Search

The present study deals with the performance of ZnSnO3 nanopowder as a photocatalyst in degrading the Congo red (CR) dye. The samples were prepared by co-precipitation method and sintered at different temperatures. The size, specific surface area and morphology of the nanopowder depend on the sintering temperature. The sintering temperatures are selected depending upon Thermo Gravimetric Analysis (TGA). Confirmation of the single phase crystalline structure is done using Powder X-ray diffraction (XRD). FESEM and TEM micrographs provide information on the morphology. The surface area was estimated by Brunauer-Emmett-Teller (BET) analysis and the band gap energy by ultraviolet-visible spectroscopy (UV–Vis). The photoluminescence (PL) spectra confirm the existence of oxygen vacancies. Fourier transform infrared spectroscopy (FTIR) was performed to identify the functional groups. Raman spectroscopy was used to identify the vibrational modes. The study shows that the photocatalytic efficiency increases with increasing sintering temperature. The electron scavenger H2O2 increases the degradation rate. The catalyst is very stable, as confirmed by the cyclic stability test. [ABSTRACT FROM AUTHOR]

In addition to enthalpy–entropy compensation (EEC), anti-enthalpy–entropy compensation (AEEC) phenomenon is also found in literature. The reports on the latter are limited, and analyses and justifications are so far unclear. Herein we present demonstration on the nature and possibility of the AEEC phenomenon. Although literature reports so far have mostly shown linear AEEC, we have found both linear and non-linear dependences. The non-linearity we consider arises from large “free energy window” (FEW) like EEC, recently presented and discussed. Attempts have been made to rationalize the observations in terms of solvation–desolvation phenomenon of the involved processes anticipated in previous studies. We have found that enthalpy and entropy of formation of gaseous and solid materials may also exhibit AEEC, it can be thus classified as a global phenomenon. In addition to AEEC, the phenomenon of no-enthalpy–entropy compensation (NEEC) is also reported. Thus, the phenomena EEC, AEEC and NEEC are thermodynamic puzzles that require close attention and analysis. With the help of wide range of physical chemical processes, an elaborate general understanding of the linear and non-linear AEEC phenomena has been attempted. The experimental data herein used are collected from literature reports, new measurements were not done. A variety of examples have supported possible generality of AEEC. [ABSTRACT FROM AUTHOR]

Background Two long sewerage canals in the city of Kolkata, India were heavily infested with larvae, pupae and egg rafts of the mosquito Culex quinquefasciatus. Although the burden of bancroftian filariasis and other diseases transmitted by C. quinquefasciatus in the city is practically zero, the night-biting mosquitoes are a great nuisance to residents living alongside the canals. It is known that mosquitoes survive poorly in water agitated by wave and wind action. Method The health department of Kolkata Municipal Corporation undertook, from November 2010 to April 2012, a programme of plying speedboats along the canals to prevent C. quinquefasciatus breeding. At the same time, along stretches of canal too shallow to permit the use of speedboats and where the canal banks are inaccessible to spraymen, the edges were treated with larvicidal spray, Temephos 50% EC (emulsifiable concentrate), using small rowing boats as transport. Result The densities of egg rafts and immature and adult insects declined dramatically when the speedboats were deployed and remained low for the duration of the project. For Feburary, the peak month for C. quinquefasciatus breeding, densities for egg rafts, larvae, pupae and adults, respectively, declined from 800, 2942, 1457 and 662 to 3, 75, 15 and 27. The cost was comparable to that of using larvicidal spray where this required the use of rowing boats. Conclusion Speedboat-generated waves are effective in preventing the breeding of mosquitoes in otherwise mosquitogenic canals. Where use of boats is an option and use of insecticides is unfeasible or undesirable, the plying of speedboats is a potentially ecofriendly approach to mosquito control. [ABSTRACT FROM PUBLISHER]