A cyclic process for the removal of metal ions selected from the group consisting of iron, cobalt, chromium, vanadium, copper, cadmium, nickel, zinc, lead, aluminum, mercury, silver, manganese from a fluid stream comprising said metal ions, which process comprises:
- (A) contacting the fluid stream in a contacting zone with an aqueous reaction solution at between about 10.degree. and 90.degree. C. for a time sufficient to chelate the metal ions the reaction solution itself consisting essentially of an effective amount of water-soluble organic polymeric chelant to chelate the metal ion present selected from organic polymeric chelants of the formula:
- ##STR28## wherein X.sub.1 in each unit of the polymer is a pendant group independently selected from --H or a substituent selected from --CH.sub.2 COOH, --CH.sub.2 --P(.dbd.O)(OH).sub.2, ##STR29## wherein R is alkyl, aminoalkyl, hydroxyalkyl, sulfoalkyl, or carboxyalkyl, and alkyl in these substituents contains from one to four carbon atoms;
- or ##STR30## wherein R.sub.1 and R.sub.2 are each independently --CH.sub.3, --SO.sub.3 H, --Cl, --H, or --COOH;
- and n is an integer between about 5 and 20,000;
- ##STR31## wherein p is an integer between about 5 and 20,000;
- and wherein X.sub.2 in each polymer unit is each independently selected from H-- or a substituent selected from:
- ##STR32## wherein R.sub.3, R.sub.4, and R.sub.5 are each independently selected from --H, --CH.sub.2 COOH, or --CH.sub.2 P(.dbd.O)(OH).sub.2 and q is 0, 1, 2, 3, or 4;
- ##STR33## wherein r is an integer between about 10 and 20,000 and X.sub.3 in each polymer unit is independently selected from H-- or a substituent selected from:
- ##STR34## wherein R.sub.3, R.sub.4, and R.sub.5 are as defined hereinabove, and s is an integer between about 1 and 4;
- or ##STR35## wherein R is as defined hereinabove;
- ##STR36## wherein t is an integer between about 10 and 20,000;
- and X.sub.4 in each polymer unit is independently selected from H-- or a substituent selected from:
- ##STR37## wherein x is an integer between 1 and 4;
- and R.sub.3, R.sub.4 and R.sub.5 are as defined hereinabove;
- or ##STR38## wherein R is as defined hereinabove;
- ##STR39## wherein y is an integer between about 10 and 20,000;
- and X.sub.5 in each polymer unit is independently selected from --H or a substituent selected from:
- ##STR40## wherein z is an integer between about 1 and 4;
- and R.sub.3, R.sub.4 and R.sub.5 are as defined hereinabove;
- or ##STR41## wherein R is as defined hereinabove;
- ##STR42## wherein a is 6 and b is 1 to 4, and X.sub.6 in each polymeric unit is independently selected from --H or a substituent selected from:
- ##STR43## wherein q is 1 to 4, and R.sub.3, R.sub.4 and R.sub.5 are as defined hereinabove;
- or ##STR44## wherein R is as defined hereinabove;
- and x is between about 10 and 10,000;
- ##STR45## wherein X.sub.7 in each polymeric unit is independently selected from --H or a substituent;
- ##STR46## wherein q and R.sub.3, R.sub.4 and R.sub.5 are defined hereinabove;
- or ##STR47## wherein R is as defined hereinabove;
- and m is an integer from 1 to 4 and x is as defined hereinabove;
- ##STR48## wherein X.sub.8, X.sub.9, and X.sub.10 are each independently selected from --H or a substituent selected from:
- ##STR49## wherein q, R.sub.3, R.sub.4 and R.sub.5 are as defined hereinabove, or ##STR50## wherein R is as defined hereinabove;
- and w is between about 10 and 10,000;
- with the proviso that the overall ratio of H to substituent in X.sub.1, H to substituent in X.sub.2, H to substituent in X.sub.3, H to substituent in X.sub.4, H to substituent in X.sub.5, H to substituent in X.sub.6, H to substituent in X.sub.7, --CH.sub.2 CH(OH)CH.sub.2 OH or --CH.sub.2 CH(OH)CH.sub.2 Cl to substituent in each of X.sub.8, X.sub.9, or X.sub.10 in each organic polymeric chelant described hereinabove is between about 10/90 and 90/10 and wherein the polymeric chelant has a molecular weight of between about 600 and 1,000,000;
- (B) treating the aqueous solution produced in step (A) by membrane separation means effective to remove water and other low molecular weight reaction products having a molecular weight of 500 or less from the aqueous solution as a single phase;
- (C) contacting the concentrated aqueous solution produced in step (B) with a mineral acid under conditions effective to release the metal ion from the chelant and form a regenerated chelant;
- and
- (D) removing the released metal ion by a second membrane separation means effective to separate the released metal ion as a single phase from said regenerated chelant;
- and
- (E) recycling the concentrated aqueous solution including said regenerated chelant from step (D) to the contacting zone of step (A).