Carbon black graphitisation

Figure 5.6 Stepwise isotherm for the adsorption of krypton at 90 K on carbon black (graphitised at 3000 K)166 (By courtesy of the Canadian Journal of Chemistry)...

The sample pretreatment steps for surfactant analysis such as extraction and concentration can be carried out in a variety of ways. Most of the common and well tested procedures have been described by Schmitt [46]. Solid phase extraction (SPE) with C2, Cg or Cis and divinyl benzene resins as well as special phases, e.g. graphitised carbon black (GCB), can be adequate methods, especially for SPE of metabolites from... 

In an area where domestic wastewater was discharged through cesspools, Crescenzi et al. [76] could identify LAS and DATS in a groundwater sample. After preconcentration of the aqueous sample on a graphitised carbon black (GCB) cartridge, co-extracted basic, neutral and weakly acidic compounds were removed from the cartridge by a... 

As stated earlier the procedure for this analysis is based largely on the methods developed by Hangartner.(4) Figure 1 outlines the scheme utilised for sample processing and analysis. In addition to the detection system already discussed the only other significant difference in this work is the choice of adsorbent which is Carbotrap D-l a graphitised carbon black (GCB). The use of GCB s in environmental analysis is well documented in the literature both as column materials and adsorbants. (7, 8) Initial work within Severn Trent confirmed the claimed superiority of GCB s compared with adsorbents based on porous polymers such as Tenax GC. No evaluation of the relative merits of GCB s and activated carbons have been made at this laboratory but tests with the latter are likely in the future. 

These phases are composed of adsorbing materials molecular sieves, alumina, porous glass and gels (such as Chromosorb 100, Porapak and PoraPLOT1 ), and graphitised carbon black. They are mainly used to separate gases or volatile compounds. Capillary columns made by deposition of these materials in the form of very fine particulates are called PLOT (porous layer open tubular) columns. 

This technique seems to have been introduced in late 1998, and consists of extracting organic contaminants from the soil with a solvent, generally sub-critical water, and then passing the extract through a small disc of solid sorbent. The solid sorbents discussed to date include graphitised carbon black [123], styrene-divinyl benzene [124],Carbograph-4 [122] and polyisobutylene [193]. 

Di Corcia [368] used subcritical water (phosphate-buffered) extraction with a graphitised carbon black cartridge to recover terbuthylazine herbicide and its metabolites from soil. 

The following results refer to the adsorption of nitrogen on a graphitised sample of carbon black, and give the ratio of the nitrogen pressures for temperatures of 90 K and 77 K which are required to achieve a given amount of adsorption ... 

Samples of atmospheric mercury were obtained by pre-concentration of mercury on columns of graphitised carbon black (Carbotrap). The columns, at ambient temperature, retained mercury vapour and alkylmercury compounds (Bloom and Fitzgerald, 1988). Methylmercury chloride, ethylmercury chloride and dimethylmercury were held on the column at temperatures as high as 29°C and air flow rates as high as 790cm3min 1. At high flow rates and high temperature,... 

Simazine, atrazine herbicides Concentration on graphitised carbon black U V at 220nm ppt range [125]... 

Polyethylene surfactants Graphitised carbon black preconcentration LC-MS with electrospray interface ppt [15]... 

Phenols Acid washed graphitised carbon black, modified with trimesic acid and PEG 20M [243]... 

The adsorption isotherms for carbon black and graphitised carbon black (graphon) are completely different. For graphitised carbon black a step-like adsorption isotherm is... 

The Type VI isotherm, in which the sharpness of the steps depends on the system and the temperature, represents stepwise multilayer adsorption on a uniform nonporous surface. The step height now represents the monolayer capacity for each adsorbed layer and, in the simplest case, remains nearly constant for two or three adsorbed layers. Amongst the best examples of Type VI isotherms are those obtained with argon or krypton on graphitised carbon blacks at liquid nitrogen temperature. 

Carbopak B and C are graphitised carbon black, having siuface areas of 12 and 1(X) mVg, respectively. They e usually modified with a light coating of a polar stationary phase. DifiGcult separations of the Cj to CjQ hydrocarbons can be achieved... 

The attainable enrichment and clean-up in SPE depend primarily on the selectivity and affinity of the sorbent for the selected target analyte or analytes, the sample load capacity for the analytes and the rate of mass transfer to and from the binding sites, the latter affecting the minimum desorption volume and thus the enrichment that can be obtained. Other factors of importance are the reproducibility of the recovery yields and the stability and reusability of the sorbent when online procedures are desired. For hydrophobic analytes satisfactory results are usually obtained using standard reversed phase sorbents. Thus hydrophobised silica (C8, Cl8), styrene-divinylbenzene copolymers (PS-DVB) and graphitised carbon black (GCB) are the conventional sorbent materials used in SPE (Fig. 15.2)... 

Several examples may be quoted from the literature to illustrate the adsorption of surfactant ions onto soHd surfaces. For a model hydrophobic surface, carbon black has been chosen [22, 23], and Figure 5.5 shows the typical results for the adsorption of sodium dodecyl sulphate (SDS) onto two carbon black surfaces, namely Spheron 6 (untreated) and Graphon (graphitised), which also describes the effect of surface treatment. 

The separation of the cis- and trans-isomers of l,2-bis(trimethylsilyl)-, 1-tri-methylgermanyl-2-trimethylsilyl- and l,2-bis(trimethylgermanyl)ethylene is possible by gas-solid chromatography on graphitised carbon black and by gas-liquid chromatography on Chromosorb W supporting Apiezon L, with helium as carrier gas and a thermal conductivity or flame ionisation detector445. 

HEAT CAPACITIES OF ETHYL AND TERTIARY BUTYL ALCOHOLS IN ADSORPTIOLN LAYERS ON GRAPHITISED CARBON BLACK. 

HEAT CAPACITIES OF ALCOHOLS ADSORBED ON GRAPHITISED CARBON BLACK. //ENGLISH TRANSLATION OF ZH. FIZ. 

Orlando, FI., 21st-23rd Sept.1999, paper 122 RAMAN STUDY OF KINETICS OF GRAPHITISATION OF CARBON BLACKS... 

The amount of adsorption that takes place at each step is evaluated by integrating the difference in the detector response to changes in the effluent composition after it leaves the cell filled with the adsorbent, and a parallel response obtained when the cell is filled with a non-adsorbing solid. This is illustrated in Figure 3 by the concentration profiles obtained for adsorption of n-butanol from n-heptane on a graphitised carbon black (Graphon). 

Figure 3. Computer graphics of (a) changes in the refractive index of the effluent from the adsorption cell filled with the adsorbent, graphitised carbon black, and a non-adsorbing solid (PTFE) and, (b) thermal output of the thermistors measuring heat effects due to interactions at solid-water interface caused by adsorption and desorption of n-butanol from its 10 gf solution in water on 0.0696 g of GRAPHON at 25°C. Flow rate of water carrier - 3 mlh. ...

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