Chitosan based macromolecular probes for the selective detection and removal of Fe3+ ion

Chitosan has been widely used due to its biodegradable, cost-effective and environmentally friendly properties. Modification of chitosan attracts much attention as promising methods to detect and remove organic and inorganic pollutants. In this work, chitosan-based macromolecular probes were designed and synthesized. The probes can detect Fe³⁺ in the presence of other metal ions. The detection mechanism is investigated as well. The probe's fluorescence quenching upon the addition of Fe³⁺ ion could be ascribed to the complexation between the electron-deficient ion Fe³⁺ and "C=N" (electron-rich group) of fluorescent chitosan probes. What's more, the obtained fluorescent macromolecular probes can be used for the removal of Fe³⁺ in solution. The probes could adsorb the Fe³⁺ in solution and the removal efficiency can reach as high as 62.0% while the removal efficiency of original chitosan is only 16.0%. The probes have good selective detection for Fe³⁺ and the detection limit reaches 1.2 μM.

Iron can be microbially extracted from Lunar and Martian regolith simulants and 3D printed into tough structural materials

In-situ resource utilization (ISRU) is increasingly acknowledged as an essential requirement for the construction of sustainable extra-terrestrial colonies. Even with decreasing launch costs, the ultimate goal of establishing colonies must be the usage of resources found at the destination of interest. Typical approaches towards ISRU are often constrained by the mass and energy requirements of transporting processing machineries, such as rovers and massive reactors, and the vast amount of consumables needed. Application of self-reproducing bacteria for the extraction of resources is a promising approach to reduce these pitfalls. In this work, the bacterium Shewanella oneidensis was used to reduce three different types of Lunar and Martian regolith simulants, allowing for the magnetic extraction of iron-rich materials. The combination of bacterial treatment and magnetic extraction resulted in a 5.8-times higher quantity of iron and 43.6% higher iron concentration compared to solely magnetic extraction. The materials were 3D printed into cylinders and the mechanical properties were tested, resulting in a 400% improvement in compressive strength in the bacterially treated samples. This work demonstrates a proof of concept for the on-demand production of construction and replacement parts in space exploration.

Removing Iron and Organic Substances from Water over the Course of Its Treatment with the Application of Average and Highly Alkaline Polyaluminium Chlorides

In topic-related literature pertaining to the treatment of water, there is a lack of information on the influence of iron ions in highly basic polyaluminum chlorides on the efficiency of purifying water with increased contents of organic substance. The aim of this work was to determine the changes in the content of organic substances as well as iron compounds in water intended for human consumption following unit treatment processes with particular attention paid to the coagulation process. As coagulants, polyaluminium chloride PAXXL10 with an alkalinity of 70%, as well as polyaluminium chloride PAXXL1911 with an alkalinity of 85% the composition of which also contained iron, were tested. The analysis of the obtained results showed that iron compounds and organic substances were removed to the greatest extent by the coagulation process, which also had a significant influence on the final efficiency of water treatment. The effectiveness of water treatment was determined by the type of tested polyaluminum chloride, which influenced the formation of iron-organic complexes. The reason behind the formation of colored iron-organic complexes during coagulation using PAXXL1911 coagulant was the high pH (approx. 8), at which the functional groups of organic substances, due to their dissociation, are more reactive in relation to iron, and possibly the fact of introducing additional iron ions along with the coagulant.

Rhizobactin B is the preferred siderophore by a novel Pseudomonas isolate to obtain iron from dissolved organic matter in peatlands

Bacteria often release diverse iron-chelating compounds called siderophores to scavenge iron from the environment for many essential biological processes. In peatlands, where the biogeochemical cycle of iron and dissolved organic matter (DOM) are coupled, bacterial iron acquisition can be challenging even at high total iron concentrations. We found that the bacterium Pseudomonas sp. FEN, isolated from an Fe-rich peatland in the Northern Bavarian Fichtelgebirge (Germany), released an unprecedented siderophore for its genus. High-resolution mass spectrometry (HR-MS) using metal isotope-coded profiling (MICP), MS/MS experiments, and nuclear magnetic resonance spectroscopy (NMR) identified the amino polycarboxylic acid rhizobactin and a novel derivative at even higher amounts, which was named rhizobactin B. Interestingly, pyoverdine-like siderophores, typical for this genus, were not detected. With peat water extract (PWE), studies revealed that rhizobactin B could acquire Fe complexed by DOM, potentially through a TonB-dependent transporter, implying a higher Fe binding constant of rhizobactin B than DOM. The further uptake of Fe-rhizobactin B by Pseudomonas sp. FEN suggested its role as a siderophore. Rhizobactin B can complex several other metals, including Al, Cu, Mo, and Zn. The study demonstrates that the utilization of rhizobactin B can increase the Fe availability for Pseudomonas sp. FEN through ligand exchange with Fe-DOM, which has implications for the biogeochemical cycling of Fe in this peatland.

Simultaneous denitrification, phosphorus recovery and low sulfate production in a recirculated pyrite-packed biofilter (RPPB)

The simultaneous removal of nitrate (15 mg N-NO₃^- L^-1) and phosphate (12 mg P-PO₄^3- L^-1) from nutrient-polluted synthetic water was investigated in a recirculated pyrite-packed biofilter (RPPB) under hydraulic retention time (HRT) ranging from 2 to 11 h. HRT values ≥ 8 h resulted in nitrate and phosphate average removal efficiency (RE) higher than 90% and 70%, respectively. Decrease of HRT to 2 h significantly reduced the RE of both nitrogen and phosphorus. The RPPB showed high resiliency as reactor performance recovered immediately after HRT increase to 5 h. Solid-phase characterization of pyrite granules and backwashing material collected from the RPPB at the end of the study revealed that iron-phosphate, -hydroxide and -sulfate precipitated in the bioreactor. Thermodynamic modeling predicted the formation of S⁰ during the study. Residence time distribution tests showed semi-complete mixing hydrodynamic flow conditions in the RPPB. The RPPB can be considered an elegant and low-cost technology coupling biological nitrogen removal to the recovery of phosphorus, iron and sulfur via chemical precipitation.

Characterization of Fe(III) Adsorption onto Zeolite and Bentonite

In this study, the adsorption of Fe(III) from aqueous solution on zeolite and bentonite was investigated by combining batch adsorption technique, Atomic adsorption spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses. Although iron is commonly found in water and is an essential bioelement, many industrial processes require efficient removal of iron from water. Two types of zeolite and two types of bentonite were used. The results showed that the maximum adsorption capacities for removal of Fe (III) by Zeolite Micro 20, Zeolite Micro 50, blue bentonite, and brown bentonite were 10.19, 9.73, 11.64, and 16.65 mg.g⁻¹, respectively. Based on the X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) analyses of the raw samples and the solid residues after sorption at low and high initial Fe concentrations, the Fe content is different in the surface layer and in the bulk of the material. In the case of lower initial Fe concentration (200 mg.dm⁻³), more than 95% of Fe is adsorbed in the surface layer. In the case of higher initial Fe concentration (4000 mg.dm⁻³), only about 45% and 61% of Fe is adsorbent in the surface layer of zeolite and bentonite, respectively; the rest is adsorbed in deeper layers.

A Comparative Study on Cu2+, Zn2+, Ni2+, Fe3+, and Cr3+ Metal Ions Removal from Industrial Wastewaters by Chitosan-Based Composite Cryogels

Materials coming from renewable resources have drawn recently an increased attention in various applications as an eco-friendly alternative in the synthesis of novel functional materials. Polysaccharides, with their prominent representative - chitosan (CS), are well-known for their sorption properties, being able to remove metal ions from dilute solutions either by electrostatic interactions or chelation. In this context, we proposed here a comparative study on Cu2+, Zn2+, Ni2+, Fe3+, and Cr3+ metal ions removal from industrial wastewaters by CS-based composite cryogels using batch technique. The composite cryogels consisting of CS embedding a natural zeolite, namely clinoptilolite, were synthesized by cryogelation, and their sorption performance were compared to those of CS cryogels and of acid-activated zeolite. A deeper analysis of thermodynamics and kinetics sorption data was performed to get insights into the sorption mechanism of all metal ions onto sorbents. Based on the optimized sorption conditions, the removal of the above-mentioned ions from aqueous solutions by the composite sorbent using dynamic technique was also evaluated.

Long-term leaching characteristic study of coal processing waste streams

A study of the mobility of major and potentially hazardous trace elements from coal processing waste materials was conducted using two types of leaching tests. The baseline leaching test simulates stable waste storage under water, whereas the kinetic test models the storage of waste under more variable conditions including intermittent exposure to air and variations in humidity. Coarse and fine refuse materials were obtained from three commercial coal preparation plants that were being used to upgrade US bituminous run-of-mine coal containing low-to-high amounts of pyritic sulfur. X-ray diffraction analyses revealed a large variation in mineralogy between the coarse and fine refuse streams due to the mineral fractionation that occurs in the processing units and plant. The coarse refuse samples contained higher pyrite contents while the fine refuse samples had high clay content and a minor amount of calcite. This variation in mineralogy resulted in relatively large difference in the leaching characteristics of the waste streams. The most acidic pH and highest release of trace elements were observed in the leachate of coarse refuse containing medium-to-high amounts of coal pyrite, while the fine refuse samples released lower amounts of trace elements in their circumneutral leachate. The least amount of trace elements was observed in the leachate of low pyritic refuse streams. The test data suggested that the most effective disposal practice for coal waste material is segregation and isolation of the coal pyrite and co-disposal of the coarse and fine refuse streams.

Osmium isotope analysis as an innovative tool for provenancing ancient iron: A systematic approach

The innovation of iron production is often considered one of the greatest technological advances in human history. A reliable provenancing method for iron is instrumental for the reconstruction of economic, social and geo-political aspects of iron production and use in antiquity. Although the potential of osmium isotopes analysis for this purpose has been previously suggested, here we present for the first time the results of osmium isotope analysis of ores, bloom and metal obtained from a set of systematic, bloomery iron-smelting experiments, utilizing selected ores from the Southern Levant. The results show that the ¹⁸⁷Os/¹⁸⁸Os ratio is preserved from ore to metal, with no isotopic fractionation. In addition, enrichment/depletion of osmium content was observed in the transition from ore to metal and from ore to slag. This observation has potential significance for our ability to differentiate between the various processes and sheds light on the suitability of various production remains for this method, which emerges as a robust and promising tool for the provenancing of archaeological ferrous metals.

Effect of microbial nutrients supply on coal bio-desulfurization

Research on coal desulfurization is very important for economic, social, and environmentally sustainable development. In this study, three batches of shake flask experiments were conducted for coal bio-desulfurization using Acidithiobacillus ferrooxidans to explore the relationship between microbial nutrients (iron-free M9 K medium) supply and coal bio-desulfurization efficiency. The results showed that the removal rates of pyritic sulfur and total sulfur from coal effectively increased following reintroduction of coal into the filtrate from previous batch. The removal rates of pyritic sulfur and total sulfur were 55.6% and 10.0%, 77.1% and 16.1%, and 86.5% and 28.2%, respectively, in the three batch experiments without iron-free M9 K medium addition. In contrast, the removal rates of pyritic sulfur and total sulfur reached 87.5% and 28.2%, 89.1% and 31.6%, and 92.0% and 29.1%, respectively, in the three batch experiments with 6.7% iron-free M9 K medium addition. However, addition of excessive iron-free M9 K medium was detrimental to coal bio-desulfurization because of the synthesis of jarosite (MFe₃(SO₄)₂(OH)₆, M = K⁺, NH₄⁺) and gypsum (CaSO₄·2H₂O), which further declined the pyritic sulfur bio-oxidation efficiency and total sulfur removal efficiency.

Pesticide-derived bright chlorine-doped carbon dots for selective determination and intracellular imaging of Fe(III)

Inspired by the conversion from organics or biomass to fluorescent carbon dots (C-dots), the use of pesticide 4-chlorophenol (4-CP) as a precursor to prepare C-dots has been reported. The as-prepared chlorine-doped C-dots display a brightly blue emission at ∼445 nm with ∼22.8% quantum yield. Also, the surface of C-dots enriches functional groups, such as phenolic hydroxyl and carboxylic acid, etc., which can capture ferric ion (Fe(III)), resulting in the quenching of blue fluorescence of C-dots through an inner filter effect. The quantitative assay for Fe(III) was therefore realized by this probe with a 0.36 μM detection limit in the 0.6-25 μM concentration range. Most significantly, the cytotoxicity on Hela cells indicates the 4-CP-derived C-dots have a negligible cytotoxicity. The C-dots were applied in detection in environmental samples and imaging in Hela cells of Fe(III), demonstrating their good applicability, low toxicity and good biocompatibility, and providing an alterative approach to totally eliminate the harm of chlorophenols (CPs).

Adsorption of indium by waste biomass of brown alga Ascophyllum nodosum

The biosorption capacities of dried meal and a waste product from the processing for biostimulant extract of Ascophyllum nodosum were evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents: waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, and natural-biomass which was harvested, dried and milled as a commercial, "kelp meal" product. Two systems have been evaluated: ideal system with indium only, and double metal-system with indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In the ideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed, waste biomass and 63 mg/g for the natural biomass), than in the double metal-system where the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in the A. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.

Long-term operation and autotrophic nitrogen conversion process analysis in a biofilter that simultaneously removes Fe, Mn and ammonia from low-temperature groundwater

One lab-scale biofilter that simultaneously removes Fe, Mn and ammonia from 4 °C groundwater was established to investigate the nitrogen conversion process. The results showed that 333 days were needed to achieve the required standards for Fe, Mn and ammonia under a filtration rate of 3 m/h. Effluent nitrite concentration was the key factor determining the final operation parameters. Both nitrification and anaerobic ammonium oxidation (ANAMMOX) contributed to nitrogen conversion. The calculation results demonstrated that autotrophic nitrogen removal proportion was about 15.92% in steady operation period. Meanwhile, 7 genera of Mn oxidizing bacteria (MnOB) were detected; Candidatus Brocadia was the only detected ANAMMOX genera. The corresponding functional oxidizing bacteria could be acclimated sufficiently in biofilter treating low-temperature groundwater.

Fluorescent probes for the detection of catalytic Fe(II) ion

Iron (Fe) is the most abundant redox-active metal ion in the human body, and its redox-active inter-convertible multiple oxidation states contributes to numerous essential biological processes. Moreover, iron overload can potentially cause cellular damage and death, as wel as numerous diseases through the aberrant production of highly reactive oxidative species (hROS). Protein-free or weakly-protein-bound Fe ions play a pivotal role as catalytic reactants of the Fenton reaction. In this reaction, hROS, such as hydroxyl radicals and high valent-iron-oxo species, are generated by a reaction between hydrogen peroxide and Fe(II), which is re-generated through reduction using abundant intracellular reductants, such as glutathione. This results in the catalytic evolution of hROS. Thus, selective detection of the catalytic Fe(II) in the living systems can explain both of the pathological and physiological functions of Fe(II). Written from the perspective of their modes of actions, this paper presents recent advances in the development of fluorescent and bioluminescent probes that can selectively detect catalytic Fe(II) together with their biological applications.

[Mechanism of Removing Iron and Manganese from Drinking Water Using Manganese Ore Sand and Quartz Sand as Filtering Material]

Two lab-scale biofilters packed with manganese ore sand and quartz sand were constructed to reveal the behavior in removing iron and manganese during the start-up period. Meanwhile, the removal mechanism of the two sands was also investigated by means of EDS, XPS, and SEM. With the influent iron (2-3 mg·L^-1) and manganese (0.3-0.6 mg·L^-1), the start-up operational results indicated that the quartz sand biofilter needed 15 and 30 d to achieve the removal of iron and manganese, respectively. The manganese ore sand only required 10 d to remove iron, while the effluent manganese was always below of 0.1 mg·L^-1. The results confirmed that the natural iron and manganese oxides coated on the manganese ore sand surface could explain its better removal behavior as compared to quartz sand. However, the generated iron oxide could also act as the adsorbent and catalyst like natural iron oxide, only when iron removal occurred in the quartz sand biofilter. The final product of iron removal was a complex consisting of divalent and trivalent iron, with a specific value of 1:1.44-1:1.54. Moreover, during the start-up period, manganese ore sand transformed manganese from divalent to trivalent by the catalytic effect, while the latter tended to be converted to the quadrivalent state under the bioactivity. The quartz sand could adsorb manganese but easily became saturated, and then the removal was dominated by bioactivity. The product generated by the manganese removal process was also a complex with the three valences. Moreover, the two complexes could coat onto the surface of the sands, but most of the iron complex was easily washed out of the filtering layer. Conversely, the manganese complex tended to coat onto the manganese ore sand surface or accumulate between the pores of quartz sand.

Manganese and iron recovery from groundwater treatment sludge by reductive acid leaching and hydroxide precipitation

In this study, the recovery of manganese (Mn) and iron (Fe) from groundwater treatment sludge through reductive acid leaching and hydroxide precipitation was investigated. Maximum leached Mn (100%) was obtained using sulfuric acid and hydrogen peroxide at 25 °C. Leached Mn and Fe decreased with the increase in the solid-liquid ratio. Leaching time had minimal effect on Mn and Fe leaching beyond 5 min, while agitation rate had minimal effect beyond 150 rpm. At 25 °C, the rate-limiting step of Mn leaching was diffusion through inert solid components of the sludge, composed mainly of insoluble sand particles. Fe leaching was governed by diffusion through the insoluble components of the sludge, including the unreacted manganese dioxide (MnO₂). Maximum precipitation of Fe and separation from Mn in the leachate through addition of potassium hydroxide occurred at pH 4.0. The results demonstrated that reductive acid leaching and hydroxide precipitation is an effective means of recovering Mn and Fe from groundwater treatment sludge. The applicability of the recovered Mn for nickel ion removal from aqueous solution was also explored in the study. Highest nickel ion uptake by the MnO₂ synthesized from the recovered Mn was at 111.67 mg g^-1, even exceeding the adsorption capacities of previously studied nickel adsorbents.

House hold unit for the treatment of fluoride, iron, arsenic and microorganism contaminated drinking water

A first of its kind hybrid electrocoagulation-filtration prototype unit was fabricated for the removal of fluoride, iron, arsenic and microorganisms contaminated drinking water. The unit comprised of 3 chambers, chamber A consisting of an inlet for the water to be treated and an outlet for the treated water along with one block of aluminum electrodes. Chamber B consisted of ceramic membrane filtration assembly at the bottom over a metallic support which filters the flocs so produced in chamber A and chamber C consisting of space to collect the treated water. Operating parameters were maintained as current density of 625 A m^-2 and an electrode distance of 0.005 m. Contaminated drinking water containing mixture of fluoride (10 mg L^-1), iron (25 mg L^-1), arsenic (200 μg L^-1) and microorganisms (35 CFU ml^-1) was used for the experiment. A removal of 98.74%, 95.65%, 93.2% and 100% were obtained for iron, arsenic, fluoride and microorganisms, respectively. The apparatus and method made it possible to efficiently treat contaminated drinking water to produce drinkable water as per WHO specification. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDX and XRD and explained.

Electrochemical removal and recovery of iron from groundwater using non-corrosive electrodes

Iron contamination in groundwater has attracted much attention from environmentalists and government agencies because it can cause many problems in human life and in industrial and agricultural activities when groundwater is directly used without any treatment. This study aims to investigate the electrochemical oxidation of Fe(II) to Fe(III) and recovery of insoluble Fe(III) using non-corrosive graphite electrode which serves as a controllable, low-cost, low maintenance and virtually unlimited electron acceptor for Fe(II) oxidation. The lab-scale results indicated that Fe(II) removal up to 100% was obtained at an applied voltage higher than 2 V. The Fe(II) removal efficiency was linearly increased with the increase of potential supply in the range of 1-4 V in the salinity 0.5%. The Fe(II) removal rate could no longer be enhanced at the applied potential higher than 8 V in the condition without salinity. The results from SEM-EDS and XRD revealed that Fe was recovered as FeOOH by conventional filtration with a recovery efficiency of 82.7-92.1%. The electrochemical Fe(II) removal might be an alternative for the conventional method of the in situ Fe removal from groundwater. Besides, the recovered FeOOH can be used as a raw material for environmental remediation and pigment industry.

[Start-up and Operation of Biofilter Coupled Nitrification and CANON for the Removal of Iron, Manganese and Ammonia Nitrogen]

A pilot-scale bio-filter coupled nitrification and CANON was started up to remove iron, manganese and ammonia nitrogen from groundwater in a plant, and the main removal route of ammonia nitrogen was analyzed. The experiment showed that the bio-filter could be started up successfully and achieved stable operation after 164 days of culture development. The value of △NH₄⁺-N/△NO₃^--N was 1.49, and the oxidation and removal of Fe(Ⅱ), Mn(Ⅱ), and NH₄⁺-N were (9.87±1.17), (2.25±0.06), and (1.51±0.06) mg·L^-1, respectively. The calculation based on the quantitative relationship between nitrogen conservation and dissolved oxygen (DO) measurement indicated that the contribution of CANON to NH₄⁺-N removal was 33.48%-38.87%, and the average ratio of ammonia nitrogen removal amount to DO was 1:3.79-1:3.94. The removal ratio of ammonia nitrogen was lower with lower temperature.

[Removal of High Concentration of Iron, Manganese and Ammonia Nitrogen from Low Temperature Groundwater Using Single Bio-filter]

A pilot-scale bio-filter was constructed for the removal of high concentrations of iron (TFe 9.0-12.0 mg·L^-1, Fe(Ⅱ) 6.5-8.0 mg·L^-1), manganese (1.9-2.1 mg·L^-1), and ammonia nitrogen (1.4-1.7 mg·L^-1) simultaneously from low temperature (5-6℃) groundwater in a plant. The results showed that iron was removed at the beginning of the bio-filter start-up, and manganese and ammonia nitrogen were removed on day 72 and day 75, respectively. The start-up period was influenced by the culture temperature and the raw water quality. For higher filtration rates, the removal of manganese was lower. When the filtration rate was more than 1.0 m·h^-1, the maximum removal of manganese was about 3.0 mg·L^-1. Manganese was the limiting factor for the increase of filtration rate, and the maximum filtration rate of the single bio-filter was 4.5 m·h^-1. When the filtration rate was less than 6.0 m·h^-1, the removal of ammonia nitrogen was about 1.5 mg·L^-1, which was not affected by the filtration rate. Dissolved oxygen (DO) deficiency led to failure with the removal of more ammonia nitrogen. The required thickness of the bio-filter required for purification increased as the concentration of manganese and ammonia nitrogen increased when DO was sufficient. The removed iron, manganese, and ammonia nitrogen move to the depth of the filter layer, and there will be "manganese dissolution" when the filtration rate is increased. Iron and ammonia nitrogen in the filter layer can be oxidized and removed simultaneously. Manganese is oxidized and removed after the iron and ammonia nitrogen. The effective oxidation and removal section of manganese, iron, and ammonia nitrogen are obviously graded.

Nigrosome 1 visibility at susceptibility weighted 7T MRI-A dependable diagnostic marker for Parkinson's disease or merely an inconsistent, age-dependent imaging finding?

Background

Visualisation of nigrosome 1, a substructure of the healthy substantia nigra, was restricted in susceptibility weighted MR imaging in almost all patients with Parkinson's disease studied so far. The purpose of this study was to determine the degree of visibility of this substructure in subjects without Parkinson’s disease and to examine the potential link between increasing brain iron accumulation with age and its detectability.

Methods

In 46 subjects (21 women, 25 men; 19 to 75 y; mean age: 44.5; SD: 15.6) examined with susceptibility weighted MR imaging at 7T visibility of nigrosome 1 was rated and classified. We assessed differences related to age and to signal intensities in the substantia nigra, red nucleus and putamen as correlates of the individual iron concentration.

Results

In 93% nigrosome 1was at least unilaterally clearly present. In 24% at least one-sided limited visibility was observed. Using predefined classification criteria the specificity of the visibility across all age groups reached approximately 94%. We found no correlation with increasing iron concentrations with age.

Conclusion

Aging with a related increase in iron concentration probably does not affect the visibility of nigrosome 1 at 7T SWI MRI. Our results support the role of this feature as a future differential diagnostic tool but further large-scale prospective studies are needed to better define the extent of a “limited visibility” to which an individual can be considered healthy.

Iron species determination by task-specific ionic liquid-based in situ solvent formation dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry

BACKGROUND

The task-specific ionic liquid (TSIL) of 1-ethyl-3-methylimidazolium bromide functionalized with 8-hydroxyquinoline was used as a chelating agent and extracting solvent for dispersive liquid-liquid microextraction and subsequent determination of Fe(III) by flame atomic absorption spectrometry. The in situ solvent formation of TSIL using KPF₆ provided the desired water-immiscible ionic liquid. The total Fe concentration could be determined after pre-oxidation of Fe(II) to Fe(III). Various factors affecting the proposed extraction procedure were optimized.

RESULTS

The proposed analytical conditions were: sample pH 5, TSIL amount 0.3% (w/v), KPF₆ amount 0.15% (w/v), anti-sticking 0.1% (w/v) and salt concentration 5% (w/v). Under optimal conditions, the linear dynamic ranges for Fe(III) and total Fe were 20-80 and 20-110 ng mL^-1 , respectively, with a detection limit of 6.9 ng mL^-1 for Fe(III) and relative standard deviation of 2.2%. The proposed method was successfully applied to the determination of trace Fe(III) in water (underground, tap, refined water and artificial sea water) and beverage (apple, tomato, and tea) samples.

CONCLUSION

The developed method offers advantages such as simplicity, ease of operation, and extraction of Fe(III) from aqueous solutions without the use of organic solvent. It was successfully applied for iron speciation in different real samples. © 2017 Society of Chemical Industry.

[Iron metabolism and neonatal hypoxic ischemic brain damage]

Iron is an essential element for nervous system development, and maintaining a normal iron level in nervous system is controlled by multiple factors. Recent studies reported that iron dysregulation and the following iron metabolic pathways played an important role in hypoxic ischemic brain damage (HIBD) in neonates. Circulatory iron level is altered after hypoxia-ischemia exposure, which may cause abnormal iron deposition in the nervous system followed by neuronal injury. Finding the causing factors for abnormal iron metabolism after hypoxia-ischemia exposure, as well as understanding the mechanisms how iron metabolism contributes to HIBD, will shed lights on HIBD prevention and treatment. In this mini-review, we summarized changes in iron metabolism after neonatal hypoxia-ischemia exposure, its possible regulatory factors and how iron abnormalities contribute to HIBD.

Iron removal, energy consumption and operating cost of electrocoagulation of drinking water using a new flow column reactor

The goal of this project was to remove iron from drinking water using a new electrocoagulation (EC) cell. In this research, a flow column has been employed in the designing of a new electrocoagulation reactor (FCER) to achieve the planned target. Where, the water being treated flows through the perforated disc electrodes, thereby effectively mixing and aerating the water being treated. As a result, the stirring and aerating devices that until now have been widely used in the electrocoagulation reactors are unnecessary. The obtained results indicated that FCER reduced the iron concentration from 20 to 0.3 mg/L within 20 min of electrolysis at initial pH of 6, inter-electrode distance (ID) of 5 mm, current density (CD) of 1.5 mA/cm², and minimum operating cost of 0.22 US $/m³. Additionally, it was found that FCER produces H₂ gas enough to generate energy of 10.14 kW/m³. Statistically, it was found that the relationship between iron removal and operating parameters could be modelled with R² of 0.86, and the influence of operating parameters on iron removal followed the order: C₀>t>CD>pH. Finally, the SEM (scanning electron microscopy) images showed a large number of irregularities on the surface of anode due to the generation of aluminium hydroxides.

Alterations of Hair and Nail Content of Selected Trace Elements in Nonoccupationally Exposed Patients with Chronic Depression from Different Geographical Regions

The aim of this study was to determine if altered levels of selected trace elements manifest themselves during chronic depression. To identify elements strongly associated with chronic depression, relationships between the elemental contents of hair and nails and the interelement correlations were checked. Inductively coupled plasma mass spectrometry and ion chromatography were used to evaluate the contents of Zn, Cu, Co, Pb, Mn, and Fe in hair and nail samples from a total of 415 subjects (295 patients and 120 healthy volunteers). The study included logistic regression models to predict the probability of chronic depression. To investigate possible intercorrelations among the studied elements, the scaled principal component analysis was used. The research has revealed differences in TE levels in the group of depressed men and women in comparison to the healthy subjects. Statistically significant differences in both hair and nails contents of several elements were observed. Our study also provides strong evidence that the intermediary metabolism of certain elements is age- and gender-dependent. Zn, Mn, Pb, and Fe contents in hair/nails seem to be strongly associated with chronic depression. We found no statistically significant residence-related differences in the contents of studied elements in nonoccupationally exposed patients and healthy subjects.

A novel recovery method of copper from waste printed circuit boards by supercritical methanol process: Preparation of ultrafine copper materials

In this study, supercritical methanol (SCM) process was successfully used for the preparation of ultrafine copper materials from waste printed circuit boards (PCBs) after nitric acid pretreatment. Waste PCBs were pretreated twice in nitric acid. Sn and Pb were recovered by the first nitric acid pretreatment. The leach liquor with a high concentration of copper ions after the second nitric acid leaching was subjected to SCM process. The mixture of Cu and Cu₂O with poor uniformity of particle size was formed due to the effect of ferric iron contained in the leach liquor of waste PCBs, while more uniform and spherical Cu particles with high monodispersity and smaller size could be prepared after the removal of Fe. The size of Cu particles increased obviously with the decline of SCM temperature, and particles became highly aggregated when the reaction temperature decreased to 300°C. The size of Cu particles decreased markedly with the decrease of initial concentration of copper ion in the leach liquor of waste PCBs. It is believed that the process developed in this study is simple and practical for the preparation of ultrafine copper materials from waste PCBs with the aim of recycling these waste resources as a high value-added product.

Closed circuit recovery of copper, lead and iron from electronic waste with citrate solutions

An integral closed circuit hydrometallurgical process is presented for base metal recovery from electronic waste. The leaching medium consists of a sodium citrate solution, from which base metals are retrieved by direct electrowinning, and the barren solution is recycled back to the leaching stage. This leaching-electrowinning cycle was repeated four times. The redox properties of the fresh citrate solution, as well as the leach liquors, were characterized by cyclic voltammetry to determine adequate conditions for metal reduction, as well as to limit citrate degradation. The leaching efficiency of electronic waste, employing the same solution after four complete cycles was 71, 83 and 94% for copper, iron and lead, respectively, compared to the original leach with fresh citrate solution.

Optimization of a cloud point extraction procedure with response surface methodology for the quantification of dissolved iron in produced water from the petroleum industry using FAAS

The characterization of inorganic elements in the produced water (PW) samples is a difficult task because of the complexity of the matrix. This work deals with a study of a methodology for dissolved Fe quantification in PW from oil industry by flame atomic absorption spectrometry (FAAS) after cloud point extraction (CPE). The procedure is based on the CPE using PAN as complexing agent and Triton X-114 as surfactant. The best conditions for Fe extraction parameters were studied using a Box-Behnken design. The proposed method presented a LOQ of 0.010μgmL^-1 and LOD of 0.003μgmL^-1. The precision of the method was evaluated in terms of repeatability, obtaining a coefficient of variation of 2.54%. The accuracy of the method was assessed by recovery experiments of Fe spiked that presented recovery of 103.28%. The method was applied with satisfactory performance to determine Fe by FAAS in PW samples.

Flow of essential elements in subcellular fractions during oxidative stress

Essential trace elements are commonly found in altered concentrations in the brains of patients with neurodegenerative diseases. Many studies in trace metal determination and quantification are conducted in tissue, cell culture or whole brain. In the present investigation, we determined by ICP-MS Fe, Cu, Zn, Ca, Se, Co, Cr, Mg, and Mn in organelles (mitochondria, nuclei) and whole motor neuron cell cultured in vitro. We performed experiments using two ways to access oxidative stress: cell treatments with H₂O₂ or Aβ-42 peptide in its oligomeric form. Both treatments caused accumulation of markers of oxidative stress, such as oxidized proteins and lipids, and alteration in DNA. Regarding trace elements, cells treated with H₂O₂ showed higher levels of Zn and lower levels of Ca in nuclei when compared to control cells with no oxidative treatments. On the other hand, cells treated with Aβ-42 peptide in its oligomeric form showed higher levels of Mg, Ca, Fe and Zn in nuclei when compared to control cells. These differences showed that metal flux in cell organelles during an intrinsic external oxidative condition (H₂O₂ treatment) are different from an intrinsic external neurodegenerative treatment.

Immobilization of iron- and manganese-oxidizing bacteria with a biofilm-forming bacterium for the effective removal of iron and manganese from groundwater

In this study, three bacteria with high Fe- and Mn-oxidizing capabilities were isolated from groundwater well sludge and identified as Acinetobacter sp., Bacillus megaterium and Sphingobacterium sp. The maximum removal ratios of Fe and Mn (99.75% and 96.69%) were obtained by an optimal combination of the bacteria at a temperature of 20.15°C, pH 7.09 and an inoculum size of 2.08%. Four lab-scale biofilters were tested in parallel for the removal of iron and manganese ions from groundwater. The results indicated that the Fe/Mn removal ratios of biofilter R4, which was inoculated with iron- and manganese-oxidizing bacteria and a biofilm-forming bacterium, were approximately 95% for each metal during continuous operation and were better than the other biofilters. This study demonstrated that the biofilm-forming bacterium could promote the immobilization of the iron- and manganese-oxidizing bacteria on the biofilters and enhance the removal efficiency of iron and manganese ions from groundwater.

The shift of microbial communities and their roles in sulfur and iron cycling in a copper ore bioleaching system

Bioleaching has been employed commercially to recover metals from low grade ores, but the production efficiency remains to be improved due to limited understanding of the system. This study examined the shift of microbial communities and S&Fe cycling in three subsystems within a copper ore bioleaching system: leaching heap (LH), leaching solution (LS) and sediment under LS. Results showed that both LH and LS had higher relative abundance of S and Fe oxidizing bacteria, while S and Fe reducing bacteria were more abundant in the Sediment. GeoChip analysis showed a stronger functional potential for S0 oxidation in LH microbial communities. These findings were consistent with measured oxidation activities to S0 and Fe2+, which were highest by microbial communities from LH, lower by those from LS and lowest form Sediment. Moreover, phylogenetic molecular ecological network analysis indicated that these differences might be related to interactions among microbial taxa. Last but not the least, a conceptual model was proposed, linking the S&Fe cycling with responsible microbial populations in the bioleaching systems. Collectively, this study revealed the microbial community and functional structures in all three subsystems of the copper ore, and advanced a holistic understanding of the whole bioleaching system.

Sulfidization of Organic Freshwater Flocs from a Minerotrophic Peatland: Speciation Changes of Iron, Sulfur, and Arsenic

Iron-rich organic flocs are frequently observed in surface waters of wetlands and show a high affinity for trace metal(loid)s. Under low-flow stream conditions, flocs may settle, become buried, and eventually be subjected to reducing conditions facilitating trace metal(loid) release. In this study, we reacted freshwater flocs (704-1280 mg As/kg) from a minerotrophic peatland (Gola di Lago, Switzerland) with sulfide (5.2 mM, S(-II)spike/Fe = 0.75-1.62 mol/mol) at neutral pH and studied the speciation changes of Fe, S, and As at 25 ± 1 °C over 1 week through a combination of synchrotron X-ray techniques and wet-chemical analyses. Sulfidization of floc ferrihydrite and nanocrystalline lepidocrocite caused the rapid formation of mackinawite (52-81% of Fesolid at day 7) as well as solid-phase associated S(0) and polysulfides. Ferrihydrite was preferentially reduced over lepidocrocite, although neoformation of lepidocrocite from ferrihydrite could not be excluded. Sulfide-reacted flocs contained primarily arsenate (47-72%) which preferentially adsorbed to Fe(III)-(oxyhydr)oxides, despite abundant mackinawite precipitation. At higher S(-II)spike/Fe molar ratios (≥1.0), the formation of an orpiment-like phase accounted for up to 35% of solid-phase As. Despite Fe and As sulfide precipitation and the presence of residual Fe(III)-(oxyhydr)oxides, mobilization of As was recorded in all samples (Asaq = 0.45-7.0 μM at 7 days). Aqueous As speciation analyses documented the formation of thioarsenates contributing up to 33% of Asaq. Our findings show that freshwater flocs from the Gola di Lago peatland may become a source of As under sulfate-reducing conditions and emphasize the pivotal role Fe-rich organic freshwater flocs play in trace metal(loid) cycling in S-rich wetlands characterized by oscillating redox conditions.

Comparative studies on adsorptive removal of heavy metal ions by biosorbent, bio-char and activated carbon obtained from low cost agro-residue

In this study, Fe(III) and Cr(III) metal ion adsorption processes were carried out with three adsorbents in batch experiments and their adsorption performance was compared. These adsorbents were sesame stalk without pretreatment, bio-char derived from thermal decomposition of biomass, and activated carbon which was obtained from chemical activation of biomass. Scanning electron microscopy and Fourier transform-infrared techniques were used for characterization of adsorbents. The optimum conditions for the adsorption process were obtained by observing the influences of solution pH, adsorbent dosage, initial solution concentration, contact time and temperature. The optimum adsorption efficiencies were determined at pH 2.8 and pH 4.0 for Fe(III) and Cr(III) metal ion solutions, respectively. The experimental data were modelled by different isotherm models and the equilibriums were well described by the Langmuir adsorption isotherm model. The pseudo-first-order, pseudo-second-order kinetic, intra-particle diffusion and Elovich models were applied to analyze the kinetic data and to evaluate rate constants. The pseudo-second-order kinetic model gave a better fit than the others. The thermodynamic parameters, such as Gibbs free energy change ΔG°, standard enthalpy change ΔH° and standard entropy change ΔS° were evaluated. The thermodynamic study showed the adsorption was a spontaneous endothermic process.

Iron-mineral accretion from acid mine drainage and its application in passive treatment

This study demonstrates substantial removal of iron (Fe) from acid mine drainage (pH ≈3) in a passive vertical flow reactor (VFR) with an equivalent footprint of 154 m(2) per L/s mine water and residence times of >23 h. Average Fe removal rate was 67% with a high of 85% over the 10-month trial. The fraction of Fe passing a 0.22 µm filter (referred to here as Fe-filt) was seen to be removed in the VFR even when Fe(II) was absent, indicating that the contribution of microbial Fe(II) oxidation and precipitation was not the dominant removal mechanism in the VFR. Removal rates of Fe-filt in the VFR were up to 70% in residence times as low as 8 h compared with laboratory experiments where much smaller changes in Fe-filt were observed over 60 h. Centrifugation indicated that 80-90% of the influent Fe had particle sizes <35 nm. Together with analyses and geochemical modelling, this suggests that the Fe-filt fraction exists as either truly aqueous (but oversaturated) Fe(III) or nanoparticulate Fe(III) and that this metastability persists. When the water was contacted with VFR sludge, the Fe-filt fraction was destabilized, leading to an appreciably higher removal of this fraction. Heterogeneous precipitation and/or aggregation of nanoparticulate Fe(III) precipitates are considered predominant removal mechanisms. Microbial analyses of the mine water revealed the abundance of extracellular polymeric substance-generating Fe-oxidizing bacterium 'Ferrovum myxofaciens', which may aid the removal of iron and explain the unusual appearance and physical properties of the sludge.

Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam

Household sand filters are used in rural areas of Vietnam to remove As, Fe, and Mn from groundwater for drinking water purposes. Currently, it is unknown what role microbial processes play in mineral oxide formation and As removal during water filtration. We performed most probable number counts to quantify the abundance of physiological groups of microorganisms capable of catalyzing Fe- and Mn-redox transformation processes in a household sand filter. We found up to 10(4) cells g(-1) dry sand of nitrate-reducing Fe(II)-oxidizing bacteria and Fe(III)-reducing bacteria, and no microaerophilic Fe(II)-oxidizing bacteria, but up to 10(6) cells g(-1) dry sand Mn-oxidizing bacteria. 16S rRNA gene amplicon sequencing confirmed MPN counts insofar as only low abundances of known taxa capable of performing Fe- and Mn-redox transformations were detected. Instead the microbial community on the sand filter was dominated by nitrifying microorganisms, e.g. Nitrospira, Nitrosomonadales, and an archaeal OTU affiliated to Candidatus Nitrososphaera. Quantitative PCR for Nitrospira and ammonia monooxygenase genes agreed with DNA sequencing results underlining the numerical importance of nitrifiers in the sand filter. Based on our analysis of the microbial community composition and previous studies on the solid phase chemistry of sand filters we conclude that abiotic Fe(II) oxidation processes prevail over biotic Fe(II) oxidation on the filter. Yet, Mn-oxidizing bacteria play an important role for Mn(II) oxidation and Mn(III/IV) oxide precipitation in a distinct layer of the sand filter. The formation of Mn(III/IV) oxides contributes to abiotic As(III) oxidation and immobilization of As(V) by sorption to Fe(III) (oxyhydr)oxides.

Tracking the Flow of Resources in Electronic Waste - The Case of End-of-Life Computer Hard Disk Drives

Recovery of resources, in particular, metals, from waste flows is widely seen as a prioritized option to reduce their potential supply constraints in the future. The current waste electrical and electronic equipment (WEEE) treatment system is more focused on bulk metals, where the recycling rate of specialty metals, such as rare earths, is negligible compared to their increasing use in modern products, such as electronics. This study investigates the challenges in recovering these resources in the existing WEEE treatment system. It is illustrated by following the material flows of resources in a conventional WEEE treatment plant in Denmark. Computer hard disk drives (HDDs) containing neodymium-iron-boron (NdFeB) magnets were selected as the case product for this experiment. The resulting output fractions were tracked until their final treatment in order to estimate the recovery potential of rare earth elements (REEs) and other resources contained in HDDs. The results further show that out of the 244 kg of HDDs treated, 212 kg comprising mainly of aluminum and steel can be finally recovered from the metallurgic process. The results further demonstrate the complete loss of REEs in the existing shredding-based WEEE treatment processes. Dismantling and separate processing of NdFeB magnets from their end-use products can be a more preferred option over shredding. However, it remains a technological and logistic challenge for the existing system.

Efficacy of the low-dose Saccharum iron treatment of idiopathic restless legs syndrome

AIM

The aim of the study was to determine the efficacy of low-dose and high-dose Saccharum iron injected intravenously in patients with idiopathic restless legs syndrome (RLS) by detecting levels of serum ferritin (SF) and international RLS Severity Scale.

METHODS

For this purpose, 38 patients with idiopathic RLS were randomly divided into the following two groups: low-dose group (18 cases) and high-dose group (20 cases). Low-dose group received Saccharum iron intravenously (200 mg/dose); once a week for 5 weeks with a total dose of 1000 mg. High-dose group received Saccharum iron intravenously (500 mg/dose); once every two weeks for 4 weeks with a total dose of 1000 mg. The pre- and post-treatment (at 2, 4, and 6 weeks) level of SF and RLS scores were determined and the differences were compared between two groups.

RESULTS

Post-therapeutic SF levels increased significantly in both groups as compared with before treatment (P<0.05). At 6-week post-therapy, SF levels in low-dose group were significantly higher than those in high-dose group (P<0.05). The clinical symptoms were improved and RLS scores were lower than pretreatment ratings in both groups (P<0.05). After 6 weeks of treatment, RLS scores of low-dose group were lower than those of high-dose group (P<0.05).

CONCLUSION

Both the low-dose and high-dose Saccharum iron treatments increased the SF levels and improved clinical symptoms in patients with idiopathic RLS; however, the low-dose iron treatment was found to be more effective and had fewer side effects.

Synergy in Extraction System Chemistry: Combining Configurational Entropy, Film Bending, and Perturbation of Complexation

Iron-uranium selectivity in liquid-liquid extraction depends not only on the mole fraction of extractants, but also on the nature of the diluent used, even if the diluent has no complexation interaction with the extracted ions. Modeling strong nonlinearity is difficult to parametrize without a large number of parameters, interpreted as "apparent constants". We determine in this paper the synergy curve versus mole fraction of HDEHP-TOPO (di(2-ethylexyl) phosphoric acid/tri-n-octyl phosphine oxide) and compare the free energy of aggregation to the free energy of extraction in various diluents. There is always a concomitant maximum of the two quantities, but with a gradual influence on intensity. The diluent is wetting the chains of the reverse aggregates responsible of the extraction. We show here that the intensity of the unexplained synergy peak is strongly dependent on the "penetrating" or "nonpenetrating" nature of the diluent. This experimental determination allows us to attribute the synergy to a combination of entropic effects favoring extraction, opposed to perturbation of the first coordination sphere by penetration as well as surfactant film bending energy.

Regeneration of magnetic biochar derived from eucalyptus leaf residue for lead(II) removal

Regeneration of Pb-loaded magnetic biochar prepared with eucalypts leaf residue was studied by using EDTA-2Na as a regenerant. The desorption efficiency was found to be 84.1% in 120 min with iron leaching amount of 1.1 mg g(-1). Higher SBET and pore volume were observed in regenerated magnetic biochars and no significant band shifts occurred in FTIR spectra during 6 regeneration cycles. The decrease of Pb(II) adsorption capacity (from 52.4 to 41.5 mg g(-1)) was only found in the first regeneration cycle. Magnetic separation performance of adsorbents was not significantly affected by multiple regeneration cycles.

Effectiveness of Man-Made Wetland Systems in Filtering Contaminants from Urban Runoff in Milledgeville, Georgia

A wetland system made up of linked basins was investigated to determine its role in local flood control and contaminant filtration. The study focused on a wetland basin that is dominated by the Celtis laevigata plant and is underlain by clay, with a small sandy layer approximately 1 m below surface. Field and laboratory data were collected to understand the transport and filtration of phosphate, iron, and nitrate. Field results showed the wetland to effectively reduce iron and phosphates from runoff via groundwater flow. These results also showed an increase in the phosphate concentration of surface water while within the basin, resulting from agitation of wetland sediments. Laboratory column experiments showed more than 90% reduction in phosphorus and iron while nitrate concentrations increased above the input concentration. Phosphate and iron were high in wetland water immediately after a rain event. Nitrate concentrations increased as the water filtered through the sediments due to desorption of previously adsorbed nitrates. This wetland could potentially act as a temporal hot spot and rain events as hot moments for these substances. Therefore, the best flood control measure for this site would be to increase residence time in the wetland. This would help to better manage/control the concentration of phosphate, iron and nitrate pollution in surface waters.

[Composition Analysis of Remaining Metal Particles on Ferrochrome Kitchen Knife]

OBJECTIVE

To establish a feasible evaluation index and method to identify composition of remaining metal particles on ferrochrome kitchen knife.

METHODS

The small samples of remaining metal particles were rubbed from the knives using filter paper. The composition of remaining metal particles was detected by scanning electron microscopy and energy dispersive X-ray spectrometer (SEM-EDX) and GSR particle analysis function, using mathematical methods to calculate the ratio (relative amount) of Fe and Cr in remaining metal particles.

RESULTS

The ratio (relative amount) of Fe and Cr of remaining metal particles had significant differences among most ferrochrome kitchen knives (P < 0.05).

CONCLUSION

Using GSR particle analysis function to quantitatively detect the ratio (relative amount) of Fe and Cr of remaining metal particles on ferrochrome kitchen knife, which can establish the feasible evaluation method to estimate such injury tool.

Selective recovery of dissolved Fe, Al, Cu, and Zn in acid mine drainage based on modeling to predict precipitation pH

Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na2CO3 were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na2CO3 as neutralizing agents.

Pilot test of pollution control and metal resource recovery for acid mine drainage

The study was undertaken in order to recover the metal resources from acid mine drainage (AMD). A 300 m(3)/d continuous system was designed and fractional precipitation technology employed for the main metals Fe, Cu, Zn, and Mn recovery. The system was operated for six months using actual AMD in situ. The chemicals' input and also the retention time was optimized. Furthermore, the material balance was investigated. With the system, the heavy metals of the effluent after the Mn neutralization precipitation were below the threshold value of the Chinese integrated wastewater discharge limit. The precipitates generated contained 42%, 12%, 31%, and 18% for Fe, Cu, Zn, and Mn, respectively, and the recovery rates of Fe, Cu, Zn, and Mn were 82%, 79%, 83%, and 83%, respectively. The yield range of the precipitate had significant correlation with the influent metal content. Using the X-ray diffraction analysis, the refinement for Fe, Cu, and Zn could be achieved through the processes of roasting and floatation. Cost-benefit was also discussed; the benefit from the recycled metal was able to pay for the cost of chemical reagents used. Most important of all, through the use of this technology, the frustrating sludge problems were solved.

Separation and removal of Cu2+, Fe2+, and Fe3+ from environmental waste samples by N-benzoyl-n-phenylhydroxylamine

This study was conducted to determine the optimum extraction conditions for the effective separation and removal of Cu2+, Fe2+, and Fe3+ using N-benzoyl-n-phenylhydroxylamine (BPA) as an analytical reagent. An efficient liquid-liquid extraction method was developed for the separation and removal of Cu2+, Fe2+, and Fe3+ from environmental waste samples. In this method, BPA was used as a chelating agent and the effect of different parameters- including solvents, pH, stripping agents, extraction time, and the interference of other ions- on the quantitative removal of these metals was investigated. This study demonstrates that chloroform is the most effective solvent for BPA. The maximum extraction of the selected metallic species was found between pH 3 and 5. It was demonstrated that the maximum percentage recovery of the metals can be attained using 1 M HCl as a stripping agent. Optimized conditions of different parameters could be beneficial for industry and environmental laboratories.

Iron and arsenic speciation and distribution in organic flocs from streambeds of an arsenic-enriched peatland

Iron-rich organic flocs are frequently observed in surface waters of wetlands and show a high affinity for trace metal(loid)s. To date, spectroscopic speciation analyses of Fe and trace elements in these mineral-organic matter (OM) associations are missing. In this study, we investigated the speciation and distribution of Fe and As in flocs collected from low-flow streams (pH 5.3-6.3) of the naturally As-enriched peatland Gola di Lago (Switzerland) using (57)Fe Mössbauer spectroscopy and synchrotron X-ray techniques. The flocs were rich in acid carbohydrates and contained up to 22.1 wt % Fe, 34.9 wt % C, and 2620 mg/kg As. Mössbauer analyses revealed small quantities (<5%) of Fe(II) and Fe(III)-OM complexes and the predominance of ferrihydrite (∼ Fe(5)HO(8) · 4H2O, 51-59%) and lepidocrocite (γ-FeOOH, 34-46%). The latter was not observed by synchrotron X-ray diffraction, implying a coherent scattering domain size of <10 nm. Iron X-ray absorption spectroscopy (XAS) confirmed the Mössbauer results, and bulk As XAS indicated the prevalence of arsenate (71-84%) in the flocs. Shell-fit analyses showed that As was entirely sorbed to Fe(III)-(oxyhydr)oxides and that both arsenate and arsenite exclusively formed monodentate-binuclear ("bridging") complexes (R(As-Fe) = 3.31-3.34 Å). Microfocused X-ray fluorescence spectrometry documented a strong correlation between As and Fe in the flocs. These analyses also revealed intense As hotspots coinciding with abundant freshwater green algae (Closterium spp.). Microfocused As X-ray absorption near-edge structure spectra collected at algae-specific points identified up to 29% As(III), which, in combination with ∼ 5% As(III) detected at Fe-rich points, suggests As(V) bioreduction in the algae. Our findings imply that floc (bio)organics serve primarily as nucleation sites for the precipitation of nanocrystalline Fe(III)-(oxyhydr)oxides, rendering flocs effective sorbents for trace metal(loid)s. Thus, Fe-rich freshwater flocs likely play a pivotal role for the speciation and cycling of trace elements in wetlands.

Remediation and selective recovery of metals from acidic mine waters using novel modular bioreactors

Mine waters are widely regarded as environmental pollutants, but are also potential sources of valuable metals. Water draining the Maurliden mine (Sweden) is highly acidic (pH 2.3) and rich in zinc (∼ 460 mg L(-1)) and iron (∼ 400 mg L(-1)), and contains smaller concentrations (0.3-49 mg L(-1)) of other transition metals and arsenic. We have developed novel techniques that promote the concurrent amelioration of acidic waste waters and selective recovery of metals, and have used these systems to treat synthetic Maurliden mine water in the laboratory. The two major metals present were removed via controlled biomineralization: zinc as ZnS in a sulfidogenic bioreactor, and iron as schwertmannite by microbial iron oxidation and precipitation of ferric iron. A small proportion (∼ 11%) of the schwertmannite produced was used to remove arsenic as the initial step in the process, and other chalcophilic metals (copper, cadmium and cobalt) were removed (as sulfides) in the stage 1 metal sulfide precipitation reactor. Results from this work have demonstrated that modular biomineralization units can be effective at processing complex mine waters and generating metal products that may be recycled. The economic and environmental benefits of using an integrated biological approach for treating metal-rich mine waters is discussed.

Reduction behavior of zinc ferrite in EAF-dust recycling with CO gas as a reducing agent

EAF-dust containing metal oxides can be regarded as an important source for zinc and iron. In this study, the reduction behavior of zinc ferrite with CO gas as a reducing agent under different temperatures was investigated to develop a new process for the recovery of zinc and iron from EAF-dust. The results of the phase studies with synthetic franklinite show that zinc substituted wustite, and spinel with low zinc content formed at lower temperatures from 450 to 850 °C due to incomplete zinc-iron-separation. Zinc ferrite was completely reduced to metallic zinc and iron at 950 °C. After evaporation and condensation, metallic zinc was collected in the form of zinc powder while iron, the reduction residue, was obtained in the form of direct reduced iron (DRI). The mass balance indicates a high zinc recovery ratio of over 99%. The new treatment process by thermal reduction with CO gas as a reducing agent achieved higher recovery and metallization grade of both zinc and iron from EAF-dust at lower temperatures than other commercial processes. The metallic products can be used directly as semi-products or as raw materials for refinery.

Stepwise extraction of valuable components from red mud based on reductive roasting with sodium salts

The feasibility of an integrated technological route for comprehensive utilization of red mud was verified in this study. Valuable components in the mud, including Fe2O3, Al2O3 and SiO2 were stepwise extracted by magnetic separation and sulfuric acid leaching from reduced red mud, and meanwhile TiO2 was enriched in the leaching residue. Sodium salts were proved to be favorable for the magnetic separation of metallic iron and the subsequent acid leaching of Al and Si, through facilitating the reduction of iron oxides and the growth of metallic iron grains, together with enhancing the activation of Al and Si components during the roasting process. After reductive roasting in the presence of 6% Na2CO3 and 6% Na2SO4, a magnetic concentrate containing 90.2% iron with iron recovery of 95.0% was achieved from the red mud by magnetic separation. Subsequently, 94.7% Fe, 98.6% Al and 95.9% Si were extracted by dilute sulfuric acid leaching from the upper-stream non-magnetic material, yielding a TiO2-rich material with 37.8% TiO2. Furthermore, value-added products of silica gel and Al(OH)3 were prepared from the leachate by ripening and neutralizing.

Simple and fast method for iron determination in white and red wines using dispersive liquid-liquid microextraction and ultraviolet-visible spectrophotometry

This work reports the development of a method for Fe extraction in white and red wines using dispersive liquid-liquid microextraction (DLLME) and determination by ultraviolet-visible spectrophotometry. For optimization of the DLLME method, the following parameters were evaluated: type and volume of dispersive (1300 μL of acetonitrile) and extraction (80 μL of C(2)Cl(4)) solvents, pH (3.0), concentration of ammonium pyrrolidinedithiocarbamate (APDC, 500 μL of 1% m/v APDC solution), NaCl concentration (not added), and extraction time. The calibration curve was performed using the analyte addition method, and the limit of detection and relative standard deviation were 0.2 mg L(-1) and below 7%, respectively. The accuracy was evaluated by comparison of results obtained after Fe determination by graphite furnace atomic absorption spectrometry, with agreement ranging from 94 to 105%. The proposed method was applied for Fe determination in white and red wines with concentrations ranging from 1.3 to 4.7 mg L(-1).

Distribution and genetic diversity of the microorganisms in the biofilter for the simultaneous removal of arsenic, iron and manganese from simulated groundwater

A biofilter was developed in this study, which showed an excellent performance with the simultaneous removal of AsIII from 150 to 10mg L(-1) during biological iron and manganese oxidation. The distribution and genetic diversity of the microorganisms along the depth of the biofilter have been investigated using DGGE. Results suggested that Iron oxidizing bacteria (IOB, such as Gallionella, Leptothrix), Manganese oxidizing bacteria (MnOB, such as Leptothrix, Pseudomonas, Hyphomicrobium, Arthrobacter) and AsIII-oxidizing bacteria (AsOB, such as Alcaligenes, Pseudomonas) are dominant in the biofilter. The spatial distribution of IOB, MnOB and AsOB at different depths of the biofilter determined the removal zone of FeII, MnII and AsIII, which site at the depths of 20, 60 and 60cm, respectively, and the corresponding removal efficiencies were 86%, 84% and 87%, respectively. This process shows great potential to the treatment of groundwater contaminated with iron, manganese and arsenic due to its stable performance and significant cost-savings.