Chromium uptake from tricomponent solution in zeolite fixed bed

Abstract

Removal of Cr 3+ , Ca 2+ , Mg 2+ and K + in equilibrium isotherms and in tricomponent solutions (Cr/Ca/K, Cr/Ca/Mg and Cr/Mg/K) were investigated in NaX and NaY packed beds at 30 • C. The equilibrium selectivity was obtained as Cr +3 > Mg 2+ > Ca 2+ ≈ K + for zeolite NaY and Ca 2+ Cr 3+ > Mg 2+ ≈ K + for zeolite NaX. The breakthrough curves showed sequential ion exchange where chromium ions are able to replace the competing cations. Some mass transfer parameters, such as length of unused bed and overall mass transfer coefficient, were investigated. Chromium retention was also investigated through a mass balance. Based on the breakthrough results, it was concluded that chromium-uptake mechanism was hardly influenced by the competition and interaction between the entering ions. NaY showed a higher affinity towards Cr 3+ for both equilibrium and dynamic systems and its sites were more efficiently used in the ion exchange process. Chromium was less retained in NaX due to the high selectivity towards calcium ions.

<b>Comparative study of the adsorption of cadmium and zinc on activated bone char

“…Small values of this parameter (MTZ) mean that the breakthrough curve is close to an ideal step with negligible mass-transfer resistance (Barros, Zola, Arroyo, Tavares, & Sousa-Aguiar, 2006).…”

An Ion Adsorption Model Related to the Change in the Standard Chemical Potential of Adsorption Reactions

“…Although measurement errors cannot be excluded, the irregular variation in Gun'ko et al (2003) used the plot of x versus P/P 0 (where P stands for pressure) to describe the adsorption properties of fumed silicas, while Chirkova et al (2004) applied a similar plot for determining the standard sorption isotherms of various vapours onto cellulose. In a similar manner, Barros et al (2004) plotted the equivalent fraction of the in-going cation in the solid phase as a function of the equivalent fraction of the same cation in solution. All these studies confirmed that x and A/A 0 are strongly correlated.…”

Trivalent Metal Adsorption Properties on Synthesized Viscose Rayon Succinate

“…4 Trivalent heavy metal ions (THM) such as Al 3þ , Cr 3þ , and Fe 3þ in aqueous solution are toxic to all living organisms including human beings, microbes, plants, fish, and mammals. [5][6][7] Especially, the toxicity Al 3þ in drinking is well reported, and its involvement to Alzheimer's disease has been documented. 8,9 Even though Cr 3þ is an essential nutrient, its oxidation to toxic Cr 6þ can cause lung cancers and ecological problems.…”