Solid phase extraction, preconcentration and separation of indium with methylene crosslinked calix[4]- and calix[6]arene carboxylic acid resins

Calixarene-based cation exchange resins have been developed by methylene crosslinking of calix[4]- and calix[6]arene carboxylic acid derivatives and solid phase extraction behavior of the resins towards some multivalent metal ions has been studied. The extraction profile of metal ions as a function of pH follows the order In(III)> Ga(III)> Fe(III)> Zn(II). The cooperativity effect of plural ion exchangeable groups as well as the rigid cyclic structure of calixarene contributed significantly for indium selectivity and both the resins were selective for uptake of indium. Equilibrium of indium extraction was reached within 4 h. The resins exhibited outstanding indium uptake capacity due to the aggregating effect of functional groups. The maximum indium uptake capacity of calix[4]arene resin was 109 mg g−1 resin while that of calix[6]arene resin was 213 mg g−1 resin. The extracted indium was easily and almost quantitatively back extracted with dilute hydrochloric acid solution and the extractant was regenerated without any physical/chemical damage. Preconcentration and mutual separation of indium from zinc was achieved using the column separation technique. The calix[6]arene based resin is a promising candidate for selective recovery of indium from the mixture containing substantial quantity of zinc such as zinc refinery residues.

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► Fabrication of cation-exchange resins by methylene crosslinking of calixarene carboxylic acids.
► High extraction efficiency and remarkable indium selectivity of the resins.
► High indium uptake capacity of the resins than those ever reported in the literature.
► Convenient and quantitative release of extracted indium ion on changing the pH.
► Recyclable sorbent having tremendous promise for preconcentration and separation of indium.