Fe Leaching Research Articles

Electro-Fenton oxidation of printing and dyeing wastewater with CO2 activated CuFeC and CuMnC aerogel cathode

An electro-Fenton (EF) system with CuFeC and CuMnC aerogel cathodes was proposed without an additional Fe2+ or H2O2 for the efficient degradation of actual printing and dyeing wastewater (PDW). The CO2 activated CuFeC aerogel as the cathode showed the highest chemical oxygen demand (COD) removal efficiency compare to other cathodes. Structural characterization revealed that CO2 activation significantly enlarged the cathode porosity and surface area to increase the exposure of active sites to catalysis. During a 60 min experiment, the COD removal in the EF system with CO2–activated CuFeC and CuMnC aerogel cathodes reached 72.8 % and 51.5 %, respectively. The high COD removal of PDW with CO2-activated CuFeC aerogel could be achieved at a wide range of pH values (3~8). The enhanced mineralization efficiency of the CuFeC aerogel was mostly attributed to the synergistic effect between Fe and Cu, which benefited the oxygen reduction reaction (ORR) ability to produce more H2O2 and generate more in-situ ·OH. The possible oxidation pathway of 2, 4, 6-trichlorophenol was proposed via an intermediate study. Moreover, the CO2–activated CuFeC aerogel presented low Fe and Cu leaching in an acidic solution and a long operational life span. This material can provide a feasible way for actual PDW purification through the EF process.

Activation of persulfate by heterogeneous nano zero-valent iron/halloysite nanotubes: reaction behavior, mechanism, and implication for tetracycline hydrochloride degradation.

A novel composite (nZVI/HNTs) was prepared via incorporating nano zero-valent iron (nZVI) on halloysite nanotubes (HNTs) for degrading tetracycline hydrochloride (TCH) with existence of persulfate (PS). The adsorption process of nZVI/HNTs to TCH conformed to the Freundlich isotherm model and pseudo-second-order kinetic model, and its maximum adsorption capacity was 76.62mg·g-1. Furthermore, the nZVI/HNTs + PS system exhibited satisfactory degradation efficiency (84.21%) for TCH, and stable nZVI/HNTs (Fe leaching < 0.001mg·L-1) could be reused. When nZVI/HNTs dosage, PS dosage and temperature increased, TCH degradation could be enhanced. After four cycling, nZVI/HNTs + PS system had still 65.8% degradation for TCH. The quenching tests and EPR analysis evidenced that SO4•- was predominant instead of •OH in such system. Three possible pathways of TCH degradation were provided through the liquid chromatograph-mass spectrometer (LC-MS) determination. Meanwhile, the biological toxicity prediction analysis indicated that the nZVI/HNTs + PS system would be an environment friendly treatment method toward TCH pollution.

Red mud with enhanced dealkalization performance by supercritical water technology for efficient SO2 capture

The total de-alkalization treatment of industrial solid waste red mud (RM) has been a worldwide challenge. Removing the insoluble structural alkali fraction from RM is the key to enhancing the sustainable utilization of RM resources. In this paper, supercritical water (SCW) and leaching agents were used for the first time to de-alkalize the Bayer RM and to remove sulfur dioxide (SO2) from flue gas with the de-alkalized RM slurry. The results showed that the optimum alkali removal and Fe leaching rates of RM-CaO-SW slurry were 97.90 ± 0.88% and 82.70 ± 0.95%, respectively. Results confirmed that the SCW technique accelerated the disruption of (Al–O) and (Si–O) bonds and the structural disintegration of aluminosilicate minerals, facilitating the conversion of insoluble structural alkalis to soluble chemical alkalis. The exchangeable Ca2+ displaced Na+ in the remaining insoluble base, producing soluble sodium salts or alkalis. CaO consumed SiO2, which was tightly bound to Fe2O3 in RM, and released Fe2O3, which promoted Fe leaching. RM-SCW showed the best desulfurization performance, which maintained 88.99 ± 0.0020% at 450 min, followed by RM-CaO-SW (450 min, 60.75 ± 6.00%) and RM (180 min, 88.52% ± 0.00068). The neutralization of alkaline components, the redox of metal oxides, and the liquid-phase catalytic oxidation of Fe contributed to the excellent desulfurization performance of the RM-SCW slurry. A promising approach shown in this study is beneficial to RM waste use, SO2 pollution control, and sustainable growth of the aluminum industry.

A bifunctional graphene-based cathode for wastewater treatment in heterogeneous electro-fenton: Taking textile, old landfill leachate and simulated antibiotic wastewater as examples

Enhancing heterogeneous electro-Fenton (EF) efficiency to deal with water pollution cannot avoid the limitation of Fe(II) regeneration and low efficiency of H2O2 production. Herein, we demonstrate an efficient and robust strategy for the growth of reduced graphene oxide (rGO) and iron layered double hydroxide (FeIIFeIII-LDH) composites on graphite felt (rGO-FeIIFeIII-LDH/GF). rGO-FeIIFeIII-LDH/GF shows accelerated Fe(II) regeneration, and excellent 2e− oxygen reduction reaction (ORR) activity. It was revealed by electrochemical measurements and density functional theory (DFT) calculations that rGO acted as an electron mediator, which enables a feasible fast electron transfer pathway (rGOHOMO(−0.99 eV) → FeIIFeIII-LDHLUMO(0.53 eV)) for Fe(II) regeneration. The 2e− ORR activity can be attributed to the electron transfer number (1.77–1.94), N-doping and Fe occupied the defect site of rGO. The heterogeneous (total Fe leaching meet GB 5740–2006) EF process enabled immediate activation of H2O2 into OH and O2−. Various wastewaters including simulated dye and antibiotic wastewater, textile effluent, old landfill leachate can be efficiently treated in 120 min. Moreover, after avoiding the influence of Cl− in the actual water body, the pollution load and toxicity of the effluent were more acceptable. These results provide new insights into the heterogeneous EF system constructed with carbon fiber-based bifunctional electrode for the treatment of various actual wastewaters.

CORROSION INHIBITOR AND OXIDANTS EFFECT ON IRON LEACHING FROM CARBON STEEL DURING MERCURY REMOVAL

The Iodine/potassium iodide (I2/KI) lixiviant chemical possesses efficient treatment capabilities for elemental mercury (Hg°) removal on carbon steel’s porous surface. However, the mercury removal process on the contaminated carbon steel was observed to cause iron (Fe) to leach on the material’s surface. The results showed that the addition of imidazole as the corrosion inhibitor reduces 78.9% of Fe leaching with only 55% of Hg° removal. Compared to the oxidants of sodium hypochlorite (NaOCl) and tert-Butyl hydroperoxide (TBHP), only peroxyacetic acid (PAA) possesses a positive influence on the I2/KI reaction. Interestingly, PAA oxidant does not only enhance the Hg° removal up to 99% and reduce 73% of the Fe leaching but also reduces half of the treatment time from 16 to 8 h. While in the addition of NaOCl and TBHP oxidants, the efficiency of the decontamination process was only obtained at 54% and 59% for Hg° removal with 28.4% and 35.8% of Fe leaching, respectively.&#x0D;

Insight into Iron Leaching from an Ascorbate‐Oxidase‐like Fe−N−C Nanozyme and Oxygen Reduction Selectivity**

AbstractAscorbate (H2A) is a well‐known antioxidant to protect cellular components from free radical damage and has also emerged as a pro‐oxidant in cancer therapies. However, such “contradictory” mechanisms underlying H2A oxidation are not well understood. Herein, we report Fe leaching during catalytic H2A oxidation using an Fe−N−C nanozyme as a ferritin mimic and its influence on the selectivity of the oxygen reduction reaction (ORR). Owing to the heterogeneity, the Fe‐Nx sites in Fe−N−C primarily catalyzed H2A oxidation and 4 e− ORR via an iron‐oxo intermediate. Nonetheless, trace O2⋅− produced by marginal N−C sites through 2 e− ORR accumulated and attacked Fe‐Nx sites, leading to the linear leakage of unstable Fe ions up to 420 ppb when the H2A concentration increased to 2 mM. As a result, a substantial fraction (ca. 40 %) of the N−C sites on Fe−N−C were activated, and a new 2+2 e− ORR path was finally enabled, along with Fenton‐type H2A oxidation. Consequently, after Fe ions diffused into the bulk solution, the ORR at the N−C sites stopped at H2O2 production, which was the origin of the pro‐oxidant effect of H2A.

Insight into Iron Leaching from an Ascorbate-Oxidase-like Fe-N-C Nanozyme and Oxygen Reduction Selectivity.

Ascorbate (H2 A) is a well-known antioxidant to protect cellular components from free radical damage and has also emerged as a pro-oxidant in cancer therapies. However, such "contradictory" mechanisms underlying H2 A oxidation are not well understood. Herein, we report Fe leaching during catalytic H2 A oxidation using an Fe-N-C nanozyme as a ferritin mimic and its influence on the selectivity of the oxygen reduction reaction (ORR). Owing to the heterogeneity, the Fe-Nx sites in Fe-N-C primarily catalyzed H2 A oxidation and 4 e- ORR via an iron-oxo intermediate. Nonetheless, trace O2 ⋅- produced by marginal N-C sites through 2 e- ORR accumulated and attacked Fe-Nx sites, leading to the linear leakage of unstable Fe ions up to 420 ppb when the H2 A concentration increased to 2 mM. As a result, a substantial fraction (ca. 40 %) of the N-C sites on Fe-N-C were activated, and a new 2+2 e- ORR path was finally enabled, along with Fenton-type H2 A oxidation. Consequently, after Fe ions diffused into the bulk solution, the ORR at the N-C sites stopped at H2 O2 production, which was the origin of the pro-oxidant effect of H2 A.

Potential of the main magnetic iron oxides synthesized over graphene oxide in integrated adsorption and photocatalysis of inorganic and organic emergent contaminants

There is significant recent research into the development of iron-oxide/graphene-oxide materials for the removal of contaminants from water. However, studies are limited to simple synthetic samples and single-treatment operations. This work aimed to evaluate the efficiency of Graphene Oxide (GO), magnetite-(FeO.Fe2O3), and hematite-(α-Fe2O3) decorated GO as Integrated Photocatalyst Adsorbents (IPCAs) in the uptake of toxic metal cations and oxidation of organic dyes by simultaneous adsorption and photocatalysis for the first time. Higher adsorption affinities for Ni2+ were observed in single-cation adsorption, however, competition for active sites was observed in multi-metal systems by displacing Ni2+ ions to increase Cu2+ and Pb2+ uptakes. GO-αFe2O3 presented the highest removal rates of metal cations. The cationic organic dyes exhibited maximum color removal while anionic dye only exhibited considerable removal rates with iron-decorated nanomaterials (GO-αFe2O3 > GO-Fe3O4 > GO). In cycle experiments, the treatment of equimolar Pb2+/Methyl Blue samples was investigated and CaCl2 displayed the best performance to recover Pb2+ with minor Fe leaching. All nanomaterials were able to keep their photocatalytic activity for five cycles with TOC removal ranging between 86% and 95%. Despite GO and GO-αFe2O3 achieved appreciable metal removal rates, GO-Fe3O4 was not able to adsorb metal cation from the third cycle. Characterization analyzes (XPS, FTIR, XRD, UV-Vis, and DRS) corroborated the success of the syntheses and pointed out the iron-oxygen interaction in the materials. The structure of the nanomaterials after five cycles was observed to change by XPS and XRD.

Microwave heating of iron-rich Enteromorpha for Fe single-atom catalysts for the activation of peroxymonosulfate: Mechanisms and structure–activity relationships

To address the defects of uneven sites, atom aggregation, and poor pore structures of single-atom catalysts (SACs) prepared by conventional heating, this study prepared high-performance Fe SACs (Fe-NC) by microwave heating using Enteromorpha rich in iron and nitrogen as the precursor. The as-prepared catalysts were used to activate peroxymonosulfate (PMS) for the degradation of chloroquine phosphate (CQP). The results showed that hierarchical porous Fe-NCs with abundant surface functional groups, defective structures, and large specific surface area (SSA) were obtained by microwave heating by providing high-temperature hotspots. When using the catalyst (Fe-NC-800-15) prepared by microwave heating, the rates of PMS activation and CQP degradation were 74.48% and 99.76%, respectively, which were 8.84% and 55.65% higher than when using the catalyst prepared by conventional heating. Stronger signals of SO4·-, ·OH, 1O2, and ·O2–, lower interface resistance, and better electron transfer ability were the main reasons for better performance of the Fe-NC-800-15/PMS/CQP system. Quenching experiments showed that 1O2 and electron transfer were the dominant pathways for the degradation of CQP in the Fe-NC-800-15/PMS/CQP system. After 5 cycles of use, the degradation rate of CQP decreased to 63.37%. The deactivation of the catalyst was mainly caused by the slow circulation of Fe3+/Fe2+, loss of graphitic N, Fe leaching, reduction of defect degree and SSA, and consumption of OH/COOH and C≡N in the catalyst.

Removal of gatifloxacin by activated peroxymonosulfate using co-pyrolysis materials of water treatment residuals and biomass: Nonradical-dominated mechanisms enhanced by adsorption

Magnetic porous biochar derived from water treatment residuals and corn stalk (WTR-CS) was prepared by one-step pyrolysis method and applied for peroxymonosulfate (PMS) activation for gatifloxacin (GAT) removal. The results demonstrated that the adsorption and degradation efficiency of the WTR-CS/PMS system increased with the increasing pyrolysis temperature by changing their porosity, iron species and carbon configurations. WTR-CS obtained at 1000 °C (WTR–CS–1000) exhibited the best GAT removal effect, slight Fe leaching, strong stability and reusability. About 42.77% of GAT (40 mg L−1) was removed in the adsorption phase and 95.12% in total (90 min), accompanied by a 77% reduction in total organic carbon (TOC). The kinetic analysis demonstrated that adsorption was a key step in the overall catalytic process. Based on the quenching experiments, ESR and electrochemical tests, free radicals (SO4•-, ·OH and O2•-) and nonradical (1O2 and electron transfer) pathways jointly acted in the reaction, and nonradical pathway was dominant in the reaction. Four degradation pathways were proposed based on the intermediates detected by LC-MS, and the eco-toxicity of degradation intermediates was predicted by ECOSAR program. This study provides a new strategy for simultaneous iron-containing WTRs resource utilization and pollutant removal by synergistic adsorption and oxidative degradation.

A Stable Fe-Zn Modified Sludge-Derived Biochar for Diuron Removal: Kinetics, Isotherms, Mechanism, and Practical Research.

To remove typical herbicide diuron effectively, a novel sludge-derived modified biochar (SDMBC600) was prepared using sludge-derived biochar (SDBC600) as raw material and Fe-Zn as an activator and modifier in this study. The physico-chemical properties of SDMBC600 and the adsorption behavior of diuron on the SDMBC600 were studied systematically. The adsorption mechanisms as well as practical applications of SDMBC600 were also investigated and examined. The results showed that the SDMBC600 was chemically loaded with Fe-Zn and SDMBC600 had a larger specific surface area (204 m2/g) and pore volume (0.0985 cm3/g). The adsorption of diuron on SDMBC600 followed pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum diuron adsorption capacity of 17.7 mg/g. The biochar could maintain a good adsorption performance (8.88-12.9 mg/g) under wide water quality conditions, in the pH of 2-10 and with the presence of humic acid and six typical metallic ions of 0-20 mg/L. The adsorption mechanisms of SDMBC600 for diuron were found to include surface complexation, π-π binding, hydrogen bonding, as well as pore filling. Additionally, the SDMBC600 was tested to be very stable with very low Fe and Zn leaching concentration ≤0.203 mg/L in the wide pH range. In addition, the SDMBC600 could maintain a high adsorption capacity (99.6%) after four times of regeneration and therefore, SDMBC600 could have a promising application for diuron removal in water treatment.

Degradation of formaldehyde by photo-Fenton process over n-ZVI/TiO2 catalyst.

The degradation of formaldehyde in a photo-Fenton reaction was studied using n-ZVI/TiO2 as the catalyst. The effects of %n-ZVI loading, catalyst dosage, H2O2, and pH on formaldehyde degradation were studied. The n-ZVI/TiO2 catalysts were prepared by impregnation with chemical reduction, and their catalytic activity was evaluated in a batch reactor under UVC light. Transmission electron microscopy (TEM) was used to determine that the n-ZVI nanoparticle size was 39.41nm. X-ray photoelectron spectroscopy (XPS) was used to study the oxidation states of 2%n‑ZVI/TiO2, and the Fe 2p spectrum of 2%n-ZVI/TiO2 indicated the presence of Fe0. The optimal conditions for the complete removal of formaldehyde within 30min were an n-ZVI loading of 2 wt.%, a catalyst dosage of 0.5g/L, 30mM H2O2, and an initial pH of 3. After the reaction, the C-H functional group of formaldehyde was not observed due to the •OH radicals generated by Fe0 and H2O2 attacking the formaldehyde molecule. Moreover, no Fe leaching was observed, presenting an advantage compared with homogeneous Fe catalysts. Therefore, 2%n‑ZVI/TiO2 shows excellent potential as a photo-Fenton catalyst for the environmentally friendly degradation of formaldehyde.

Fe3S4/biochar catalysed heterogeneous Fenton oxidation of organic contaminants: Hydrogen peroxide activation and biochar enhanced reduction of Fe (III) to Fe (II)

Greigite and biochar are two important materials recently gaining importance in Fenton catalysis to remove organic contaminants. Each material, however, has significant drawbacks. For instance, biochar is challenging to remove from reaction media despite having good Fenton activities, whereas greigite (FS) exhibits limited Fenton activities in the absence of light. To make both materials useful, we prepared Fe3S4/ biochar (FSBC) composite to enhance the reactivity, stability, and reusability, which could be used for large-scale applications in organic pollutant degradation. At room temperature, the developed catalysts demonstrated good Fenton degradation efficiency toward cationic and anionic dyes as well as phenols. About 90.2 % of Eriochrome Black T (EBT) degradation was accomplished at pH 4 within 1 h without light irradiation. The activation of H2O2 to generate hydroxyl radicals was enhanced by the addition of biochar to the Fe3S4 for the degradation of pollutants. The electrons produced by the biochar and the S-generated specie on the Fe3S4 surface boost the surface iron redox cycle with the regeneration of Fe2+ ions. The biochar has a crucial role in enhancing the activity by 10 % in 1 h in the presence of magnetic Fe3S4 with a rate constant of 0.0372 min−1.The biochar provides stability to the Fe3S4/ biochar composite with minimum Fe leaching and is recovered magnetically from the reaction mixture by using external magnets, which can be used for five catalytic cycles without significant loss of catalytic activity. The reported catalyst, which overcame the individual limitations of both the FS and biochar to improve catalyst activity and magnetic separation, will serve as the foundation for creating novel catalyst systems for the future degradation of organic pollutants.

Phosphorus recovery from wastewater using extracellular polymeric substances (EPS)-like hydrogels

Phosphorus (P) recovery from wastewater is meaningful in wastewater treatment and resource recycling. Natural extracellular polymeric substances (EPS) of microbes show impressive P uptake ability. However, natural EPS is difficult to assist in P recovery due to the high harvesting cost in extraction. Thus, EPS-like hydrogels constructed by sodium alginate (SA)-Fe(III) and humic acids(HA) were designed. The results showed that the optimal formation conditions of EPS-like hydrogel were 0.1 M Fe(III) and m(HA):m(SA) = 1. Fe(III) ions were the key crosslinkers in constructing the 3-dimensional sodium alginate (SA)-Fe(III) hydrogels and in the embedding of humic acid (HA) for HA@SA-Fe(III) hydrogels. HA@SA-Fe(III) hydrogels showed bigger pore sizes, lesser Fe leaching, and higher phosphate selectivity in SO42− compared to SA-Fe(III) hydrogels. The highest P adsorption amounts were 56 and 134.33 mg-P/g for the HA@SA-Fe(III) and SA-Fe(III), respectively. The adsorption isotherm results exhibited that when the initial P concentration was in a range of 0–35 mg/L, the adsorption mainly existed on the surface of the adsorbent. While in the pore-filling stage (i.e., the initial P concentration was higher than 35 mg/L), internal diffusion controlled the adsorption process based on the kinetics. The X-ray photoelectron spectroscopy (XPS) analysis detected an appearance of Fe-O-P and O-P bonds and a disappearance of chloride ions in the hydrogels after adsorption, which confirmed the major driving forces on adsorption (ligand exchange and ion exchange). Moreover, HA@SA-Fe(III) hydrogel saturated by P adsorption passed a test as sustainable-release P fertilizers. Overall, the EPS-like hydrogels developed here provide new absorbents for P recovery.

Carbon nanotube membrane armed with confined iron for peroxymonosulfate activation towards efficient tetracycline removal

The water treatment performance of metal-based peroxymonosulfate (PMS) catalytic membrane is always limited by the finite residence time and complex water matrixes. Therefore, the development of high efficiency and anti-interference PMS catalytic membrane is of great significance. In this work, an oxidized carbon nanotube membrane with Fe2O3 nanoparticle confined inside (Fe2O3@OCNT) has been fabricated for enhanced PMS activation in the membrane filtration process (MFPA process). The experiment results showed that through fine-tuning the confinement degree of Fe2O3 in OCNT, the non-radical electron transfer pathway was gradually enhanced and became the dominant process. Under the suitable confinement condition, the tetracycline (TC) removal in the Fe2O3@OCNT MFPA process was up to 96.1 % with a residence time of only 8.0 s, which remarkably outperformed the powder-based or batch process. The high efficiency of the membrane was attributed to the enhanced mass transfer and non-radical electron transfer process due to the nanoconfinement effect. This was supported by theoretical calculations, where it was showed that confining Fe2O3 inside OCNT not only enhanced the electron activity in the lumen of OCNT, but also increased the adsorption energy for PMS. In addition, the four possible degradation pathways of TC were proposed based on Fukui function analysis and LC-MS results. This system displayed reusability and good stability for TC removal (5 cycles > 85 %, low Fe leaching of 10 μg·L-1, and long-term running of 48 h) and wide applicability for different pollutants, while also demonstrated unique anti-interference property in the presence of inorganic ions and in real water matrixes.

Grafting amino groups to enhance the adsorption of antimonate by MIL-100(Fe) for from natural water: Performance and mechanism

MIL-100(Fe) was modified by amino groups (MIL-100(Fe)-NH2) to enhance the removal of antimonate (Sb(V)) with low concentration (50−200 μg/L) from natural water through batch adsorption experiments. With the initial Sb(V) concentration up to 200 μg/L, the residual Sb(V) concentration after treated by MIL-100(Fe)-NH2 was only 3.52 ± 0.131 μg/L, lower than the drinking water standards (5 μg/L) in China, while that was much higher (94.2 ± 3.52 μg/L) after pristine MIL-100(Fe) treatment. Based on results of XPS analysis, and adsorption kinetics and isotherms, we concluded that Sb(V) substituted the terminal −OH groups of MIL-100(Fe) to form inner-sphere complexes by coordination reactions with Fe nodes and be adsorbed by hydrogen bonding as well. The grafted amino groups (−NH2) adsorbed Sb(V) by hydrogen bonding and facilitated the coordination reactions between Sb(V) and Fe nodes. The higher KL value (0.0116 ± 0.00,118 L/μg) obtained by fitting with the Langmuir isotherm model, while that of unmodified MIL-100(Fe) was 4.74 × 10−4 ± 5.85 × 10−5 L/μg, also confirmed that the −NH2 groups greatly enhanced the affinity between MIL-100(Fe) and Sb(V). Furthermore, MIL-100(Fe)-NH2 still worked nicely in a wide pH range (2 − 12), with varied ionic strength (0.05 µmol/L−1.5 mol/L), coexisting ions (CO32−, NO3−, SO42−, Cl−, H2PO4−), and even in the real water bodies. Additionally, MIL-100(Fe)-NH2 exhibited good reusability and low Fe leaching (99.92 μg/L). We hope MIL-100(Fe)-NH2 become a candidate for effective removal of Sb(V), even other heavy metals from natural waterbodies.

Effect of temperature on the leaching of heavy metals from nickel mine tailings in the arctic area, Norway

The leaching of heavy metals from tailings deposit due to the oxidation of sulphidic tailings and formation of acidic leachate is considered a high risk to the surrounding environment. Temperature plays an important role in the leaching of heavy metals from tailings in changing acid-based environment, especially in the Arctic area. To investigate how the temperature variation affected metal release from tailings in the Arctic area, a series of column leaching experiments was conducted under four temperature situations (5°C, 10°C, 14°C and 18°C). Physicochemical properties, Fe, Zn, Ni and Mn concentrations of leachates at each cycle were measured, and multivariate statistical analysis was applied to research the effect of temperature on heavy metals leaching from tailings in the Arctic area. The results showed that higher temperatures encouraged tailings to oxidation and sulfuration of and promoted heavy metal release from the tailings through precipitation and erosion. Ni, Zn and Mn have similar releasing resources from tailings and positive correlation in the leaching activity. Rising temperature accelerated Fe leaching; Fe leaching promoted leaching of the other metals, especially of Mn. Appropriately increase temperature will accelerate oxidization and sulfidization of the tailings, promote acid generation and increase TDS and, finally, promote the release of heavy metals. Climate change, with rising temperatures increasing the risk of heavy metals leaching from the tailings, should be given greater attention. Keeping tailings away from the appropriate temperature and in a higher alkalinity is a good method to control the leaching of heavy metals from tailings. Keywords: tailings, heavy metals, leaching, temperature, Norway DOI: 10.25165/j.ijabe.20231602.7216 Citation: Fu S, Lu J M, Walder I, Wu D S. Effect of temperature on the leaching of heavy metals from nickel mine tailings in the arctic area, Norway. Int J Agric & Biol Eng, 2023; 16(2): 152－158.

Kinetika Leaching Ni dan Fe dari Bijih Laterit Tipe Limonite Morowali

Nickel (Ni) deposits are depleting, while demand for the metal is increasing. To address this problem, valuable metals such as Ni and Fe can be extracted from secondary sources such as limonite-type laterite ores. The goal of this study was to investigate the influence of leaching temperature on Ni and Fe recovery, as well as the best kinetic model to represent the leaching process of these metals. Temperature has a considerable impact on the leaching process of Ni and Fe. Increasing the temperature from 30 to 90 oC can increase the recovery of Ni by 50% and Fe by 70 %. Ni and Fe recoveries were highest at 93.21 % and 95 %, respectively. Kinetic analysis of the two metals' leaching processes was also performed. It was discovered that the diffusion process controls Ni leaching, which can be represented using the Zhuravlev kinetic model, whereas chemical reactions on the surface of the unreacted core controls Fe leaching. The activation energies for leaching Ni and Fe are 36.53 and 40.32 kJ/mol, respectively. 1930 exp ((-36.53 kJ/mol)/(R.T))t=[(1-X)-1/3)-1]2 is the kinetic equation for Ni leaching. The kinetic equation for Fe leaching is 3903 exp ((- 40.32 kJ/mol)/(R.T)t=1-(1-X)1/3.

Molten-salts assisted preparation of iron-nitrogen-carbon catalyst for efficient degradation of acetaminophen by periodate activation

Highly efficient and stable heterogeneous catalysts were desired to activate periodate (PI) for sustainable pollution control. Herein, iron-nitrogen-carbon catalyst was synthesized using a facile molten-salts mediated pyrolysis strategy (denoted as FeNC-MS) and employed to activate PI for the degradation of acetaminophen (ACE). Compared with iron-nitrogen-carbon catalyst prepared by direct pyrolysis method (marked as FeNC), FeNC-MS exhibited superior catalytic activity due to its large specific surface area (1600 m2 g−1) and the abundance of FeNx sites. The batch experiments revealed that FeNC/PI process achieved 37 % ACE removal within 20 min, while ACE removal in FeNC-MS/PI process was 98 % under the identical conditions. Integrated with electron paramagnetic resonance tests, quenching experiments, chemical probe identification, and electrochemical experiments, we demonstrated that FeNC-MS-PI complexes-mediated electron transfer was the predominant mechanism for the oxidation of ACE. Further analysis disclosed that FeNx sites in FeNC-MS were the main active sites for the activation of PI. Additionally, FeNC-MS/PI process exhibited significant resistance to humic acid and background electrolyte, and avoided the secondary pollution imposed by Fe leaching. The possible degradation pathways of ACE were proposed. The germination experiments of lettuce seeds showed that the ecotoxicity of ACE solution was significantly reduced after treatment with FeNC-MS/PI process. Overall, this study provided a facile strategy for the synthesis of efficient iron-nitrogen-carbon catalysts and gained fundamental insight into the mechanism of PI activation by iron-nitrogen-carbon catalysts for pollutants degradation.

Enhanced removal of heavy metals by α-FeOOH incorporated carboxylated cellulose nanocrystal: synergistic effect and removal mechanism.

Simultaneous and highly efficient removal of heavy metal cations and oxyanions is significant for both water and soil remediation, but it remains a major challenge due to the complexity. In this work, a novel hybrid of α-FeOOH incorporated carboxylated cellulose nanocrystal (Fe/CNC) is synthesized via a hydrothermal process, which shows improved α-FeOOH dispersion and heavy metal removal capacity. In single adsorbate system, maximum adsorption capacities toward Pb(II), Cd(II), and As(V) by Fe/CNC reach 126.06, 53.07, and 15.80mgg-1, respectively, and the Fe leaching is much lower than that of α-FeOOH. In binary and ternary adsorption systems, simultaneous removal of Pb(II), Cd(II), and As(V) is proved, and the competition and synergy coexist among heavy metals. FTIR and XPS spectra have revealed the synergistic removal mechanism: Pb(II) and Cd(II) are mainly removed by surface complexation with oxygen-containing functional groups on C-CNC and α-FeOOH, and precipitation on the surface of α-FeOOH, while ligand exchange with Fe-OH is responsible for As(V) removal. The soil incubation experiments show that exchangeable and carbonate-bound Pb, Cd, and As are transformed into more stable forms in contaminated soil containing Fe/CNC composites. This work provides a novel composite material for remediation of heavy metal-contaminated environments.