Synthesis of new solid-supported phosphorus reagents and application to metal ion recovery

A new series of solid-supported phosphorus reagents has been developed. The first (Part I) is a bifunctional phosphorus ion exchange resin containing primary phosphinic acid and secondary phosphinic acid or secondary phosphine oxide ligands which have been covalently bound to polystyrene beads. These ion exchange resins have been evaluated for their Zn⁺², Cu⁺², and Rb⁺extraction ability. In general, when compared with sulfonic acid and carboxylic acid ion exchange resins, the phosphinic acid resins show superior extraction ability and selectivity. Recent studies have shown that phosphinic acid resins operate by both a redox and ion exchange mechanism depend ing on the reduction potential of the metal.

Part II is a discussion of high stability solid-supported liquid complexing agents. The high stability is obtained by incorporating polymerizable double bonds into the phosphorus complexing agent. The polymerizable extractants are swollen into polymer supports (macroporous polystyrene beads and macroporous polypropylene membranes) with toluene and polymerized with AIBN to form interpenetrating polymer networks (IPN's).

Diundecenyl phosphoric acid (DUP) IPN's show increased stability over polymer absorbed extractants (PAE's) as long as the DUP concentration in the swelling solution is 0.5M or greater. Copolymerization of DUP with acrylonitrile (AN) allows for IPN formation which can incorporate up to 85% of the DUP. This DUP/AN IPN can not be eluted from the solid-support with ethanol. Totally stable IPN's have been developed by incorporating styrene groups into the phosphorus complexing agent. These IPN's are 100% stable at 0.5M or higher or if copolymerized with styrene.

A high stability solid-supported liquid membrane has been synthesized by copolymerizing DUP with AN within a polypropylene membrane. Its permeability coefficient vs. time gives a slope of -0.007 (cm sec^-1 day^-1) over 42 days while that for a di-2-ethylhexyl phosphoric acid solid-supported liquid membrane gave a slope of -0.031 under the same conditions which limits its lifetime to six days.