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摘要
Batch adsorption experiments of four divalent metals, copper, nickel, cobalt and zinc, on porous glass from citric acid aqueous solution were performed at 298 K. The maximal adsorption of each metal was obtained in the pH range of 2.0-2.5 from solution containing 20 mM citric acid. The amount of metal adsorbed decreased at higher pH values than that of maximal adsorption because of the formation of citric acid complex ions. This indicated that the metal was adsorbed by an ion exchange reaction.
Separation experiments of the four metals were conducted in a porous glass packed column by using citric acid eluent at 298 K. The maximal retention time occurred in the same pH range as that of the adsorption amount when 20 mM citric acid eluent was used. This indicated that the retention time was remarkably influenced by the adsorption amount. Copper and nickel were separated using 5 mM citric acid as eluent at pH 3.0. On the other hand, zinc and cobalt were not separated at pH 5 or below at any concentration of citric acid, because the formation curves of citric acid complex ions of these metals lie close to each other.
For citric acid concentrations up to 1 mM, the retention times of copper, nickel, and cobalt decreased monotonously with increasing pH at pH 5.0 or above. On the other hand, the retention time of zinc increased at pH 6.5, because of the generation and precipitation of zinc hydroxide. Thus, the four metals were successfully separated with 0.25 mM citric acid eluent at pH 7.0.
- 出版日期2011
