Exfoliation of Hexagonal Boron Nitride (h-BN) in Liquide Phase by Ion Intercalation

International audienceA green approach to prepare exfoliated hexagonal boron nitride nanosheets (h-BNNS) from commercially pristine h-BN involving a two-step procedure was investigated. The first step involves the dispersion of pristine h-BN within an aqueous solution containing gelatin and potassium or zinc chloride using a sonication method. The second involves the removal of larger exfoliated h-BNNS through a centrifugation procedure. The exfoliation was caused not only by the sonication effect but also by intercalation of K+ and Zn2+ ions. Transmission electronic microscopy, X-ray diffraction and Raman spectroscopy techniques show that the obtained h-BNNS generally display a thickness of about a few (2-3) layers with an exfoliation efficiency as high as 16.3 +/- 0.4%

On the adsorption mechanisms of diethylamine by medically-certified activated carbons: Investigation of critical parameters controlling sorption properties

International audienceThis study investigates the adsorption mechanisms and reaction pathways involved in the adsorption ofdiethylamine (DEA) by medically-certified activated carbons (ACs). DEA is used as a model of aminessecreted during healing process of chronic wounds. DEA adsorption kinetics/isotherms were performedin liquid phase. Based on a preliminary assumption of a sorption favoured by surface chemical functions,it was found that the sorption kinetics followed accurately a pseudo-second order model. In addition, ouranalysis revealed that surface diffusion strongly influenced DEA sorption. If Langmuir and Redlich–Peterson models provided the most accurate fit of the adsorption isotherms, the Freundlich isothermgave a fair representation of experimental data as well. L-type isotherms supported the occurrence ofstrong surface interactions. Also, a negative correlation was drawn between the micropore volumepercentage and adsorption capacity at equilibrium. Further, acid/base reactions were believed to occur,along with the establishment of numerous H-bonds between the sorbent and DEA. This study is ended bya discussion of the effect of AC entrapment within a polymeric matrix on the adsorption properties. IfDEA removal was still observed, a serious decrease of sorption properties was measured. We concludedthat AC must be treated during the activation process in order to possess a high BET surface, an importantmesopore/macropore content and a high content of acidic surface functions, in order to balance thedecreasing of adsorption properties owed to its entrapment

Preparation of Nanofiltration Membrane Modified with Sawdust-Derived Cellulose Nanocrystals for Removal of Nitrate from Drinking Water

In this work, cellulose nanocrystals (CNC) derived from sawdust were successfully incorporated into a nanofiltration membrane produced by the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). The characteristics of unmodified and CNC-modified membranes were investigated using scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), zeta potential measurement, X-ray photoelectron spectroscopy (XPS), and contact angle measurement. The performance of the membranes in terms of nitrate removal and water flux was investigated using 60 mg/L of potassium nitrate solution in a dead-end test cell. The characteristics of the modified membrane revealed a more nodular structure, higher roughness, increased negative surface charge, and higher hydrophilicity than the pristine membrane, leading to nitrate rejection of 94%. In addition, the membrane gave an average water flux of 7.2 ± 1.8 L/m2/h/bar. This work implies that nanofiltration, a relatively low-pressure process compared to reverse osmosis, can be used for improved nitrate removal from drinking water using an NF membrane modified with sawdust-derived cellulose nanocrystals

Design of graphene-like boron nitride/gelatin electro spun nanofibers as new bio nanocomposite material for tissue engineering

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Development of novel h-BNNS/PVA porous membranes via Pickering emulsion templating

International audiencePolymer-based membranes play an important role in water filtration, in particular in the removal of particles, microorganisms and organic pollutants. Developing a reliable fabrication method for membranes presenting both high flux and good selectivity remains challenging. Polyvinyl alcohol (PVA) is a well-known polymer with promising perspectives due to its specific properties such as nontoxicity, biocompatibility and biodegradability which is of great interest within the context of developing green technologies. Herein, a new strategy using mainly water as a solvent to produce porous membranes based on PVA has been developed using emulsion templating involving hexagonal boron nitride nanosheets (h-BNNS) as a stabilizer. The membranes displaying a pore size around 1 m show a water permeability over 2000 L m(-2) h(-1) bar(-1) and a rejection efficiency of approximate to 100%. Moreover, the membranes did not show a significant reduction of their performances after particle filtration. The results indicated that the h-BNNS/PVA porous membranes fabricated via Pickering emulsion templating are good candidates to be used as microfiltration membranes

Inverse pickering emulsion stabilized by exfoliated hexagonal-boron nitride (h-BN)

International audienceThe formation of inverse Pickering emulsions using exfoliated hexagonal boron nitride (h-BN) as an effective particulate stabilizer without using any surfactants is reported for the first time. The stability and the type of h-BN Pickering emulsions formulated with different BN concentrations and by varying oil/water (o/w) ratios are studied and discussed. First the emulsion structure is analyzed microscopically through optical and epifluorescence microscopy and macroscopically by the study of the rheological behavior. The average droplet size decreases with h-BN concentration whereas the emulsions achieve good stability at 2 wt % BN concentrations and for a 1:1 o/w ratio. In all formulations, the emulsions are of water-in-oil (w/o) type due mainly to the hydrophobicity of h-BN

Development and characterization of composite chitosan/active carbon hydrogels for a medical application

International audienceComposite chitosan/active carbon (AC) hydrogels were elaborated by a novel route, consisting in exposing the chitosan solution to ammonia vapors. This vapor-induced gelation method was compared with the conventional elaboration process, a direct immersion of the chitosan solution in liquid ammonia. The hydrogels were characterized to evaluate their potential application as wound-dressings, mostly regarding their morphology, mechanical properties, swelling behavior, and sorption capacities for malodorous compounds emitted from wounds as diethylamine (DEA). The influence of elaboration route, chitosan concentration, and AC incorporation was studied. The results show that freeze-dried hydrogels have a porous asymmetric structure dependent on the chitosan concentration and which promotes exudates drainage. The nanostructure of the parent hydrogel is semi-crystalline and slightly dependent on the gelation conditions. It confers on hydrogel an acceptable mechanical behavior (compressive modulus up to 1.08 center dot 105 Pa). Hydrogels including AC display enhanced sorption kinetics for DEA, with sorption capacities up to 49 mg g1

Design of graphene oxide/gelatin electrospun nanocomposite fibers for tissue engineering applications

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