arid regions of Haryana. So, in order to evaluate soil manganese dynamics and its uptake in wheat influenced by chloride (Cl-) and Mn application, laboratory as well as a screen house experiment was conducted at CCS HAU, Hisar, Haryana. Results revealed that a decreased grain and straw yield and Mn uptake in wheat with graded doses of Cl- application. The highest grain and straw yield of wheat were recorded with 25mg Mn/kg and without chloride application. However, maximum Mn content and its uptake in wheat was recorded under treatment of 50 mg Mn/kg. Among all Mn fractions in post-harvest soils, maximum Mn was associated with residual (RES) fraction followed by MnOX > AFeOX > CFeOX > EX > CARB > OM fractions. Organic matter bound (OM) showed a very little amount of Mn content due to low content of organic carbon in experimental soil. Thus, chloride application along with Mn fertilizers showed antagonistic effect on wheat yield and its uptake as well as Mn dynamics in soil.

Innovative reference material for improving the quality control in the sucroenergetic sector

Analytical techniques in the sucroenergetic sector can now for the first time be supported by an innovative matrix-matching reference material produced from sugarcane leaves. This will further enhance the validity of the measurement results and contribute significantly to the quality assurance of plant nutrition analysis. The candidate reference material obtained had a low residual moisture and appropriate particle size. Neutron activation analysis was used to determine the mass fraction of Al, Br, Ca, Cl, Ce, Co, Cs, Cu, Fe, Hf, K, La, Mg, Mn, Mo, Na, P, Rb, Sb, Sc, Sm, Sr, Th, V and Zn, and the Kjeldahl method for N. Statistical techniques were applied to evaluate minimum sample mass and within-bottle homogeneity (ANOVA, Tukey test and PCA) and between-bottles homogeneity (ANOVA). It is demonstrated in this paper that the material is homogeneous using 50 mg mass sample for most chemical elements. However, sample masses of 200 mg or greater are required for Co, Na, Sb and V.

English

A speciation study of selected heavy metals in soil and stream sediments around a hospital waste dumpsite was investigated. Sequential extraction procedure was used to fractionate the metals into 4 fractions: Exchangeable and bound to carbonate, oxyhydroxide of Fe and Mn, organic matter and the residual fraction. Speciation analysis of Fe, Mn, Zn, Cu, Cd and Pb in soil revealed that a major portion of the metals were associated with the residual fraction. The exchangeable and carbonate fraction was the most important fraction for Mn(Dry/Wet) and Zn(Dry/Wet) with an average of (27%, 35.6%) Mn and (20.8%, 27.3% ) Zn. Cd, Fe and Cu were associated with the oxyhydroxide of Fe and Mn fraction with an average of (61%, 44.2%) Cd(Dry/Wet), (41%, 21%) Fe(Dry/Wet) and (25.3%, 22.5%) Cu(Dry/Wet). A significant amount of Pb(Dry/Wet) (10.7%, 21.8%) was bound to  organic fraction during dry and wet season respectively. In sediments, Mn(Dry/Wet) occurred mainly in exchangeable and carbonate fraction (45.2%, 29.3%), Fe(Dry/Wet) and Cd(Dry/Wet) in the oxyhydroxide of Fe and Mn fraction were (41%, 31.2%) and (26.6%, 93.6%) respectively and the amount of Pb(Dry/Wet) bound to the organic fraction was (86.9%, 27.3%). A significant amount of Cu(Dry/Wet) (20.8%, 29.4%) was bound to the organic fraction and Zn(Dry/Wet) (35.5%, 73%) was retained in the residual fraction. In soil and sediments, Mn was potentially more bioavailable.  However, the level of lead in organic matter fraction of soil suggest that it may be remobilized under oxidizing condition, hence, bioavailable.   Keywords: Speciation, hospital waste, heavy metal, sediments, soil.

BCR Sequential Leaching for Geochemical Fractions and Assessment of Fe, Ni, and Mn in the Coastal Sediments Sendang Biru Port, East Java, Indonesia

The changes in the aquatic environment by either natural or anthropogenic sources may affect the presence of heavy metals in the sediment of Sendang Biru Port. Heavy metals such as Fe, Ni, and Mn possibly give a negative impact on ecological and biological systems in the sea water. To monitor the status of sediment of the Port Sendang Biru, we investigated the geochemical fraction of Fe, Ni, and Mn in sediment using the BCR (European Community Bureau of Reference) sequential leaching method. The precision test of BCR method showed that Fe, Ni, and Mn has 4.82; 3.73; and 3.16 Relative Standard Deviation (RSD), respectively. The accuracy test of BCR method showed that percentage recovery for Fe, Ni, and Mn were 85.5%; 96.2%; and 63.0%, respectively. The fractionation of Fe, Ni, and Mn in the sediment of Sendang Biru Port showed that Fe was dominant in residual fraction (90.7%), whereas Ni and Mn were dominant in non-residual fraction (78.8% Ni and 77.2% Mn). The dominance of Fe in the residual fraction indicated that Fe was from natural sediment minerals bound to silicate and aluminate, whereas the dominance of Ni and Mn in non-residual fractions was possibly derived from anthropogenic effects. Assessment from index calculation of sediment had the category contaminated at moderate levels by Ni and contaminated at low levels by Fe and Mn.

Role of phosphoric acid in the bioavailability of potentially toxic elements in hydrochars produced by hydrothermal carbonisation of sewage sludge

The effect of phosphoric acid addition to the feed-water on the speciation and transformation behaviour of potentially toxic elements (PTEs) in the hydrothermal carbonisation (HTC) of sewage sludge was explored. Over 70% of each of the PTEs (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) was in the directly bioavailable and potentially bioavailable fraction in the raw sludge, and especially Cu and Zn at 97.5 and 98.6%, respectively. Through the HTC process the directly bioavailable and potentially bioavailable fractions of PTEs in the sludge hydrochar clearly decreased, and the residual fraction in the hydrochar showed an observable increase. Further stabilisation of PTEs in hydrochar occurred during HTC with the addition of phosphoric acid solution to the feed-water. As the concentration of phosphoric acid in the feed-water increased the percentages of the residual fraction of Cd, Cr, Ni, Pb and Zn in hydrochars each exceeded 80%, but different PTEs behaved differently with increasing phosphate molar ratio in the feed-water. When the molar ratio of phosphate was 15%, the percentages of the residual fractions of Cd, Mn and Zn reached their maximum values in accordance with the changing trend in aromaticity of the hydrochar. Moreover, a large number of phosphate mineral crystals effectively occluded the PTEs in hydrochar. In conclusion, the addition of phosphoric acid to the feed-water during HTC further deactivated PTEs leading to a substantial decline in the potential environmental risk associated with the land application of the sewage sludge.

Influence of thermal and marine water and time of interaction processes on the Cu, Zn, Mn, Pb, Cd and Ni adsorption and mobility of silty-clay peloid

In order to improve the technical properties of raw clays for cosmetic and medical treatments, maturation processes are used for peloid preparation. As for metals, only their total concentrations are usually controlled. However, the dosage of the mobile fractions that could be absorbed by the skin is overlooked. By means of data monitoring, we assessed the risks that adsorbed and mobilized metals pose to humans through natural clay maturation. To do so, the total concentrations and mobile fractions of Pb, Zn, Mn, Ni and Cd were determined using a BCR procedure. Except in the case of Cd, metal concentrations in peloids that had been matured with thermal (TW) and marine water (MW) for 12 months were higher than those present in raw clay. The metal mobility indexes equaled zero were very low in raw clay, but they increased systematically with maturation (except in the case of Ni). The increases in metal concentration and mobility were higher in the case of marine than in the case of thermal water. We concluded that the matured mud can be toxic. Thus, the assessment of mobile metal fractions is highly recommended so as to protect human health.

The Migration and Transformation of Heavy Metals in Sewage Sludge during Hydrothermal Carbonization Combined with Combustion.

The migration and transformation behaviors of heavy metals (HMs), including Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb, during the hydrothermal carbonization (HTC) of sewage sludge (SS) were investigated. The immobilization of HMs during the combustion of solid residual (SR) produced from HTC of SS was also analyzed. With increasing HTC temperature and residence time, the majority of HMs (except As) accumulated in the SR. The residual rate of As in the SR decreased from 73.95% to 56.74% when the residence time was increased from 1h to 3h and reduced significantly from 73.95% to 37.48% when the temperature increased from 220°C to 280°C, implying that numerous arsenic compounds dissolved into liquid phase products. Although the HTC process has a positive influence on the transformation of HMs from weakly bound fractions to the more stable fractions, the exchangeable and reducible fractions of Mn, Zn, As, and Cd in the SR were still high. In addition, the leached amounts of Zn and As were high (14.61 and 6.16 mg/kg, respectively) and showed a high leaching risk to the environment. An increase in HTC temperature and residence time led to an increase of the residual rate of HMs in the combustion residual of SR, implying that the HTC process promotes the stabilization of HMs in the combustion process.

The effect of earthworm and arbuscular mycorrhizal fungi on availability and chemical distribution of Zn, Fe and Mn in a calcareous soil

Micronutrient deficiencies most frequently occur in calcareous soils. In sustainable soil management enhanced soil biological activity has been proposed as a method for improving soil fertility. Therefore, the objective of this study was to evaluate the effect of earthworm and arbuscular mycorrhizal fungi (AMF) on fractionation and availability of Zn, Fe and Mn in a calcareous soil under maize cultivation. For this purpose a greenhouse experiment was conducted with four treatments including control, earthworm addition (E), AMF inoculation (AMF) and both earthworms addition and AMF inoculation (E + AMF). The results showed that the biological treatments (E, AMF and E + AMF) significantly increased Zn, Fe and Mn uptake by maize. Although the presence of earthworms in E + AMF treatment had no significant effect on mycorrhizal colonization but decreased the concentration of Zn and Mn in shoot compared to AMF treatment. Dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased in all biological treatments. The highest amount of DOC and MBC were found in treatments containing earthworms (E and E + AMF) and E + AMF treatment respectively. The biological treatments significantly decreased bound to Fe-MnO fraction of studied elements compared to control. Due to the slight changes in other fractions, it seems that biological treatments increased the uptake of Zn, Mn and Fe by maize probably with impact on bound to Fe-MnO fractions.

Chemical fractionation and bioavailability of Fe, Mn, Pb, and Cd in soils around Meyghan Lake, Arak, Iran

The chemical fractionation and bioavailability of iron, manganese, lead, and cadmium in soils around Meyghan Lake, Arak, Iran, were studied. The samples were obtained from four sites of water entrance to the lake using a sequential extraction method. The soil sampled from the release site of wastewater of sodium sulfate plant had the lowest total heavy metal contents compared to other sites. Although the HNO3 extractable fraction was the most important phase for the four heavy metals, this fraction in salty soils was not the main fraction for Cd. The KNO3 extractable and bioavailability and contamination factor (CF) of the heavy metals were considerably high in the salt-affected soils. The NaOH extractable Fe of the non-salty soils was higher than that of the salty soils. The order of metal reactivity assessed by CF in the studied soils was observed to be Cd > Pb > Mn ≫ Fe. However, the increasing effect of salinity on promoting the metal-soluble and exchangeable form (mobility) followed the order of Cd > Mn > Pb ≫ Fe.

Oxygen isotope analysis of bacterial and fungal manganese oxidation.

The ability of micro-organisms to oxidize manganese (Mn) from Mn(II) to Mn(III/IV) oxides transcends boundaries of biological clade or domain. Many bacteria and fungi oxidize Mn(II) to Mn(III/IV) oxides directly through enzymatic activity or indirectly through the production of reactive oxygen species. Here, we determine the oxygen isotope fractionation factors associated with Mn(II) oxidation via various biotic (bacteria and fungi) and abiotic Mn(II) reaction pathways. As oxygen in Mn(III/IV) oxides may be derived from precursor water and molecular oxygen, we use a twofold approach to determine the isotope fractionation with respect to each oxygen source. Using both 18 O-labeled water and closed-system Rayleigh distillation approaches, we constrain the kinetic isotope fractionation factors associated with O atom incorporation during Mn(II) oxidation to -17.3‰ to -25.9‰ for O2 and -1.9‰ to +1.8‰ for water. Results demonstrate that stable oxygen isotopes of Mn(III/IV) oxides have potential to distinguish between two main classes of biotic Mn(II) oxidation: direct enzymatic oxidation in which O2 is the oxidant and indirect enzymatic oxidation in which superoxide is the oxidant. The fraction of Mn(III/IV) oxide-associated oxygen derived from water varies significantly (38%-62%) among these bio-oxides with only weak relationship to Mn oxidation state, suggesting Mn(III) disproportionation may account for differences in the fraction of mineral-bound oxygen from water and O2 . Additionally, direct incorporation of molecular O2 suggests that Mn(III/IV) oxides contain a yet untapped proxy of δ18OO2 of environmental O2 , a parameter reflecting the integrated influence of global respiration, photorespiration, and several other biogeochemical reactions of global significance.

Enrichment characteristics, thermal stability and volatility of hazardous trace elements in fly ash from a coal-fired power plant

Release of hazardous trace elements (HTEs) during re-use of coal-fired fly ash involving heat treatment process can cause health risks for on-site workers and contaminate the surrounding environment. Enrichment characteristics, thermal stability and volatility of five HTEs (Hg, As, Pb, Cr, Mn) in fly ash collected from a 660 MW coal-fired power plant were investigated. Brunauer-Emmett-Teller (BET), scanning electron microscope- energy dispersive spectrometer (SEM-EDS), and X-ray power diffraction spectrometry (XRD) were used to characterize pore structure and chemical composition of the coal-fired fly ash (CFA) samples. Results show that the coal belongs to bituminous, containing low content of S, Cl, and the HTEs analyzed. CFA samples have low content of Hg (0.04–0.20 mg/kg) and As (3.0–8.7 mg/kg), and high content of Mn (782.46–1115.85 mg/kg). Burnout degree and specific surface area result in the decreasing HTEs concentration in CFA samples when increasing the particle size. Relative enrichment index (REI) of HTEs in the raw CFA are in the order of Mn > Cr > Pb > 1 > As > Hg. Increase in particle sizes leads to decrease of the REI value, implies that HTEs are enriched more in finer fractions. Thermal stability of HTEs in CFA samples becomes weaker at higher temperature. The smaller the particle size is, the worse the thermal stability becomes. Volatilization fractions of Hg, As, Pb, Cr, and Mn in CFA samples at four temperatures (350 °C, 550 °C, 750 °C, 950 °C) range 88.35%–99.50%, 2.32%–23.17%, 4.08%–22.59%, 20.36%–34.43%, and 1.21%–23.43%, respectively. The derivative of the concentration-fitted curve to the temperature in the range of 20–900 °C at heating rate of 10 °C/min indicates volatility of HTEs in CFA follows the decreasing order of Hg > As, Cr > Mn, Pb.

Direct ICP-OES multielement analysis of infused black and green teas and chemical fractionation of selected essential and non-essential elements prior to evaluation of their bioavailability and classification of teas by pattern recognition

Operationally defined chemical fractionation of Al, Ba, Ca, Cu, Fe, Mg, Mn, Ni, Sr and Zn in infusions of loose leaf and bagged black and green teas was carried out. It was based on tandem-column solid phase extraction using reverse-phase and strong cation-exchange extraction tubes connected in series. Concentrations of elements in resultant infusions as well as column effluents and eluates were determined with the aid of inductively coupled plasma optical emission spectrometry and a newly developed simplified sample preparation procedure. It was established that information on separated chemical fractions, particularly the fraction of residual species of elements, had better discrimination power than information about total concentrations of these elements. Differences in chemical fractionation patterns of elements in infusions of analyzed four types of tea led to simple classification of different black and green teas by principal component analysis and linear discriminant analysis.

Influence of potassium hydroxide activation on characteristics and environmental risk of heavy metals in chars derived from municipal sewage sludge

To investigate the influence of KOH activation on characteristics and environmental risk of heavy metals in chars, sludge was pyrolyzed with varying amount of KOH. The analyzation of characteristics and potential ecological risk evaluation of heavy metals were conducted by surface area analyzer, FTIR, XRD and BCR sequential extraction. The activated chars have higher surface area and lower content of silica compared to those without being activated. The activation of KOH promoted residual fraction of Cd, meanwhile, Zinc, Cr, Ni and Mn were converted to relatively unstable fractions (F2 and F3). The results of risk assessment indicated that the potential ecological risk level of Cd was reduced in activated chars, while risk level of Zn, Cr, Ni and Mn were increased after pyrolysis with KOH activation. The potential ecological risk of heavy metals in activated chars was further declined, and the risk level transformed from moderate to low.

Associations between age and 50 trace element contents and relationships in intact thyroid of males.

It is unclear why a prevalence of thyroid dysfunction is higher in the elderly as compared to the younger population. An excess or deficiency of trace element contents in thyroid may play important role in goitre- and carcinogenesis of gland. To examine the variation with age of the mass fraction of 50 trace elements in intact (normal) male thyroid. Samples of thyroid parenchyma obtained from 72 healthy males (mean age 37.8years, range 2-80years) was investigated. Measurements were performed using a combination of non-destructive and destructive methods: instrumental neutron activation analysis and inductively coupled plasma mass spectrometry, respectively. Tissue samples were divided into two portions. One was used for morphological study while the other was intended for trace element analysis. There is a statistically significant increase in Cd and Se mass fraction, as well as a decrease in Al, Be, Dy, Ga, Gd, Li, Mn, U, and Y mass fraction in the normal thyroid of male during a lifespan. Moreover, a disturbance of intra-thyroidal chemical element relationships (correlations) with increasing age was found. Our findings suggest that, at least, a goitrogenic and carcinogenic effect of Cd overload and Mn deficiency in the thyroid of old males may be assumed. Many trace elements in human thyroid behave themselves as antagonists or synergists. Therefore, an age-related disturbance in correlations between Mn and other trace element mass fractions in thyroid parenchyma may also contribute to harmful effects on the gland. Age-related changes in intra-thyroidal trace element contents and disturbances in trace element relationships are involved in goitre- and carcinogenesis.

Bromate Inhibition during Ozonation of Bromide-Containing Water by the Presence of Mn Incorporated MCM-41

The mesoporous Mn incorporated MCM-41 was employed to inhibit bromate formation during catalytic ozonation of bromide-containing water, Mn-MCM-41 was synthesized via hydrothermal method and the influences of temperature ramping rate (0.5, 1 and 2 K min-1) during calcination were investigated. It was characterized by XRD, TEM, SEM, XPS and H2-TPR, indicating that temperature ramping rate could affect the valence states of active Mn species, the dispersion of Mn on the surface of catalyst and the formation of oxygen vacancies, which could increase surface hydroxyl groups on Mn-MCM-41 and accelerated ozone decomposition to generate oxygen species. Compared with 0.5 K min-1 and 2 K min-1, Mn-MCM-41 with 1 K min-1 showed much better performance in bromate inhibition process, Mn100-MCM-41 (molar ratio of Si/Mn=100) achieved 96.7% inhibition efficiency at pH 6.5, which was attributed to higher fraction of Mn(II)/Mn(III) and oxygen vacancies. The influence of pH, TBA and intermediate HOBr/OBr- were explored to investigate the mechanism. The results showed that more H2O2 generation and decreased O3 exposure to Br- in Mn-MCM-41 catalytic ozonation process, the oxidative transformation from Br- to HOBr/OBr- was blocked, resulting to less bromate formation. Highlights: • Temperature ramping rate during calcination of Mn-MCM-41 was crucial. • Oxygen vacancy and variation Mn state are responsible for catalytic performance. • Mn-MCM-41 achieved high bromate inhibition efficiency (96.7%) at pH 6.5. • Mn-MCM-41 inhibited BrO3 - by reducing HOBr/OBr-.

Environmental risk assessment of cobalt and manganese from industrial sources in an estuarine system.

A total of 74 samples of soil, sediment, industrial sludge, and surface water were collected in a Mediterranean estuarine system in order to assess the potential ecological impact of elevated concentrations of Co and Mn associated with a Terephthalic (PTA) and Isophthalic (PIPA) acids production plant. Samples were analyzed for elemental composition (37 elements), pH, redox potential, organic carbon, and CaCO3 content, and a group of 16 selected samples were additionally subjected to a Tessier sequential extraction. Co and Mn soil concentrations were significantly higher inside the industrial facility and around its perimeter than in background samples, and maximum dissolved Co and Mn concentrations were found in a creek near the plant's discharge point, reaching values 17,700 and 156 times higher than their respective background concentrations. The ecological risk was evaluated as a function of Co and Mn fractionation and bioavailability which were controlled by the environmental conditions generated by the advance of seawater into the estuarine system during high tide. Co appeared to precipitate near the river mouth due to the pH increase produced by the influence of seawater intrusion, reaching hazardous concentrations in sediments. In terms of their bioavailability and the corresponding risk assessment code, both Co and Mn present sediment concentrations that result in medium to high ecological risk whereas water concentrations of both elements reach values that more than double their corresponding Secondary Acute Values.