Study of chromium(VI) adsorption onto modified activated carbons with respect to analytical application

Abstract

Two different types of modification of activated carbon, by treatment with concentrated solution of HNO 3 and outgassing treatment at high temperature, were studied in order to obtain the most effective adsorption of chromium(VI) ions from water solution. The basic parameters affecting the adsorption capacity of Cr(VI) ions on modified activated carbons were studied in details and the effect of modifications of activated carbons has been determined by studying the initial runs of adsorption isotherms. The obtained Cr(VI) adsorption isotherms were well fitted in the Freundlich equation. The reduction of Cr(VI) to Cr(III) and further ion exchange mechanism of adsorption onto oxidizing activated carbon and surface precipitation to Cr(OH) 3 in case of outgassing activated carbon were found as the main adsorption mechanisms of Cr(VI) ions onto modified activated carbons. Presence of chlorides and nitrates in studied adsorption system strongly decreased the adsorption ability of Cr(VI) onto outgassing activated carbon and mechanism of this behavior is proposed.

Development of sensitive determination method for platinum in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry

“…The adsorption mechanism of Pt(IV) on the modified activated carbon is quite different from those of Au(III) or Pd(II) on the same sorbent reported in other studies [35,36]. The XPS studies confirmed that Pt(IV) adsorption onto activated carbon is probably connected with both ion exchange and reduction processes on the activated carbon surface.…”

“…Activated carbon is characterized by a large surface area, well-developed micro pore structure, high adsorption capacity and high degree of surface reactivity. What is more, the activated carbon surface can be easily modified in several ways to provide varying adsorption capacity and selectivity for different ions [26]. The most important phenomena, which affect the ion adsorption capacity, are ion exchange, nonspecific sorption, redox reactions, surface precipitation and formation of surface chelates.…”

Determination of nickel and cobalt in reference plant materials by carbon slurry sampling GFAAS technique after their simultaneous preconcentration onto modified activated carbon

“…It is worth to mention that sorption capacity for the DMGC* carbon is much higher when compared with the BSPDI impregnated activated carbon (2.1 mg/g for both ions) (Ghaedi et al, 2008). The great adsorption properties of OC* carbon towards Ni(II) and Co(II) ions are probably caused by the presence of humic acids on its surface, which in the form of Ni(II) and Co(II) complexes can adsorb on the carbon active centers (Dobrowolski and Otto, 2010). Despite excellent sorption capacity, that carbon has not been selected for enrichment of nickel and cobalt ions from certified reference materials because of insufficient selectivity in NO 3 À and Cl À matrix.…”

Atomic spectrometry update. Elemental speciation

“…treatment with concentrated solution of HNO 3 and outgassing treatment at high temperature, were studied in order to obtain the most effective adsorption of Cr VI ions from solution. 222 The reduction of Cr VI to Cr III and further ion exchange mechanism of adsorption onto oxidizing activated carbon and the surface precipitation to Cr(OH) 3 in case of outgassed activated carbon were found as the main adsorption mechanisms of Cr VI ions onto modified activated carbons. The presence of chlorides and nitrates strongly decreased the adsorption of Cr VI onto outgassing activated carbon.…”