Phosphonomethylated polyethylenimine resin for recovery of uranium from seawater

Summary

Branched polyethylenimine (BPEI) was crosslinked by a bis-epoxide to give a resin (CL-BPEI), which was further functionalized by phosphorous acid / formaldehyde leading to phosphonomethylated CL-BPEI (PhosCL-BPEI). The latter resin has been found to recover uranium from natural seawater very efficiently but not the former resin; with column method PhosCL-BPEI recovered 85-64 % of uranium in the original seawater at SV=170–680 hr⁻¹. The highest recovery rate obtained so far was 46.8 μg-U/g-resin/6 hr at SV=680 hr⁻¹. PhosCL-BPEI could be used repeatedly without appreciable decrease of the efficiency. The molar ratio of phosphonomethyl group to amino groups in the resin affects the adsorption ability very much, the adequate P/N ratio being ∼0.25. Both PhosCL-BPEI and CL-BPEI showed a large adsorption capacity from an aqueous solution of uranyl ions. It is stressed, however, that the phosphonomethylation of CL-BPEI is very important for the uranium recovery from seawater.