Iron Oxide Hydroxide Research Articles

Optimized precipitation process for the treatment of radioactive effluents from Ni-alloy decontamination using a chemical oxidation reduction process

Nuclear power plays a major role in the generation of electricity with low carbon emissions. However, it generates significant amounts of radioactive waste, mainly from contaminated metallic components such as steam generators. Decontamination is essential for the safe handling and eventual recycling or disposal of these materials. Various decontamination techniques can be utilized but chemical processes are recommended for complex geometries such as the tubular parts of steam generators. COREMIX (Chemical Oxidation REduction using nitric permanganate and oxalic acid MIXture) is a process that is similar to the CORD (Chemical Oxidation Reduction Decontamination) process currently utilized in the industry which involves dissolving the contaminated oxide layers from metallic surfaces. This process generates a large quantity of radioactive effluent that requires appropriate treatment. The objective is to reduce metallic concentration and the radioactivity by precipitating metals in solution as hydroxides M(m-n)(OH)n (with m the oxidation number of the metal M). The optimization of a two-step precipitation protocol is presented here, with a study of the contact time (1–24 h) and the reagents used (NaOH and KOH). The resulting precipitates from this process are characterized using several techniques (FTIR, TGA and XRD). Tests were conducted on surrogate samples to demonstrate the viability of the process on more complex samples. Finally, the optimized protocols were implemented on radioactive Ni-alloy samples. Decontamination factors were calculated portraying the efficiency of both the COREMIX and the subsequent two-stage precipitation process. Characterization of the sludge produced during the process shows that the precipitate obtained at pH 8.5 consists mainly of iron (III) oxide-hydroxides, whereas the precipitate obtained at pH 12 is mainly composed of manganese (II,III) oxide. The optimization steps show that the contact time during the first precipitation and the choice of precipitants does not influence the efficiency of the protocol while the destruction of oxalic acid proves to be critical to quantitatively precipitate chromium. Ultimately, the COREMIX process can effectively decontaminate contaminated Ni-alloy samples, removing between 12% and 14% of the contamination in each cycle. Decontamination of effluent using the precipitation protocol results in a very high decontamination factor of between 3000 and 6000.

Cobalt based bimetallic catalysts for heterogeneous electro-Fenton adapting to vary pH for HEDP and MIT degradation

ABSTRACT Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process.

Transformative Dynamics: Self-Assembly of Iron Oxide Hydroxide Nanorods into Iron Oxide Microcubes for Enhanced Perfluoroalkyl Substance Remediation.

We report the controlled synthesis of iron oxide microcubes (IOMCs) through the self-assembly arrays of ferric oxide hydroxide nanorods (NRs). The formation of IOMCs involves a complex interplay of nucleation, self-assembly, and growth mechanisms influenced by time, thermal treatment, and surfactant dynamics. The self-assembly of vertically aligned NRs into IOMCs is controlled by dynamic magnetism properties and capping agents like cetyltrimethylammonium bromide (CTAB), whose concentration and temperature modulation dictate growth kinetics and structural uniformity. These controlled structural growths were obtained via a hydrothermal process at 120 °C at various intervals of 8, 16, 24, and 32 h in the presence of CTAB as the capping agent. In this hydrothermal method, the formation of vertically oriented NR arrays was observed without the presence of ligands, binders, harsh drying techniques, and solvent evaporation. The formation of the self-assembly of NRs to IOMCs is obtained with an increase in saturated magnetization to attain the most stable state. The synthesized IOMCs have a uniform size, quasi-shape, and excellent dispersion. Due to its excellent magnetic and catalytic properties, IOMCs were employed to remove the various emerging pollutants known as per- and polyfluorinated substances (PFAS). Various microscopic and spectroscopic techniques were employed for the characterization and interaction studies of IOMCs with various PFAS. The interaction between IOMCs and perfluoroalkyl substances (PFAS) was investigated, revealing strong adsorption tendencies facilitated by electrostatic interactions, as evidenced by UV-vis and FT-IR spectroscopic studies. Furthermore, the higher magnetic and positive surface charge of IOMCs is responsible for an effective remediation eliminating any secondary pollution with ease of recovery after the sorption interaction studies, thereby making it practically worthwhile.

Multifunctional iron oxide‐hydroxide based nanorods for hydrogen sulfide scavenging assisted synergistic photothermal-chemotherapy of colon cancer

The tumor microenvironment responsive multifunctional nanoplatforms with integrated diagnosis and therapy have recently received great attention in anti-cancer treatment. In this study, we developed biocompatible iron oxide-hydroxide-based nanorods (DOX-FPT NRs) for MR imaging and H2S scavenging assisted synergistic photothermal-chemotherapy of colon cancer, which is fabricated by modifying polydopamine (PDA) and transferrin (Tf) on the surface of iron oxide hydroxide (FeOOH) nanorods. The prepared DOX-FPT NRs could precisely target the colon cancer cells through transferrin ligand-receptor-mediated targeting and effectively scavenge endogenous H2S to prohibit the growth of colon cancer. Meanwhile, the considerable drug loading capability and outstanding photothermal conversion efficiency are permitted by the PDA shell modification. In addition, the H2S scavenging assisted photothermal-chemotherapy showed an excellent therapeutic effect on CT26 cells via in vitro cell test. Therefore, the prepared DOX-PFT NRs will be a promising nanoplatform to enhance the therapeutic effect of colon cancer through the treatment strategy of H2S scavenging-assisted synergistic photothermal chemotherapy.

Crystalline metal phosphide-coated amorphous iron oxide-hydroxide (FeOOH) with oxygen vacancies as highly active and stable oxygen evolution catalyst in alkaline seawater at high current density

In this study, we employed a straightforward phosphorylation approach to achieve a dual objective: constructing c-a heterostructures consisting of crystalline Ni12P5 and amorphous FeOOH, while simultaneously enhancing oxygen vacancies. The resulting oxygen evolution reaction (OER) catalyst, Ni12P5/FeOOH/NF, exhibited remarkable performance with current densities of 500 mA cm−2 in both 1 M KOH and 1 M KOH + seawater, requiring low overpotentials of only 288 and 365 mV, respectively. Furthermore, Ni12P5/FeOOH/NF exhibited only a slight increase in overpotential, with increments of 18 mV and 70 mV in 1 M KOH after 15 and 150 h, and 32 mV and 108 mV in 1 M KOH + seawater at 500 mA cm−2 after 15 and 150 h, respectively. This minimal change can be attributed to the stabilized c-a structure, the protective coating of Ni12P5, and superhydrophilic. Through in-situ Raman and ex-situ XPS analysis, we discovered that Ni12P5/FeOOH/NF can undergo a reconfiguration into an oxygen vacancy-rich (Fe/Ni)OOH phase during OER process. The elevated OER activity is mainly due to the contribution of the oxygen vacancy-rich (Fe/Ni)OOH phase from the reconfigure of the Ni12P5/FeOOH/NF. This finding emphasizes the critical role of oxygen vacancies in facilitating the production of OO species and overcoming the limitations associated with OOH formation, ultimately enhancing the kinetics of the OER.

EFFECT OF ADDING RED AND YELLOW PIGMENTS TO GEOPOLYMER CONCRETE

This study examined the feasibility of producing colored geopolymer concrete using slag as the binder and investigated the effects of pigment on various properties of geopolymer concrete. The geopolymer concrete was supplemented with two varieties of pigment, namely iron oxide hydroxide in the shades of "red" and "yellow", then the following tests of compressive strength, rebound number, density, and ultrasonic pulse velocity were carried out on it. The highest compressive strength value was achieved when adding 1% of pigments, which increased the red and yellow values from the reference value by 2.7 percent and 1.8 percent, respectively. The best rebound number values can be obtained by adding 1% yellow and 3% red, which increased the red and yellow values from the reference value by 8% and 15%, respectively. The density increases as the proportion of the additional pigment rises. The maximum density values were achieved by incorporating 1% of red and yellow pigment, with a respective increase of 1% and 3% for red and yellow. The highest values of ultrasonic pulse velocity when adding 1% of yellow and red color pigments increased by 1.7% for yellow and 2% for red. The optimal addition is 1.2% as it enhances properties and reduces expenses when utilizing smaller pigments.

Passively mode-locked fiber lasers with broadband FeOOH saturable absorber

In this contribution, we synthesized iron oxide hydroxide (FeOOH) nanomaterials and successfully demonstrated the application of FeOOH-based saturable absorbers in ultrafast photonics at 1 μm and 1.5 μm. Various characterizations were conducted to analyze the morphological and structural features of FeOOH nanomaterials. Subsequently, a tapered fiber coated with FeOOH was integrated into the resonator as a saturable absorber, exhibiting the significant saturable absorption effect with modulation depths of 1.26 % at 1 μm and 2.61 % at 1.5 μm, respectively. In an Yb-doped fiber laser, stable noise-like mode-locking pulses were achieved with a pulse duration of 519 fs at the operating wavelength of 1037.2 nm with a full-width at half-maximum (FWHM) spectral bandwidth of 4.7 nm, yielding a maximum single pulse energy of 1.23 nJ with a high signal-to-noise ratio (SNR) of 47.8 dB. Meanwhile, the conventional soliton pulses were produced in the passively mode-locked Er-doped fiber laser, featuring a pulse duration of 1.02 ps, and an SNR of 42.5 dB at a peak wavelength of 1559.25 nm with a FWHM bandwidth of 2.8 nm. This work demonstrates the considerable nonlinear optical properties of FeOOH nanomaterials in the near-infrared range, proposing a promising saturable absorber for ultrafast photonics applications.

Elemental distributions of solid waste collected from the germanium extraction process.

The solid waste produced from the germanium extraction process has attached much attention to its potential germanium sources. However, the elemental distribution of solid waste is still unclear. Therefore, the solid waste was studied using a sequential extraction procedure and characterizations including XRD, FTIR, XPS, SEM-EDS, and XAFS. It has been found that Ca, S, Fe, and Si could present crystal occurrence forms such as calcium sulfate, iron oxide hydroxide, or quartz. Furthermore, Si and Al can form a certain amount of amorphous substance. Accordingly, the sequential leaching results tell that Ca and S can be mostly leached out in pure water or weak acid solution, and more than 50% of Fe, Al, and Si were leached out in the reducible or oxidizable environment. Additionally, a part of S could be associated with Pb, generating a mostly Pb-bearing sulfate structure. Most of Zn was leached out from the reducible step, and only a very small part of Zn presented in the residual state, indicating that the majority of Zn might exist in an oxidation state and a small amount of Zn is associated in the amorphous phase. In terms of Ge, As, and Cr, almost all of them existed in the residual state. Ge should be in the occurrence of Si/Al amorphous structure. Similarly, Cr should be most likely to associate with silicates. Furthermore, As is mainly associated with iron mineral through the formation of the binuclear bidentate corner-sharing complex.

Iron-doped carbon nanotubes with magnetic enhanced Fe(VI) degradation of arsanilic acid and inorganic arsenic: Role of intermediate iron species and electron transfer

Arsanilic acid (p-AsA), a prevalently used feed additive, is frequently detected in environment posing a great threat to humans. Potassium ferrate (Fe(VI)) was an efficient way to tackle arsenic contamination under acid and neutral conditions. However, Fe(VI) showed a noneffective removal of p-AsA under alkaline conditions due to its oxidation capacity attenuation. Herein, a magnetic iron-doped carbon nanotubes (F-CNT) was successfully prepared and further catalyzed Fe(VI) to remove p-AsA and total As species. The Fe(VI)/F-CNT system showed an excellent capability to oxidize p-AsA and adsorb total As species over an environment-related pH range of 6–9. The high-valent iron intermediates Fe(V)/Fe(IV) and the mediated electron-transfer played a significant part in the degradation of p-AsA according to the probes/scavengers experiments and galvanic oxidation process. Moreover, the situ formed iron hydroxide oxide and F-CNT significantly improved the adsorption capacity for total As species. The electron-donating groups (semiquinone and hydroquinone) and high graphitization of F-CNT were responsible for activating Fe(VI) based on the analysis of X-ray photoelectron spectroscopy (XPS). Density functional theory calculations and the detected degradation products both indicated that the amino group and the C–As bond of p-AsA were main reactive sites. Notably, Fe(VI)/F-CNT system was resistant to the interference from Cl−, SO42−, and HCO3−, and could effectively remove p-AsA and total As species even in the presence of complex water matrix. In summary, this work proposed an efficient method to use Fe(VI) for degrading pollutants under alkaline conditions and explore a new technology for livestock wastewater advanced treatment.

Iron(III) oxide-hydroxide modification on Pterocarpus macrocarpus sawdust beads for direct red 28 dye removal

The releasing of wastewater contaminated with direct red 28 (DR28) dye into receiving water is a concern because it is a polyaromatic structure with difficult biodegradation. It results in being persistent in the environment and being toxic to the ecosystem from accumulating through a food chain. Thus, it needs to eliminate DR28 dye from contaminated wastewater. Sawdust beads (SDB) and sawdust mixed with iron(III) oxide-hydroxide beads (SDFB) are prepared and characterized for DR28 dye removals. DR28 dye removal efficiencies are examined with various affecting factors by the batch tests and adsorption–desorption tests, and their adsorption patterns, rates, and mechanisms are determined by isotherms and kinetics models. Moreover, the thermodynamic studies are examined for the temperature effect. SDFB demonstrated a higher surface area and smaller pore size than SDB. SDB and SDFB were uneven shapes and heterogeneous fibrillar structures. Carbon, oxygen, calcium, chloride, sodium, OH, CH, CC, COOH, and CO were found in SDB and SDFB. The points of zero charge of SDB and SDFB were 4.65 and 6.11. The conditions of 3.5 g, 50 ℃, pH 3, 60 mg/L and 2.5 g, 40 ℃, pH 3, 60 mg/L illustrated the highest DR28 dye removals of more than 82 % for SDB and SDFB, respectively. Thus, the material modification by iron(III) oxide-hydroxide improved the DR28 dye removal efficiency of sawdust material. Moreover, they could be reusability more than three times with DR28 dye removal of more than 63 %. SDB and SDFB corresponded to Langmuir and Freundlich models, respectively, and a pseudo-second-order was a good model to describe their adsorption mechanism. Both materials did not favor DR28 dye adsorptions with increasing temperature. Therefore, SDFB was a potential material for removing DR28 dye removal in the industrial wastewater.

Features of obtaining a vacuum-dense weakly conductive ceramics based on barium aluminate

Ceramics based on barium aluminate with additives of iron (III) oxide and lithium hydroxide were obtained by solid-phase synthesis. It has been established that high-temperature treatment in an oxidizing medium contributes to the production of vacuum-dense samples that meet the «absolutely impermeable» tightness criterion, with a density of 3,75 g/cm3 , with a compressive strength limit of 597,1 MPa and a specific electrical conductivity in the range of 1,50·10‒7‒1,05·10‒4 Cm/ cm (at 90‒300 °C).

Chitosan-coated magnetic nanorods and nanospheres: physicochemical characterizations and potential as methotrexate carriers for targeted drug delivery

Abstract Spherical magnetite nanoparticles were employed in the almost all magnetic based drug delivery studies. But as we all know the shape of employed particles is one of the major deterministic properties that can significantly affect the physicochemical and biological features of nanostructures and so can fluctuate efficiency of drug delivery. However, it is worthy of consideration that so far no study has investigated the effect of the shape of nanoparticles in drug delivery. To some extent this deficiency in publications may be due to the fact that the synthesis of other forms of magnetite nanoparticles is not as developed as spherical nanoparticles. But recent experiments paved the way for the synthesis of magnetite nanoparticles specially magnetite nanorods (MNRs). So, for the first time, in the current experiment magnetite nanospheres (MNSs) and MNRs were compared in the potential for drug delivery. Chitosan is a natural and biocompatible compound that widely employed as coating material for the fabrication of anticancer drug nano-carriers. So in the present study this carbohydrate was chosen as coating material for the magnetic nanostructures. MNSs were synthesized via a co-precipitation reaction, and MNRs were obtained from the chemical reduction of iron oxide hydroxide (FeOOH) nanorods. Both nanostructures were loaded with methotrexate (MTX), and the release of the drug was measured. The chitosan-coated MNSs (C@MNSs) were 7–18 nm in diameter, and the chitosan-coated MNRs (C@MNRs) were 5–21 nm in width and 29–108 nm in length and had a porous structure. The C@MNSs had a magnetic saturation of ∼80 emu/g, whereas that for the C@MNRs was ∼45 emu/g. The synthesized nanostructures exhibited low toxicity and were able to release the drug inside the cells. The findings of this study demonstrate the suitability of C@MNRs as an alternative to spherical nano-carriers for the efficient and contained delivery of anticancer drugs to designated target cells.

Application of FeOOH nanorods as a heterogeneous Fenton catalyst: The Matter of aspect ratio

Due to the growing global population and shift towards industrialized societies, water pollution and the management of wastewater are becoming significant issues. Hence, there is a need for innovative approaches to remove contaminants from effluent streams to protect the environment and human health. The Fenton's reaction is an established method for wastewater treatment, and iron oxide hydroxide (FeOOH) nanorods have immense potential as heterogeneous Fenton catalysts. The catalytic potency of nanorods is determined by their morphology, especially their length. Therefore, this study aimed to synthesize FeOOH nanorods of different mean lengths (49–101 nm) and evaluate their catalytic activity in a Fenton's reaction. Nanorods with an average length of 78 nm had the highest catalytic activity, and 87% of methyl orange was degraded over the reaction. The greater catalytic activity of these nanorods can be attributed to their larger surface area compared to the other investigated sizes. FeOOH nanorods have a porous structure; thus, their surface area is not directly related to their particle size. These outcomes indicate that the porosity and surface area play a significant role in determining the performance of heterogeneous catalysts and, as a result, must be considered to develop efficient catalysts for environmental remediation.

Recycling of NdFeB magnets: Model supported iron minimization via in-situ hydrolysis during leaching and hematite precipitation in an autoclave

The NdFeB magnets are a significant component of technological applications, which contain a remarkable quantity of rare earth elements (REEs). For this reason, the recycling of NdFeB magnets is essential for the reuse of these elements. This research represents the recycling strategy of NdFeB magnets, which consists of iron minimization through in-situ hydrolysis during oxidative leaching and hematite precipitation in an autoclave. The influence of the experimental parameters in the hydrolysis of Fe3+ in a nitric acid medium on the formation of a mixture of iron oxide hydroxide was examined in detail. Afterward, the effect of the temperature, time and, water addition on the iron and REEs precipitation in the autoclave was investigated by the ANOVA analysis based on the Box-Behnken design. According to the particle swarm optimization algorithm, maximum REEs extraction and minimum iron extraction were achieved in a solution of 1.82 mol/L nitric acid, at a solid/liquid ratio of 11/100, a temperature of 60 °C, and a stirring speed of 415 rpm. The mean leaching efficiencies of REEs and iron are calculated to be 76% and 7%, respectively. The optimal parameters for hematite precipitation in the autoclave were determined to be a process temperature of approximately 137 °C, a processing time of approximately 3 h and 55 min, and a water addition of approximately 20%. The optimum parameters are in harmony with the validation experiments.

Description and evolutionary biogeography of the first Miocene jumping spider (Aranaea: Salticidae) from a southern continent

Abstract Examination of a fossil from a Miocene Konservat-Lagerstätte (c. 11–16 Mya) from Australia shows it to be an astioid jumping spider that is here described as Simaetha sp. indet. Fossilization in the iron oxide–hydroxide mineral goethite led to a high-fidelity preservation of not only the exterior, but of the pharyngeal plate and a neuropile in the cephalothorax. The discovery of the fossil supports the molecular-based hypothesis that the Late Oligocene/Early Miocene radiation of astioid genera occurred in Australasia. Modern Asian genera then would be the result of northward migrations from Australia rather than a movement in the other direction. Biogeographically, the Miocene Simaetha fits within the predicted bioclimatic distribution of the genus today, though the bioclimatic requirements of the fossil species are now found in eastern Queensland rather than in central New South Wales. Simaetha, it seems has retained its original bioclimatic profile for 15 Myr, even though climatic and ecological conditions in Australia have changed significantly. The fossil record now shows the independent evolution of modern genera during the Early Miocene in at least five different salticid lineages on two continents. These salticid radiations occurred at a time of planet-wide, rapid climatic and ecological change.

Innovative Low-Cost Composite Nanoadsorbents Based on Eggshell Waste for Nickel Removal from Aqueous Media.

In a contemporary sustainable economy, innovation is a prerequisite to recycling waste into new efficient materials designed to minimize pollution and conserve non-renewable natural resources. Using an innovative approach to remediating metal-polluted water, in this study, eggshell waste was used to prepare two new low-cost nanoadsorbents for the retrieval of nickel from aqueous solutions. Scanning electron microscopy (SEM) results show that in the first eggshell-zeolite (EZ) adsorbent, the zeolite nanoparticles were loaded in the eggshell pores. The preparation for the second (iron(III) oxide-hydroxide)-eggshell-zeolite (FEZ) nanoadsorbent led to double functionalization of the eggshell base with the zeolite nanoparticles, upon simultaneous loading of the pores of the eggshell and zeolite surface with FeOOH particles. Structural modification of the eggshell led to a significant increase in the specific surface, as confirmed using BET analysis. These features enabled the composite EZ and FEZ to remove nickel from aqueous solutions with high performance and adsorption capacities of 321.1 mg/g and 287.9 mg/g, respectively. The results indicate that nickel adsorption on EZ and FEZ is a multimolecular layer, spontaneous, and endothermic process. Concomitantly, the desorption results reflect the high reusability of these two nanomaterials, collectively suggesting the use of waste in the design of new, low-cost, and highly efficient composite nanoadsorbents for environmental bioremediation.

INVESTIGATION OF THE PHOSPHATE IONS ADSORPTION FROM ALUMINATE SOLUTIONS BY Fe-AС NANOCOMPOSITE

The adsorption of phosphate ions from model solutions by a nanocomposite based on trivalent iron oxide-hydroxide and activated carbon (Fe-AС) was studied. Factors studied affecting the adsorption of phosphate ions: solution pH; adsorbent amount; initial concentration of phosphate ions in solution; contact duration. The efficiency of phosphate ion extraction increased with increasing adsorbent dosage (from 2.5 to 10 g/l) with an initial concentration of phosphate ions of 0.1 g/l. Adsorption is well described by the Langmuir and Frendlich isotherms. The results of the work showed that the Fe-AС nanocomposite has a good potential for adsorption of phosphate ions from aluminate solutions, which was confirmed by SEM/EDS analysis.

Influence of duck eggshell powder modifications by the calcination process or addition of iron (III) oxide-hydroxide on lead removal efficiency

Lead-contaminated wastewater causes toxicity to aquatic life and water quality for water consumption, so it is required to treat wastewater to be below the water quality standard before releasing it into the environment. Duck eggshell powder (DP), duck eggshell powder mixed iron (III) oxide-hydroxide (DPF), calcinated duck eggshell powder (CDP), and calcinated duck eggshell powder mixed iron (III) oxide-hydroxide (CDPF) were synthesized, characterized, and investigated lead removal efficiencies by batch experiments, adsorption isotherms, kinetics, and desorption experiments. CDPF demonstrated the highest specific surface area and pore volume with the smallest pore size than other materials, and they were classified as mesoporous materials. DP and DPF demonstrated semi-crystalline structures with specific calcium carbonate peaks, whereas CDP and CDPF illustrated semi-crystalline structures with specific calcium oxide peaks. In addition, the specific iron (III) oxide-hydroxide peaks were detected in only DPF and CDPF. Their surface structures were rough with irregular shapes. All materials found carbon, oxygen, and calcium, whereas iron, sodium, and chloride were only found in DPF and CDPF. All materials were detected O–H, C=O, and C–O, and DPF and CDPF were also found Fe–O from adding iron (III) oxide-hydroxide. The point of zero charges of DP, DPF, CDP, and CDPF were 4.58, 5.31, 5.96, and 6.75. They could adsorb lead by more than 98%, and CDPF illustrated the highest lead removal efficiency. DP and CDP corresponded to the Langmuir model while DPF and CDPF corresponded to the Freundlich model. All materials corresponded to a pseudo-second-order kinetic model. Moreover, they could be reusable for more than 5 cycles for lead adsorption of more than 73%. Therefore, CDPF was a potential material to apply for lead removal in industrial applications.

Synthesis, characterization, and lead removal efficiency of orange peel powder and orange peel powder doped iron (III) oxide-hydroxide

Lead contamination in wastewater causes toxicity to aquatic life, the environment, and water quality, and it causes many human dysfunctions and diseases. Thus, it is necessary to remove lead from wastewater before discharging it into the environment. Orange peel powder (OP) and orange peel powder doped iron (III) oxide-hydroxide (OPF) were synthesized, characterized, and investigated lead removal efficiencies by batch experiments, adsorption isotherms, kinetics, and desorption experiments. The specific surface area of OP and OPF were 0.431 and 0.896 m2/g, and their pore sizes were 4.462 and 2.575 nm, respectively which OPF had a higher surface area than OP, whereas its pore size was smaller than OP. They were semi-crystalline structures that presented the specific cellulose peaks, and OPF also detected the specific iron (III) oxide-hydroxide peaks. The surface morphologies of OP and OPF were irregular and porous surfaces. Carbon (C), oxygen (O), calcium (Ca), O–H, C–H, C=C, C–O, C=O, and –COOH were observed in both materials. The pHpzc of OP and OPF were 3.74 and 4.46. For batch experiments, OPF demonstrated a higher lead removal efficiency than OP because of spending less on material dosage than OP, and OPF demonstrated high lead removal by more than 95% while OP could remove lead at only 67%. Thus, the addition of iron (III) oxide-hydroxide helped to increase material efficiency for lead adsorption. Both materials corresponded to the Freundlich model relating to physiochemical adsorption, and they also corresponded to a pseudo-second-order kinetic model relating to a chemisorption process. Moreover, both materials could be reusable for more than 5 cycles for lead adsorption of more than 55%. Therefore, OPF was potential material to apply for lead removals in industrial applications.

Corrosion behaviour of friction stir processed, metastable, dual-phase, Fe49.5Mn30Co10Cr10C0.5, multi-principal element alloy

The corrosion behaviour of Friction Stir Processed (FSPed), dual-phase, Multi-Principal Element Alloy (MPEA), Fe49.5Mn30Co10Cr10C0.5, was investigated. The microstructure of the alloy in the annealed condition consisted of Face Cantered Cubic (FCC) and Hexagonal Closed Pack (HCP) phases, with the HCP phase present as laminates inside the equiaxed FCC grain. Fine carbide particles were found to be precipitated at the grain boundaries and also inside the grains. FSP engendered a reduction in the grain size due to dynamic recrystallization and an increase in the fraction of strain-induced HCP phase in the microstructure. The potentiodynamic polarisation and Electrochemical Impedance Spectroscopy (EIS) studies showed that the one-pass FSPed sample exhibited best corrosion resistance compared to the annealed and two-pass FSPed samples. The reason for this was ascribed to two factors: the reduced grain size and the smaller fraction of the HCP phase induced by strain in the microstructure. Mott-Schottky results indicated the presence of n- type semiconducting passive layer on the surface of annealed and FSPed samples. The one-pass sample had the lowest defect density (ND value) compared to annealed and the two-pass FSPed sample. Scanning Electron Microscopy (SEM) studies performed on the annealed, one-pass and two-pass samples, after immersion in 3.5 wt% NaCl solution, revealed the presence of large number of pits and corrosion products in the annealed sample compared to that in the FSPed samples. Results obtained from X-ray Photoelectron Spectroscopy (XPS) studies confirmed the presence of iron oxide, chromium oxide, cobalt oxide, chromium & cobalt hydroxides as the major constituents, together with a low concentration of manganese, in the passive layer formed on the FSPed samples.