Fe Removal Research Articles

Re-use of passive treatment Fe-sludge for remediation of As-contaminated waters

With a number of legacy metal mine sites in Japan, it is becoming increasingly important to accelerate the technological shift towards more sustainable and economical acid mine drainage (AMD) treatment. As one of the few passive treatment sites in the country to date, this study monitored the Fe-removal performance of a large-scale microbiological passive treatment plant and its required Fe-sludge waste disposal. The plant has been successfully operating for the past 4 years, with average Fe2+ oxidation and Fe removal efficiencies of 92% and 82%, respectively, to meet the effluent standard. The resulting Fe-sludge waste had to be removed twice to date and its reusability was investigated. The Fe-sludge, consisting mainly of amorphous goethite, was found to be an effective adsorbent, especially for As(V). The As(V) adsorption capacity of acidic as-received Fe-sludge was 49.2 mg/g, and the As(III) adsorption capacity of alkali pre-washed Fe-sludge was 25.1 mg/g. Based on a series of continuous column tests, for As solutions of pH 7–5, the removal capacity of Fe-sludge was almost identical for As(V) and As(III) (∼19 mg/g at HRT 6 h for the period of >99% As removal). For acidic As solutions of pH 5–2, the removal capacity of As(V) became greater (∼40 mg/g) than that of As(III) (∼13 mg/g) at HRT 6 h for the period of >99% As removal. A significant amount of As(III) can be rapidly desorbed from the Fe-sludge surface, especially at acidic pH, so the usability of the Fe-sludge was found to be more favorable for As(V). The application of a post-treatment at pHinitial 1.0, 70 °C was effective in inducing a phase transformation of As(V) ions to scorodite-like minerals. This effect was significantly accelerated by the addition of scorodite seed crystals to the post-treatment reaction, resulting in a > 100-fold improvement in TCLP As leachability from 45.1 (mg/L) to 0.37 (mg/L), well below the US disposal standard of 5.0 mg/L.

The effect of ozone on the removal of ferrous iron from zinc sulphate solution by oxidative precipitation

ABSTRACT Iron is a harmful constituent in zinc hydrometallurgy solution owing to the negative effects on the current efficiency and the quality of cathode zinc, and should be deeply removed before zinc electrowinning. The thermodynamics and kinetics for ozone precipitation of Fe2+ from ZnSO4 solution is presented. In thermodynamics the Gibbs free energy for possible precipitation reactions is calculated, and the potential-pH diagrams for Fe–H2O and Zn–H2O systems are presented. The results show that the oxidation of Fe2+ using O3 to form FeOOH at 298∼373 K prevails spontaneously. Meanwhile, the effect of O3 flow rate (Qozone) on the kinetics of Fe removal and the performance of precipitates is studied. The reaction fits better on the pseudo-first order kinetics and follows a 1.899 order rate with respect to Qozone. The rate constant kobs increases from 0.0084 to 0.045 min−1 with Qozone increasing from 4.08 to 10.3 g/h. The obtained precipitates are comprised of FeOOH and ZnSO4·H2O, and have good filterability. Ozonation precipitation can be used as an efficient method for deep removal of Fe.

Improving Iron and Copper Uptake by Changing the Ratios in Root of Vetiver Grass

Phytoremediation using Vetiver grass (VG) has been used in the past few decades all over the world, but the effectiveness of its uptake mechanism in water has less been discussed especially in mixed metal conditions. Hence, the focus of this research was to determine and evaluate the heavy metal removal effectiveness of two heavy metals, copper (Cu) and iron (Fe), based on vetiver grass uptake and toxicity. Three treatments of Fe and Cu mixture were chosen, and individual concentrations act as a control. The vetiver grass at a height of 10 cm and a root length of 25 cm for each treatment was used and harvested on days 0,1, 3, 6 and 7. The roots were randomly cut, oven-dried and used the digestion method to extract the Fe and Cu in the root. From the result, vetiver grass has better Fe and Cu uptake ability in the mixture treatment compared to the individual treatment. Fe uptake is increasing up to 25.3 % in the presence of Cu (mixture 1). Meanwhile, for Cu, mixture 3 is an ideal ratio to increase the Cu uptake by 14.5%. It shows that both Fe and Cu facilitated each other’s uptake in real wastewater conditions. There were also observed minimal toxicity signs such as necrosis throughout the experiment. The appearance of vetiver grass has changed in this experiment starting day 3 and remains yellowish. In conclusion, wastewater that contains a high concentration of Fe than Cu can promise the improvement of both Fe and Cu uptake by vetiver grass. This study benefits researchers that apply phytoremediation to remove heavy metals in wastewater by providing a guideline for Fe and Cu removal by vetiver grass. In future, the study will focus on the mechanism and interaction of Fe and Cu uptake by root

Recycled membrane for drinking water treatment with high iron and manganese concentrations

Membrane recycling by oxidative treatment is one alternative to minimize the impacts of the disposal of end-of-life (EoL) reverse osmosis (RO) membranes. In parallel, iron (Fe) and manganese (Mn) contamination in surface and groundwater is increasing. This study aims to develop recycled membranes that retain dissolved Fe and Mn from water for supply purposes. EoL RO membranes were recycled with sodium hypochlorite (NaClO, 10–12%) solution at exposure dose between 4000−80,000 ppm∙h to produce a recycled membrane with high flowrate and high Fe and Mn rejection. EoL RO treated by 40,000 ppm·h showed water permeability of 54.30 L∙h−1∙m−2∙bar−1 and Fe and Mn rejection of 99% and 65%, respectively. Potability for Mn (> 98%) was enhanced by integrating pre-oxidation stage with NaClO (5 mg∙L−1 of Cl- and pH 8) to the recycled membrane process. Recycled module performance was evaluated for water treatment from Paraopeba River on pilot scale, in continuous operation (51 h) and pressure of 1 bar. At pilot scale, recycled membrane obtained a water permeability of 40.33 L∙h−1∙m−2∙bar−1, like a moderately open ultrafiltration membrane. Fe and Mn removals were > 99% and > 90%, respectively, with high color and turbidity removal efficiency. Membrane recycling cost was predicted to be US$ 4.08/m², and the capital (CapEX) and operating (OpEX) expenditures for the single-household system was US$ 671.18 and US$ 22.52 to m3·day−1 of treated water. Therefore, the recycled membrane was shown to be efficient in removing dissolved Fe and Mn, and it is promising for decentralized water treatment.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe2+) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L-1 towards purification of groundwater for safe drinking water.

Impact of Bacillus species on Fe reduction of kaolin in bioleaching: surface, structural, and chemical studies.

Conventional techniques to remove Fe impurities in kaolin typically involve high environmental impact and cost. Alternative methods have been focused on the use of bioleaching where Fe in kaolin is reduced with microorganisms. Early results established a noticeable effect of the bacteria on the redox state of Fe, but knowledge gaps persist such as details on the bacterial-kaolin interactions during attachment of bacteria onto kaolin surface, the metabolites produced by bacteria, and changes in Fe(II)/Fe(III) ion equilibria in solution. To bridge these gaps, this study was conducted to determine the detailed physicochemical changes in bacteria and kaolin during bioleaching through surface, structural, and chemical analysis. Bioleaching experiments were conducted for 10days where each of the three Bacillus sp. was put in contact (at 9 × 108CFU) with 20g of kaolin powder using 200mL of 10g/L glucose solution. All samples treated with bacteria showed increasing trends in Fe(III) reduction up until day 6 or 8 followed by a slight decrease towards the end of the ten-day period. Examination of scanning electron microscope (SEM) images suggests that bacterial activity damaged the edges of kaolin particles during bioleaching. Ion chromatography (IC) results showed that during bioleaching, Bacillus sp. produced organic acids such as lactic acid, formic acid, malic acid, acetic acid, and succinic acid. EDS analysis of kaolin before and after bioleaching showed Fe removal efficiencies of up to 65.3%. Analyses of color properties of kaolin before and after bioleaching showed an improvement in whiteness index of up to 13.6%. KEY POINTS: • Dissolution of iron oxides by Bacillus species proven with phenanthroline analysis. • Organic acid type and concentration unique to species detected during bioleaching. • Whiteness index of kaolin is improved after bioleaching.

Influence of filter age on Fe, Mn and NH4+ removal in dual media rapid sand filters used for drinking water production

Rapid sand filtration is a common method for removal of iron (Fe), manganese (Mn) and ammonium (NH4+) from anoxic groundwaters used for drinking water production. In this study, we combine geochemical and microbiological data to assess how filter age influences Fe, Mn and NH4+ removal in dual media filters, consisting of anthracite overlying quartz sand, that have been in operation for between ∼2 months and ∼11 years. We show that the depth where dissolved Fe and Mn removal occurs is reflected in the filter medium coatings, with ferrihydrite forming in the anthracite in the top of the filters (< 1 m), while birnessite-type Mn oxides are mostly formed in the sand (> 1 m). Removal of NH4+ occurs through nitrification in both the anthracite and sand and is the key driver of oxygen loss. Removal of Fe is independent of filter age and is always efficient (> 97% removal). In contrast, for Mn, the removal efficiency varies with filter age, ranging from 9 to 28% at ∼2–3 months after filter replacement to 100% after 8 months. After 11 years, removal reduces to 60–80%. The lack of Mn removal in the youngest filters (at 2–3 months) is likely the result of a relatively low abundance of mineral coatings that adsorb Mn2+ and provide surfaces for the establishment of a microbial community. 16S rRNA gene amplicon sequencing shows that Gallionella, which are known Fe2+ oxidizers, are present after 2 months, yet Fe2+ removal is mostly chemical. Efficient NH4+ removal (> 90%) establishes within 3 months of operation but leakage occurs upon high NH4+loading (> 160 µM). Two-step nitrification by Nitrosomonas and Candidatus Nitrotoga is likely the most important NH4+ removal mechanism in younger filters during ripening (2 months), after which complete ammonia oxidation by Nitrospira and canonical two-step nitrification occur simultaneously in older filters. Our results highlight the strong effect of filter age on especially Mn2+but also NH4+ removal. We show that ageing of filter medium leads to the development of thick coatings, which we hypothesize leads to preferential flow, and breakthrough of Mn2+. Use of age-specific flow rates may increase the contact time with the filter medium in older filters and improve Mn2+ and NH4+ removal.

Assessment of Iron Contamination in Groundwater of Catchment Area Water

This study investigates the occurrence of iron (Fe) in the catchment area water in Derwiche from Hodh El Chargui in Mauritania. The study area was monitored during January and August. The occurrence of Fe in the groundwater showed significant spatial and temporal fluctuations. The relationship between Fe and some physicochemical parameters was also analyzed statistically using Pearson’s correlation matrix. Firstly, the results suggested that the concentration of Fe was influenced by the dissolution of iron minerals. Secondly, the results show that the pH value was an important factor that influenced the Fe concentrations in the groundwater. The Water Quality Index (WQI) method was used to evaluate the suitability for human consumption. The results show that WQI is strongly influenced by Fe indicating that Fe removal would contribute to excellent well water. The Treatability Index (TI) is used to assess water quality. TI confirms the results obtained by the WQI. However, TI also shows that the pH is a parameter to be optimized for possible potabilization. These results show that there would be a close relationship between the recorded Fe levels and the pH. TI confirms the results obtained by Pearson’s correlation matrix. Therefore, the presence of high Fe concentrations in groundwater in the study area could have a natural origin. The results recommended that different treatment techniques should be employed to purify groundwater before consumption. The primary focus should be cascaded toward Fe contamination.

Removal of Fe(III)/Al(III)/Mg(II) by phosphonic group functionalized resin in wet-process phosphoric acid: Mechanism and intrinsic selectivity.

The removal of iron ions (Fe(III)), aluminum ions (Al(III)), and magnesium ions (Mg(II)) in phosphoric acid (H3PO4) solution is vital for the production of H3PO4 and supply of phosphate fertilizer. However, the mechanism and intrinsic selectivity for removal of Fe(III), Al(III), and Mg(II) from wet-process phosphoric acid (WPA) by phosphonic group (-PO3H2) functionalized MTS9500 are still unclear. In this work, the removal mechanisms were determined via combined analysis of FT-IR, XPS, molecular dynamics (MD), and quantum chemistry (QC) simulations based on density functional theory (DFT). The metal-removal kinetics and isotherms were further studied to confirm the removal mechanisms. The results indicate that Fe(III), Al(III), and Mg(II) interact with the -PO3H2 functional groups in MTS9500 resin with sorption energies of -126.22 kJ·mol-1, -42.82 kJ·mol-1, and -12.94 kJ·mol-1, respectively. Moreover, the intrinsic selectivities of the resin for Fe(III), Al(III), and Mg(II) removal were quantified by the selectivity coefficient (Si/j). The SFe(III)/Al(III), SFe(III)/Mg(II) and SAl(III)/Mg(II)are 18.2, 55.1 and 3.02, respectively. This work replenishes sorption theory that can be used in the recycling of electronic waste treatment acid, sewage treatments, hydrometallurgy, and purification of WPA in industry.

Kinetics and equilibrium adsorption studies of chromium (VI) and iron (III) from aqueous solution systems using hydroxyapatite, activated carbon and their composites

Industrial effluents have become an environmental issue harming the ecosystem, remediation of these effluents is critical in order to mitigate some of this issue. Three adsorbents, activated carbon from sugarcane bagasse (ASB), hydroxyapatite (HAP), and their composites (ncpA), were prepared for the adsorption of Cr (VI) and Fe (III) from wastewater in this work. The hydroxyapatite was synthesized using the wet precipitation method, and the activated carbon was derived from sugarcane bagasse, resulting in a composite with a hydroxyapatite to activated carbon ratio of 1:1. The adsorbents surface and chemical properties were determined by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller 2 2 -1 (BET), and X-ray diffraction (XRD). The BET surface areas were 1.34 ± 0.04 m2/g and 26.4 ± 0.4 m2g4 for HAP and ASB respectively. The influence of initial concentration of metal ions, adsorbent dosage, pH, contact time and temperature on the adsorption process were investigated. Two isotherm models and different kinetic models were used in fitting the experimental data. The adsorption of Cr (VI) and Fe (III) fitted well into the Langmuir isotherm model with maximum monolayer adsorption capacities of 19.92 mg/g, 16.69 mg/g and 10.33 mg/g respectively for Cr (VI) and 113.64 mg/g, 113.64 mg/g and 107.54 mg/g respectively for Fe (III) removal onto HAP, ASB and ncpA respectively. The pseudo-second-order model that best suited the kinetic data was chemisorption-controlled, and this is referred to as the mechanism of the adsorption. Sum of square 2 error (SSE) and non-linear chi-square (ꭓ2 ) were used to further validate the mechanism.

TECHNOLOGICAL INDICATORS OF THE CATHODIC PROCESS IN THE REGENERATION OF USED SULFO-ACID SOLUTIONS FOR ETCHING STEEL

The current state of regeneration of sulfate solutions was analyzed, it was established that the existing physico-chemical methods do not solve the problem of regeneration of sulfuric acid, but only neutralize it, for transfer according to the standards of the MPC to neutralization and into the sewage system with subsequent disposal. It has been confirmed that it is advisable to carry out the regeneration by an electrochemical method using a three-chamber electrolyzer, when the solution is fed into the middle chamber, the concentration of regenerated sulfuric acid increases to 180-200 g/l, with simultaneous iron deposition, with a current yield of 65-70%. This method reduces waste and allows switching to a closed cycle on sulfuric acid. It was found that in the process of digestion, the concentration of sulfuric acid decreases from 2.0 to 0.5 mol·dm-3, and the concentration of iron (II) sulfate increases accordingly. Under the conditions of a decrease in the concentration of sulfuric acid, its chemical activity also decreases when interacting with iron oxides and hydroxides. To increase the reactivity of pickling solutions, an increase in the temperature of the entire process is used. The kinetic regularity of combined cathodic processes in model solutions of iron (II) sulfate with sulfuric acid was established. Platinum, copper and carbon steel were used as cathode material. The choice of the cathode material was based on the different electrochemical properties of these selected metals with respect to the hydrogen reaction. The main process at the platinum cathode is hydrogen release in a wide range of current densities. At current densities greater than 0.1 A/cm2, a sharp increase in potential was observed due to the incorporation of Fe2+ into the composition of the cathode-electrolyte interface, but Fe2+ reduction potentials were not reached. When replacing the cathode material from platinum to carbon steel, a significant inhibition of hydrogen release was observed, which made it possible to reach the potentials for the simultaneous reduction of hydrogen and iron, however, the maximum current of the rectilinear section of the electrochemical process with electrochemical control was reduced from 10 at 20 0C to 3 times at 80 0C. The use of a copper cathode made it possible to reveal the influence of the hydrogen reaction on the course of Fe2+ reduction. The release of hydrogen at the copper cathode was accompanied by a significant inhibition of the hydrogen ion discharge. When using an iron cathode, electrochemical desorption is the limiting stage, which leads to the existence of layers of adsorbed hydrogen firmly attached to the surface of the iron cathode. A comparative analysis of the voltage-current dependences for the final investigated temperatures indicates a significant effect of an increase in temperature from 20 0C to 80 0C by approximately 120-150 mV. The cathodic process at 20 0C takes place in the mode of increased kinetics for both combined processes. At 80 0С, rectilinear sections of electrochemical control of the cathodic process appear on the voltage–voltage dependences, at Fe2+ concentrations of 1.0 and 1.5 mol/dm3. These areas range from 20 to 60 mA/cm2. The concentration of iron ions and the temperature of electrolysis have a significant effect on the process of electrochemical reduction of Fe2+, which was confirmed experimentally. Since the target process in the electrochemical regeneration of spent pickling solutions is the regeneration of sulfuric acid itself, and not the removal of Fe2+ from this solution, the cathodic mode of operation of the electrode unit was determined according to the technological indicators of the anodic process.

Low-cost biosorption of Fe(II) and Fe(III) from single and binary solutions using Ulva lactuca-derived cellulose nanocrystals-graphene oxide composite film

The marine algal biomass of Ulva lactuca was utilized for the extraction of cellulose and the development of cellulose nanocrystals/graphene oxide film. Cellulose nanocrystals with 50–150 nm were produced by H2SO4 hydrolysis of the algal cellulose. The adsorption efficiency of the nanocomposite film for Fe(II) and Fe(III) ions was successfully evaluated using Box-Behnken design. The maximum removal for Fe(II) (64.15%) could be attained at pH 5.13, adsorbent dosage 7.93 g L−1 and Fe(II) concentration 15.39 mg L−1, while the biosorption of Fe(III) was 69.92% at pH 5.0, adsorbent dosage 2 g L−1, and Fe(III) concentration 15.0 mg L−1. However, in the binary system, the removal efficiency of Fe(II) was enhanced to 95.48% at Fe(II):Fe(III) ratio of 1:1, while the Fe(III) removal was increased to 79.17% at ratio 1:2. The pseudo-second-order kinetics exhibited better fitting to the experimental results of Fe(II) and Fe(III) adsorption in both single and binary systems. The intra-particle diffusion was prominent during the biosorption, but the effect of the external mass transfer was significant. The Langmuir, Freundlich, Langmuir–Freundlich, Temkin, and Dubinin-Radushkevich isotherms showed satisfactory fitting to the experimental data, but they differ in priority based on iron state and pH. The adsorption of Fe(II) in the presence of Fe(III) in a mixture was best represented by the extended Langmuir model, while the extended Langmuir–Freundlich model best fitted the adsorption of Fe(III). The FT-IR analysis indicated that physisorption through electrostatic interaction/complexation is the predominant mechanism for the adsorption of iron using the nanocomposite film.

Iron Removal as Goethite from Synthetic Laterite Leach Solutions.

The aim of this study was to precipitate goethite from high-iron(II)-bearing atmospheric and heap leach solutions of lateritic nickel ore generated either by reductive leaching of the ore or by reducing Fe(III) of the leach solution to Fe(II) using a suitable reducing agent and to understand the Ni and Co losses during the iron precipitation. Removal of Fe was carried out using an oxidative hydrolysis technique targeting goethite precipitation from a synthetic laterite leach solution containing Fe as ferrous (Fe(II)), Al, Mg, Ni, Co, Cr, Mn, Cu, and Zn using limestone as the neutralizing agent and air as an oxidant. The behavior of goethite precipitation and the losses of Ni and Co were examined under various conditions of pH, temperature, and Fe concentration. The precipitation of Fe increased with increasing pH, temperature, and feed Fe(II) concentration. Precipitation at pH ∼4.0-4.1 (measured at ambient temperature) and 90 °C resulted in ∼96-97% Fe removal from a feed solution containing more than 50 g/L Fe(II), giving ∼1 g/L Fe in the final liquor. Goethite formation was confirmed as a result of the Fe precipitation, and it appeared to take place via ferrihydrite/schwertmannite intermediate phases. The crystallinity of the goethite increased with time, temperature, and feed Fe(II) concentration. The goethite precipitate was found to be associated with an alunite phase. Losses of Ni and Co during Fe precipitation increased with pH, temperature, and feed Fe(II) concentration. The losses were significant above pH 4 and found to be ∼7-22% Ni and 4-19% Co in the pH range 4.1-5. The test results indicate that efficient Fe removal via goethite precipitation can be achieved from reduced atmospheric and heap leach solutions of laterite ore; however, careful pH control is required to minimize the loss of Ni and Co during this precipitation.

A Feasibility Study on the Recall of Metallophilic Fungi from Fe(III)-Contaminated Soil and Evaluating Their Mycoremediation Capacity: Experimental and Theoretical Study

Mycoremediation is one of the most attractive, eco-friendly, and sustainable methods to mitigate the toxic effects of heavy metals. This study aimed to determine the mycoremediation capacity of metallophilic fungi isolated from heavy-metal-contaminated soil containing a high Fe(III) concentration (118.40 mg/kg). Four common fungal strains were isolated, including Curvularia lunata, Fusarium equiseti, Penicillium pinophilum, and Trichoderma harzianum. These fungal strains were exposed to gradually increasing concentrations of Fe(III) of 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000 mg/L. Sophisticated techniques and tests were employed to investigate the mycoremediation capability, including tolerance index (TI), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and adsorption isotherm. Furthermore, the impacts of initial concentration, pH, and temperature on the Fe(III) removal (%) and uptake capacity (mg/g) of the studied samples were investigated. The results were validated by statistical analysis using one-way ANOVA. It was found that the Fe(III) uptake with different ratios triggered alterations in the Fe(III) tolerance (TI) morphological (SEM), chemical (FTIR), and adsorption capacity properties. The highest Fe(III) tolerance for all studied fungal strains was achieved at 100 mg/L. Moreover, the optimum conditions of Fe(III) removal (%) for all studied fungal strains were within pH 7 and 28 °C, with similar performance at the initial Fe(III) concentration ranging from 50-200 mg/L. At the same time, the maximum Fe(III) uptake was achieved at pH 7, 20 °C, and 200 mg/L. Compared to other strains, the Fe(III) tolerance of T. harzianum was rise in the Fe(III) concentration. The Fe(III) uptake reaction was corroborated by best fitting with the Langmuir model, achieving optimum adsorption capacities of 61.34, 62.90, 63.30, and 72.46 mg/g for C.lunata, F. equiseti, P. pinophilum, T. harzianum, respectively. It can be deduced that the addressed fungi species can be applied in mycoremediation according to the utilized Fe(III) concentrations with more superiority for live T. harzianum.

Mechanism of Fe removal by Sn addition in Al-7Si-1Fe alloy

Excess impurity Fe will form various intermetallic compounds in Al-based alloys, such as α-Al8Fe2Si and β-Al5FeSi, which greatly reduce the elongation of alloys. Therefore, Fe removal is a promising approach for high performance Al-based alloy. In this paper, we propose an effective method for the Fe removal from Al-7Si alloys by adding Sn. Based on the thermodynamic calculations, the element Sn was selected for Fe removal. The microstructure of Fe-rich compounds and Fe content in alloy were compared by optical microscope (OM), scanning electron microscopy (SEM) and inductively coupled plasma generation spectrometer (ICP). It was observed that the reduction of Fe content in Sn can reach 33.8%, comparable to the level of adding B. More Fe-rich compounds deposited at the bottom after addition of Sn. However, the phase type and morphology of Fe-rich compound were unchanged. The β-Sn attached to the β-Al9Fe2Si2 which was determined by transmission electron microscopy (TEM), and a coherent interface between β-Sn and β-Al9Fe2Si2 phase was observed with the orientation of (0 0 1)[1 1 0]β-Sn∥(2 2 0)[0 0 1]β-Al9Fe2Si2. It deduced that the attached β-Sn with larger density than alloy would lead to more deposition of β-Al9Fe2Si2. This study provides an insight into the preparation of high-performance Al-Si alloy by removing Fe from secondary Al alloy with Sn addition.

A new evaluation system of iron bioavailability in seaweed

In marine ecosystems, the avid binding of iron (Fe) to organic ligands influences Fe bioavailability in seaweed. This study aimed to elucidate Fe's biological availability to seaweed and develop a simple and rapid bioassay method as a new evaluation system. Undaria pinnatifida was used as a model seaweed species and the actual seaweed samples were collected using the 0.5 m × 0.5 m quadrat from the Mashike Bay area of Hokkaido, Japan. Chlorophyll fluorescence measurements were utilized as an index to evaluate the biological -effectiveness of Fe and compared with the results of culture tests based on growth. The effect of Fe content on media, pre-culture, concentrations and types of chelating and reducing agents in clearing solutions, cleaning time, Fe removal effect, and resistance to seaweed were systematically optimized to obtain the maximum efficacy of the washing solution. A bioassay was developed to evaluate the Fe environment by combining chlorophyll fluorescence measurements. The findings suggest that the tolerance of seaweeds to the wash solution is strongly influenced by the concentrations of the chelating and reducing agents than their types. Washing with 0.02 M Ti-Citrate/EDTA solution for 80 s was the most effective in terms of maximum Fe removal with minimum cell damage. The application of pre-culture and chemical pre-treatment methods under Fe deficiency to the culture strain confirmed the maximum reproducibility in the culture test. Finally, the developed method was applied to actual seaweed samples and was found to be applicable to many seaweed species. However, the method was less robust for some seaweed species and depended on the seaweed growth stage.

Agro-waste-based functionalized and economic adsorbents for the effective treatment of toxic contaminants from tannery effluent

The present investigation explored two novel adsorbents, i.e., hydroxyapatite (HAP) and moringa-modified activated carbon (MMAC) from eggshell and moringa (Moringa oleifera) seeds, respectively, for the treatment of tannery effluents (TE). Particular emphasis was given to Cr(VI) adsorption when varying equilibration time, effluent pH, initial concentration of Cr(VI) and temperature. The adsorbents' characteristics suggested significant Cr(VI) accumulation onto the adsorbent's surface, whereas adsorption modelling recommended pseudo-second-order (PSO) and Langmuir models fitted well with the experimental data based on the regression coefficient (R2) values with minimum errors. The surface complexation model (SCM) indicated that speciation of Cr(VI) sorbed complexes formed an inner-sphere compound dominated by acidic pH, validated by pHpzc. The maximum adsorption capacities (qmax) of Cr(VI) were accounted to be 295 and 280 mg/g for HAP and MMAC, correspondingly. Interestingly, both adsorbents effectively removed other metallic ions; Fe, Pd, Cu and Zn removal was 85 %, while Cd, Ni, and Mn removal was 70 %. The Cr(VI) adsorption processes followed chemisorption mechanisms dominated by the surface complexation phenomenon. The performance of a 100 L packed-bed reactor was evaluated, and the breakthrough time of Cr(VI) adsorption for both adsorbents was 15 min. The adsorbents had splendid regeneration capacities and could be re-used numerous times. In essence, the present study concludes that both adsorbents are highly effective at removing Cr(VI) and other contaminants. The adsorbents are innovative and economical and can be one of the breakthrough feasible options for treating toxic contaminants in a large-scale TE.

Development of a novel sizing approach for passive mine water treatment systems based on ferric iron sedimentation kinetics

The removal of dissolved and particulate iron (Fe) from contaminated mine drainage is an omnipresent challenge in, and legacy of, the mining industry worldwide. The sizing of settling ponds and surface-flow wetlands for passive Fe removal from circumneutral, ferruginous mine water is based either on a linear (concentration-independent) area-adjusted removal rate or flat assignment of an experience-based retention time, neither of which reflects the underlying Fe removal kinetics. In this study, we evaluated the Fe removal performance of a pilot-scale passive system operating in three identical, parallel lines for treatment of mining-influenced, ferruginous seepage water to determine and parameterise a robust, application-orientated model approach for sizing of settling ponds and surface-flow wetlands, each. By systematically varying flow rates (and thus residence time), we were able to demonstrate that the sedimentation-driven removal of particulate hydrous ferric oxides in settling ponds may be approximated by a simplified first-order approach at low to moderate Fe levels. The first-order coefficient was found in the order of 2.1(±0.7) × 10−2 h−1, which corresponds well with previous laboratory studies. The sedimentation kinetics may be combined with the preceding Fe(II) oxidation kinetics to estimate the required residence time for pre-treatment of ferruginous mine water in settling ponds. In contrast, Fe removal in surface-flow wetlands is more complex due to the phytologic component, which is why we advanced the established area-adjusted Fe removal approach by parameterising the underlying concentration-dependency for polishing of pre-treated mine water. The quantitative results of this study provide a novel, conservative approach for customised sizing of settling ponds and wetlands in integrated passive mine water treatment systems.

Treating mechanical washing wastewater with iron-in-oil characteristics by changing the fate of iron.

The mechanical washing wastewater contained a large amount of oil, and the iron wrapped in the oil was slowly released into water. This caused the effluent quality to fluctuate, causing common polymeric aluminum chloride (PAC) to ineffectively remove the water-in-oil. The method uses Ca2+ to demulsify and ClOx- to destroy the water-in-oil structure, which releases Fe from the oil droplets. The active oxygen produced by NaClOx further converts Fe2+ into Fe3+ and then combines with NaOH to form Fe(OH)3-flocs core, which improves the flocculation efficiency of PAC. The optimal ratio was approximately 400 μL of NaClOx, 200 μL of 1 mol L-1 CaO, and 12 mL of 12.8 g L-1 PAC. The oil removal rate reached 99.88% and the residue density was 178.42 mg L-1. The maximum Fe and chemical oxygen demand (COD) removal rates were close to 49.2 and 99.89%, respectively. In field applications, wastewater should be acidified first, and acidification oxidation is more effective than direct oxidation. In short, a novel way for treating mechanically washed wastewater with iron-in-oil characteristics by changing the environmental fate of iron is provided.

Thermodynamics of Formation of Al&lt;sub&gt;3&lt;/sub&gt;Fe Inter-Metallic Compound for Fe Removal from Molten Al–Mg Alloy

Thermodynamics of Formation of Al&lt;sub&gt;3&lt;/sub&gt;Fe Inter-Metallic Compound for Fe Removal from Molten Al–Mg Alloy