A sustainable cationic chitosan/E. coli fiber biosorbent for Pt(IV) removal and recovery in batch and column systems

• We presented a sustainable biosorbent for removal and recovery of Pt(IV) from acidic aqueous solution.
• Powder form of poly(allylamine hydrochloride)-modified E. coli was immobilized as the fiber form.
• The mechanical strength of biosorbent was good even in a strong acidic solution in both batch and column systems.
• The sorption performance was best comparing other three kinds of ion exchange resin.
• The column was successfully eluted with high desorption efficiency of 99.7%, opening up the possibility of regeneration.

In this study, the cationic bacterial biosorbent, poly(allylamine hydrochloride) (PAA/HCl)-modified Escherichia coli, was successfully immobilized as a chitosan fiber, which was proved to be a sustainable biosorbent for platinum removal and recovery from aqueous solutions in batch and column systems. Compared to the commercial ion exchange resins, PAA/HCl-modified E. coli chitosan fiber showed a quite good performance for Pt(IV) removal. Two-parameter (Langmuir and Freundlich) and three-parameter (Sips and Redlich–Peterson) models were employed to describe the batch isotherm experimental data. Among these four models, the Redlich–Peterson model fit best, with higher coefficient of determination, chi-square and average percentage error values. Thermodynamic parameters (ΔG0 < 0 and ΔH0 > 0) showed the spontaneity and endothermic nature of biosorption process. The kinetics of Pt(IV) biosorption with different initial concentrations were better fit by the pseudo-second-order model, with higher coefficient of determinations and more closely predicted qe values. An acidified 0.005 M thiourea was used to regenerate platinum from exhausted biosorbent maintaining desorption efficiencies over 90.2% until five cycles. In the column studies, the breakthrough curve showed a typical S-shaped curve, with breakthrough and exhaustion times appearing at 36.0 h and 52.5 h, respectively, which was opened up a possibility of column regeneration.