Process and composition for removal of metal ions from aqueous solutions

Claim 1

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° and 90° 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 1 in each unit of the polymer is a pendant group independently selected from --H or a substituent selected from --CH 2 COOH, --CH 2 --P(═O)(OH) 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 1 and R 2 are each independently --CH 3 , --SO 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 2 in each polymer unit is each independently selected from H-- or a substituent selected from: ##STR32## wherein R 3 , R 4 , and R 5 are each independently selected from --H, --CH 2 COOH, or --CH 2 P(═O)(OH) 2 and q is 0, 1, 2, 3, or 4; ##STR33## wherein r is an integer between about 10 and 20,000 and X 3 in each polymer unit is independently selected from H-- or a substituent selected from: ##STR34## wherein R 3 , R 4 , and R 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 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 3 , R 4 and R 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 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 3 , R 4 and R 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 6 in each polymeric unit is independently selected from --H or a substituent selected from: ##STR43## wherein q is 1 to 4, and R 3 , R 4 and R 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 7 in each polymeric unit is independently selected from --H or a substituent; ##STR46## wherein q and R 3 , R 4 and R 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 8 , X 9 , and X 10 are each independently selected from --H or a substituent selected from: ##STR49## wherein q, R 3 , R 4 and R 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 1 , H to substituent in X 2 , H to substituent in X 3 , H to substituent in X 4 , H to substituent in X 5 , H to substituent in X 6 , H to substituent in X 7 , --CH 2 CH(OH)CH 2 OH or --CH 2 CH(OH)CH 2 Cl to substituent in each of X 8 , X 9 , or X 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).