Adsorptive removal of ciprofloxacin and isoniazid from aqueous solution

This paper describes study of ciprofloxacin and isoniazid removal from aqueous solutions using coal fly ash (FA), kaolinite, perlite, talc and vermiculite. The adsorptive features of the adsorbents were evaluated for ciprofloxacin and isoniazid with regards to the effects of contact time, pH, the solid/liquid ratio and antibiotic concentration. All adsorbents were sterilised by dry heat before use to avoid the proliferation of antimicrobial resistance by the bacteria present on the adsorbents during experiments. The regression correlation coefficients indicate that the Langmuir model gives the best fit for the sorption of both antibiotics onto FA and talc, ciprofloxacin onto kaolinite, and isoniazid onto perlite and vermiculite with R2 values ranging from 0.908 – 0.999. The Freundlich isotherm best describes the sorption of ciprofloxacin onto vermiculite and isoniazid onto kaolinite with R2 values of 0.999 for both. The Tempkin model best describes the sorption of ciprofloxacin onto perlite with an R2 = 0.997. The values of the Freundlich exponent, 1/n, range from 0.221 – 0.998, indicating a favourable adsorption of ciprofloxacin and isoniazid onto the adsorbents. The heat of sorption, B, calculated from the Temkin plots has values ranging from 0.018 – 10.460 J/mol, indicating a physical adsorption process (physisorption). Adsorption equilibrium was achieved after 30 min for both antibiotics and the kinetic data obtained conforms best to the pseudo-second order equation with R2 values ranging from 0.998 – 0.999. The removal of ciprofloxacin and isoniazid by all adsorbents except FA was strongly influenced by the pH suggesting that electrostatic interactions play a major role in the adsorption processes

Structure-physical properties relationships of biocomposites based on biopolymer filled with clays : influence of the nature and the content of the filler

L’utilisation des polymères biosourcés en industrie, bien qu’en constant développement, est encore limitée principalement en raison de leurs propriétés physiques insuffisantes. L’incorporation d’argile est l’une des voies permettant de compenser ces limites. L’objectif principal de cette thèse à vocation industrielle a été de formuler et caractériser de nouveaux matériaux composites à base de biopolymères et de charges minérales pour des applications dans l’emballage, en s’intéressant notamment à l’influence de la nature de la charge ajoutée. En outre l’une des originalités de ces travaux réside dans l’utilisation de taux d’argile élevés (≥ 30 wt%). De plus le rôle de l’interface entre la matrice polymère et le renfort minéral sur la structure et les propriétés thermomécaniques et barrière du biomatériau élaboré a été plus particulièrement étudié. Un screening de différents couples biopolymère/argile a tout d’abord été réalisé sur des matériaux élaborés " à l’échelle laboratoire ". Des formulations d’intérêt ont ensuite été sélectionnées et mises en œuvre « à l’échelle pilote ». Les résultats obtenus sur les systèmes PLA/argile ont permis de montrer que bien plus que le taux d’argile incorporé ou le degré de dispersion, c’est la nature de la charge qui influence davantage les propriétés thermomécaniques. Par ailleurs, appliquer un procédé tel que le biétirage permet de palier à la fragilité du PLA et d’augmenter considérablement ses propriétés barrière. Enfin, concernant la matrice d’alginate, la plastification donne lieu à un matériau hétérophasé et l’ajout d’argile n’induit pas de baisse de l’étirabilité tout en améliorant la rigidité du matériau.Although in constant development, the use of biobased polymers for industrial applications is still limited mainly because of their intrinsically limited physical properties. Adding clay is one solution to outclass these limitations. The main goal of this thesis, with an applied nature, was to elaborate and characterize new composite materials based on biopolymers and clays for applications in the packaging field. More especially, the influence of the clay nature was assessed. One of the distinctive features of this PhD work is the use of a high clay contents (≥ 30 wt%). Moreover, a particular attention was paid to study the role of the interface between the polymer matrix and the mineral filler on the structure as well as on the thermomechanical and barrier properties of the elaborated biocomposite.A screening of different biopolymer/clay compound elaborated at the laboratory scale was firstly studied in terms of structure, morphology and physical properties. Then the most promising formulations were selected and elaborated at a larger scale using industrially processes. The results obtained on Polylactide (PLA)/clay compounds showed that rather than the content of clay or its dispersion degree, it is the nature of the clay, i.e. its chemistry and its crystallography, that mainly govern the thermomechanical properties. Furthermore it was highlighted that applying a biaxial stretching on this kind of materials offsets the PLA brittleness and increases its barrier properties. Finally, regarding the alginate based composites, plasticization leads to a heterogeneous material and adding clay involves an increase of the material rigidity without any decrease of stretchability

Water dynamics in poly(vinyl pyrrolidone)–water solution before and after isothermal crystallization

5 páginas, 6 figuras.In this work we have studied the low-temperature dynamics of water molecules after isothermal crystallization at different temperatures (Tc) and times (tc) of an aqueous solution of poly(vinyl pyrrolidone) (PVP) by broadband dielectric spectroscopy (BDS) and optical microscopy. Three differentwater concentrations (cw=45, 50 and 55 wt.%) were explored. Two major different phases were observed by optical microscopy during crystallization: one related with the core ice formed during crystallization and the other one related with the amorphous phase. Between them a rich interface was also seen. By BDS, two dielectric processes (I and II) are observed in the amorphous samples whereas, in the partially crystallized samples a third relaxation (process III) emerges in the dielectric spectra. Process II is related with the rotational dynamics of water molecules in the amorphous phase with similar characteristics to that found in the complete amorphous solutions whereas the process III is attributed to the rotation of water molecules at the interface between the ice cores and the amorphous water–PVP phase. Typical characteristics of these processes on the relaxation map are discussed.The authors gratefully acknowledge the support of the Spanish Ministry of Science and Innovation, project CSD2006-00053 and MAT2007-63681; the European Union, project 502235-2 and the Basque Government, and project IT-436-07.Peer reviewe

Influence of the Filler Nature on the Crystalline Structure of Polylactide-Based Nanocomposites: New Insights into the Nucleating Effect

This work deals with the influence of the nature of a filler on the thermally induced crystalline structure of polylactide (PLA)-based nanocomposites. Particularly two types of silicated clay both having a platelet-like shape, i.e., talc and kaolin, were melt compounded with PLA, and the crystalline structure involved during isothermal crystallization was followed <i>in situ</i> by means of both wide- and small-angle X-ray scattering techniques. Results indicate that even if the two types of clay are chemically similar, i.e., they both exhibit silicate surfaces, only talc plays the role of nucleating agent on the PLA crystallization. Moreover, structural analyses reveal that for PLA nanocomposites filled with talc a transcrystallization process occurs and that, in addition to the perpendicular growth of the PLA crystals toward the clay surface, a well-ordered nanometer scaled structure can be formed depending on the crystallization temperature. Particularly, for the first time, an epitaxial growth process has been evidenced, and crystallographic orientation relationships between the PLA crystals and the talc platelets have been determined. In opposition, the same behavior was not encountered for the kaolin-based nanocomposites. From a fundamental point of view, this study shows that the existence of favorable interactions between the polymer and the filler is not the only parameter involving the nucleating effect process. Indeed, the existence of crystallographic relationships between the filler and the polymer crystalline structure is also a necessary condition to observe a nucleating effect. Finally, this work also highlights that incorporating a well-chosen filler into a polymer matrix can be an efficient route to induce nanostructured materials

Comparison of the influence of talc and kaolinite as inorganic fillers on morphology, structure and thermomechanical properties of polylactide based composites

International audiencehis work deals with the effect of both nature and content of two chemically different layered silicates (i.e. talc and kaolinite) on the morphology, structure and thermomechanical properties of polylactide/clay minerals composites. Composites with filler contents up to 30 wt.% were studied. Regarding the morphology it was found that kaolinite–PLA nanocomposites display a better filler dispersion with a majority of particle sizes at the nanometer scale. This better degree of dispersion has been ascribed to the electrochemical properties of kaolinite which exhibit a lower Zeta potential than talc. It was also found that talc has a pronounced nucleating effect on PLA crystallization, whatever the clay mineral content. By contrast this effect is very limited in kaolinite–PLA nanocomposites. Investigation of the mechanical behavior indicates that a reinforcing effect is observed for the two types of clay minerals for filler contents beyond 10 wt.%. This shows the interest of filling PLA with high clay minerals contents. This reinforcing effect is significantly higher for the talc based composites. These differences are ascribed to a better affinity between PLA macromolecules and talc surface, due to the presence of only silicate layers. In addition to the demonstration of the interest of using high clay minerals loadings, a main result of this work is that filler dispersion is not the only parameter that governs the gain in properties. It is shown that interfacial effects and more especially affinity between the polymer and the clay mineral also play a key role

Thermal behavior of extruded and injection-molded poly(lactic acid)-talc engineered biocomposites: Effects of material design, thermal history, and shear stresses during melt processing

Reinforced biocomposites were compounded by the reactive extrusion of poly(lactic acid) (PLA) and chemically modified microlamellar talcs. Talc was functionalized by the hydrolysis and condensation reaction of its surface hydroxyl groups with different kinds of organosilanes, namely, 3-aminopropyl triethoxysilane and (3-glycidoxypropyl)trimethoxysilane, and commercially available tri-isocyanates, namely, Bayhydur 3100 and Desmodur 3900, which feature hydrophilic and hydrophobic behaviors, respectively. PLA-talc biocomposites were also compounded by the addition of two types of reactive biodegradable compatibilizing agents, namely, maleic anhydride and glycidyl methacrylate modified PLA. The resulting compounds were melt-processed by injection molding to get flat substrates with different formulations. The thermal responses of the extruded compounds and injection-molded items, specifically the first and second thermal transitions, were analyzed by differential scanning calorimetry. In particular, the influence of the different material formulations, their thermal history, and/or shear stress in single- or multiple-stage heating and/or melt processing on the glass transition, crystallinity, and melting behavior of the biocomposites was investigated. The experimental findings revealed that the macroscopic thermal response of the compounds (i.e., extruded pellets) and substrates (i.e., injection-molded flat slabs) manufactured by the melt processing of the available formulations, was controlled and significantly improved by the fine-tuning of the chemical (i.e., reaction mechanisms, chemical bonds) and physical interactions (i.e., steric hindrances, physical bonds) among the modified talc, PLA, and compatibilizing agents. These results are of great practical importance and open up broader scenarios for the industrial application of biopolymers and biocomposites, specifically in all of those consumer goods where thermal stability and the preservation of mechanical performance at moderate and high temperatures of the materials are pivotal

Effect of well-dispersed surface-modified silica nanoparticles on crystallization behavior of poly (lactic acid) under compressed carbon dioxide

The final publication is available at Elsevier via https://doi.org/10.1016/j.polymer.2016.06.019. © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this work, the crystallization behavior of poly (lactic acid) (PLA)/amine-modified silica nano- composites at different loadings of amine-modified silica (1, 2, and 8 wt %) under isothermal, non- isothermal, and isothermal under compressed CO2 is studied. A significant improvement in crystalliza- tion rate was observed after introduction of the nanoparticles. A modified Hoffman-Lauritzen nucleation theory was utilized to explain the facilitation and acceleration of the crystallization process of nano- composites with introducing the surface energy of the nanoparticles and interfacial energy between polymer/nanoparticle into the rate equation. After incorporation of the nanoparticles, three-dimensional spherulites formed sporadically in the PLA matrix based on the prediction of the Avrami exponents of the nanocomposites. High-pressure DSC results also showed an increase in the crystallization rate at 15 bar compared with the atmospheric pressure condition. However, an increase in pressure up to 21 bar had no significant effect on the crystallization rate. The PLA nanocomposites with lower molecular weights and D-content also showed a significant increase in the crystallization rate but with no change in the crys- tallization mechanism.Natural Sciences and Engineering Research Council (NSERC) of Canada || Network for Innovative Plastic Materials and Manufacturing Processes (NIPMMP) || Ontario Centers of Excellence || Canada Research Chairs (CRC)