چكيده به لاتين
Different nanoscale modifications on silicon lead to the production of silicon nanostructures such as porous silicon, which has completely different properties than bulk silicon. Although porous silicon has been widely recognized and studied since the 1990s, many of its unique features have not yet been discovered. In this study, silicon powder was etched in different methods. The properties and characteristics were studied and identified. Properties and efficiency of etched silicon in two stages were investigated as a photocatalyst. By increasing the specific surface area after porosification of pyramids structured silicon, the absorption of radiation increased, especially in the short wavelength range. The band gap of porous-pyramids structured silicon estimated as 1.6 eV from Tauc relation. The presence of combining pyramids and nano porosification was the key factor to capture solar energy for eliminating environmental pollutants. 0.1 g of porous-pyramid silicon as a photocatalyst degraded 30ml of methyl red 1× 10-4 M after 1 h with an efficiency of 95.8%.
In addition, other etched silicon samples were used as a supporter of metal nanoparticles. Molybdenum, iron, and ruthenium salts were used for the catalysts preparation for oxidative desulfurization of model oil and iron and copper salts for loading of metal nanoparticles on the surface of the etched silicon to reduce the chemical denitrification of water. Surface structure, chemical composition, morphology and metal nanoparticle size have been studied with different methods.
The catalytic oxidation of dibenzothiophene to dibenzothiophene sulfone was investigated in the presence of hydrogen peroxide as the oxidizing agent and with MoO3 / Si, Fe2O3 / Si and RuO2 / Si catalysts. In each case, the factors affecting efficiencies such as temperature, time, sulfur concentration and metal content were optimized. The MoO3/Si/PVA catalyst was synthesized and granulated to increase the efficiency and the recovery. MoO3/Si/PVA catalyst efficiency is 93.7% on the optimum conditions, 150 min and at 60◦C. The beads could be easily separated from the solution and indicated reusability after 5 cycles.
Zero-valent iron nanoparticles between 30-100 nm loaded on etched silicon in the alkaline solution for chemical reduction of nitrate in water. The synthesized composite can remove nitrate (100ppm) in the short time, independent of the initial pH of the solution. This composite completely was separated from the solution with the external magnetic field. Copper loaded on the surface of etched silicon can remove by photocatalytic reduction of nitrate (50ppm) in water after 120 min (⁓92%).
Keywords: Porous silicon, Metal nanoparticles, catalyst, Oxidative desulfurization, Nitrate.
