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The recovery and extraction of uranium is vital to ensure sustainability of nuclear energy production and safety of environment. Herein, we report a facile method to synthesise diglycolamic-acid-functionalized iron oxide@titanium dioxide magnetic nanocomposite (Fe 3 O 4 @TiO 2 -DGA) as an efficient adsorbent for effective removal of uranium (VI) from aqueous medium. Fe 3 O 4 @TiO 2 -DGA showed high uranium adsorption performance, with a sorption capacity of 371.8 mg g–1 at pH 6.0 and reached equilibrium within 40 min. The adsorption isotherm fits well with Langmuir and the kinetics follows pseudo-second-order model, respectively. The plausible mechanism of U(VI) adsorption involves the electrostatic interaction between the diglycolamic acid and hydrolysed uranium species. Thermodynamic studies revealed that the adsorption was spontaneous and exothermic in nature. The U(VI)-loaded Fe 3 O 4 @TiO 2 -DGA could be conveniently separated from aqueous solutions using an external magnet, and further U(VI) is desorbed by adding dil. HCl. Fe 3 O 4 @TiO 2 -DGA showed exceptional selectivity for U(VI) in presence of various coexisting metal ions and it can be effectively reused for more than 5 times with negligible change in sorption capacity. Thus, Fe 3 O 4 @TiO 2 -DGA can be considered as an effective and potential sorbent for U(VI) remediation from aqueous solutions. [Display omitted] • Fe 3 O 4 @TiO 2 -DGA is synthesized through facile method for enhanced adsorptive removal of U(VI) from aqueous solutions. • Fe 3 O 4 @TiO 2 -DGA can selectively extract U(VI) with a maximum adsorption capacity (q max) of 371.8 mg g−1 at pH 6.0. • Equilibrium adsorption is achieved with minimum contact time of 40 min • The nanocomposite exhibited significant reusability even after several adsorption cycles. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 has the advantages of unique magnetic stability and low biological toxicity, which can improve pollutants separation efficiency. MXenes are two-dimensional materials and easy surface functionalization that can provide suitable carriers for Fe 3 O 4. In this work, we synthesized magnetic MXene composites by a one-pot method that relies on doping Fe 3 O 4 particles onto Ti 3 C 2 MXene nanosheets by heat treatment. The Fe 3 O 4 /Ti 3 C 2 MXene was analyzed by SEM, XRD, FTIR and XPS techniques, which showed that the material has good tetracycline (TC) removal properties and magnetic separation ability. The results showed that the adsorption capacity of it was 46.42 mg g−1, and the removal efficiency of 0.06 g adsorbent for 50 mL of 30 mg L−1 TC could reach 92.1% in a wide pH range of 4–10, when the adsorption temperature was 25 °C, and the adsorption time was 3 h. The adsorption data were consistent with Langmuir and the proposed second-order kinetic model, and the thermodynamic experiments confirmed that the adsorption of TC was a monolayer physicochemical adsorption coexisting heat-trapping process (ΔH = 15.72 kJ mol−1). In addition, the adsorption of TC by Fe 3 O 4 /Ti 3 C 2 MXene was attributed to the synergistic effect of electrostatic attraction, hydrogen bonding and π-π packing. In conclusion, the saturation magnetization of Fe 3 O 4 /Ti 3 C 2 MXene is 27.3 emu/g and it can not only be separated from water using its strong magnetic properties to avoid secondary contamination, but also can be used as a promising material to effectively remove antibiotics from aqueous media. [Display omitted] • A kind of magnetically recyclable, regenerative adsorbent for tetracycline adsorption (Q max = 46.42 mg g−1) has been obtained. • The mechanisms of Fe 3 O 4 /Ti 3 C 2 adsorbing tetracycline: endothermic adsorption; the quick absorption of pollutants is facilitated by the electrostatic interactions, π−π bonds and hydrogen bonds. • The adsorption occurs over a wide pH range of 4–10. [ABSTRACT FROM AUTHOR]

Iron oxide-based adsorbents showed potential to reach ultra-low phosphorus (P) concentrations to prevent eutrophication and recover P. High affinity, high capacity at low P concentrations (<1 mg L−1), good stability, and reusability of the adsorbent are key factors for economic viability. In this study, nanoparticles of goethite (α-FeOOH), a highly stable phase, have been synthesized with increasing Zn2+-doping, 0–20 %at. Zn/Fe, to manipulate the surface properties, following the results of a previous work. Mössbauer spectroscopy showed preserved goethite phase and increased point of zero charge (pzc) at low Zn-doping percentages, while at higher percentages (>5%at.) co-existing phases with increased specific surface area formed. Low concentrations (0.1–10 mg L−1) batch adsorption tests showed increased P removal per unit mass with increasing doping. However, the highest pzc, affinity and P removal per unit area were observed for the 5%at. doped sample, suggesting this dopant concentration to provide the most effective surface. A regeneration test, performed at a lower pH than usual, showed preserved, even improved P desorption with increasing doping. Mössbauer spectroscopy showed that the nanoparticle phase and composition, up to 5%at., doping was preserved throughout the process. These results are promising to develop a stable effective Zn-doped goethite-based adsorbent for P recovery at ultra-low concentrations. [Display omitted] [ABSTRACT FROM AUTHOR]

To remove the harmful dye Congo red (CR) from water, porous Fe 2 O 3 Al 2 O 3 composite was designed using a sol-gel and an organic solvent sublimation drying (OSSD) strategy. The composite contained mainly γ-Al 2 O 3 , together with various amounts of γ-Fe 2 O 3, α-Fe 2 O 3 , and/or AlFeO 3 if Fe/Al and heating strategy were properly controlled. It has high specific surface areas ranging from 126 to 210 m2/g. Its pores (10–30 nm) were formed between the homogeneously mixed Fe 2 O 3 and Al 2 O 3 spherical nano particles. Its CR adsorption behaviour was affected by such factors as pH, initial CR concentration and contact time, and had reached a maximum equilibrium adsorption capacity of ~941 mg/g under the neutral pH condition (~7.5) and an initial CR concentration of 100 mg/L. Such adsorption behaviour obeyed the Weber-Morris intra-particle diffusion, pseudo-second-order kinetic and Freundlich isotherm models, suggesting that the adsorption behaviour was kinetically limited by the intra-particle diffusion and chemical adsorption steps and it was likely to be multi-layer adsorption. Furthermore, it also showed a magnetization of around 3.48–5.51 emu/g under the magnetic field (3T), ensuring decent magnetic properties for recycling. This work may provide new insights for the efficient removal of organic dyes. [ABSTRACT FROM AUTHOR]

Iron-based materials (IBMs) have shown promise as adsorbents due to their unique physicochemical properties. This review provides an overview of the different types of IBMs, their synthesis methods, and their properties. Results found in the adsorption of emerging contaminants to a wide range of IBMs are discussed. The IBMs used were evaluated in terms of their maximum uptake capacity, with special consideration given to environmental conditions such as contact time, solution pH, initial pollutant concentration, etc. The adsorption mechanisms of pollutants are discussed taking into account the results of kinetic, isotherm, thermodynamic studies, surface complexation modelling (SCM), and available spectroscopic data. A current overview of molecular modeling and simulation studies related to density functional theory (DFT), surface response methodology (RSM), and artificial neural network (ANN) is presented. In addition, the reusability and suitability of IBMs in real wastewater treatment is shown. The review concludes with the strengths and weaknesses of current research and suggests ideas for future research that will improve our ability to remove contaminants from real wastewater streams. [Display omitted] • Summarizes recent research on using iron-based materials as adsorbents for wastewater treatment. • Adsorption processes involved in metal ion and contaminant removal are discussed. • Iron-based composites show great promise as a very effective adsorbent in wastewater applications. • Adsorption mechanism, optimization process, challenges, and perspective have been highlighted. [ABSTRACT FROM AUTHOR]

In this study, eco-friendly and magnetic sucrose-derived Fe-containing mesoporous carbon (Fe-MC) composites have been prepared by carbothermal reduction. The Fe-MC3-1000 prepared from sucrose and FeSO 4 with a mass ratio of 1:1 at 1000 °C has a uniform mesoporous structure with a BET surface area of 184 m2/g. The carbothermal reduction of Fe 2 O 3 had dual effects of the pore-forming and the loading. Batch adsorption experiments and electrochemical measurements show that the Fe-MC3-1000 has the optimum performance in both adsorption and supercapacitor applications. For adsorption, the maximum adsorption capacity for Congo red (CR) arrived at 972.1 mg g−1 with a removal percentage of 97.2 %. The adsorption process has good agreement with Langmuir isotherm and Elovich kinetic models. Besides, the Fe-MC3-1000 exhibits good recyclability after five adsorption-desorption cycles. For supercapacitor, the Fe-MC3-1000 electrode has a capacitance value of 179.23 F g−1 and a capacitance retention of 92.8 % at 10 A g−1 after 2000 cycles. The outstanding adsorption and electrochemical performances suggest that the Fe-MC3-1000 is a competitive bi-functional material for adsorption and supercapacitor. [Display omitted] • Magnetic Fe-containing mesoporous carbon was prepared via carbothermal reaction. • Low cost and eco-friendly raw materials promote its economy and sustainablity. • The carbothermal reduction of Fe 2 O 3 had dual effects of pore-forming and loading. • Both high adsorption capacities and removal percentages for CR were achieved. • The Fe-MC3-1000 had good electrochemical performance at a high current density. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pigment adsorption onto iron oxides is mainly due to electrostatic attraction. • The pigment-binding capacity is in the order of ferrihydrite > goethite > hematite. • The affinity of iron oxide towards pigment is in the sequence of AR > TA > BB. • Different mechanisms involved in pigment adsorption vary with pH values. • Pigments and Cu2+ have a mutual promotion effect on their adsorption. The knowledge about the adsorption properties of pigments onto different iron oxide minerals is still limited. The adsorption behaviors of three typical pigments, including amaranth (AR), tartrazine (TA), and brilliant blue (BB), onto three iron oxides (ferrihydrite, goethite, and hematite) were investigated. The primary mechanism of their interactions was the electrostatic attraction. The affinities of iron oxides toward any pigment were generally in the sequence of ferrihydrite > goethite > hematite (e.g., the maximum adsorption amounts (q max) of AR onto the three iron oxides were 35.5 mg/g, 11.6 mg/g, and 4.2 mg/g, respectively), which was related to the differences in physicochemical properties of minerals (e.g., specific surface area, surface hydroxyl density, and crystal structure). Interestingly, for a given iron oxide, the pigment-binding capacity of the mineral was in the order of AR > TA > BB. This effect was attributed to variations in pigment molecular sizes and electrostatic interactions between pigments and minerals. The pigment-binding capabilities of iron oxides changed as the solution pH varied. Hydrogen-bonding and electrostatic interactions were the main mechanisms below and above pH > pH PZC (pH value at zero point charge), respectively. Furthermore, adding Cu2+ facilitated pigment adsorption, mainly stemming from the surface-bridging effect. Pigments also enhanced Cu2+ adsorption onto iron oxides due to the decreasing electrostatic repulsion between Cu2+ and particles as well as the complexion between Cu2+ with pigment molecules adsorbed on mineral surfaces. The insightful information demonstrates that ubiquitous iron oxide minerals can affect the fate of pigments in natural environments. [ABSTRACT FROM AUTHOR]

Phosphorus (P) removal from freshwater bodies to ultra-low concentrations is fundamental to prevent eutrophication, while its recovery is necessary to close the P usage cycle. Iron oxide-based adsorbents seem promising candidates, being abundant, cheap, and easy to synthesize compounds, with good affinity for P. Affinity is the key parameter when targeting ultra-low concentrations. Also, adsorbent regeneration and re-use is fundamental for the economic viability, hence the adsorbent stability is important. Goethite, (α-FeOOH), is one of the most stable iron (Fe3+) (hydr)oxide species, with higher affinity, but lower adsorption capacity (per kg) compared to other species. Doping could change goethite surface properties, to boost the adsorption capacity, while preserving the high stability and affinity for P. In this work, pure goethite was compared to goethite doped (5%at.) with different elements of different preferential oxidation states: Zn2+, Mn3+, and Zr4+. Doping was successfully achieved for all elements, albeit Zr showed a lower Fe substitution than targeted. Zn doping increased the goethite point of zero charge and adsorption capacity (per mass and per surface area), preserving the high affinity, while Mn- and Zr- doping displayed a decrease in all the parameters. These could be explained with surface protonation as a charge compensation mechanism in Zn2+-for-Fe3+ substitution. The regeneration test showed improved P recovery for Zr- and Zn-doped goethite. All samples remained stable throughout the whole process. This work provides promising insights on doping as a strategy to manipulate iron oxides surface properties and for developing a highly performing and long-lasting goethite-based adsorbent. [Display omitted] • Three different elements with different oxidation states were used as dopants for goethite: Zn2+, Mn3+, Zr4+. • Zn-doped goethite showed the highest point of zero charge and P adsorption. • Zr doping of goethite, which has never been attempted before, was successful. • Mn- and Zr-doped goethite displayed a decrease in P adsorption performances. • Charge compensation mechanism during doping interesting for adsorbent development. [ABSTRACT FROM AUTHOR]

• Fe(OH) 3 and α-FeOOH show highest efficiency for H 2 S/O 2 removal among the 35 samples. • BET surface area and Bronsted acid sites drive adsorption of H 2 S and O 2. • Performance of α-FeOOH was substantiated in a pilot plant with raw biogas. This study deals with the development of iron oxide/hydroxide adsorbents for the alternating removal of H 2 S and O 2 from natural gas and biogas. The considered procedure initially implies the chemisorption of H 2 S. In the second step, O 2 is removed by reaction with the H 2 S-treated substrate accompanied by regeneration of the adsorbent. 35 different iron-based samples were physical-chemically characterized and tested towards H 2 S/O 2 break through behavior and adsorption capacity to evaluate structure-performance correlations. It was derived that high BET surface area, high proportion of meso and micro pores, small average pore diameter, low crystallinity and high number of Bronsted acid sites are crucial properties of the adsorbents. As a consequence, Fe(OH) 3 and α-FeOOH revealed highest efficiency for the successive adsorption of H 2 S and O 2 , while α-Fe 2 O 3 provided rather low performance. Mechanistic investigations were carried out with α -FeOOH and α -Fe 2 O 3 indicating rapid dissociation of H 2 S on α -FeOOH, while slow molecular adsorption prevailed on α -Fe 2 O 3. With proceeding H 2 S exposure, the adsorbents were partially transformed into sulfide and sulfate species with some formation of elemental sulfur. In subsequent reaction with O 2 , the H 2 S-exposed samples were re-oxidized under partial restructuring, whereas elemental sulfur and sulfate entities were additionally produced. Finally, the concept of the alternating adsorption of H 2 S and O 2 on best α -FeOOH substrate was technically evaluated in a biogas pilot plant. The investigations showed efficient conversion of H 2 S for 40–100 h, while subsequent O 2 conversion was achieved for ca. 5.5 h. [ABSTRACT FROM AUTHOR]

Highlights • Hydrothermally synthesized iron oxide and zinc oxide nanocomposite. • Adsorptive removal of Cr(VI) ions using iron oxide and zinc oxide nanocomposite. • Imparting antibacterial and antioxidant properties to the treated water using iron oxide and zinc oxide nanocompsite. • Achieving removal efficiency of 97.8% for Cr(VI) ions using iron oxide and zinc oxide nanocomposite. • Achieving adsorption capacity of 36.5 mg/g using iron oxide and zinc oxide nanocomposite. Abstract The synthesis of a multifunctional composite using Fe 2 O 3 and ZnO endowed with antioxidant and antibacterial properties for the adsorption of chromium(VI) ions was reported. Typical approaches of eliminating metal ions from wastewater focus on removing only the contaminants. In this research, a composite was developed that is not only highly efficient in removing Cr(VI) ions but also imparts antibacterial and antioxidant properties to the treated water. The characterizations of the composite were conducted using powder X-ray diffraction (pXRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET). BET surface area revealed that the sheet-like Fe 2 O 3 were present alongside hexagonal ZnO rods. The adsorption data corroborated well with Freundlich isotherm (R 2= 0.99844) better than the Langmuir model (R 2= 0.97993) indicating the prevalence of multi-layer sorption. Pseudo-second-order kinetics model described the adsorption process well implying chemisorption was the major contributor to the adsorption capacity. The composite exhibited additional useful character by inhibiting up to 12% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals when used in the concentration range of 10–50 µL. It also showed antibacterial property by removing more than 99% of Staphylococcus aureus after an exposure time of six hours. It is proposed that Fe 2 O 3 –ZnO composite may be highly effective for multi-purpose water treatment. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Fe-clay composite is an efficient adsorbent material for phenol removal. • Textural and chemical properties of the adsorbent have been assessed. • Kinetics and thermodynamics studies of phenol adsorption have been performed. • Statistical physics models were applied to understand the adsorption mechanism. Water pollution by phenolic compounds is considered a primary environmental concern. The adsorption of phenol on iron-modified clay and its mechanism were evaluated in this study. A new hybrid material, "Clay-Iron oxide," has been synthesized for its possible use in phenol removal from wastewater. Textural and chemical properties of this new composite have also been assessed using a variety of techniques such as XRD, XRF, SEM-EDX, FTIR, and BET. On the other hand, phenol adsorption performance has been studied in terms of pH, temperature, and initial concentration. Theoretically, the phenol adsorption onto modified clay was satisfactorily modeled with pseudo-second-order kinetics and the Langmuir isotherm; the maximum phenol adsorption capacities, obtained with the Langmuir model, are 15.24, 17.55, 20.24, and 20.10 mg/g at 303, 313, 323, and 333 K, respectively. Furthermore, five advanced statistical physics models were adopted to understand the adsorption mechanism better. The combination of experimental and modeling approaches revealed that: i) the present material is competitive compared to other adsorbents, ii) phenol molecules interact with clay/iron oxide functional groups via several mechanisms, iii) the number of phenol molecules adsorbed per site increases with temperature, iv) phenol adsorption process is spontaneous, physisorption and endothermic, and v) Iron increases the phenol removal efficiency. Thus, the novelty of this research paper lies in the phenol adsorption mechanism study based on the spatial and energetic properties, the determination of the adsorption process effect on the adsorbent, and finally, the assessment of the iron-modified clay's efficiency in removing phenol from wastewater. [ABSTRACT FROM AUTHOR]

Adsorptive removal of phosphorus from wastewater effluents has attracted attention because of its reduced sludge production and potential P recovery. In this study, we investigated granular activated carbons (GACs) impregnated with amorphous ferrihydrite (FH@GAC) for the sorption of phosphorus from aqueous solutions. Preoxidation of intact GAC surfaces using an oxidant (e.g., hypochlorite) and strong acids (e.g., HNO 3 /H 2 SO 4 ) was performed to create active functional groups (e.g., carboxyl or phenolic) for enhanced iron binding, leading to greater phosphorus uptake. Both the rate and the capacity of phosphorus sorption onto FH@GAC had significant, positive relationships (Pearson correlation coefficient r > 0.9) with the product of surface area and Fe content. The pseudo-second-order reaction kinetics explained the P sorption rate better than the pseudo-first-order reaction kinetics, whereas the Langmuir model fit the P sorption isotherm better than the Freundlich model. The iron content in the FH@GAC increased significantly (>10 mg/g) when GAC (e.g., BMC1050) was preoxidized by a 1:1 (w/w) concentrated HNO 3 /H 2 SO 4 mixture. The Langmuir maximum P sorption capacity of a functionalized FH@BMC1050 adsorbent prepared with acid pretreatment was estimated to be substantial (5.73 mg P/g GAC corresponding to 526 mg P/g Fe). This sorption capacity was superior to that of a FH slurry, possibly because the nano-sized FH formed inside the GAC pores (<2.5 nm) can bind phosphate ions more effectively than FH aggregates. Fixed-bed column reactor operation with bicarbonate regeneration showed potential for efficient, continuous phosphorus removal by FH@GAC media. [ABSTRACT FROM AUTHOR]

Organoarsenicals are widely used as antibiotics in the livestock industry and largely discharged into water environment directly, their safe, efficient and cost-effective treatment are actively perused. Herein, a heterogeneous iron-based Fenton-like technology was designed and validated with much reduced secondary pollution, mainly attributed to the bi-functional properties of both Fenton-active and arsenic-affinitive iron oxides. This simple one-step strategy not only exhaustively degraded organoarsenicals, but also selectively adsorbed the released high-toxicity arsenic from treated water. With Roxarsone as target, the FeOOH-based Fenton-like system exhibited a much superior capacitie for both Roxarsone degradation and arsenic adsorption in various water matrices, compared to typical homogeneous systems under similar conditions. More than 80% of Roxarsone was degraded after 3.0 h, and most of the released AsO 4 3− was removed simultaneously, without any additional post-treatment. The superior capacity of FeOOH might be mainly attributed to its strong redox-cycling capacity of surface central Fe atoms from their thermodynamically favorable electronic structure. Taking the important advantages of iron oxides and Fenton technology into account, our findings might provide a new chance to develop simple and efficient technologies for organoarsenicals removal from water with much reduced secondary pollution at a low cost. [ABSTRACT FROM AUTHOR]

Magnetisation of carbonaceous adsorbents using iron oxides has been found to be one of the potential solutions for easy recovery of adsorbent after use. We evaluated the effects of Fe 3 O 4 nanoparticle addition on the physico-chemical properties of biochar and its sorption properties. Five adsorbents with varying amount of Fe 3 O 4 per mass of adsorbent (0%, 25%, 50%, 75% and 100%) were used to adsorb sulfamethoxazole (SMX), an emerging micropollutant. Five isotherm models were used to evaluate the sorption behaviour of SMX onto the adsorbents where Redlich-Peterson model was found to best describe the data. Based on this model, the approximate site energy distribution for each adsorbent was determined. Surface area and sorption capacity had strong negative linear relationship with the amount of Fe 3 O 4 per mass of adsorbent while the pore volume and saturation magnetisation of the adsorbent increased with increasing percentage of Fe 3 O 4 . The results of the approximate site energy distribution analysis showed that the addition of Fe 3 O 4 on biochar reduced the area under the frequency distribution curve of sorption site energies leading to the lowering of the sorption sites available for SMX. This could be attributed to the blockage of the hydrophobic surface of biochar reducing the hydrophobic interaction between SMX and biochar. [ABSTRACT FROM AUTHOR]

The removal of copper ions by magnetic Fe 3 O 4 /carbon nanotube (CNT) composite adsorbents, prepared by co-precipitation method, in aqueous solution has been investigated. The influence of magnetite loading (35.5‒64.1 wt.%) onto oxidized CNT support on the adsorption capacity and regeneration efficiency is investigated. The adsorption isotherms of Cu 2+ ions are well characterized by Langmuir, Freundlich, and Dubinin–Radushkevich models within the temperature range of 303‒323 K. The decoration of magnetic Fe 3 O 4 significantly enhances the removal efficiency, equilibrium rate constant, and adsorption capacity, as analyzed by these models. The appropriate loading of magnetite nanoparticles on the CNT supports not only increases adsorption capacity but also facilitates regeneration efficiency. Accordingly, the Fe 3 O 4 /CNT composite can be used as an effective adsorbent for rapid removal of Cu 2+ ions from aqueous solution. [ABSTRACT FROM AUTHOR]

Durian, which is also known as the king of fruits, is one of the widely consumed fruits in South east Asia, especially in Malaysia, Thailand, Indonesia, Philippines and Singapore. The high demand for durian in Malaysia has led to the accumulation of waste durian rind without proper disposable management in place. Therefore, a novel magnetic biochar was synthesized utilizing the durian rind in the presence of iron oxide, by employing the pyrolysis process in an electrical muffle furnace in a vacuum condition. The effect of pyrolysis temperature, pyrolysis time and sonication frequency was studied to determine the optimum condition for the production of magnetic biochar. The analysis shows that a pyrolysis temperature of 800 °C, pyrolysis time of 25 min and sonication frequency 70 are required for the production of magnetic biochar with a high yield and surface area. These newly produced magnetic biochar have a high surface area of 820 m 2 /g which provide 98% removal of congo red from the aqueous solution with an adsorption capacity of 87.32 mg/g. [ABSTRACT FROM AUTHOR]

Arsenic, one of the elements having most terrible impact on the human being, is threatening the world continuously. It exists in the combined form in rocks under earth which on dissolution contaminates ground water. The contamination has led to a massive epidemic in East and South-East Asia, and the problem is more dangerous for Bangladesh and adjoining province, Bengal of India, where more than 100 million people are currently affected by arsenic contaminated ground water. Arsenic exists in water as oxyacids in two oxidation states, As(III) and As(V), the former is more toxic. Various techniques are under use for the removal of both forms of arsenic but most of these are not suitable for As(III) form. Adsorption has been proved most preferable technique for the removal of both forms of arsenic. Various types of solid materials had been used as adsorbent but nanomaterials have been reported more effective. However, some of these materials are toxic, difficult to separate after adsorption, and ineffective in the presence of water constraints. Iron oxides and its modified forms overcome all these shortcomings. Arsenic adsorption using various types of iron oxides has been surveyed and their sorption efficiencies have been compared herein. The effect of presence of other competitive ions in water has also been discussed. The valuable literature available on arsenic remediation, latest advancement, implementation of iron oxides in filters, and future perspective along with safe disposal of sludge produced have been incorporated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel magnetic LLP@Fe 3 O 4 composite was successfully synthesized and characterized. • LLP@Fe 3 O 4 composite possessed a high surface area and good magnetic separation. • The adsorption capacity for MO was 282.3 mg/g by LLP@Fe 3 O 4 at 298 K. • Electrostatic interaction played an important role in the adsorption mechanism. • The removal rate of MO still reached 78.4% after five cycle regenerations. The goal of this work was to prepare a novel magnetic nanocomposite of Lotus leaf powder@iron oxide (LLP@Fe 3 O 4) to remove Methyl Orange (MO) from a liquid medium. The co-precipitation approach was used to successfully synthesize the LLP@Fe 3 O 4 composite, which was then characterized using FT-IR, XRD, pH PZC , SQUID-VSM, BJH/BET, and FE-SEM/EDX analysis. Batch tests were carried out to investigate the adsorption behaviour and mechanisms. The optimal MO removal efficiency of LLP@Fe 3 O 4 reached up to 94.3% under the optimum reaction conditions (LLP@Fe 3 O 4 dosage = 50 mg/30 mL, stirring speed = 200 rpm, contact period = 120 min, MO initial concentration = 20.8 mg/L, temperature = 298 K, and pH = 5.1). Adsorption isotherms and kinetics were analyzed using Temkin, Freundlich, Langmuir, Dubinin-Radushkevich (D-R), pseudo-second-order (PSO), intra-particle diffusion (IPD), pseudo-first-order (PFO), and Elovich models. Adsorption of MO on LLP@Fe 3 O 4 is best matched to the Langmuir isotherm and PSO kinetic models. The data was analyzed utilizing four errors (SSE, ARE, RMSE, and χ2) and regression coefficient functions to estimate the best-fitting kinetic and isotherm models. The maximal monolayer adsorption uptake of MO was estimated to be 282.3 mg/g at 298 K. The thermodynamic variables, namely entropy (Δ So = -98 J/mol K), enthalpy (Δ Ho = -35.6 kJ/mol), and Gibbs free energy (Δ Go = -6.2808 kJ/mol at 298 K), indicated that the adsorption of MO onto LLP@Fe 3 O 4 was spontaneous, exothermic, and feasible. The LLP@Fe 3 O 4 composite may be regenerated and readily separated from the liquid medium without losing any weight. After regeneration, the LLP@Fe 3 O 4 still has good adsorption efficiency for up to five cycles of adsorption and desorption. The experimental findings of this study output could be confirmed that LLP@Fe 3 O 4 is a potential adsorbent to remove dyestuff from wastewater. [ABSTRACT FROM AUTHOR]

Se is an essential nutrient at trace levels, but also a toxic environmental contaminant at higher concentrations. The mobility of the trace element Se in natural environments is mainly controlled by the occurrence of the highly soluble Se oxyanions – selenite [Se(IV)] and selenate [Se(VI)] - and their interaction with geological materials. Since iron oxides are ubiquitous in nature, many previous studies investigated Se retention by adsorption onto iron oxides. However, little is known about the retention of Se oxyanions during the formation process of iron oxides. In this paper, we therefore studied the immobilization of Se oxyanions during the crystallization of hematite from ferrihydrite. In coprecipitation studies, hematite was synthesized by the precipitation and aging of ferrihydrite in an oxidized Se(IV)- or Se(VI)-containing system (pH 7.5). Hydrochemical data of these batch experiments revealed the complete uptake of all available Se(IV) up to initial concentrations of c(Se) 0 = 10 −3 mol/L ( m / V ratio = 9.0 g/L), while the retention of Se(VI) was low (max. 15% of c(Se) 0 ). In case of high initial Se(IV) concentrations, the results also demonstrated that the interaction of Se with ferrihydrite can affect the type of the final transformation product. Comparative adsorption studies, performed at identical conditions, allowed a distinction between pure adsorption and coprecipitation and showed a significantly higher Se retention by coprecipitation than by adsorption. Desorption studies indicated that Se coprecipitation leads to the occurrence of a resistant, non-desorbable Se fraction. According to time-resolved studies of Se(IV) or Se(VI) retention during the hematite formation and detailed spectroscopic analyses (XPS, XAS), this fraction is the result of an incorporation process, which is not attributable to Fe-for-Se substitution or the Se occupation of vacancies. Se initially adsorbs to the ferrihydrite surface, but after the transformation of ferrihydrite into hematite, it is mostly incorporated by hematite. In systems without mineral transformation, however, Se remains as a sorption complex. In case of Se(VI), an outer-sphere complex forms, while Se(IV) forms a mixture of bidentate mononuclear edge-sharing and bidentate binuclear corner-sharing inner-sphere complexes. The results of this study demonstrate that incorporation of Se oxyanions by hematite is an important retention mechanism in addition to pure adsorption, which may affect the migration and immobilization of Se oxyanions in natural systems or polluted environments. [ABSTRACT FROM AUTHOR]

To remove cesium ions from water and soil, a novel adsorbent was synthesized by following a one-step co-precipitation method and using non-toxic raw materials. By combining ammonium-pillared montmorillonite (MMT) and magnetic nanoparticles (Fe 3 O 4 ), an MMT/Fe 3 O 4 composite was prepared and characterized. The adsorbent exhibited high selectivity of Cs + and could be rapidly separated from the mixed solution under an external magnetic field. Above all, the adsorbent had high removal efficiency in cesium-contaminated samples (water and soil) and also showed good recycling performance, indicating that the MMT/Fe 3 O 4 composite could be widely applied to the remediation of cesium-contaminated environments. It was observed that the pH, solid/liquid ratio and initial concentration affected adsorption capacity. In the presence of coexisting ions, the adsorption capacity decreased in the order of Ca 2 + > Mg 2 + > K + > Na + , which is consistent with our theoretical prediction. The adsorption behavior of this new adsorbent could be expressed by the pseudo-second-order model and Freundlich isotherm. In addition, the adsorption mechanism of Cs + was NH 4 + ion exchange and surface hydroxyl group coordination, with the former being more predominant. [ABSTRACT FROM AUTHOR]

Shut-down or reduced treated water supply of a seawater reverse osmosis (SWRO) plant due to membrane fouling during a red tide event is currently an important issue in regions where red tide frequently occurs. Algal organic matter (AOM) released by algae through metabolic activity is known as a major membrane foulant and the primary cause of the suspension of SWRO plants. In this study, iron oxide was utilized to develop an AOM removal process in seawater since activated carbon and advanced oxidation process (AOP) have limited removal efficiencies due to the high ionic strength of the seawater. Dynamic membrane filtration was applied as an iron oxide application method because additional process is not required for temporary operation during only algal bloom. The results showed that the dissolved organic carbon (DOC) removal efficiencies of the iron oxide were improved at high ionic strength compared to organics removal in fresh water. Although only a partial adsorption rate (below 50%) was achieved using iron oxide, significant reduction of the ultrafiltration (UF) membrane fouling was observed through the continuous operation of dynamic membrane filtration since relatively high molecular weight faction of organics was more readily adsorbed in the oxide surface. Given the continuous lab-scale experimental results and economic aspect, dynamic membrane filtration using powdered iron oxide can be a potential option as an emergency plan during a red tide event. [ABSTRACT FROM AUTHOR]

Spillage of effluents containing high concentration levels of pesticides into water has been considered as one of the serious environmental problems. In this study Fe 3 O 4 /reduced graphene oxide (rGO) nanocomposite has been efficiently utilized for the adsorption of five harmful pesticides namely ametryn, prometryn, simazine, simeton and atrazine in an aqueous medium. Electrostatic interaction between the pesticides and Fe 3 O 4 /rGO nanocomposite was analyzed by the zeta potential analysis, which is strongly related to the adsorption capacity of the adsorbent. The kinetics parameters of adsorption followed the pseudo second-order linear model. The adsorption isotherm studies show that, the maximum adsorption capacity of 54.8 mg g −1 is achieved at pH 5 and it was enhanced in the presence of different ions (Mg 2+ , Ca 2+ , Na + and SO 4 2 ) and maximum (63.7 mg g −1 ) for ametryn adsorption was found in seawater medium. Thermodynamic parameter shows that, the adsorption process is physisorption and spontaneity in nature. The mechanism of the adsorption process was established by the DRIFT spectroscopy analysis. Efficient adsorption (93.61%) of pesticides was observed due to electrostatic, hydrophobic and π–π interactions of composite towards the heterocyclic conjugation of pesticide molecules. Further, Fe 3 O 4 /rGO nanocomposite was easily and rapidly separated from an aqueous medium using the external magnet for reuse and 88.66% adsorption efficiency was observed up to seven cycles. [ABSTRACT FROM AUTHOR]

Iron and chromium modified aluminosilicate microstructure adsorbents (Fe 2 O 3 -MSU-S and CrO 2 -MSU-S) were prepared in order to selectively remove nitrogen compounds from model fuel containing quinoline, carbazole, benzothiophene and dibenzothiophene. The results demonstrated that iron modification can enhance the quinoline and carbazole uptake of MSU-S by 38.8% and 24.5%, respectively. The maximum adsorption capacities of CrO 2 -MSU-S as compared to pristine MSU-S for quinoline and carbazole were improved by 22.4% and 21.1%, respectively. According to the equilibrium results, data fitting for quinoline and carbazole is achieved better by the Freundlich model than Langmuir model for CrO 2 -MSU-S and Fe 2 O 3 -MSU-S. The pseudo-second order model presented the best fitting of adsorption data for all species over each adsorbent compared to the pseudo-first order model. According to the breakthrough order, the adsorptive selectivity for the four adsorbates increases in the order of DBT < BT < carbazole < quinoline. [ABSTRACT FROM AUTHOR]

Properties of boehmite and hematite powders formed under hydrothermal conditions are well known. However, a synergistic effect is expected when the γ-AlOOH/α-Fe 2 O 3 composite powders are obtained under the same conditions. Hence, it should be possible to improve the properties (including adsorption) as compared to these of pure γ-AlOOH and α-Fe 2 O 3 . The γ-AlOOH/α-Fe 2 O 3 composite powders were synthesized by hydrothermal method using metal nitrate solutions and urea as precursors. The influence of the [Al 3+ ]:[Fe 3+ ] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The γ-AlOOH/α-Fe 2 O 3 composite powders had a smaller particle size and showed higher specific surface area and sorption capacity as compared to these of pure γ-AlOOH and α-Fe 2 O 3 . The sample prepared by using a solution with [Al 3+ ]:[Fe 3+ ] = 1 showed the highest specific surface area (98.1 m 2 /g) and adsorption capacity (4.17 mg/g) in the removal of Cr(VI) from aqueous solutions. Sorption experiments showed that the mean free adsorption energy is below 8 kJ/mol for all samples, indicating the adsorption process as the physical in nature and suggesting the possibility of Cr(VI) desorption and adsorbent regeneration. [ABSTRACT FROM AUTHOR]

Hematite (Fe 2 O 3 ) has been identified as the dominant structure of the outermost layer of the passive film formed on iron surfaces in alkaline environment but chloride has been suggested to play a major role in the depassivation of this passive film under the same conditions. Here we study the effects of OH and Cl adsorption as well as co-adsorption at different coverages on the structure of α-Fe 2 O 3 Fe-terminated (0 0 0 1) surface using DFT + U. The adsorption of both OH and Cl alters the structure of the surface, by affecting mostly the positions of the top two layers. The structural change increases with coverage for two adsorbates on a (1 × 1) surface and the study on a larger (2 × 2) surface shows that the effects are localized. The large effect of the OH and co-adsorption of OH and Cl on the surface suggests that OH could play an important role in the Cl-induced depassivation process. [ABSTRACT FROM AUTHOR]

Magnetisation of carbonaceous adsorbent using iron oxide (Fe x O y ) has potential to decrease the recovery cost of spent adsorbent because it could be separated magnetically. However, formation of various phases of Fe x O y and iron hydroxide (Fe x (OH) y ) during synthesis particularly the non-magnetic phases are difficult to control and could significantly reduce the magnetic saturation of the adsorbent. Hence, formation of the most magnetic Fe x O y , Fe 3 O 4, on biochar via oxidative hydrolysis of FeCl 2 under alkaline media was performed to synthesise magnetic adsorbent using pine sawdust biochar (magnetic pine sawdust biochar: MPSB). The Fe 3 O 4 nanoparticles on the surface of biochar contributed to high saturation magnetisation of MPSB, 47.8 A m 2 /kg, enabling it to be separated from aqueous solution using a magnet. MPSB were examined physically and chemically using various techniques. Sorbent-stability, parametric, kinetics, isotherm, thermodynamic and sorbent-regeneration studies were performed to comprehend the potential of MPSB as adsorbent to remove an emerging contaminant, sulfamethoxazole (SMX) from aqueous solution. Results showed that MPSB was stable within solution pH 4–9. Adsorption of SMX onto MPSB was favourable at low pH, fast and best described by Redlich-Peterson model. Adsorption was exothermic with physisorption possibly due to hydrophobic interaction and spent adsorbent could be regenerated by organic solvents. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is a naturally-occurring trace element in drinking water. Most commonly, molybdate anions (MoO 4 2-) are in well water and breast milk. In addition, it is used in medical image testing. Recently, the EPA classified Mo as a potential contaminant, as exposure can lead to health effects such as gout, hyperuricemia, and even lung cancer. We have assessed the sorptive removal of aqueous molybdate using Douglas fir biochar (DFBC) and a hybrid DFBC/Fe 3 O 4 composite containing chemically-coprecipitated iron oxide (Fe 3 O 4). Adsorption was studied at various: pH values, equilibrium times (5 min-24 h), initial Mo concentrations (2.5–1000 mg/L), and temperatures (5, 25, and 40 °C) using batch sorption and fixed-bed column equilibrium methods. Langmuir capacities for DFBC and DFBC/Fe 3 O 4 (at pH 3, 2 hrs equilibrium) were within 459.3–487.9 mg/g and 288–572 mg/g, respectively. These adsorbents and their Mo-laden counterparts were characterized by elemental analysis, BET, PZC, SEM, TEM, EDS, XRD, and XPS. MoO 4 2- adsorption on DFBC is thought to be governed primarily via electrostatic attraction. Adsorption by DFBC/Fe 3 O 4 is primarily governed by chemisorption onto magnetite surface hydroxyl groups, while electrostatics prevail in the DFBC-exposed phase. Stoichiometric precipitation of iron molybdates triggered by iron dissolution was also considered. The data suggest that DFBC and DFBC/Fe 3 O 4 are promising candidates for molybdate sorption. [Display omitted] • Douglas fir biochar and its iron oxide analogue removed ∼500 mg/g aqueous molybdate. • Adsorption from anion mixtures and complex natural water was robust. • Fixed-bed column capacity for iron oxide/biochar was ∼19 mg/g. • Uptake was governed by chemisorption, hydrogen bonding and preciptiation. [ABSTRACT FROM AUTHOR]

In the current work, granular activated carbon (GAC) materials doped with 5 and 10 wt% of Fe were prepared via incipient wetness impregnation method utilizing two different solvents (water and ethanol) and calcined in N 2 and static air atmosphere. The prepared materials were thoroughly characterized by FE-SEM, EDS, XRD, FT-IR, XPS and BET surface area techniques. The Fe doped materials were examined for adsorptive removal of lead (Pb2+) ions from aqueous solution. According to the adsorption screening experiments, the 5 wt% Fe doped GAC impregnated in ethanol and calcined under nitrogen demonstrated the highest removal of Pb2+ ions (86.6%). The adsorption results were found consistent with the surface and porous properties of the doped GAC. The 5 wt% Fe-GAC/ethanol/nitrogen illustrated the maximum surface area (715 m2/g), the largest pore diameter and volume, and the lowest size of Fe nanoparticles. The adsorption kinetics, isotherm and thermodynamics were evaluated for the remediation of Pb2+ ions by the optimized adsorbent. The kinetic analysis outcomes found well matched with the pseudo-second order model while the isotherm results modelling were well correlated with Redlich-Peterson, Sips and Langmuir models. The Langmuir highest adsorption capacity of Pb2+ ions was 124.3 mg/g at pH 4.7 and room temperature. The process of Pb2+ ions removal by Fe modified GAC was found as endothermic and spontaneous process as confirmed by the analysis of thermodynamic adsorption parameters. It was anticipated that both chemical and physical mechanisms were participated in the adsorption process including electrostatic interactions, complexation, ion exchange and surface adsorption. [Display omitted] • The 5 wt% and 10 wt% Fe doped granular activated carbon were calcinated under static air and N 2 atmosphere. • Detailed Fe doped GAC adsorbent characterization and adsorption studies. • The 5 wt% Fe/GAC (ethanol/N 2) demonstrated the maximum Langmuir Pb2+ adsorption capacity of 124.3 mg/g. • Kinetics were pseudo-second order, rate dependent on the number of surface sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The preparation of multifunctional clay graphene oxide iron oxide nanocomposite was reported. • They prepared nanocomposite showed excellent methyl blue removal efficiency from wastewater. Multifunctional clay graphene oxide iron oxide nanocomposite was prepared for exploring the multiple applications by using single composite. Activated MM clay (local clay "Multani Matti") and graphene oxide (16 and 5%) were mixed gradually to already prepared Fe 2 O 3 nanoparticles followed by annealing at 550 °C to get the fine structured nanocomposite. Clay graphene oxide iron oxide nanocomposite structure was revealed to be face centered cubic with the average particle size of 13.31 nm. The JCPDS data card # (00–013-0458), (00–039-1894) and (00–001-0646) were used to confirm the XRD peaks of synthesized nanocomposite. The prepared nanocomposite showed colorimetric detection of ascorbic acid using paper sensor when treated with uric acid and ascorbic acid respectively. Antibacterial results confirmed the biologically active nature of synthesized material. The photo-luminescence peaks at higher absorption range correlate the minimum efficiency of photocatalytic application than that of adsorption. The adsorption and photocatalytic degradation of organic dyes are main perspectives observed for synthesized Clay/GO/Fe 2 O 3 nanomaterial. BET result shows a higher surface area confirming the capability of Clay/GO/Fe 2 O 3 nanomaterial an improved adsorbent material for removal of toxic dyes even in lower concentration. The nanocomposite showed capability of all the parameters of adsorption studies in terms of effect of contact time, initial dye concentration, adsorbent dosage, pH and temperature by removing methylene blue (MB). Results showed that adsorption of MB followed second order kinetic model. The improved performance of the nanocomposite compared to single phase materials proved to be an appealing contender being used as an efficient adsorbent which could replace conventional and multiple methods for treatment of waste waters as well. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic biochar derived brown algae were produced by pyrolysis. • Fe-BAB exhibited high Cu (II) adsorption capacity (105.3 mg g−1). • Multi-adsorption mechanisms were responsible for Cu adsorption on Fe-BAB. • The Fe-BAB can be gathered by a magnet and recycled for several uses. In this study, the brown algae Sargassum Hemiphyllum was used as a carbon source for synthesis of magnetic porous biochar via pyrolyzing at high temperature and and doping iron oxide particles (Fe-BAB). Cu (II) species were removed from aqueous solutions using Fe-BAB under various conditions. Fe-BAB demonstrated superior Cu (II) adsorption (105.3 mg g−1) compared to other biochars. On the surface of Fe-BAB, there are several oxygen-containing functional groups, such as –COOH and –OH, which are likely responsible for the excellent heavy metal removal performance. By utilizing magnet, the Fe-BAB can be conveniently separated from the solution and ready for further usage. Multi-adsorption mechanisms were responsible for Cu adsorption on Fe-BAB. Using the magnetic algal biochar for heavy metal removal is feasible due to its high adsorption efficiency and simplicity of separation. [ABSTRACT FROM AUTHOR]

Thermal oxidation of iron foil was done at 400 °C and 500 °C in for 2 h to form multilayered oxide scale with outer oxide layer of α-Fe 2 O 3 comprising of nanowires and nanosheets respectively. Iron oxidized at 300 °C formed a rather compact film with no noticeable nanostructures. The morphologies of oxide formed in different oxidation environment (water vapour or dry air) were compared; densely packed nanostructures were produced in water vapour compared to dry air. Time variation study indicated rapid growth of nanostructure whereby for 1 min at 500 °C dense nanowires with some noticeable nanosheets were already observed. The nanowires and nanosheets were used to adsorb Cr(VI) from aqueous solution. Adsorption of 10 ppm of Cr(VI) on the nanowires and nanosheets was found to be successful with much faster removal efficiency for the nanosheets. Both samples displayed complete adsorption for less than 1 h. [ABSTRACT FROM AUTHOR]

Aminodextran (AMD) polymer was prepared via chemical grafting of hexamethylenediamine on oxidized dextran. Magnetic latex particles were successfully obtained by adsorption of positively charged AMD on negatively charged submicron magnetic emulsion. The adsorbed amount was found to be ranged from 20 to 1280 mg of AMD per gram of dried magnetic dispersion. The AMD-coated magnetic emulsions were characterized by positive zeta potential in the pH range from 3 to 9 compared to bare seed magnetic emulsion. All the samples showed to be superparamagnetic property, even after the adsorption of the polymer. The developed magnetic submicron particles exhibited good potential for in vivo biomedical diagnosis applications as demonstrated by their higher T 2 contrast‐ability compared to Gd in magnetic resonance imaging (MRI) and hyperthermia. [ABSTRACT FROM AUTHOR]

Composite porous silica-iron oxide nanoparticles with the ability to store chemical payloads and release them upon triggering a radiofrequency field were prepared. The particle structure consisted of a hollow porous silica core, covered with a layer of iron oxide nanoparticles bound to the silica surface by electrostatic forces. The particle size distribution, morphology, porosity and stability was systematically studied together with their sorption capacity and heating properties under the effect of a radiofrequency magnetic field. It was observed that the particles are able to achieve a heat dissipation rate of nearly 200 W/g, which was high enough for using the radiofrequency field as a trigger mechanism for the remote release (desorption) of a chemical payload from the particles. [ABSTRACT FROM AUTHOR]

Nano metal oxides are of interest for aqueous selenium (Se) remediation, and as such, nano-hematite (nα-Fe 2 O 3 ) was examined for use as a Se adsorbent. The effect of surface area on adsorption was also studied. nα-Fe 2 O 3 particles were synthesized from Fe(NO 3 ) 3 and FeCl 3 via forced hydrolysis. The resulting particles have similar sizes, morphologies, aggregate size, pore size, and PZC. The nα-Fe 2 O 3 from FeCl 3 (nα-Fe 2 O 3 -C) differs from the nα-Fe 2 O 3 from Fe(NO 3 ) 3 (nα-Fe 2 O 3 -N) with a ∼25 ± 2 m 2 /g greater surface area. Selenite Se(IV) adsorption capacity on nα-Fe 2 O 3 has a q max ∼17 mg/g for the freeze-dried and re-suspended nα-Fe 2 O 3 . The Δ q max for nα-Fe 2 O 3 from Fe(NO 3 ) 3 and FeCl 3 that remained in suspension was 4.6 mg/g. For selenate Se(VI), the freeze-dried and re-suspended particles realize a Δ q max = 1.5 mg/g for nα-Fe 2 O 3 from Fe(NO 3 ) 3 and FeCl 3 . The nα-Fe 2 O 3 from Fe(NO 3 ) 3 and FeCl 3 that remained in suspension demonstrated Se(VI) Δ q max = 5.4 mg/g. In situ ATR–FTIR isotherm measurements completed for Se(VI) at a pH 6 suggest that Se(VI) forms primarily outer–sphere complexes with nα-Fe 2 O 3 synthesized from both salts. [ABSTRACT FROM AUTHOR]

In this work, iron oxide nanosheets (NSs) and nanowires (NWs) were fabricated by thermal oxidation of iron foils at 500 and 800 °C in the presence of water vapour. Oxidation resulted in multi-scale oxide with the surface oxide comprising of α-Fe 2 O 3 and inner oxide comprising of mostly Fe 3 O 4 . The mechanism of formation is discussed to be based on stress-driven mechanism and diffusion paths of iron ions. It was found that the NSs formed could adsorb 112 mg/L aqueous Cr(VI) and the NWs could adsorb 200 mg/L of Cr(VI). It is suggested that the Cr(VI) removal by the iron oxide NSs/NWs due to the electrostatic reaction between the adsorbent and adsorbate. [ABSTRACT FROM AUTHOR]

Recently, magnetic adsorbents have aroused a significant attention because of their excellent adsorption capacity. An Algerian palygorskite/magnetic iron oxide was prepared by chemical co-precipitation and characterized using infrared spectroscopy, X-ray diffraction and X-ray fluorescence. The results prove the formation of a red brick powder, with magnetic character, showing a high percentage of iron oxide on palygorskite. To verify the ability of the magnetic palygorskite for retaining organic pollutants, three different samples were evaluated for the adsorption of the fungicide fenarimol from aqueous samples: sifted palygorskite, purified palygorskite and Fe 2 O 3 /palygorskite. The effects of different variables were assessed: adsorbent mass, reaction time, initial pesticide concentration and desorption stability. Fenarimol adsorption kinetics followed a pseudo-second order model. The adsorption rates were 11%, 50% and 70%, for sifted, purified and Fe 2 O 3 /palygorskite, respectively. Both Langmuir and Freundlich models could be used to describe fenarimol adsorption on sifted and purified palygorskites. However only the Freundlich model could fit the adsorption data on Fe 2 O 3 /palygorskite, probably due to the adsorbent heterogeneity. Stability of fenarimol desorption from the three samples, where the fungicide had been previously preadsorbed, showed that the extent of desorbed fenarimol from Fe 2 O 3 /palygorskite remained constant along the studied period (15 days). [ABSTRACT FROM AUTHOR]

Rectorite-TiO2-Fe3O4 (RTF) composites were assembled by orderly depositing anatase TiO2 and magnetic Fe3O4 nanoparticles on rectorite (REC) surfaces. Rectorite-TiO2 (RT) and RTF composites were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). TiO2 particles partially exfoliated the REC layers, while Fe3O4 particles completely exfoliated the REC sheets. Fe3O4 particles was absorbed by REC and consequently appeared on its surface instead of being on the TiO2 particles. RTF can be easily separated from aqueous solution by magnet. The adsorption and photodegradation of methylene blue (MB) by RT and RTF were also investigated. The kinetic adsorption fit the pseudo-second-order model and the isotherm data followed the Langmuir model. The maximum adsorption capacities for MB were 187.61 and 169.20 mg/g for RT and RTF, respectively. RTF exhibited a good capability for removal of MB from aqueous solution, and about 95% MB was removed after 12 h UV-light irradiation, and about 75% MB removal for RT. And RTF exhibited the similar photocatalytic activity with RT for the persistent organic pollutant 4-nitrophenol (4-NP) under UV irradiation. [ABSTRACT FROM AUTHOR]

Adsorption onto iron oxide and bacterial surfaces can affect the fate of many dissolved ions, but currently there is a poor understanding of ion adsorption onto mixtures of these two sorbents. This study used chemical analyses of the aqueous and solid phases and electron microscopy to observe the adsorption of dissolved selenate (SeO 4 2 − ) onto composites of iron oxide and Escherichia coli during the addition, oxidation, hydrolysis of Fe(II) aq and precipitation of Fe(III)-oxide. No SeO 4 2 − adsorption onto E. coli was observed under the conditions of this study ([SeO 4 ] total = 3 ppm, biomass concentration 0.11–0.44 dry g/l, ionic strength = 0.01 M, pH 3–8, reaction time 0–24 h). SeO 4 2 − adsorption onto abiotic and biotic iron oxides decreased with time which was attributed to blockage of iron oxide surface sites by other mineral particles. Adsorption onto bacteria–iron oxide composites was significantly reduced compared to the end-member systems. Surface complexation models (SCMs) were developed to fit the experimental data and suggested that the reduction in SeO 4 2 − sorption by the composites was due to masking of iron oxide surface sites by both bacteria and other iron oxides and also via interactions with the bacterial supernatant. This study has shown that SeO 4 2 − adsorption in bacteria-bearing systems cannot be evaluated without considering redox processes like Fe(II) aq oxidation, hydrolysis and precipitation. [ABSTRACT FROM AUTHOR]

Iron oxides with different flower-like nanostructures have been successfully synthesized by decomposition of the iron alkoxide precursor at different conditions. The effect of reaction time (reflux time) and the calcination conditions on the morphology and composition of prepared iron oxides were investigated. Characterizations of the prepared powders were performed by scanning electronic microscopy, X-ray diffraction and N 2 adsorption/desorption isotherm. The results show that the prepared nanostructured iron oxides can be used as adsorbent for rapid removal of dye pollutants from water. [ABSTRACT FROM AUTHOR]

In this study, rice husks were charred at 550°C in a partially sealed ceramic vessel for 30minutes to create a high specific surface area (SSA) rice husk char (RHC). The RHC was then amended with iron oxides using dissolved ferric nitrate, Fe(NO3)3 ⋅ 9H2O, to provide a surface chemistry conducive to arsenic adsorption. The 550°C iron oxide amended rice husk char’s (550 IOA-RHC’s) SSA was nearly 2.5 orders of magnitude higher and the arsenate adsorptive level was nearly 2 orders of magnitude higher than those reported for iron oxide amended sand, thus indicating a positive relationship between post-amendment SSA and arsenate adsorptive levels. Rice husks were then charred at temperatures ranging from 450°C to 1050°C to create an even higher SSA material, which might further increase arsenate adsorptive levels. The 950°C RHC was chosen for amendment due to its high SSA and feasibility of being produced in the field. Once amended, the 950°C iron oxide amended rice husk char (950 IOA-RHC) improved the arsenate adsorption capacity by thus confirming a positive relationship, though not a linear relationship, between post-amendment SSA and arsenic adsorptive capacity. Further study demonstrated that post-amendment mesoporous volume and mesoporous surface area appear to be better indicators of arsenic adsorptive capacity than SSA or iron content. [ABSTRACT FROM AUTHOR]

Highlights: [•] Porous iron oxide nanoparticles were deposited on AC by microwave radiation. [•] Uniform deposition with high loadings was obtained within very short time. [•] 20.27% of iron loading was obtained in 9min. of microwave hydrothermal synthesis. [•] High As(V) uptakes were obtained in the range of pH 6.0–8.0. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel zeolite/Fe2O3 composite material was prepared from coal fly ash. [•] The new composite material showed a neutral pH value of 6.60. [•] The new composite material had a high affinity for phosphate and ammonium. [•] The new material can be used to simultaneously retain cationic and anionic pollutants. [•] Synthesis of the composite material yielded rather cleaner effluent. [Copyright &y& Elsevier]

• The adsorption mechanism of monolayer graphene and graphene oxide on the surface of iron oxide was studied by DFT calculations. • The presence of functional groups (hydroxyl and epoxy group) is beneficial for the enhancement of interfacial interaction of GO layer with iron oxide surface. • The enhancement of interfacial interaction has a strong correlation with the adsorption sites of functional groups. Density functional theory (DFT) calculations are performed to explore the effect of functional groups (hydroxyl and epoxy groups) on the interfacial interaction of graphene oxide (GO) with iron oxide (Fe 2 O 3) substrate. The calculation results indicate that the adsorbed functional groups can improve the interaction strength between GO and Fe 2 O 3 substrate, and the magnitude of binding energy enhancement is associate with the adsorption sites of functional groups. For the GO/Fe 2 O 3 -O models with a neighboring C atom of the oxidized atom at the top of a surface O atom, the binding energy is significantly enhanced, which arises from the formation of interfacial C−O covalent bonds. Moreover, the maximum binding energy of GO/Fe 2 O 3 -O model is more than four times that of Gr/Fe 2 O 3 -O model. For the other GO/Fe 2 O 3 -O and GO/Fe 2 O 3 -Fe models studied in this work, the GO layer is physisorption on Fe 2 O 3 surface and the binding energy enhances slightly. This study contributes to a deeper understanding of the protection properties of graphene-based coating materials on iron oxide surface. [Display omitted] [ABSTRACT FROM AUTHOR]

We prepared two-dimensional (2D) stack-structured magnetic iron oxide (Fe 3 O 4) nanoparticle anchored titanium carbide (Ti 3 C 2 T x) MXene material (Ti 3 C 2 T x /Fe 3 O 4). It was used as a potential adsorbent to remove carcinogenic cationic dyes, such as methylene blue (MB) and rhodamine B (Rh B), from aqueous solutions. Ti 3 C 2 T x /Fe 3 O 4 exhibited maximum adsorption capacities of 153 and 86 mg g−1 for MB and Rh B dyes, respectively. Batch adsorption experimental data fits the Langmuir model well, revealing monolayer adsorption of MB and Rh B onto the adsorption sites of Ti 3 C 2 T x /Fe 3 O 4. Additionally, Ti 3 C 2 T x /Fe 3 O 4 showed rapid MB/Rh B adsorption kinetics and attained equilibrium within 45 min. Moreover, Ti 3 C 2 T x /Fe 3 O 4 demonstrated recyclability over four cycles with high stability due to the presence of magnetic Fe 3 O 4 nanoparticles. Furthermore, it exhibited remarkable selectivities of 91% and 88% in the presence of co-existing cationic and anionic dyes, respectively. Given the extraordinary adsorption capacities, Ti 3 C 2 T x /Fe 3 O 4 may be a promising material for the effective removal of cationic dyes from aqueous media. [Display omitted] • Magnetic 2D MXene material towards multiple cationic dye sequestration. • Unprecedented MB and Rh B adsorption capacities of 153 and 86 mg g−1, respectively. • Presence of Fe 3 O 4 provides excellent regeneration capability with high stability. • High selectivities of 91 % and 88 % for MB and Rh B, respectively, with rapid kinetics. • MB and Rh B removal via electrostatic attraction and hydrogen bonding with MXene. [ABSTRACT FROM AUTHOR]

Highlights: [•] One kind of porous biomorph-genetic composite of α-Fe2O3/Fe3O4/C was prepared. [•] The material retained the hierarchical porous structure of eucalyptus wood. [•] The material has three different pore sizes of 50–120, 4.1–6.4 and 0.1–1.3μm. [•] The pseudo-second-order equation and Freundlich isotherm generated the best fit. [•] The adsorption capacity for P(V) is comparable to nanoparticles of iron oxides. [ABSTRACT FROM AUTHOR]

Abstract: Spheres containing iron oxide and/or aluminum oxide were tested in the phosphate adsorption, in order to contribute with the studies of this process. These samples were characterized by ICP-OES, SEM, XRD, Mössbauer Spectroscopy and Zeta potential. It was observed that it is necessary to prepare a sphere with a large specific surface area and relatively high iron content to obtain high phosphate adsorption capacity. Among the adsorbents tested (100Al, 10FeAl, 30FeAl, 50FeAl and 100Fe) under the same experimental condition, the solid 50FeAl showed the best adsorption capacity (61.5mg of per gram of absorbent in pH 3) with the best value of Fe/Al molar ratio. Therefore, the results confirm that the iron oxide is the major site of adsorption, while the aluminum oxide plays a secondary role during the adsorption of phosphate ions. [Copyright &y& Elsevier]

Abstract: The Pepper Mild Mottle Virus (PMMoV) is a soil-borne virus that causes the mosaic disease to Capsicum ssp. This virus disease had been controlled by soil fumigation using methyl bromide, but the method was banned in 2005. Therefore, a new management and control technology that replaces methyl bromide is required. In the present study, the adsorption of PMMoV by soils that is considered to be one of the most important factors of the virus inactivation was examined. We used eight soil samples with different types of clay compositions and humus contents for the PMMoV adsorption experiments at three different pH levels (pH 4, 5 and 7). Large amounts of PMMoV particles were adsorbed by the soil samples with a low humus content at the low pH. This was attributed to the increase in the positive charges of the soil samples. On the other hand, low virus adsorptions were observed at the pH levels in the soils with a high organic matter content. There were close negative correlations (P <0.05) between the PMMoV adsorption by the soils and the humus content of the soil samples. We considered that the inhibitory effect of humus against the virus adsorption is rather important in most soils in Japan. [Copyright &y& Elsevier]