Many of the current strategies for removing pollutants from water are based on nanomaterials and 18nanotechnology. Lower values of Biological Oxygen Demand (BOD5) and Chemical Oxygen De- 19 mand (COD) in water results in reduction in the amount of oxidizable pollutants. We present a study 20 on the reduction of COD and BOD5in water from Wadi El Bey River (Tunisia), using magnetite na- 21 noparticles (MNPs) and magnetic fields. The COD and BOD5 removal reached values higher than 22 50% after 60 min, with optimum efficiency at pH values of ≈8 and for MNPs concentrations of 1 g/L. 23 The use of a permanent magnetic field (0.33 T) showed an increase of COD and BOD5 removal from 2461% to 76% and from 63% to 78%, respectively. This enhancement is discussed in terms of the MNPs 25coagulation induced by the magnetic field and the adsorption of ionic species onto the MNPs sur- 26face due to Fe3O4 affinity.

The treatment of wastewater containing heavy metals and the utilization of wool waste are very important for the sustainable development of textile mills. In this study, the wool keratin modified magnetite (Fe3O4) powders were fabricated by using wool waste via a co-precipitation technique for removal of Cu2+ ions from aqueous solutions. The morphology, chemical compositions, crystal structure, microstructure, magnetism properties, organic content, and specific surface area of as-fabricated powders were systematically characterized by various techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), thermogravimetric (TG) analysis, and BET surface area analyzer. The effects of experimental parameters such as the volume of wool keratin hydrolysate, the dosage of powder, the initial Cu2+ ion concentration, and the pH value of solution on the adsorption capacity of Cu2+ ions by the powders were examined. The experimental results indicated that the Cu2+ ion adsorption performance of the wool keratin modified Fe3O4 powders exhibited much better than that of the chitosan modified ones with a maximum Cu2+ adsorption capacity of 29.2 mg/g under favorable conditions (0.05 g powders; 50 mL of 40 mg/L CuSO4; pH 5; temperature 293 K). The high adsorption capacity towards Cu2+ ions on the wool keratin modified Fe3O4 powders was primarily because of the strong surface complexation of -COOH and -NH2 functional groups of wool keratins with Cu2+ ions. The Cu2+ ion adsorption process on the wool keratin modified Fe3O4 powders followed the Langmuir adsorption isotherm model and the pseudo-second-order adsorption kinetic model. After Cu2+ ion removal, the wool keratin modified Fe3O4 powders were easily separated using a magnet from aqueous solution and efficiently regenerated using 0.5 M EDTA-H2SO4 eluting. The wool keratin modified Fe3O4 powders possessed good regenerative performance after five cycles. This study provided a feasible way to utilize waste wool textiles for preparing magnetic biomass-based adsorbents for the removal of heavy metal ions from aqueous solutions.

In this work, pure TiO₂ and nano-magnetic of Fe₃O₄/TiO₂ were synthesized for degradation of 2,4-dichlorophenol (2, 4-DCP) as an organic pollutant. A range of analytical techniques including XRD, DRS, FESEM, and VSM were employed to reveal the crystal structure, morphology and property of the nanocomposite. The XRD results showed the prepared samples including 100% anatase phase. We obtained the band gap energy 2.9 and 2.8 eV for pure TiO₂ and Fe₃O₄/TiO₂ respectively. VSM results demonstrate that easy, fast separation and redispersion of Fe₃O₄/TiO₂ sample can be realized. We obtained 62% and 31% degradation of 2,4-DCP in the presence of Fe₃O₄/TiO₂ and pure TiO₂ under visible light respectively.

In this research, first a binary nanocomposite of magnetic recyclable photocatalyst Fe₃O₄/TiO₂, was synthesized by sol gel technique. Then, in order to enhance the photocatalytic activity of the synthesized nanocomposite, it was deposited by silver nanoparticles for using in degradation of organic pollutants 2, 4-dichlorophenol (2, 4-DCP) under visible light. A range of analytical techniques including XRD, FESEM/EDX, DRS, VSM and N₂ physisorption were employed to reveal the crystal structure, morphology and property of the nanocomposites. We obtained 32% and 55% degradation of 2, 4-DCP under visible light after 180 min irradiation in the presence of Fe₃O₄/TiO₂ and Fe₃O₄/TiO₂/Ag respectively. Thus, the excellent visible light photocatalytic activity of Fe₃O₄/TiO₂/Ag sample can be attributed to the surface plasmon resonance effect of Ag nanoparticles deposited on Fe₃O₄/TiO₂ nanocomposite.

A magnetite (CDC@Fe3O4) heterogeneous photocatalyst was synthesized via treated and modified cotton in two steps. The designed nanocomposites were characterized by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesized magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. (CDC@Fe3O4) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe3O4) nanomaterials were also used in a heterogeneous catalytic optimized protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91-97%) at room temperature and under ultrasound irradiation. Generally, a synthesized recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis.

In this work, pure TiO₂ and binary nanocomposites of Fe₃O₄/TiO₂ and Ag/TiO₂ were synthesized in order to improve photocatalytic performance of these samples for degradation of 2, 4-dichlorophenol (2, 4-DCP) as an organic pollutant. A range of analytical techniques including XRD, DRS, SEM/EDX, and elemental mapping were employed to reveal the crystal structure, morphology and property of the nanocomposites. XRD data demonstrated that the prepared samples are purely in TiO₂ anatase phase and cubic spinel Fe₃O₄ exist in the synthesized nanocomposite. We calculated the TiO₂ crystal size from XRD patterns, in the range of 8.35-11.09 nm. The presence of Ag, Fe, O, and Ti atoms in the synthesized nanocomposites was confirmed by SEM/EDX. We obtained 30.43, 32.02 and 42.40 % degradation of 2, 4-DCP (100 ml 2, 4-DCP 40 ppm and 0.01 g catalyst) for pure TiO₂, Fe₃O₄/TiO₂ and Ag/TiO₂, respectively, after 180 min of irradiation under visible light. Similar conditions were employed for 2, 4-DCP degradation under UV irradiation, we obtained 53.05, 51.00 and 71.50 % degradation of 2, 4-DCP pure TiO₂, Fe₃O₄/TiO₂ and Ag/TiO₂, respectively. Thus, the synthesized binary nanocomposites exhibited higher photocatalytic activity compared to pure TiO₂ under visible light.

We report here the synthesis of uniform nanospheres-like silver nanoparticles (AgNPs, 5-10 nm) and the dumbbell-like Fe3O4-Ag hybrid nanoparticles (FeAgNPs, 8-16 nm) by the use of seeding growth method in the presence of oleic acid (OA)/oleylamine (OLA) as surfactants. The antibacterial activity of pure nanoparticles and nanocomposites by monitoring the bacterial lag–log growth has been investigated. The electron transfer from AgNPs to Fe3O4NPs which enhances the biological of silver nanoparticles has been proven by nanoscale Raman spectroscopy. The lamellae structure in the spherulite of FeAgNPs/PE nanocomposites seems play the key role to the antibacterial activity of nanocomposites, which has been proven by nanoscale AFM-IR. An atomic force microscopy coupled with nanoscale infrared microscopy (AFM-IR) is use to highlight the distribution of nanoparticles on the surface of nanocomposite at the nanoscale. The presence of FeAgNPs in PE nanocomposites has a better antibacterial activity than that reinforced by AgNPs due to the faster Ag+ release rate from the Fe3O4-Ag hybrid nanoparticles and the ionization of AgNPs in hybrid nanostructure.

There was a question on “how lanthanides doping in iron oxide affects cure kinetics of epoxy-based nanocomposites?” To answer, we synthesized samarium (Sm)-doped Fe3O4 nanoparticles via electrochemical method and characterized it using FTIR, XRD, FE-SEM, EDX, TEM, and XPS analyses. The magnetic particles were uniformly dispersed in epoxy resin to increase the curability of the epoxy/amine system. The effect of the lanthanide dopant on the curing reaction of epoxy with amine was explored by modeling DSC experimental data based on model-free methodology. It was found that Sm3+ in the structure of Fe3O4 crystal participates in cross-linking of epoxy by catalyzing the reaction between epoxide rings and amine groups of curing agents. In addition, the etherification reaction of active OH groups on the surface of nanoparticles reacts with epoxy rings which prolongs the reaction time at the late stage of reaction where diffusion is the dominant mechanism.

A theoretical analysis of haemoglobin (Hb) concentration detection is presented in this work with the objective of achieving more sensitive detection and monitoring low concentrations. Surface-enhanced SPR spectroscopy on silver nanoparticles was employed for recording Hb concentrations less than 10 g/L. In this paper, Fe₃O₄@Au core-shell, nanocomposite spherical nanoparticle consisting of a spherical Fe₃O₄ core covered by Au shell, was used as an active material for biomolecules detection in the Surface Plasmon Resonance (SPR)-based biosensor in the wavelength 632.8 nm. We present the simulation of detection amplification technique through Attenuated Total Reflection (ATR) spectrum in the Kretschmann configuration. The system consists of a four-layer material i.e prism/Ag/Fe₃O₄@Au+Hb/air. Dielectric function determination of the core-shell nanoparticle (Fe₃O₄@Au) and the composite (Fe₃O₄@Au+Hb) was done by applying the Effective Medium Theory approximation and the calculation of the reflectivity is carried out by varying the size of core-shell (r₀). In this simulation, the refractive index of the BK7 prism is 1.51; the refractive index of Ag thin film is 0.13455+3.98651i with the thickness of 40 nm, and the refractive index of the composite is varied depending on the size of nanoparticle core-shell. Our results show that by varying the radius of the core and the shell thickness, the dip of the reflectivity (ATR) spectrum is shifted to the larger angle of incident light and the addition of core-shell in the conventional SPR-based biosensor leads to enhancement of the SPR biosensor sensitivity, for the core-shell radius 10 nm, the sensitivity increased by 1.35% for F = 0.1, and by 4.89% for F =0.8 compared to the sensitivity of the conventional SPR-based biosensor without core-shell addition.

Iron-based materials are widely applied in Fenton chemistry and they have promising prospects in the processing of wastewater. The composition complexity and rich chemistry of iron and/or oxides, however, hamper the precise understanding on the active sites and the working mechanism which still remain highly controversial. Herein, iron oxides of four different model systems are designed through a conventional precipitation method plus H2 reduction treatment. These systems feature Fe@Fe3O4 with abundant oxygen vacancy, Fe0 and Fe3O4 particles with interface structures, and Fe3O4-dominated nanoparticles of different sizes. These materials are applied in the decomposition of methyl orange as a model reaction to assess the Fenton chemistry. The Fe@Fe3O4 with core-shell structures exhibited significantly higher decomposition activity than the other Fe3O4-rich nanoparticles. A thin Fe3O4 layer formed by auto-oxidation of iron particles when exposing to air can boost the activity as compared with the Fe0 and Fe3O4 particles with interface structures but poor oxygen vacancy. The unique hetero-structure with the co-existence of both metallic iron and oxygen vacancy displayed excellent redox propensity which might account for the superior Fenton activity. This finding provides a new perspective to understand and design highly efficient iron-based Fenton catalysts.

Concern over potential antimony mediated toxicity from mining and smelting activities has instigated novel concepts toward removing aqueous antimony ions. The iron based adsorbent Fe3O4/HCO was found to be efficient for treating antimony-containing wastewater However, ineffective methodology for preparation limited its effective adsorption capacity and thus wider application. In this study, a new type of HCO-doped-(Fe3O4)x adsorbent was prepared by co-precipitation method for doping Fe3O4 into HCO sludge (HCO), thereby improving adsorption performance for Sb(III) and Sb(V) ions, with the maximum adsorbing capacity being 44.46 mg/g and 47.91 mg/g, respectively. According to the results of BET, SEM-EDS, XRD and XPS, it were confirmed that the FeOOH and X≡Fe-OH were formed during the preparation process, bring about the increased the surface area, thus resulting in further increase of surface area, hydroxyl groups and the net negative ionic charge. Moreover, the adsorption kinetics followed the pseudo-second-order kinetic model which indicated that adsorption process of Sb(III)/Sb(V) by HCO-doped-(Fe3O4)x adsorbent was controlled by chemical reaction. The main adsorption mechanism is that antimony ion and amorphous iron oxide X≡Fe-OH undergo coordination exchange reaction and complexation reaction with CeO2 or Ce2O3. Furthermore, HCO-doped-(Fe3O4)x could adapt to wide pH and had stable adsorption ability after regeneration. The good adsorption performance of HCO-doped-(Fe3O4)x makes it a potential applications of adsorbent for removal of antimony.