30 research outputs found
Enhancement of NMP degradation under UV light by nitrogen-doped TiO2 thin films using a design of experiment
Doping nitrogen within TiO2 is an effective way to enhance visible light photocatalysis due to a direct electron excitation from the N2p states within the band gap. However, nitrogen doping is not always efficient for UV photocatalytic activity. Here, different structures of N-doped TiO2 (TiOxNy) have been prepared by reactive RF (13.56 MHz) magnetron sputtering. The morphological, optical, structural, and photocatalytic properties of the films have been studied in order to investigate the competitive effect of the morphology and the chemical composition on the efficiency of the photocatalytic activity. The variation of surface wettability of the film over time in the dark and under visible and UV irradiation was also studied. The reduction in wettability by dark storage can be explained by the adsorption of hydrocarbon contamination on the thin film’s surface. Additionally, from water contact angle experiments, it was found that these films developed hydrophilic properties upon UV and visible illumination. The photoinduced change in the contact angle of water was due to the removal of hydrocarbon contamination on the surface and also the photo-oxidation of the water droplet. Samples prepared at high pressure gave the best photocatalytic activity, even though the deposition rate was lower at higher pressures (lower film thicknesses), due to the high specific surface area and the optimal presence of TiOxNy crystals in the lattice. However, at low pressure, the TiN crystals became more predominant, and acted as recombination centers for the photo-generated charge carriers. A design of experiments was used in order to optimize the deposition parameters to have the best photocatalytic activity. The high photocatalytic activity under UV light was found to be due to the introduction of discrete energy levels within the band gap, the increased sample wettability, and the higher specific surface area. However, the post annealing process did not effect the activity under UV irradiation. Using the response surface methodology, RSM, based on a design of experiment, DOE, we are able to achieve a good understanding of the complex processes involved in the deposition of the thin films and their effect on the photocatalytic activity.
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CEMENT WASTE REDUCTION FRAMEWORK IN TEHRAN'S CONCRETE STRUCTURE RESIDENTIAL BUILDINGS
In sustainable management of solid waste, decreasing construction waste generation is an important step. In developing countries, modern construction techniques are not adopted as in developed countries and contractors follow wasteful manners when utilizing building materials. The result is building material waste which unfavorably affects environment. At the same time, it is considered an earnest concern and a solemn environmental problem all over the world requiring a reliable database to be managed, whereas investigations done by the authors imply that no official organization maintains any related authenticated data, making thriving construction waste management policies too difficult to be defined and implemented in Tehran, Iran. In this article, variables affecting materials waste were derived from accessible reviewed literature, then using the first questionnaire survey quantities of variables were collected for thirty two representative residential buildings in Tehran. Primary analysis showed that cement is wasted more than other studied materials (about 8.6\% by weight). Due to huge amounts of energy and raw materials used in production of cement and pertained destructive effects on environment such as air pollutants emission, cement waste reduction leads to emission abatement and cost saving. This is why cement waste was targeted to be diminished in this paper.After quantifying cement waste versus dependent variables of this study, it was resulted that ``lump sum'' contract is preferable to ``cost plus'' contract in terms of cement waste. Furthermore, designing smaller buildings with more stories is suggested instead of bigger buildings with fewer stories. Since no construction waste reduction policy is implemented in Iran so far, authors conducted a subsequent questionnaire survey to evaluate different waste reduction policies. As a result, defining a financial-based incentive plan ranked the first in order of preference based on opinions of construction experts. Therefore, a financial-based incentive plan was structured. This plan was proven to be both viable economically and justifiable environmentally. These suggestions could be proposed to Tehran municipality to be implementable in sustainable residential building projects