Abstract
Four types of polybenzimidazole (PBI)-based polymers (m-PBI, p-PBI, pyridine-based m-PBI and alkylated m-PBI) have been prepared and characterized. Extraction behaviour of heavy metal ions, viz. U(VI), Th(IV) and Pd(II), with these polymers was investigated. Distribution ratios for the extraction of these metal ions were measured as a function of nitric acid concentration. Extraction data reveal that, in general, p-PBI exhibits a higher distribution ratio for U(VI), Th(IV) and Pd(II) compared with the other polymeric resins evaluated in the present study. Column chromatography experiments were carried out with a solution of U(VI), Th(IV) and Pd(II) in dilute nitric acid media using columns packed with m- and p-PBI polymeric material for understanding the sorption and elution behaviour. The p-PBI-based resin has shown higher palladium sorption capacity (1.8 mmol g−1). The studies also established that p-PBI resin is a potential candidate material for the recovery of U(VI) and Th(IV) (capacity 0.22 mmol g−1 and 0.13 mmol g−1) from an aqueous stream, e.g. mine water samples.
Highlights
Uranium nitrate supplied by nuclear fuel complex (NFC), Hyderabad, thorium nitrate (Indian Rare Earths Limited (IREL), Udyogamandal, Kerala, India) and palladium nitrate (Aldrich) were used as such without further purification
Entire Pd(II) was subsequently eluted (732 mg) in a small volume in stripping experiments; p-PBI resin can be re-used for the removal of palladium from the aqueous stream as the sorbed metal ion species can be effectively removed in small volumes
Among the four polymers examined in the present study, p-PBI exhibited higher capacity for these metal ions both at lower acidity and in higher acid medium compared to other polymeric resins, m-PBI, pyridine-based m-PBI and alkylated m-PBI
Summary
All the chemicals used in the present work were of AR or GR grade (Loba Chemicals) and used without further purification. Toluene and triethylamine (Avra Chemicals) were used in the present study after purification by the standard distillation procedure. Uranium nitrate supplied by nuclear fuel complex (NFC), Hyderabad, thorium nitrate (Indian Rare Earths Limited (IREL), Udyogamandal, Kerala, India) and palladium nitrate (Aldrich) were used as such without further purification
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