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1.
Environ Sci Technol ; 50(7): 3530-6, 2016 Apr 05.
Article in English | MEDLINE | ID: mdl-26936001

ABSTRACT

Photolysis of nitric acid and nitrate (HNO3/nitrate) was investigated on the surfaces of natural and artificial materials, including plant leaves, metal sheets, and construction materials. The surfaces were conditioned in the outdoor air prior to experiments to receive natural depositions of ambient HNO3/nitrate and other atmospheric constituents. The photolysis rate constant (JHNO3(s)) of the surface HNO3/nitrate was measured based on the production rates of nitrous acid (HONO) and nitrogen oxides (NOx). The JHNO3(s) values, from 6.0 × 10(-6) s(-1) to 3.7 × 10(-4) s(-1), are 1 to 3 orders of magnitude higher than that of gaseous HNO3. The HONO was the major product from photolysis of HNO3/nitrate on most plant leaves, whereas NOx was the major product on most artificial surfaces. The JHNO3(s) values decreased with HNO3/nitrate surface density and could be described by a simple analytical equation. Within a typical range of HNO3/nitrate surface density in the low-NOx forested areas, photolysis of HNO3/nitrate on the forest canopy can be a significant source for HONO and NOx for the overlying atmosphere.


Subject(s)
Nitrates/radiation effects , Nitric Acid/radiation effects , Photolysis , Atmosphere/chemistry , Kinetics , Nitrogen Oxides/radiation effects , Nitrous Acid/radiation effects , Photolysis/radiation effects , Plants/radiation effects , Sunlight , Surface Properties
2.
Environ Technol ; 35(1-4): 36-41, 2014.
Article in English | MEDLINE | ID: mdl-24600838

ABSTRACT

In this paper, the effect of urea-hydrogen peroxide (UHP) solution on desulphurization and demineralization of coal with high sulphur and high ash by using HNO3 and microwave pretreatment was investigated. The oxidation process is strongly dependent on irradiation power and time for microwave pretreatment, UHP concentration, leaching time and temperature of the UHP solution. X-ray diffraction and Fourier transform infrared technique have been performed for the raw and treated coals. Compared with the UHP alone, successive treatments with HNO3 and microwave pretreatment resulted in the significant removal of total sulphur and mineral matter from the coal. The proposed experimental method has the meaning of practical guide to the desulphurization and deashing of coal by microwave.


Subject(s)
Coal Ash/isolation & purification , Coal/analysis , Coal/radiation effects , Hydrogen Peroxide/chemistry , Nitric Acid/chemistry , Sulfur Compounds/isolation & purification , Urea/chemistry , Coal Ash/chemistry , Coal Ash/radiation effects , Hydrogen Peroxide/radiation effects , Microwaves , Nitric Acid/radiation effects , Oxidation-Reduction/radiation effects , Radiation Dosage , Sulfur Compounds/chemistry , Sulfur Compounds/radiation effects , Urea/radiation effects
3.
Nanotechnology ; 23(49): 495714, 2012 Dec 14.
Article in English | MEDLINE | ID: mdl-23154484

ABSTRACT

To decrease single-wall carbon nanotube (SWCNT) lengths to a value of 100-200 nm, aggressive cutting methods, accompanied by a high loss of starting material, are frequently used. We propose a cutting approach based on low temperature intensive ultrasonication in a mixture of sulfuric and nitric acids. The method is nondestructive with a yield close to 100%. It was applied to cut nanotubes produced in three different ways: gas-phase catalysis, chemical vapor deposition, and electric-arc-discharge methods. Raman and Fourier transform infrared spectroscopy were used to demonstrate that the cut carbon nanotubes have a low extent of sidewall degradation and their electronic properties are close to those of the untreated tubes. It was proposed to use the spectral position of the far-infrared absorption peak as a simple criterion for the estimation of SWCNT length distribution in the samples.


Subject(s)
Crystallization/methods , Nanotubes, Carbon/chemistry , Nitric Acid/chemistry , Sonication/methods , Sulfuric Acids/chemistry , Cold Temperature , Complex Mixtures/chemistry , Complex Mixtures/radiation effects , Materials Testing , Nanotubes, Carbon/radiation effects , Nitric Acid/radiation effects , Particle Size , Sulfuric Acids/radiation effects
4.
Ultrason Sonochem ; 18(5): 1124-7, 2011 Sep.
Article in English | MEDLINE | ID: mdl-21393047

ABSTRACT

Sonochemical oxidation of benzyl alcohols into corresponding aldehydes by FeCl(3)/HNO(3) in acetone at room temperature has been reported. All substrates give good yield of the products within 10-25 min. The reaction of selected substrates were also studied under reflux and at the room temperature. Further, various Lewis acids were used to evaluate their catalytic efficacy.


Subject(s)
Acetone/chemistry , Acetone/radiation effects , Benzyl Alcohols/chemistry , Benzyl Alcohols/radiation effects , Chlorides/chemistry , Ferric Compounds/chemistry , Nitric Acid/chemistry , Sonication/methods , Chlorides/radiation effects , Ferric Compounds/radiation effects , Nitric Acid/radiation effects , Oxidation-Reduction/radiation effects , Radiation Dosage
5.
Ultrason Sonochem ; 14(1): 41-5, 2007 Jan.
Article in English | MEDLINE | ID: mdl-16563845

ABSTRACT

Phenols are selectively nitrated to o-nitrophenol along with rate enhancement using dilute nitric acid (6 wt%)/tetra butyl ammonium bromide (TBAB) under sonication. The selectivity can also be reversed to p-nitrophenol using NaBr as a catalyst. Kinetic analysis of nitration of phenol both with and without sonication has been investigated by variation of reaction parameters such as catalyst, nitric acid and substrate concentration.


Subject(s)
Nitrates/chemistry , Nitric Acid/chemistry , Nitric Acid/radiation effects , Phenols/chemistry , Sonication , Catalysis , Kinetics , Nitrates/radiation effects , Phase Transition , Phenols/radiation effects
7.
Chemphyschem ; 5(11): 1663-9, 2004 Nov 12.
Article in English | MEDLINE | ID: mdl-15580925

ABSTRACT

This Minireview gives an account of the photochemical decay of nitric acid HNO3 in the gas phase, which has been well investigated under bulk and molecular-beam conditions. Due to the importance of this molecule in atmospheric chemistry, attention was paid to the irradiation regions around 300 and 200 nm, where solar photolysis of HNO3 is expected to be particularly efficient. While the low-energy region is characterized by the products OH and NO2, the high-energy region gives rise to a variety of photochemical decay pathways, dominated by channels which lead to the products HONO + O in different electronic states.


Subject(s)
Atmosphere , Nitric Acid/chemistry , Nitric Acid/radiation effects , Gases/chemistry , Photochemistry
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