Volume 4, Issue 6

In this study, we for the first time reported green synthesis of silver nanoparticles from silver nitrate solution using leaf extract of Dahlia pinnata . Green synthesis was chosen over conventional physical or chemical synthesis procedures due to eco-friendliness, simplicity and low cost. Formation of silver nanoparticles was monitored at regular intervals using UV-Vis spectroscopy. Different phases and the crystal nature of silver nanoparticles were studied by X-ray diffraction (XRD). Transmission electron microscopy (TEM) was performed to realize the shape, size and morphology of the nanoparticles. Fourier transform infrared (FTIR) spectroscopy of the particles revealed the role of organic molecules that reduced and capped the colloidal particles in the medium during interaction. Most importantly, the rapid colorimetric sensing activity of these biosynthesized nanoparticles was explored and the green synthesized Ag nanoparticles instantly detected the presence of hazardous Hg 2+ ions in water successfully.

Retama raetam (RR), a desert plant, was chemically modified by the reaction with succinic acid at high temperature to form succinic acid treated R. raetam (STRR). Three levels containing different carboxyl contents of STRR were prepared. Native RR and STRR were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and estimation of carboxyl content to support the adsorption of Pb(II) ions. The STRR adsorbent was utilized as adsorbent material for the removal of Pb(II) ions from aqueous solutions. The effect of various parameters like pH, adsorbent concentration, contact time, temperature and initial concentration was investigated using batch process to optimize conditions for maximum adsorption. The adsorbent data were analyzed using two-, three-, four- and five-parameter models at 30°C by non-linear regression analysis. The examination of error analysis methods showed that the Langmuir-Freundlich model provides the best fit for experimental data compared with other isotherms. The maximum biosorption capacity of Pb(II) ions was up to 270.27 mg/g at 30°C. The thermodynamics constants of the adsorption process, viz., Δ H o , Δ G o and Δ S o , were evaluated. The results showed that the adsorption of Pb(II) ions onto STRR was endothermic and spontaneous. The adsorption data followed second-order kinetics, supporting that chemisorption process was involved.

Cerium-supported nickel catalysts with Ni loading close to 15%wt were synthesized using three different methods (microemulsion, sol-gel and autocombustion) with the aim to design efficient catalysts for the dry reforming of methane to produce syngas (H 2 +CO) from methane and carbon dioxide. The catalytic test was performed after calcining the as-prepared samples at 973 K, and subsequent in situ reduction was performed under hydrogen flow at 873 K. The resulting catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherm measurements. The obtained results show that the Ni/CeO 2 sample prepared by autocombustion is more active than a catalyst prepared by the sol-gel method, and the rate conversions of CH 4 and CO 2 are about 53%, 53% and 22%, 28%, respectively. The good activity of a catalyst prepared by the autocombustion can be due to the presence of the monoclinic phase of NiO revealed by the XRD and TPR characterizations. However, the catalyst prepared by the microemulsion method does not show any catalytic activity in this catalytic test.

In this study, fabrication of Al based in situ composites and their formation mechanism is investigated through the stir casting approach. In situ composites were prepared with the addition of various amounts of V 2 O 5 particles in pure aluminum. Due to the reaction of vanadium pentoxide with the molten aluminum, Al 2 O 3 (alumina) is formed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and microscopy were used for the examination of the produced in situ composites. Increment in hardness was observed in cast in situ composites as compared to the pure aluminum. Friction and wear behaviors of cast in situ composites were studied by using a pin on disc tribo tester. The investigation showed that the wear loss and coefficient of friction increases with the load. The result indicates that wear rate increases with higher percentage of addition. The different phases formed are shown by the XRD study and the presence of Al 3 V and alumina in the composite enhanced the properties.