Sulphur uptake

Variations in the 8 34S values for plants have been summarised by Krouse et al. (1991), these range from -20 to +34%o and are comparable to those reported in sedemintary rocks. It has been found that the sulphur uptake by the plant is mainly from soil sulphate where ambient S02 levels are low. In some cases ambient S02 dominates and the 8 34S values are close to those of the S02. These two uptake mechanisms are a factor in the differing isotope ratios in different parts of an individual plant (Chukhrov et al., 1978). Thus sulphur isotope ratios are helpful in the determination of sulphur sources in the environment. 

In benzothiophen hds (620 K, 1 atm) over a sulphided Mo(8)/Al2 03 catalyst ethylbenzene was the major product with minor amounts of benzene, toluene, styrene, and dihydrobenzothiophen. The catalyst was poisoned by pyridine. The ratio (adsorbed pyridine molecules)/(Mo atom), obtained from a plot of catalyst activity vs. weight change owing to pyridine adsorption was 0.24 in agreement with the concentration of anion vacancies determined from sulphur uptake. 

Sulphur treatment/ Partial pressure (atm) Exposure duration h Sulphur uptake Carbon uptake after 75h ng/cm (b) ... 

Weight gain during lOOOh oxidation In CO, at 600 0 Deposition exposure conditions Sulphur uptak ug/cm Carbon uptakg mg/cm Deposition reduction factor a... 

After 24 h subsequently in acetone alone the carbon content of the reaction product had increased to 46.7% of the original Fe304 sample weight. The extent of deposition was lower by a factor of 1.4 x 10- than that which would have been anticipated on Fe304. The low (100-125 ppm) sulphur uptake during the initial exposure to thiophene, was unlikely to have been the sole cause of this inhibition as it is not conceivable how it could have provided greater protection to acetone decomposition than the more extensive prior sulphiding (compare with Table IV). 

With Cr203 the addition of thiophene, at pressures of either 1000 iatm or 0.1 atm, did not influence either the kinetics or extent of acetone decomposition at 600°C (Fig. 1 and Table V). The sulphur uptakes for similar exposure conditions increased with thiophene partial pressure (Table V). 

However, it was shown that the sulphur uptake was not affected by the presence of steam up to H2O/H2=10 [377]. These observations were confirmed by STM experiments [430], which illustrate how H2S displaces adsorbed oxygen as illustrated in Figure 5.41. 

The dynamics of sulphur uptake in a prereformer is like a fixed-bed absorption as seen in a zinc-oxide bed (refer to Chapter 1). However, in a tubular reformer the pore diffusion restrictions in the sulphur adsorption in a single pellet has a complex influence on the transient sulphur profiles in the reactor and a mathematical model [112] [387] [389] is required to evaluate more exactly the time for fiill saturation and the breakthrough curves of sulphur. 

The rate of sulphur uptake in a single catalyst pellet can be described by means of a modified version of the equation for diffusion-controlled elution from a catalyst pellet derived by Goring and de Rosset [210] [381] ... 

The presence of small quantities of S in steels has little effect on the initial scaling rates in air, but may be detrimental to long-term scale adhesion. Sulphur has, however, been shown to be detrimental to breakaway oxidation in CO/CO2 environments. However, sulphur has been shown to reduce the total uptake of carbon in the steel under CO/C02 and reduce the scale thickening rate. In this context, free-cutting steels were found to oxidise at a significantly lower rate, as did steels subjected to pretreatment in H2S. 

Electrolytes are used to promote the exhaustion of direct or reactive dyes on cellulosic fibres they may also be similarly used with vat or sulphur dyes in their leuco forms. In the case of anionic dyes on wool or nylon, however, their role is different as they are used to facilitate levelling rather than exhaustion. In these cases, addition of electrolyte decreases dye uptake due to the competitive absorption of inorganic anions by the fibre and a decrease in ionic attraction between dye and fibre. In most discussions of the effect of electrolyte on dye sorption, attention is given only to the ionic aspects of interaction. In most cases, this does not create a problem and so most adsorption isotherms of water-soluble dyes are interpreted on the basis of Langmuir or Donnan ionic interactions only. There are, however, some observed cases of apparently anomalous behaviour of dyes with respect to electrolytes that cannot be explained by ionic interactions alone. 

Mechanisms for metal immobilization include intracellular uptake with complexation to ligands such as sulphur-containing peptides (metallothio-neins) and carboxylic acids (citrate, malate, oxalate) (Gadd, 1993 Sarret et al., 1998, 2002 Fomina et al., 2005c). Some fungi can also precipitate... 

Hambrook, J.L., Howells, D.J., Schock, C. (1993). Biological fate of sulphur mustard (l,l -thiobis(2-chloroethane)) uptake, distribution and retention of S in skin and blood after cutaneous application of S-sulphur mustard in rat and comparison with human blood in vitro. Xenobiotica 23 537-61. 

Bromfield A. (1975) Effect of ground rock phosphate-sulphur mixture on yield and nutrient uptake of ground nuts (Arachis hypogaea) in northern Nigeria. Exp. Agri. 11, 265-272. 

Following the administration of 100-200 MBq Tc-sulphur colloid intravenously, liver cirrhosis is characterized by a reduction in the uptake of radioactivity in the liver and an increased uptake by the spleen and bone marrow. Colloidal uptake in the liver is thus a valuable parameter for assessing any functional loss of the hepatic RES and for evaluating the residual parenchyma which is still functioning. It should be noted that the phagocytic capacity of the hepatic RES is closely related to the sinusoidal blood flow, the reduction of which is a result of the development of collaterals in the area of the hepatic... 

Lopez-Gonzalez et al. [218] also failed to cite the study by Humenick and Schnoor [216], but they analyzed in some detail the effect of carbon-oxygen and carbon-sulfur surface complexes on the uptake of mercuric chloride, which is very weakly ionized in aqueous solution. (The effectiveness of sulphurized carbons in removing mercury from air or water streams had been demonstrated earlier by Sinha and Walker [219], Humenick and Schnoor [216], and more recently by G6mez-Serrano and coworkers [208].) Their key results are summarized in Fig. 9. There was a noticeable uptake decrease when the activated carbons were oxidized with H Oi (AO). This decrease was not due to a reduction in the surface area and is contrary to the behavior of cationic metallic species, whose uptake is typically enhanced as a consequence of a lower pHp/x of the oxidized carbon. Upon subsequent heat treatment in helium at 873 K (A-873), the adsorption ca-... 

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