Ion exchange and adsorption of cadmium from aqueous media in sodium-modified expanded vermiculite

The possibility of using ion-selective membrane systems based on alizarin and aluminone in measuring the quantitative composition of ions of certain trivalent metals in technological aqueous media and wastewater is considered and experimentally confirmed

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The sorption of lead, cadmium and strontium from aqueous solutions on sepiolite

Hemijska industrija ◽

10.2298/hemind0602015l ◽

2006 ◽

Vol 60 (1-2) ◽

pp. 15-22

Author(s):

Slavica Lazarevic ◽

Ivona Jankovic-Castvan ◽

Miloje Ilic ◽

Dusan Jovanovic ◽

Djordje Janackovic ◽

...

Keyword(s):

Ion Exchange ◽

Aqueous Media ◽

Nitrogen Adsorption ◽

Point Of Zero Charge ◽

X Ray Diffraction ◽

Zero Charge ◽

Ion Sorption ◽

Solid Liquid ◽

Sorption Mechanisms ◽

Bet Equation

The results of the characterization and the sorption properties of sepiolite from the locality Slovici are presented in this paper. X-Ray diffraction analysis, infrared spectroscopy and differential thermal analysis revealed sepiolite as the main phase and small amounts of magnesite as an impurity. The specific surface area of sepiolite, determined by nitrogen adsorption and by applying the BET equation was found to be 339 m2/g. The point of zero charge was determined by the batch equilibration method, under different conditions, and the shift in the point of zero charge, in the presence of Pb2+, Cd2+ and Sr2+ ions, was investigated. It was determined that the point of zero charge changed with modification of the solid/liquid ratio and by washing the powder, which indicated that under the investigated conditions some dissolution of the sepiolite and impurities took place also influencing the position of the point of zero charge. In the presence of Pb2+, Cd2+ and Sr2"1" ions, the point of zero charge was shifted toward lower pH values denoting specific ion sorption. The greatest shift and, therefore the largest specific sorption, appeared in the case of Pb2+ ions, somewhat less with Cd2+, and the least with Sr2"1" ions. The adsorption isotherms were determined for the Pb2+, Cd2+ and Sr2+ ions, as well as the amounts of these ions that were removed from aqueous media by the ion exchange of Mg2+ ions from the sepiolite structure, depending on the equilibrium ion concentrations. In the case of ion exchange, as in the case of specific sorption, the affinity of sepiolite for the investigated ions can be presented in the following order Pb2+ > Cd2+ > Sr2"1". For the removal of Sr2"1" ions from aqueous media by sepiolite, a third mechanism is important probably, the ion exchange of exchangeable ions from the sepiolite structure channels. As the result of the action of all the sorption mechanisms sepiolite is removes mostly Pb2+ ions, then Cd2+ and least of all Sr2"1" ions from the aqueous media.

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Cupric ion binding by coal humic acids at pH's 1–3

Canadian Journal of Chemistry ◽

10.1139/v77-452 ◽

1977 ◽

Vol 55 (18) ◽

pp. 3248-3254 ◽

Cited By ~ 6

Author(s):

John B. Green ◽

Stanley E. Manahan

Keyword(s):

Humic Acid ◽

Ion Exchange ◽

Humic Acids ◽

Aqueous Media ◽

Surface Adsorption ◽

Ion Binding ◽

Cupric Ion ◽

Floc Structure ◽

Intermolecular Bonding ◽

High Concentrations

The extent and mechanism of cupric ion binding by humic acid (HA) at low pH's where the material was insoluble in aqueous media was investigated. It was shown that significant amounts of Cu(II) were bound by HA even at pH's as low as 1.35. Two major types of HA—Cu2+ binding were observed. Binding which was accompanied by exchange of H+ was more prevalent at high pH's and [Cu2+]. Nonexchange bonding occurred at all pH's, but assumed greater importance at low pH's. Since the pattern of Cu(II) uptake could not be interpreted in terms of basic ion exchange or surface adsorption theory, a new model was proposed which qualitatively explained the dependence of Cu(II) on pH and [Cu2+]. The model assumed that the intermolecular bonding in flocculated HA was determined by the relative amounts of H+ and Cu2+ available for forming bridging bonds between the HA molecules. The model suggested that at high concentrations of Cu(II) and/or high pH's, the floc structure was such that the formation of copper bridge bonds was maximized.

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