Synthesis of micro-size magnetic polymer adsorbent and its application for the removal of Cu(II) ion

Novel chitosan and Laponite based nanocomposite for fast removal of Cd(II), methylene blue and Congo red from aqueous solution

A series of chitosan and Laponite based nano-composite adsorbents, which showed an excellent performance for fast and efficient removal of Cd(II), methylene blue (MB) and Congo red (CR) from aqueous solution, were prepared. In the adsorbent, with the increase of Laponite component, the surface area increased from 44.69 m2 g-1 to 64.58 m2 g-1. As a result, the adsorption rates were enhanced by increasing Laponite component. The adsorption capacities for Cd(II) and MB increased with increasing Laponite component due the cationic characteristic of two pollutants, and the opposite result was found for the removal of CR. The impacts of some factors, e.g. solution pH, temperature, pollutant concentration and salt, on the adsorption capacity were investigated. Additionally, this adsorbent could be effectively regenerated by dilute HCl solution after the adsorption of Cd(II), and the mixture of methanol and acetic acid was a suitable eluent after the adsorption of two dyes.

Bacterial magnetosome and its potential application

Bacterial magnetosome, synthetized by magnetosome-producing microorganisms including magnetotactic bacteria (MTB) and some non-magnetotactic bacteria (Non-MTB), is a new type of material comprising magnetic nanocrystals surrounded by a phospholipid bilayer. Because of the special properties such as single magnetic domain, excellent biocompatibility and surface modification, bacterial magnetosome has become an increasingly attractive for researchers in biology, medicine, paleomagnetism, geology and environmental science. This review briefly describes the general feature of magnetosome-producing microorganisms. This article also highlights recent advances in the understanding of the biochemical and magnetic characteristics of bacterial magnetosome, as well as the magnetosome formation mechanism including iron ions uptake, magnetosome membrane formation, biomineralization and magnetosome chain assembly. Finally, this review presents the potential applications of bacterial magnetosome in biomedicine, wastewater treatment, and the significance of mineralization of magnetosome in biology and geology.

Learning from magnetotactic bacteria: A review on the synthesis of biomimetic nanoparticles mediated by magnetosome-associated proteins

Much interest has gained the biomineralization process carried out by magnetotactic bacteria. These bacteria are ubiquitous in natural environments and share the ability to passively align along the magnetic field lines and actively swim along them. This ability is due to their magnetosome chain, each magnetosome consisting on a magnetic crystal enveloped by a lipid bilayer membrane to which very unique proteins are associated. Magnetotactic bacteria exquisitely control magnetosome formation, making the magnetosomes the ideal magnetic nanoparticle of potential use in many technological applications. The difficulty to scale up magnetosome production has triggered the research on the in vitro production of biomimetic (magnetosome-like) magnetite nanoparticles. In this context, magnetosome proteins are being used to mediate such in vitro magnetite precipitation experiments. The present work reviews the knowledgement on the magnetosome proteins thought to have a role on the in vivo formation of magnetite crystals in the magnetosome, and the recombinant magnetosome proteins used in vitro to form biomimetic magnetite. It also summarizes the data provided in the literature on the biomimetic magnetite nanoparticles obtained from those in vitro experiments.

Fe3O4–PVAc nanocomposites: surface modification of sonochemically prepared magnetite nanoparticles via chemical grafting of poly(vinyl acetate)

In the present study, magnetite nanoparticles (MNPs) were synthesized at room temperature under ultrasonic irradiation.

Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe₃O₄ (M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g⁻¹ with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH₀) of solution to 5, (2) no adjustment of pH₀ with value in 6.04–6.64, and (3) adjusted pH₀ = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g⁻¹, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol⁻¹, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: kinetic, isotherm and thermodynamic studies

Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)-vinylphenyl boronic acid(VPBA)) [m-poly(EG-VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG-VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG-VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG-VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin-Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG-VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic parameters (free energy change, ΔG(0) enthalpy change, ΔH(0); and entropy change, ΔS(0)) for the adsorption have been evaluated.

Polyvinyl alcohol/polysaccharide hydrogel graft materials for arsenic and heavy metal removal

Polyvinyl alcohol/polysaccharide hydrogel formation ((A)–(C)) and metallic species adsorption ((D)) for water treatment.

Mechanochemical surface functionalisation of superparamagnetic microparticles with in situ formed crystalline metal-complexes: a fast novel core–shell particle formation method

An innovative mechanochemical method is reported for the in situ formation of crystalline metal-complexes on the surface of superparamagnetic nanocomposite microparticles.

Magnetic adsorbents based on micro- and nano-structured materials

Micro- and nano-sized magnetic adsorbents based on elemental metals, iron oxides, and ferrites and supported by inorganic (carbon, graphene, silica, and zeolites) or organic (macromolecules, polysaccharides, and biomolecules) compounds are reviewed.

Synthesis of Ce3+ doped ZnFe2O4 self-assembled clusters and adsorption of chromium(VI)

A solvothermal synthetic route was used to prepare Ce(3+) doped Zn ferrites, where sphere-like clusters aggregated by nanosized particles were fabricated. The size of the cluster and the saturation magnetization of the sample are decreasing with the increase of Ce(3+). These samples can be easily separated from aqueous solutions by applying a magnetic field and have a high loading capacity of Cr(VI). The Cr(VI) adsorption experiments indicated that the adsorption was divided into two processes, in which the first one took place about 6h, the second one took place between 6 and 96 h. The maximum adsorption capacity for Cr(VI) was determined to be 57.24 mg/g. Langmuir model was employed to fit the adsorption isotherm, which implied the single layer adsorption. The data of SBET, external area and porous area of the samples can be used to explain these adsorption processes. And the Ce(3+) ions doped in the sample induced the increasing adsorption capacity of Cr(VI). The adsorption process can be described by the pseudo-second-order kinetic model.

Modified superparamagnetic nanocomposite microparticles for highly selective Hg(II) or Cu(II) separation and recovery from aqueous solutions

The synthesis of a reusable, magnetically switchable nanocomposite microparticle, which can be modified to selectively extract and recover Hg(II) or Cu(II) from water, is reported. Superparamagnetic iron oxide (magnetite) nanoparticles act as the magnetic component in this system, and these nanoparticles were synthesized in a continuous way, allowing their large-scale production. A new process was used to create a silica matrix, confining the magnetite nanoparticles using a cheap silica source [sodium silicate (water glass)]. This results in a well-defined, filigree micrometer-sized nanocomposite via a fast, simple, inexpensive, and upscalable process. Hence, because of the ideal size of the resulting microparticles and their comparably large magnetization, particle extraction from fluids by low-cost magnets is achieved.

Preparação e caracterização de microesferas poliméricas magnéticas à base de estireno, divinilbenzeno e acetato de vinila

Microesferas poliméricas magnéticas à base de estireno (STY), divinilbenzeno (DVB), acetato de vinila (VAc) e ferro foram preparadas via polimerização em suspensão e semi-suspensão. Foram estudadas as influências da concentração de VAc adicionado na polimerização e da presença de ferro sobre as características das partículas poliméricas. Estas foram caracterizadas por espectroscopia vibracional na região do infravermelho por transformada de Fourier (FT-IR), análise termogravimétrica (TGA/DTGA), microscopia óptica por reflexão (MO), microscopia eletrônica de varredura (SEM) e magnetometria de amostra vibrante (VSM). Foram obtidas com sucesso microesferas poliméricas com propriedades magnéticas à base de estireno, divinilbenzeno e acetato de vinila. Estes materiais apresentaram bom controle morfológico esférico e partículas de ferro aglomeradas por toda a superfície da microesfera. O maior rendimento de microesferas magnéticas foi encontrado na faixa de 288 μm. Apresentaram também boas propriedades magnéticas (22,62 a 73,75 emu.g-1) com comportamento próximo de materiais superparamagnéticos e boa estabilidade térmica (444 °C).

Kinetics and equilibrium of desorption removal of copper from magnetic polymer adsorbent

This study examined the desorption of copper ions, which were adsorbed on the magnetic polymer adsorbent (MPA) of polyvinyl acetate-iminodiacetic acid (M-PVAC-IDA), by ethylenediaminetetraacetic acid (EDTA). Stage-wise desorptions were applied to remove the Cu(II) ions from the Cu(II) adsorbed M-PVAC-IDA (A-M-PVAC-IDA). About seven desorption runs were needed to regenerate the A-M-PVAC-IDA. The Cu(II) desorbed M-PVAC-IDA (D-M-PVAC-IDA) was then reused to adsorb the Cu(II) ions from the Cu(II) ions-containing solution. The cyclic adsorption and desorption operations (CADOs) were performed to further elucidate the kinetics and equilibria of the desorption system of EDTA/A-M-PVAC-IDA and the adsorption system of Cu(II)-containing solution/D-M-PVAC-IDA. Two simple kinetic models, the pseudo-first-order equation and pseudo-second-order equation, were employed to simulate the kinetic behaviors of adsorption and desorption. With respect to the kinetics of adsorption behavior, the simulated results by both kinetic models exhibit good agreement with the experimental data. However, the adsorption capacities (q(e)) estimated by the pseudo-first-order equation are more accurate in comparison with those simulated by the pseudo-second-order equation. As for the desorption kinetics, the examination of correlation coefficients of model fittings of data shows that the pseudo-first-order kinetic model gives the better agreement for the cases with different initial solid-phase concentrations and can accurately compute the equilibrium concentrations of solid-phase. The values of q(e) after CADOs are consistent with the predicted results via the previous work, evidencing that the adsorption behavior and the characteristics of the regenerated adsorbent of D-M-PVAC-IDA were not altered. In the experiments of desorbing copper ions and CADOs, the desorption isotherm was set up. The Freundlich and Langmuir adsorption (or desorption) isotherms were used to simulate the equilibrium of desorption. The results indicate that the Freundlich equation shows better agreement with the experimental data than the Langmuir equation. The information thus obtained is useful for the better use of M-PVAC-IDA on the removal of heavy mental ions of Cu(II) from the Cu(II) ion-containing water solution with the consideration of its regeneration.

Synthesized layered inorganic-organic magnesium organosilicate containing a disulfide moiety as a promising sorbent for cations removal

A new-layered inorganic-organic magnesium organosilicate was synthesized through a single step template sol-gel route under mild conditions, using a new alkoxysilane, containing a 2-aminophenyldisulfide molecule. Elemental analysis data based on the nitrogen atom showed an incorporation of 1.97mmol of organic pendant groups for each gram of the hybrid formed. The X-ray diffraction patterns demonstrated that this nanocompound exhibited lamellar structure, in agreement with that found for natural inorganic silicates. Infrared spectroscopy and nuclear magnetic resonance for the (29)Si nucleus in the solid state are in agreement with the success of the proposed synthetic method. The presence of nitrogen and sulfur basic centers attached to the pendant groups inside the lamellar structure is used as basic centers to coordinate cations from aqueous solution at the solid/liquid interface. The isotherms were fitted to Langmuir and Freundlich models. The maxima adsorption capacities for copper, lead and cadmium, calculated from Langmuir model, were 3.28, 1.42 and 0.35mmol g(-1), respectively. These values are comparable to other adsorbing nanomaterials. This behavior suggested that this new inorganic-organic hybrid could be employed as a promising adsorbent for cation removal from polluted systems.