Metal Ion Uptake Behaviour of Nafion in Presence of Organic Complexing Reagents

This study examined and compared the ability of chicken feathers, human hair and animal horns, as keratin-composed biosorbents, for the removal of Zn2+ and Cu2+ ions from single metal ion aqueous solutions under different operating conditions. The three biosorbents investigated in this study were all capable of adsorbing Zn2+ and Cu2+ ions from aqueous solutions. The biosorbent showing the highest uptake of Zn2+ and Cu2+ ions was animal horns. Chicken feathers showed a higher Cu2+ ion uptake and a lower Zn2+ ion compared to human hair. Increasing the initial concentration of Zn2+ or Cu2+ ions, or increasing the initial pH value, increased the metal ion uptake. Such uptake decreased when the temperature was raised from 25°C to 50°C for all adsorbent/metal ion combinations except for Zn2+ ion/human hair where the uptake increased with temperature. It was demonstrated that the addition of NaCl salt to the metal ion solution depressed the metal ion uptake. The Freundlich isotherm model was found to be applicable to the adsorption data for Cu2+ and Zn2+ ions.

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Synthesis of functionalized phenolformaldehyde polymer resins by the reaction of 2,4-dihydroxyacetophenone formaldehyde resin with various amines and their metal ion uptake properties

Journal of Applied Polymer Science ◽

10.1002/app.20076 ◽

2004 ◽

Vol 92 (3) ◽

pp. 1501-1509 ◽

Cited By ~ 11

Author(s):

A. Ravikumar Reddy ◽

K. Hussain Reddy

Keyword(s):

Metal Ion ◽

Ion Uptake ◽

Formaldehyde Resin ◽

Metal Ion Uptake

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Properties of the mammalian and yeast metal-ion transporters DCT1 and Smf1p expressed in Xenopus laevis oocytes

Journal of Experimental Biology ◽

10.1242/jeb.204.6.1053 ◽

2001 ◽

Vol 204 (6) ◽

pp. 1053-1061 ◽

Cited By ~ 1

Author(s):

A. Sacher ◽

A. Cohen ◽

N. Nelson

Keyword(s):

Xenopus Laevis ◽

Metal Ions ◽

Metal Ion ◽

Divalent Cations ◽

Ion Uptake ◽

Xenopus Laevis Oocytes ◽

Ion Transporters ◽

Divalent Metal Ions ◽

Transport Pathway ◽

Metal Ion Uptake

Transition metals are essential for many metabolic processes, and their homeostasis is crucial for life. Metal-ion transporters play a major role in maintaining the correct concentrations of the various metal ions in living cells. Little is known about the transport mechanism of metal ions by eukaryotic cells. Some insight has been gained from studies of the mammalian transporter DCT1 and the yeast transporter Smf1p by following the uptake of various metal ions and from electrophysiological experiments using Xenopus laevis oocytes injected with RNA copies (c-RNA) of the genes for these transporters. Both transporters catalyze the proton-dependent uptake of divalent cations accompanied by a ‘slippage’ phenomenon of different monovalent cations unique to each transporter. Here, we further characterize the transport activity of DCT1 and Smf1p, their substrate specificity and their transport properties. We observed that Zn(2+) is not transported through the membrane of Xenopus laevis oocytes by either transporter, even though it inhibits the transport of the other metal ions and enables protons to ‘slip’ through the DCT1 transporter. A special construct (Smf1p-s) was made to enhance Smf1p activity in oocytes to enable electrophysiological studies of Smf1p-s-expressing cells. 54Mn(2+) uptake by Smf1p-s was measured at various holding potentials. In the absence of Na(+) and at pH 5.5, metal-ion uptake was not affected by changes in negative holding potentials. Elevating the pH of the medium to 6.5 caused metal-ion uptake to be influenced by the holding potential: ion uptake increased when the potential was lowered. Na(+) inhibited metal-ion uptake in accordance with the elevation of the holding potential. A novel clutch mechanism of ion slippage that operates via continuously variable stoichiometry between the driving-force pathway (H(+)) and the transport pathway (divalent metal ions) is proposed. The possible physiological advantages of proton slippage through DCT1 and of Na(+) slippage through Smf1p are discussed.

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