Iron Leaching Research Articles

Superior dye degradation and adsorption capability of polydopamine modified Fe3O4-pillared bentonite composite

Owing to the increasing demand of environmentally benign materials for the degradation of hazardous dyes, herein we are reporting two different synthesis approaches for the fabrication of iron loaded bentonite composites by modifying and activating bentonite surface with polydopamine (PDA) followed by pillaring with Fe3+ (Fe-PDA-bentonite) and Fe3O4 (Fe3O4-PDA-bentonite). Both the composites were assessed for their adsorption and degradation performance using crystal violet (CV), Rhodamine B and Brilliant blue dyes following adopting advanced oxidation process type Fenton reaction under variable energy sources (Sunlight, UV light and Ultrasonication), concentration of H2O2 and catalyst dosage. Under UV light irradiation, the composites achieved complete degradation of the dyes within 60 min and showed degradation rate constant of 30.5E-3-81.8E-3. Textural characterizations of the composites were achieved via XRD, FTIR, TGA, XPS, SEM-EDX, TEM, N2 adsorption, VSM and UV/Vis spectrophotometry. The adsorption data of CV over the two composites fitted well with Langmuir adsorption isotherm, exhibiting the maximum adsorption capacity of 862 mg/g and 1235 mg/g for Fe-PDA-bentonite and Fe3O4-PDA-bentonite composites respectively. LCMS analysis of the post degradation products revealed that both the composites followed different degradation pathways and Fe3O4-PDA-bentonite showed superior photocatalytic performance by accomplishing complete dye degradation without leaving any degradation products. FTIR analysis of the post-degradation composites confirmed their structural stability with negligible iron leaching. This study, accredited to its cost-effectiveness, ease of operation and high efficiency, provides useful reference information for the degradation of dyes on industrial level.

Recovery of valuable metals from copper slag

The copper smelting process produces plenty of copper slag every year, which is a hazardous solid waste, but a secondary resource. In the present study, the extraction of copper, nickel, and cobalt from copper slag was investigated through the process of sulfation roasting–water leaching and the process of sulfation roasting–sulfate decomposition roasting–water leaching respectively. Compared with the process of sulfation roasting–water leaching, the process of sulfation roasting–sulfate decomposition roasting–water leaching is a better choice, which could not only get almost the same leaching of copper, nickel, and cobalt as the former process, but has a lower leaching of iron and aluminum. For the process of sulfation roasting–sulfate decomposition roasting–water leaching, the leaching of Cu, Ni, and Co reached up to 74.2%, 71.1%, and 69.6% respectively, under the optimal conditions including sulfation roasted with 80 wt% sulfuric acid addition at 200 °C for 60 min and sulfate decomposition roasted at 650 °C for 60 min, followed by water leached at 90 °C for 30 min with a liquid–solid ratio of 2 ml/g. The leaching of Fe and Al was only 4.9% and 17.6%.

Fitting Biochars and Activated Carbons from Residues of the Olive Oil Industry as Supports of Fe- Catalysts for the Heterogeneous Fenton-Like Treatment of Simulated Olive Mill Wastewater.

A series of biochars and activated carbons (ACs) was prepared combining carbonization and physical or chemical activation of cheap and abundant residues of the olive oil industry. These materials were used as Fe-support to develop low-cost catalysts for the heterogeneous Fenton-like oxidation of simulated olive mill wastewater (OMW), the highly pollutant effluent generated by this agroindustry. Commercial ACs were also used as reference. All catalysts prepared were extensively characterized and results related with their performances in the catalytic wet peroxide oxidation (CWPO). Results showed a linear relationship of the textural properties of the catalysts with the adsorptive and catalytic performance, as well as the preferential adsorption and degradation of some phenolic compounds (caffeic and gallic acids) by specific interactions with the catalysts’ surface. Despite the best performance of catalysts developed using commercial supports, those prepared from agro-industrial residues present some advantages, including a smaller catalyst deactivation by iron leaching. CWPO results show that catalysts from physically activated olive stones are the most promising materials, reaching total organic carbon and toxicity reductions of 35% and 60%, respectively, as well an efficient use of H2O2, comparable with those obtained using commercial supports. This approach showed that the optimized treatment of this type of residues will allow their integration in the circular economic process of the olive oil production.

Developing a high-quality catalyst from the pyrolysis of anaerobic granular sludge: Its application for m-cresol degradation

This study proposes a novel approach for utilizing granular sludge discharged from anaerobic reactors to prepare an effective and stable catalyst for the removal of refractory contaminants in catalytic wet peroxide oxidation (CWPO). By implementing the response surface methodology, the experimental conditions for m-cresol degradation in CWPO with a HNO3-modified sludge carbon (GSC-M) as catalyst were explored. The removal efficiencies for m-cresol and total organic carbon (TOC) were 100% and 91.4%, respectively, at the optimal conditions of 60 °C for 120 min with a pH of 3, H2O2 dosage of 1.85 g/L, and catalyst dosage of 0.75 g/L. A continuous experiment was conducted for 6 d to investigate the durability and catalytic performance of GSC-M, resulting in a TOC removal above 90% with the catalyst maintaining its original morphology. GSC-M catalyst exhibited excellent stability and low iron leaching (0.34%). The high catalytic degradation could be attributed to a high content of iron species, various types of surface functional groups, porous structures, and the π–π interaction between aromatic clusters in sludge carbon and the benzene ring of m-cresol. Interestingly, GSC-M catalyst exhibited magnetic properties which are beneficial for recycling. Based on the identified intermediates, a possible degradation pathway of m-cresol was proposed.

TiO2 nanoparticles removal by electrocoagulation using iron electrodes: Catalytic activity of electrochemical sludge for the degradation of emerging pollutant

Increase in use of TiO2-based nanoparticles induced the presence of TiO2 nanoparticles (TNPs) in water resources. TNPs have adverse impacts of human health and the ecosystems. Although, several studies demonstrated toxicity and health effects of TNPs, TNPs removal from water resources are limited. In this work, TNPs were removed from the aqueous solution by electrocoagulation (EC) process using iron electrodes. The effect of pH, applied current, and initial concentration of TNPs was investigated on TNPs removal. More than 95% of TNPs were eliminated under neutral pH, 100 mA applied current and 50 mg/L TNPs. Electrochemical sludge (ES) produced was considered as catalyst for peroxymonosulfate (PMS) activation to degrade ciprofloxacin (CIP) as an emerging pollutant. Iron species in ES was in the form of Fe3O4, which is confirmed by several methods. ES could activate PMS effectively to degrade 88% of CIP under optimum condition of 2 mM PMS, 0.1 g/L ES, and 60 min reaction time. The pseudo-first-order model was fitted for the PMS/ES process with a rate constant of 0.047 min−1. The catalytic activity of ES was kept for three-time use. However, iron leaching was considerable for the first use. Sulfate radical was the main agent of CIP degradation. ES was compared with commercial Fe3O4 nanoparticles for PMS activation in terms of CIP degradation and TOC removal. Finally, the use of electrochemical sludge can be a suitable strategy for minimizing waste and preparation of the catalyst.

Comprehensive use of products generated during acid leaching of basic oxygen furnace sludge

A novelty process based on acid leaching basic oxygen furnace sludge by means of medium of 2,5M H2SO4 and 1M HCl was proposed. The new medium used in the study leaches franklinite ZnFe2O4 present in the tested sludge, which is hardly soluble in weak sulphuric acid solutions and well soluble in HCl solutions. This allows for 100% zinc extraction from the basic oxygen furnace sludge. The component of the leaching medium in the form of a sulphuric acid solution transforms the calcium compounds contained in the basic oxygen furnace sludge into insoluble calcium sulphate. The study examined the effect of solid to liquid ratio S/L (g/mL), temperature, time and rotational speed of stirrer on zinc and iron extraction from the sludge. Optimal leaching conditions were: t = 120 min, T = 60 °C, n = 500 min−1, S/L: 0.2. The leached solid filtration product obtained after leaching, dried and magnetically processed is separated into pure iron-bearing concentrate, which contains 77% Fe3O4 and 23% Fe2O3 and calcium sulphate waste. Their composition is confirmed by the X-ray diffraction analysis. The use of ethyl alcohol to precipitate sulphate iron compounds is a new alternative to recover and reuse the precipitant. The pure iron sulphate compounds with different hydration are obtained, which is confirmed by the X-ray diffraction analysis. The utilitarian aim of the study was to specify technological guidelines of the presented process and its material balance. Acid leaching of basic oxygen furnace sludge helps solve the problem of lack of selectivity in acid leaching of zinc and iron. This suggests the possibility of comprehensive use of the obtained products.

Synthesis of an iron-graphene based particle electrode for pesticide removal in three-dimensional heterogeneous electro-Fenton water treatment system

Herein, a novel nitrogen-doped graphene-iron based electrocatalyst was synthesized by a simple one-step high-temperature annealing of dehydrated Prussian blue (Na4Fe(CN)6·10H2O) as a cost-effective precursor. The synthesized nitrogen-doped catalytic particle electrodes (NCPEs) were then used as heterogeneous electro-Fenton (EF) catalyst in a three-dimensional (3D) system. A high degree of graphitization and rich nitrogen doping content were observed after characterization of synthesized Fe3C@nitrogen doped-graphene-iron oxide (Fe3C@N-GE-Fe3O4) that both are beneficial for promoting oxygen reduction reaction (ORR) as a critical step in electrochemical oxidation of pollutants. The promotional effect of combining 3D and EF systems was evaluated by comparing the performance of different electrochemical processes including homogeneous EF process for the removal of p-nitrosodimethylaniline (RNO) as a model pollutant. The effect of operational parameters such as voltage, pH, NCPEs loading, and reusability on RNO decolorization was also investigated to achieve optimum conditions for pesticide removal from water as the final step of this study. RNO decolorization efficiency was found to be the best in 3D-NCPEs system comparing to other processes including 3D system with granular activated carbon (GAC) as particle electrode. Synthesized particle electrode demonstrated an excellent RNO degradation ability even in its saturated state (~91% of RNO decolorization) with low concentration of iron leaching. Moreover, in the reusability experiments of NCPEs for over 1500 min and after the fifth test, RNO decolorization efficiency remained up to 87%. Finally, the synthesized catalyst was capable of removing up to 93% of targeted pesticides from the water under optimal conditions obtained from the previous step.

Cleaner extraction of alumina from coal fly ash: Baking-electrolysis method

Clean and efficient extraction of aluminum hydroxide from coal fly ash has environmental and economic benefits. The current study mainly aimed to develop an efficient and nonhazardous baking-electrolysis process to extract aluminum hydroxide from coal fly ash. During acid baking, the important parameters that affect aluminum, iron, and calcium leaching efficiency were studied. The maximum leaching efficiency of aluminum reached 86.8% (iron leaching efficiency was 61.0% and calcium leaching efficiency was 83.0%) under the optimal conditions of T = 200 °C, t (acid baking) = 90 min, and t (ball milling) = 5 min. X-ray diffraction, scanning electron microscopy and laser granulometry were used to investigate the mineralogy phases, microstructures, particle size distributions, and the mechanism of the acid baking process. X-ray diffractometry and scanning electron microscopy results revealed that aluminum hydroxide with porous plate-like structures was the main electrolytic product. The electrolysis mechanism was analyzed by cyclic voltammetry. This method offers the advantages of reusing the effluent after electrolysis, and the hydrogen product is a clean form of energy. Thus, the proposed baking-electrolysis process provides a promising technique as an efficient and potential zero-waste integrated process for sustainable valorization of coal fly ash.

Synthesis of iron modified sugarcane bagasse activated carbon for oxidation degradation of malachite green

Iron (II, III) oxide (Fe3O4), activated carbon (AC) and Fe3O4/AC composites at various weight ratios (1:1, 3:1 and 1:3) were synthesised successfully using chemical impregnation method. The synthesised composite samples were then analysed by using scanning electron microscope coupled with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). Heterogeneous photo Fenton and Fenton-like processes were applied in degrading malachite green. Fe3O4/AC composite samples showed higher catalytic activity as compared to pure Fe3O4 and AC. The composite of Fe3O4/AC at weight ratio of 1:1 (FeAC11) was determined to be the optimal mixing weight ratio as it possessed the highest heterogeneous photo Fenton and Fenton-like degradation efficiency of malachite green. The highest degradation efficiency of malachite green was achieved at initial dye concentration of 30 ppm, FeAC11 dosage of 0.8 g/L, solution pH of 5, 4 mM of H2O2 with the degradation efficiency of 89.22 % after 3 min. The composite sample FeAC11 depicted high stability as only little amount of leached iron (about 4 mg/L) was detected by inductively coupled plasma optical emission spectrometry (ICP-OES). Pseudo second-order kinetic was best fitted to the reaction kinetic of heterogeneous photo Fenton and Fenton-like on the degradation of malachite green at different solution pH.

In-situ growing of metal-organic frameworks on three-dimensional iron network as an efficient adsorbent for antibiotics removal

Abstract Considering the low recyclability of powder adsorbents, an efficient method is needed to fabricate a novel three-dimensional (3D) adsorbents. Take advantage of the 3D iron network and admirable adsorption performance of the Fe-based metal-organic framework (Fe-MOF), a solvothermal method was used to in-situ growing a series of Fe-based MOFs (MIL-53(Fe) MIL-100(Fe) and MIL-101(Fe)) onto the iron network (MIL stands for Materials of Institute Lavoisier). The successful growing of MILs(Fe) on the iron network was verified by optical microscopy, SEM, XRD, FT-IR and XPS characterizations. As expected, the 3D MILs(Fe) (Fe/MILs) inherited the high adsorption capacity of powdery MILs(Fe), while excellent recycling performance was obtained. Among them, Fe/MIL-100(Fe) exhibited the highest performance towards tetracycline (TC), more than 95% of TC could be removed at fifth adsorption cycle. Mechanism indicated that the π-π and hydrogen bonding (H-bonding) interactions between Fe/MIL-100(Fe) and TC molecules played an essential role in the adsorption process. Besides, the Fe/MIL-100(Fe) adsorbent was stable in water with negligible iron leaching in solution. It is worth noting that Fe/MIL-100(Fe) kept a high adsorption performance towards TC in a wide pH range of 2–10 and suffered minor influence from the anion and humic acid in solution. Even in actual aqueous solution (tap water, river water and pharmaceutical wastewater), high performance was presented by the Fe/MIL-100(Fe) adsorbent. This work provided a new method to synthesis 3D MILs(Fe) adsorbents for wastewater remediation.

Simultaneous reduction of Cr(VI) and degradation of tetracycline hydrochloride by a novel iron-modified rectorite composite through heterogeneous photo-Fenton processes

• The simultaneous removal of a heavy metal and organic contaminant was achieved. • The introduction of RhB induced more iron ions into the interlayers of a rectorite. • TC increased the Cr(VI) reduction rate 46.4-fold in the Fe-R-2/H 2 O 2 /LED system. • The Fe-R-2/H 2 O 2 system exhibited a great photocatalytic activity under sunlight. • The mechanism for the simultaneous removal of TC and Cr(VI) was proposed. To develop a low-cost, efficient and environmentally benign technique for the simultaneous removal of heavy metals and organic contaminants is a great challenge in practical wastewater treatment. In this work, a novel iron-modified rectorite (Fe-R) composite was prepared via the degradation of Rhodamine B (RhB) in a Fenton-like process and used for the simultaneous degradation of tetracycline hydrochloride (TC) and reduction of Cr(VI) through heterogeneous photo-Fenton processes. The results reveal that the introduction of RhB to the rectorite could induce more iron ions into its interlayers which accelerates the decomposition of H 2 O 2 , inhibits iron leaching and enhances its electrical conductivity. The presence of TC increased the Cr(VI) reduction rate 47.4-fold in the Fe-R-2/H 2 O 2 /LED system owing to the generation of reductive intermediates which effectively reduce Cr(VI) to Cr(III), while consuming hydroxyl radicals and suppressing the reoxidation of Cr(III). The effects of various operating parameters, as well as the adaptability, reusability, stability of the catalyst and the identities of the intermediates were comprehensively investigated. This work may shed light on the design of green, efficient and recyclable heterogeneous catalysts, and advance the practical utility of heterogeneous Fenton-like process for mixed contaminants remediation.

Highly efficient and stable FeIIFeIII LDH carbon felt cathode for removal of pharmaceutical ofloxacin at neutral pH

The traditional electro-Fenton (EF) has been facing major challenges including narrow suitable range of pH and non-reusability of catalyst. To overcome these drawbacks we synthesized FeIIFeIII-layered double hydroxide modified carbon felt (FeIIFeIII LDH-CF) cathode via in situ solvo-thermal process. Chemical composition and electrochemical characterization of FeIIFeIII LDH-CF were tested and analyzed. The apparent rate constant of decay kinetics of ofloxacin (OFC) with FeIIFeIII LDH-CF (0.18 min−1) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05 min−1) at pH 3 with 0.1 mM Fe2+ under same current density (9.37 mA cm-2). Also, a series of experiments including evolution of solution pH, iron leaching, OFC removal with trapping agent and quantitative detection of hydroxyl radicals (OH) were conducted, demonstrating the dominant role of OH generated by surface catalyst via ≡ FeII/FeIII on LDH cathode for degradation of organics as well contributing to high efficiency and good stability at neutral pH. Besides, formation and evolution of aromatic intermediates, carboxylic acids and inorganic ions (F–, NH4+ and NO3–) were identified by High-Performance Liquid chromatography, Gas Chromatography–Mass Spectrometry and ionic chromatography analyses. These findings allowed proposing a plausible degradation pathway of OFC by OH generated in the heterogeneous EF process.

Biooxidation of High-Sulfur Products of Ferric Leaching of a Zinc Concentrate

We have previously proposed a highly efficient technology for metal recovery from low-grade zinc sulfide concentrate by two-step treatment including ferric iron leaching and biooxidation of the produced ferrous iron to ferric iron (an oxidizer for sulfide minerals). The present work proposes joint biooxidation of the products of ferric leaching of the low-grade zinc concentrate: a solution containing 24.2 g/L ferrous iron and a residue containing 29.7% elemental sulfur. Apart from regeneration of the oxidant, joint biooxidation of the solution and the residue by microbial associations including iron- and sulfur-oxidizing organisms, also prevents alkalinization of the solution, which makes it possible to omit using sulfuric acid during bioregeneration. The most efficient bioregeneration of ferric iron occurred when a mixed microbial culture was grown at 40°C. According to the results of metagenomic analysis, predominant lithotrophs in the culture belonged to the genera Leptospirillum, Sulfobacillus, Acidithiobacillus, and Ferroplasma; organotrophic Cuniculiplasma was also present. Under these conditions, the rate of ferrous iron oxidation was 5.4 g/(L day), and the oxidation level of elemental sulfur in the residue was 59.5%. The role of mixo- and organotrophic acidophilic microorganisms is discussed. They predominated in associations during bioregeneration of the oxidant, as well as in the course of the medium detoxication in order to ensure growth of the autotrophic association by utilization of organic compounds. The latter were released by autotrophs during the initial production of the ferric leaching solution and due to autolysis of microbial cells during the high-temperature ferric leaching.

Bioleaching of iron from fly ash using a novel isolated Acidithiobacillus ferrooxidans strain and evaluation of catalytic role of leached iron in the Fenton's oxidation of Cephelaxin

Bioleaching of iron from fly ash using a novel isolated Acidithiobacillus ferrooxidans strain and evaluation of catalytic role of leached iron in the Fenton's oxidation of Cephelaxin

Activate hydrogen peroxide for efficient tetracycline degradation via a facile assembled carbon-based composite: Synergism of powdered activated carbon and ferroferric oxide nanocatalyst

Magnetic carbon@ferroferric oxide nanocatalyst (C@FONC), a composite material comprising powdered activated carbon (PAC) and ferroferric oxide nanocatalyst (FONC), was prepared using chemical co-precipitation. In this study, we evaluated the performance and complete pathway of tetracycline (TC) degradation in a C@FONC/H2O2 system. Moreover, the toxicity of TC and its intermediates was estimated. TC degradation in the C@FONC/H2O2 system followed pseudo-first-order kinetics, and the TC removal efficiency reached 97% in 120 min (TC0 = 150 ppm). The electron spin resonance (ESR) analysis and free radical quenching experiments indicated the generation of •OH and HO2• during the reaction. The investigation of the reaction mechanisms revealed the complementary performances between C@FONC adsorption and heterogeneous Fenton-like reaction in the TC degradation process. The stability of C@FONC recycling was also measured by multiple cycles of reactions, and the TC removal rate still reached 85.8% after nine cycles. In addition, the superparamagnetism and negligible iron leaching of the C@FONC/H2O2 system represented significant improvements relative to PAC and the conventional homogeneous Fenton process, making it a promising composite for applications in advanced oxidation processes.

Optimization of major elements recovery from thermal power plant fly ash using Taguchi experimental design

In this study, aluminum, iron, calcium and magnesium existing in thermal power plant fly ash were leached by the method of hydrochloric acid with 20% acetic acid. Then, solvent extraction and precipitation methods were applied for recovery processes. The effects of acid concentration, reaction time, and temperature on leaching of iron, aluminum, calcium, and magnesium were investigated considering the Taguchi experimental design. The optimal leaching efficiencies of these elements were obtained under the experimental condition of 5 molar acid concentration, a 240 min reaction time, and 90 °C reaction temperature and removal efficiencies were obtained for iron, aluminum, calcium and magnesium as 95%, 87%, 87%, and 96%, respectively. Almost all the tested elements were successfully recovered from leaching solution of elements by solvent extraction and precipitation processes, which are considered as recovery processes. This study indicated that the proposed methods could be applied in recovery of metals from fly ash samples successfully.

Enhanced heterogeneous catalytic ozonation of pharmaceutical pollutants using a novel nanostructure of iron-based mineral prepared via plasma technology: A comparative study

Plasma-treated goethite nanoparticles with high surface area and improved density of surface hydroxyl groups were synthesized from natural goethite (NG) using Argon (PTG-Ar) and Nitrogen (PTG-N2) as plasma environment to enhance the performance of heterogeneous catalytic ozonation process. Synthesized samples were characterized by FESEM, EDX, TEM, XRD, XPS, BET-BJH, FTIR, AAS and pHPZC. Results indicated a significantly different morphology for the prepared samples with negligible change in crystal structure. Furthermore, the catalytic activity and synergy factor of the NG and PTG nanocatalysts were evaluated for degradation and mineralization of Sulfasalazine antibiotic (SSZ) as an environmental hazardous contaminant. The highest removal efficiency was achieved 96.05 % under the optimal operating conditions. The kinetic study confirmed the pseudo-first-order reaction for the degradation process. Moreover, the dissolved ozone concentration and effect of organic and inorganic salts were studied in order to assess the reactive oxidant species (ROSs) and catalyst active sites in the process. The mechanism investigation showed the catalytic ozonation of SSZ was mainly performed by successive attacks of hydroxyl radicals (•OH), superoxide radicals (O2−) and direct ozone molecules. Environmentally-friendly modification of the NG, negligible iron leaching, successive reusability and superior catalytic activity are the major benefits of the PTG nanoparticles.

Mobility of aluminum and mineral elements between aluminum foil and bean cake (Moimoi) mediated by pH and salinity during cooking

The dependence of pH and salinity on the leaching of aluminum and allied metals from aluminum foil into bean cake during cooking was studied. Concentration of metals in the foil samples and prepared bean cake were determined using energy dispersive X-ray fluorescence and atomic absorption spectrophotometers respectively. Analysis of aluminum foil brands sold within the study area showed that they all contained aluminum, magnesium, iron, zinc, manganese, chromium and nickel with mean concentrations ranging between 972.45–977.10 g/kg, 16.21–19.84 g/kg, 2280–5710 mg/kg, 1140–1260 mg/kg, 400–410 mg/kg, 80–90 mg/kg and 480–540 mg/kg respectively. Maximum leaching of aluminum into bean cake wrapped in aluminum foil was observed in the saline bean paste followed by alkaline and acidic pastes. The increase in the concentration of iron and zinc in the bean cake samples indicated that these metals coleached with aluminum into the food during cooking. The loss of magnesium, nickel, manganese and chromium from the bean cakes after cooking suggested that demineralization of this food material occurred simultaneously with the leaching of aluminum, iron and zinc into it. The hazard quotient model indicated that all the metals that leached into the bean cake were at concentrations that could pose serious health risks to consumers.

Highly selective uranium adsorption on 2-phosphonobutane-1,2,4-tricarboxylic acid-decorated chitosan-coated magnetic silica nanoparticles

The separation and recovery of uranium resources from nuclear waste solutions is important for achieving uranium reuse and environmental protection. In this study, a novel adsorbent, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)-decorated chitosan-coated magnetic silica nanoparticles, was fabricated and applied to the highly selective adsorption of uranium from aqueous solution. Selective sorption in a multi-ion solution (pH 4.0) containing 14 coexisting cations resulted in CoFe2O4@SiO2@CS-PBTCA showing an excellent uranium adsorption capacity of up to 83.16 mg g−1, which was much higher than that of ungrafted CoFe2O4@SiO2@CS (29.99 mg g−1). The adsorbent also exhibited higher acid resistance than uncoated silica adsorbent under pH 1.0 conditions, with CoFe2O4@SiO2@CS-PBTCA showing barely any iron and cobalt leaching, while CoFe2O4@CS-PBTCA showed iron and cobalt leaching amounts of 2.97 and 0.93 mg L−1, respectively. The desorption experiment used 0.2 M PBTCA (pH 1.0) as eluent, with the results showing that uranium ions were readily and rapidly desorbed. Furthermore, CoFe2O4@SiO2@CS-PBTCA maintained outstanding stability and adsorption performance after five reuse cycles. The mechanism for U(VI) removal was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, with the results suggesting that the adsorbent binds to uranium mainly though oxygen atoms of carboxyl groups and phosphonic groups in PBTCA. This strategy shows strong potential for developing a variety of novel, highly active, acid resistance, and reusable immobilized functional magnetic materials for effective separation of uranium from a multi-ion solution.

Microbial Leaching of Iron from Hematite: Direct or Indirect Elution

Microbial Leaching of Iron from Hematite: Direct or Indirect Elution