Magnetic nano- and microparticles for metal removal and environmental applications: a review

International audienceA review. Besides the numerous applications of magnetic particles in the fields of medicine, diagnostics, mol. biol. and bioinorg. chem., a high potential exists for these particles in environmental sciences. Several methods have been proposed these last years for the sepn. of metals from wastewater using either micro- or nano-magnetic particles. We describe here the synthesis of such particles, compare their magnetic properties, and discuss the possibility of selectivity for metals ions, namely radionuclides

Kinetic and regeneration studies of photocatalytic magnetic separable beads for chromium (VI) reduction under sunlight

Physical adsorption and photocatalytic reduction of Cr(VI) in magnetic separable beads were investigated. In order to elucidate the kinetics of photocatalytic process, operating parameters such as catalyst dosage and the initial concentration were examined in detail. It was observed that the reduction rate of Cr(VI) increased with an increase in the catalyst loading, as this translated into an increase in the number of available active sites. Critical scrutiny of the percentage of the initial reduction rate versus time at various initial concentration of Cr(VI) revealed that the rate of substrate conversion decreased as the initial concentration increased. The kinetic analysis of the photoreduction showed that the removal of Cr(VI) satisfactory obeyed the pseudo first-order kinetic according to the Langmuir–Hinshelwood (L–H) model and the absorption of Cr(VI) on the magnetic beads surfaces was the controlling step in the entire reduction process. Furthermore, desorption experiments by elution of the loaded gels with sodium hydroxide indicated that the magnetic photocatalyst beads could be reused without significant losses of their initial properties even after 3 adsorption–desorption cycles

Synthesis of magnetic alginate beads based on maghemite nanoparticles for Pb(II) removal in aqueous solution

Magnetic alginate beads were successfully synthesized by incorporating ferrofluids based on maghemite nanoparticles (y-Fe 2O 3) and sodium alginate. The as-obtained dried sample characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the size of uncoated and citrate coated y-Fe 2O 3 to be 15nm and 9nm respectively. Fourier transform infrared (FTIR) was performed so as to ensure successful coating process. The specific saturation magnetization (Q s) value of coated particles was found to be lower than the uncoated particles. Zero coercivity of the magnetization curve indicated that the particles were superparamagnetic in nature. By using a ratio 1:10 of ferrofluids and alginate solution respectively, magnetic beads were prepared and the ability of magnetic beads to remove Pb(II) ion from aqueous solutions in batch media was investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and equilibrium contact time were also studied. The results revealed that 95.2% of the Pb(II) was removed within 2h at pH 7. The equilibrium amount of Pb(II) adsorbed onto the magnetic beads approached a constant value with increasing concentrations suggesting that the uptake of Pb(II) followed a Langmuir-type adsorption equation with q max of 50mg/g. Moreover, the presence of the magnetic particles in the beads allowed easy isolation of the beads from the aqueous solutions after the sorption process. In order to determine the reusability potential of the adsorbent, the isolated beads were used as a regenerated sorbent in repeated sorption-desorption cycles. Results revealed that the magnetic beads produced can be potentially used for the treatment of waste water contaminated with heavy metals and regenerated at least five times before losing their activity

Nouveau concept de séparation à base de nanoparticules magnétiques

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Diversity of Biorefineries and doubly green chemistry: an economic approach

Book INRA: Symposium on Biotechnology Applied to Lignocelluloses, Institut national de la recherche agronomique (França), University of Reims., & Fractionation of Agroresources and Environment. (2010). 1st Symposium on Biotechnology Applied to Lignocelluloses: March 28th - April 1st 2010 : Lignobiotech one Symposium. Reims: INRA.International audienceFor the European Commission, the development of biomass use is based on the emergence of a Knowledge BioBased Economy. The transition towards this KBBE involves two separate strategies of scientific thinking. On one hand, a part of the bodies of knowledge is dedicated to progresses in biomass manufacture, involving research on pre-treatment technologies, plant fractionation, and programs dealing with the “biomass recalcitrance”, to microbial and physico-chemical treatments or production and functionalisation of polymers. Another aspect consists in integrating the progress in the implementation of the twelve principles of green chemistry, for example focusing on energy savings, using the principle of atom economy or substitution of solvents. Scientists consider that the implementation of these principles involves systematic analysis allowing the most relevant compromises for a given situation. Therefore, the concept of doubly green chemistry is born. In this concept the goal is to report use of raw vegetable material as renewable resource and processing this resource in an environmentally friendly way, from the Anastas and Warner 12 principles of green chemistry point of view. The communication use a mapping of publications claiming the implementation of the 12 principles of green chemistry in programs connected to biomass, based on a corpus of databases, completed by the perusal of laboratories programs, and interviews.II. Principal results (1)The technological variety will last. We consider two distinct biomass treatment logics: the 1st one, regroups the main routes, and deconstructs biomass into simpler degraded molecules (thermochemical route) or via platform molecules (biochemical route) which can be used as intermediates and building block for conventional use in the chemical industry ; the 2nd logic searches more direct routes (when possible, without recovery of intermediate products) in order to decrease the biomass conversion cost, by using one pot processes or processes containing mostly multi-step reactions and continuous processes, or limited transformations such as reactive extrusion. (2) If we observe the use of the principles of green chemistry as environmental innovation, we observed that, in the case of biorefinery processes using intermediate molecules, the principles of green chemistry are being applied in the form of incremental innovation, while more radical innovations are being investigated in the case of one pot processes

Diversity of Biorefineries and doubly green chemistry: an economic approach

Book INRA: Symposium on Biotechnology Applied to Lignocelluloses, Institut national de la recherche agronomique (França), University of Reims., & Fractionation of Agroresources and Environment. (2010). 1st Symposium on Biotechnology Applied to Lignocelluloses: March 28th - April 1st 2010 : Lignobiotech one Symposium. Reims: INRA.International audienceFor the European Commission, the development of biomass use is based on the emergence of a Knowledge BioBased Economy. The transition towards this KBBE involves two separate strategies of scientific thinking. On one hand, a part of the bodies of knowledge is dedicated to progresses in biomass manufacture, involving research on pre-treatment technologies, plant fractionation, and programs dealing with the “biomass recalcitrance”, to microbial and physico-chemical treatments or production and functionalisation of polymers. Another aspect consists in integrating the progress in the implementation of the twelve principles of green chemistry, for example focusing on energy savings, using the principle of atom economy or substitution of solvents. Scientists consider that the implementation of these principles involves systematic analysis allowing the most relevant compromises for a given situation. Therefore, the concept of doubly green chemistry is born. In this concept the goal is to report use of raw vegetable material as renewable resource and processing this resource in an environmentally friendly way, from the Anastas and Warner 12 principles of green chemistry point of view. The communication use a mapping of publications claiming the implementation of the 12 principles of green chemistry in programs connected to biomass, based on a corpus of databases, completed by the perusal of laboratories programs, and interviews.II. Principal results (1)The technological variety will last. We consider two distinct biomass treatment logics: the 1st one, regroups the main routes, and deconstructs biomass into simpler degraded molecules (thermochemical route) or via platform molecules (biochemical route) which can be used as intermediates and building block for conventional use in the chemical industry ; the 2nd logic searches more direct routes (when possible, without recovery of intermediate products) in order to decrease the biomass conversion cost, by using one pot processes or processes containing mostly multi-step reactions and continuous processes, or limited transformations such as reactive extrusion. (2) If we observe the use of the principles of green chemistry as environmental innovation, we observed that, in the case of biorefinery processes using intermediate molecules, the principles of green chemistry are being applied in the form of incremental innovation, while more radical innovations are being investigated in the case of one pot processes

Photocatalytic magnetic separable beads for chromium (VI) reduction

Magnetically separable photocatalyst beads containing nano-sized iron oxide in alginate polymer were prepared. This magnetic photocatalyst beads are used in slurry-type reactors. The magnetism of the catalyst arises from the nanostructured particles ?-Fe2O3, by which the catalyst can be easily recovered by the application of an external magnetic field. These synthesized beads are sunlight-driven photocatalyst. In the system without magnetic photocatalyst beads, no chromium reduction was observed under sunlight irradiation due to the stability of the chromium (VI). Upon the addition of magnetic photocatalyst beads, the photo-reduction of Cr(VI) was completed in just after only 50 min under sunlight irradiation due to the photocatalytic activity of the beads. However when placed away from sunlight, the reduction rate of the chromium is just about 10%. These observations were explained in terms of absorption occurrence of chromium (VI) onto the catalyst surface which took place in this reaction. In addition, photo-reduction rate of chromium (VI) was more significant at lower pH. The results suggest that the use of magnetic separable photocatalyst beads is a feasible strategy for eliminating Cr(VI)