Total selenium concentration effect

Batch ELM Extraction of Selenium. A series of batch extraction experiments were carried out to assess the feasibility of an ELM process for the removal of selenium from refinery wastewater streams. To do this we developed emulsion formulations and evaluated these formulations for the capability of reducing the aqueous phase selenium concentration below 0.05 mg/L. Next, we carried out experiments to evaluate the effect of competition between the two oxidation states, the effect of total selenium concentration of the extraction behavior, the effect of external phase pH on the transport rate, and the effect of competing anions (like sulfate) on the extraction efficiency and kinetics. 

The results of the competition experiments are presented in Figures 8 and 9. Figure 8 is a plot of selenate [Se(VI)] concentration as a function of extraction time during batch extractions. Line "b" shows the extraction behavior of selenate in isolation, and line "a" shows the extraction behavior of selenate in the presence of an equal amount of selenite. It is evident that the presence of selenite [Se(IV)] has minimal effect on the extraction behavior of selenate [Se(VI)] at the concentrations studied. We still were able to reduce the concentration to a level well below our target of 0.05 mg/L within a very short time (the first two minutes). The small difference between the two rates is probably due to the difference in total selenium concentrations, rather than to competition between the two species. 

It was desired to determine if the extraction behavior of Se(IV) depends on the total selenium concentration in the external phase. To investigate the effect of external phase concentration on the rate of Se(IV) extraction, we carried out batch extraction experiments at two different initial concentrations (1 and 10 mg/L). The emulsion formulation was the same as described previously. The results are given in Figure 10 (a plot of Se(IV) concentration as a function of extraction time) and show that there is little difference in the initial extraction rates between 1 and 10 mg/L selenite. Beyond two minutes, the extraction rate of the higher amount (10 mg/L) tapers off. 

Plasma selenoprotein P, plasma GSPHx-3, and total plasma selenium concentration are aU lowered by the APR to injury or infection. This effect should be considered when interpreting plasma selenium values in postoperative patients or those with infection or inflammatory disease. 

Effect of Total Selenium(rV) Concentration on Transport Rate. As suggested by the equilibrium partitioning results and as confirmed by the competition experiments, selenate... 

Data from animal studies suggest that exposure to excessive selenium has adverse effects on testosterone levels and sperm production and increases the percentage of abnormal sperm (El-Zarkouny et al. 1999 Kaur and Parshad 1994 NTP 1994). A significant reduction (49%) in serum testosterone levels was reported for New Zealand White rabbits gavaged with 0.3 mg selenium/kg (0.001 mg selenium/kg/day) as sodium selenite once a week for 6 weeks (El-Zarkouny et al. 1999). The percentage of spermatozoa without an acrosome was also increased in treated rabbits compared with controls, but the difference was not significant. Sperm motility, ejaculate volume, sperm concentration, and total sperm output were all reduced by selenium treatment, but statistical analysis of these data was not presented. 

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