ION-EXCHANGE OF ZINC ON AN AMINOPHOSPHONATE-CHELATING RESIN

The distribution coefficient (K-D) of trace zinc in 1 M NaCl solution on an aminophosphonate-chelating resin Duolite C467 increased with pH to a peak value close to 200 000 ml/g at pH about 6. At higher pH valu es the K-D dropped to 25 000 ml/g due to competition of zinc hydrolysi s. Increasing NaCl concentration up to about 1 M improved zinc uptake on sodium-form Duolite C467 since it prevented exchanger hydrolysis, b ut at higher concentrations K-D decreased somewhat due to Zn2+/Na+ com petition. Also, increasing zinc concentration, from 6 x 10(-7) M to 1 mM, improved zinc uptake, since the exchanger is less hydrolysable in zinc form. EDTA interfered strongly with zinc uptake when present at c oncentrations higher than 1 mu M, sodium cyanide at concentration high er than 1 mM, citrate in concentrations higher than 10 mM while glucon ate did not interfere at all.