Conducting polymer based hybrid nano-composites for enhanced corrosion protective coatings

Polystyrene/calcium phosphate nanocomposites: Dynamic mechanical and differential scanning calorimetric studies

Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H2 gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2–12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H2 was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H2), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H2 were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a CrOOH phase. COPR reacted catalysts recorded a lower abundance of Cr(III) alongside a high abundance of the leachate components Ca and Si, implicating these elements in the faster onset of inactivation.

Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry.

Calcium carbonate was synthesized by in situ deposition technique and its nano size (35–60 nm) was confirmed by transmission electron microscopy (TEM). Composites of the filler CaCO3 (micro and nano) and the matrix poly(vinyl chloride) (PVC) were prepared with different filler loadings (0–5 wt%) by melt intercalation. Brabender torque rheometer equipped with an internal mixer has been used for preparation of formulations for composites. The effect of filler content both nano- and micro level on the nanostructure and properties is reported here. The nanostructures were studied by wide angle X-ray diffraction and scanning electron microscopy. The mechanical, thermal, and dynamic mechanical properties of PVC/micro- and nano-CaCO3 composites were characterized using universal testing machine, thermogravimetric analyzer, and dynamic mechanical analyzer. The results of thermal analysis indicated that the thermal stability of PVC/nano-CaCO3 composites was improved as compared with corresponding microcomposites, and that of pristine PVC and maximum improvement was obtained at 1 and 3 phr loadings. However, the tensile strength decreased significantly with increase loading of both nano- and micro-CaCO3, whereas storage modulus and glass transition temperature increased significantly.

Preparation and characterization of poly(vinyl chloride) calcium carbonate nanocomposites via melt intercalation

Nanocomposites formed from organically modified montmorillonite and poly(ethylene-co-vinyl acetate) were studied by X-ray diffraction techniques. Wide- and small-angle X-ray scattering intensities (SAXS and WAXS) were recorded by transmission mode on test bars cut from compression-molded plaques tilted by different angles with respect to the plane of the plaque. The height of the Bragg peaks characteristic of intercalated particles reduced to the baseline at tilt angles greater than 30°. Guinier analysis of the SAXS characteristic of particle scattering showed a radius of gyration of 0.69 nm and the scattering intensity was slightly dependent on the tilt angle. Recording of WAXS in the usual (i.e., in reflective) mode enhanced the effect of the structural features of the surface area and showed much higher degree of intercalation and particle size of the scattering particles than that in transmission mode.

S. Padalkar

Papers

Control of nanoparticle size of fillers by polymer blend technique