Adsorption Studies of Radioactive Silver Using Mineral Mixture

Abstract

The adsorption behavior of mineral mixture for silver ions from aqueous solutions has been carried out as a function of appropriate electrolyte, equilibration time, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature in Order to simulate the best conditions in which this material can be used as an adsorbent. The radiotracer technique was employed to determine the distribution of silver ("°"Ag) using a batch method. Maximum adsorption was observed at 0.005 mol L ' acid solutions (HNO,, H2SO4 and HCIO4) using 0.3 g of adsorbent for 1.29 X10"" mol L"' silver concentration in five minutes equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the ränge of 2.0 X IQ-' to 2.0X10"'mol L"' silver concentration. The characteristic Freundlich constants, i.e. l/n = 0.64 ±0.02 and K = 1.91 ±0.07 m mol g have been computed for the Sorption system. The uptake of silver increases with the rise in temperature (278-323 K).

Zirconium decontamination from aqueous media using lateritic minerals

“…The temperature was varied from 283 to 323 K. The amount of zirconium ion adsorbed at various temperatures is shown in Table 4, which reveals that the uptake of zirconium increases with increase in temperature, indicating better adsorption at higher temperature. Similar results have also been reported for the adsorption of silver [25] and cadmium [27] on mineral mixture and zirconium on activated charcoal [13] and silica gel [19]. The enhanced amount of zirconium adsorbed at equilibrium with the rise in temperature may be either due to acceleration of some originally slow adsorption steps or due to creation of some new active sites on the adsorbent surface.…”

“…The results presented in Fig. 1a and b show that adsorption of zirconium ions decreases with an increase in acid concentration from 0.005 to 3.0 M. Similar trends have been observed for the adsorption of silver, lead and cadmium on mineral mixture [25][26][27] and zirconium on silica gel [21]. The decrease in adsorption of zirconium with an increase in acid concentration may be attributed to the competition between the excess of H + ions in the medium and positively charged hydrolyzed species present in the solution.…”

“…The fractional value of 1/n (0 < 1/n < 1) precludes the heterogeneous surface of the lateritic minerals [36]. The applicability of Freundlich isotherm in the present system is similar to earlier adsorption studies of silver and cadmium on mineral mixture [25,27].…”

“…The LM was selected, since it is abundantly available at very low cost and the main constituents of the weathering product are goethite, hematite, magnetite, alumina and quartz, all of which are good adsorbents [22][23][24]. It is also the continuation of our previously studied naturally occurring material used for the decontamination of silver, lead and cadmium from aqueous media [25][26][27].…”

Cadmium Decontamination from Aqueous Media Using Lateritic Minerals

“…5). [24,25] To classify the physical or chemical adsorption, the data were applied to Dubinin -Radushkevich (D-R) isotherm model. The numerical values of adsorption capacity (K) and intensity (1/n) were evaluated from the intercept and slope of the straight line, using a leastsquare fit program, and were found to be 5.14 £ 10 24^1 .14 £ 10 25 mol g 21 and 0.61^0.02, respectively.…”