Carbon light absorption

The procedure of simultaneous extracting-spectrophotometric determination of nitrophenols in wastewater is proposed on the example of the analysis of mixtures of mono-, di-, and trinitrophenols. The procedure consists of extraction concentrating in an acid medium, and sequential back-extractions under various pH. Such procedures give possibility for isolation o-, m-, p-nitrophenols, a-, P-, y-dinitrophenols and trinitrophenol in separate groups. Simultaneous determination is carried out by summary light-absorption of nitrophenol-ions. The error of determination concentrations on maximum contaminant level in natural waters doesn t exceed 10%. The peculiarities of application of the sequential extractions under fixed pH were studied on the example of mixture of simplest phenols (phenol, o-, m-, />-cresols). The procedure of their determination is based on the extraction to carbon tetrachloride, subsequent back-extraction and spectrophotometric measurement of interaction products with diazo-p-nitroaniline. 

Porous carbon fiber-carbon bmder composites are a class of matenals that are not widely known, yet they fulfill a vital role in the RTG space power systems, and show considerable potential for other uses in light absorption or gas adsorption applications. These applications are enabled through the unique combmation of physical properties exhibited by the porous carbon fiber-carbon binder composites Perhaps the most significant of its physical attributes is the open, yet rugged, form of the material which contributes significantly to its utility m the fields of... 

C-doped Ti02 was employed for the photocatalytic removal of NOx. The presence of carbon, in the form of coke-like species, was responsible for visible light absorption and thus for the good activity of the photocatalyst under green light irradiation [133]. 

It has been suggested that the elusive zwitterionic state [75], or a novel nucleophilic addition/elimination mechanism at the central carbon of the exocyclic bridge [79], or solvent-solute H-bonding interactions [76, 80] might play a role in modulating cis-trans interconversion. Cis-trans isomerization gives rise also to a remarkable intrinsic photochromism of HBI, as it can be easily and reversibly induced upon light absorption [74—76, 79, 80]. 

Armstrong and Boalch [60] have examined the ultraviolet absorption of seawater, particularly in the wavelengths between 250 and 300 nm, where the absorption is considered to result from the presence of aromatic compounds. Light absorption is a particularly useful measure, if it can be made to work, since it is not too difficult to construct an in situ colorimeter which can produce continuous profiles of dissolved organic carbon with distance or depth [71]. 

Adsorption isotherm of (Aldrich) humic acid (HM) on 8-AI203 as a function of pH. Extent of adsorption was determined both by measurements of light absorption at 254 and 436 nm, respectively and by measurements of dissolved organic carbon (DOC) of the residual HM in solution (original concentration = 25 mg per liter). 

Carbon nanodots and other carbon surface species may act as efficient solid-state sensitizers to promote visible light absorption. In addition, various nanocarbons may act as semiconductors enabling to realize interesting Z-schemes for extended visible light activity. 

Filter substrates were chosen that were suited for subsequent determinations of aerosol mass, total carbon, elemental carbon, trace metals and aerosol light absorption coefficient The three filter assemblies contained, a 47 mm Pallflex Tissuquartz filter (2500 QAO), a 47 mm Nuclepore polycarbonate filter (0.40 ym pore size) and a 13 mm Pallflex Tissuquartz filter (2500 QAO). 

An upper limit to the absorption efficiency of the elemental carbon particles sampled can be obtained if it is assumed that all aerosol light absorption is due to elemental carbon. In that case the specific absorption from the slope of the line in Figure 5 is about 11.9 0.9 m g. That value is higher than would be... 

Particles can also absorb light in the atmosphere the radiant energy absorbed is then converted to heat. As discussed later, graphitic carbon is believed to be the species responsible for most of the light absorption occurring in typical urban atmospheres, although there... 

Table 9.8 summarizes some measurements of the contribution of light absorption by particles, b, for different types of locations from urban residential to remote. In urban areas, bap varies from 13 to 42% of 6cxl, whereas in very remote areas, the contribution of absorption is much less. This is not surprising since the combustion sources producing graphitic carbon tend to be in urban-industrial areas. However, it is noteworthy that soot has been found associated with many sulfate particles even over the remote oceans (Buseck and Posfai, 1999). 

Although it has been generally assumed that elemental carbon is the only component of particles that absorbs visible light, as discussed in Chapter 9, this may not be the case. Instrumentation for measuring total light absorption by all particle components based on... 

Huffman, H. D., Comparison of the Light Absorption Coefficient and Carbon Measures for Remote Aerosols An Independent Analysis of Data from the Improve Network—I, Atmos. Environ., 30, 73-83 (1996). 

The presence of clouds can also affect the net light absorption by black carbon, indeed even more than for sulfate (Haywood and Shine, 1997 Haywood and Ra-maswamy, 1998 Liao and Seinfeld, 1998). For example, Liao and Seinfeld (1998) calculate that the net heating... 

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