Effect of Morphology of Platinum Nanoparticles on Benzene Oxidation Activity.

The effect of morphology of Platinum (Pt) nanoparticles supported on alumina (γ-Al2O3) for complete catalytic oxidation of volatile organic compounds (VOCs) was investigated. Pt nanoparticles were synthesized through a simple method comprising of reduction followed by calcination of metal precursor coated chitosan templates using three different reducing agents: sodium borohydride (NaBH4), hydrazine (N2H4) and hydrogen (H2). The morphology and facet orientation of Pt nanoparticles were influenced by the reducing agents. The catalytic oxidation performance studies of these Pt nanoparticles loaded on γ-Al2O3 for VOCs showed strong dependence of their activities on their morphologies. High indexed facet (220) Pt nanosheets synthesized through NaBH4 reduction showed superior catalytic oxidation activity compared to the catalysts prepared using other reducing agents. Cyclic performance studies on these catalysts showed stable benzene oxidation performance implying their thermal stability. The absence of any shape directing agents in the synthesis of Pt nanoparticles with homogeneous morphologies and preferential orientation is an aspect that can be extended to other catalytic applications.

Carbon nanoparticles for solar disinfection of water.

The present manuscript deals with the application of carbon nano particles (CNP) and chitosan (CHIT) in the form of CHIT-CNP composite for the disinfection of water. The CHIT-CNP composite was prepared by the solution casting method and characterized by TEM, XRD and elemental analysis. In the present investigation we study the disinfection efficiency towards E. coli bacteria of both CNP and CHIT-CNP, under sunlight (SODIS) in identical experimental conditions. Both CNP and CHIT-CNP enhanced disinfection as compared to SODIS alone, and comparable performance was achieved when the same dose of CNP in the two materials was applied. However, the CHIT-CNP composite is in the form of a fabric and it is easier to use and handle as compared to the CNP powder, especially in rural and resource-constrained areas. Moreover the SODIS-CHIT-CNP setup, when used in a compound parabolic collector (CPC) reactor showed high bactericidal efficiency compared to SODIS alone, which is promising for practical applications. The disinfection potential of the CNP powder was compared with that of the well-known material TiO2 Degussa P25 (DP25): DP25 gave 6-log kill of bacteria in 180min, whereas CNP produced 6-log kill in 150min.

Low-cost catalysts for the control of indoor CO and PM emissions from solid fuel combustion.

Cu-Mn based mixed oxide type low-cost catalysts have been prepared in supported form using mesoporous Al(2)O(3), TiO(2) and ZrO(2) supports. These supports have been prepared by templating method using a natural biopolymer, chitosan. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, O(2)-TPD and TG investigations. The catalytic activity for CO as well as PM oxidation was studied, in a view of their possible applications in the control of emissions from solid fuel combustion of rural cook-stoves. The trend observed for the catalytic activity of the synthesized catalysts for CO oxidation was ZrO(2)>TiO(2)>Al(2)O(3) while for PM oxidation it was observed to be TiO(2)>ZrO(2)>Al(2)O(3). The effect of CO(2), SO(2) and H(2)O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. An effective regeneration treatment was attempted by heating the partially deactivated catalysts in presence of oxygen. Redox properties of TiO(2) and ZrO(2) and their structure appeared to be responsible for their promotional activity for CO and PM oxidation reactions. These unordered mesoporous materials could be useful for such reactions where mass transfer is more important than shape and size selectivity.

Hydrated cement: a promising adsorbent for the removal of fluoride from aqueous solution.

The present study was carried out to investigate the potential of cement hydrated at various time intervals for the removal of excess F- from aqueous solution by using batch adsorption studies. The influence of different adsorption parameters, viz. effect of adsorbent dose, initial concentration, pH, interfering ions and contact time were studied for their optimization. It was observed that the adsorbent exhibited reasonably significant F- removal over a wide range of pH. The presence of carbonate and bicarbonate ions in aqueous solution were found to affect the F- removal indicating that these anions compete with the sorption of F- on adsorbent. The equilibrium adsorption data were fitted well for both the Freundlich and Langmuir isotherms and the adsorption capacities were calculated. Comparative studies for F- removal in simulated and field water show relatively higher F- removal in simulated water. XRD and SEM patterns of the hydrated cement were recorded to get better insight into the mechanism of adsorption process. From the experimental results, it may be concluded that HC was an efficient and economical adsorbent for F- removal.

Study of the formation of perovskite type lanthanum ruthenates by heating their hydrous precursor.

Emanation thermal analysis (ETA), differential thermal analysis (DTA), thermogravimetry (TG), evolved gas analysis with mass spectrometric detection (EGA-MS), and X-ray diffraction (XRD) were used to investigate the formation of perovskite type lanthanum ruthenates on heating their hydroxide precursor in argon from 20 to 1200 degrees C. The co-precipitated lanthanum-ruthenium mixed hydroxide containing a small amount of carbonates was used as a precursor. The mass loss corresponding to the release of water and CO(2) from the precursor was determined by TG and EGA (MS), respectively. The ETA characterized the exposure of sample surface after release of water and CO(2), as well as microstructure development corresponding to the crystallization and structure ordering of LaRuO(3) and La(3.5)Ru(4.0)O(13) perovskite phases. The obtained information on formation of phases and their transformation is useful for optimizing their synthesis protocols for achieving the desired physical properties, and to estimate the thermal stability of these materials to be used as catalysts.

Highly crystalline Zeolite-A from flyash of bituminous and lignite coal combustion.

Flyash is being generated in voluminous amounts by large scale coal combustion process. It poses a serious threat to thermal power industries specifically, in India, wherein the percent of utilisation of flyash is very poor (3-5%). In view of this problem, newer methods of its disposal and utilisation are being explored. The synthesis of zeolite from flyash appears to be one of the most promising alternatives as it has emphasis on value addition to waste material. Flyashes originating from different sources of coal differ in their characteristics and have implications in this work on Zeolite-A production. These factors have been thoroughly investigated and the conditions favourable for formation of Zeolite-A have been delineated. The reactivity of flyash towards zeolite formation is directly dependent on the SiO(2)/Al(2)O(3) ratio, Fe(2)O(3) and CaO content. Amongst the flyashes investigated, so far the sub-bituminous coal based flyash with SiO(2)/Al(2)O(3) ratio of 3.47 appears to be a suitable substrate for Zeolite-A synthesis. These zeolites have been characterised with respect to XRD crystallinity, calcium binding capacity (CBC) and sorption capacity, wherein the crystallinity ranges from 50 to 100%, the CBC ranges from 290 to 560meq/100g and sorption capacity ranges from 16.6 to 23.8%.

Highly crystalline faujasitic zeolites from flyash.

The process for the synthesis of flyash-based zeolites (FAZs) are presented, which basically includes alkaline treatment of flyash by a fusion method, followed by hydrothermal crystallization. Zeolite-Y has been identified, and conditions have been optimized for their synthesis by the fusion method. Optimal conditions for synthesis of Zeolite-Y are a NaOH/flyash ratio of 1.2:1, fusion temperature between 500 degrees C and 600 degrees C, crystallization time of 8-10 h and crystallization temperature between 100 degrees C and 110 degrees C. The cation exchange capacity (CEC) of FAZ-Y ranges between 400 and 450 meq/100 g. The surface area of FAZs (500-600 m(2)/g) compare well with the commercial zeolites procured from Mobil Oil. Morphological characterization of FAZ using scanning electron microscopy (SEM) reveals cubic structure, and XRD data reveal unit cells to be cubic system.