Uphill transport and mathematical model of Pb(II) from dilute synthetic lead-containing solutions across hollow fiber supported liquid membrane

This work presents an experimental investigation and mathematical model of Pb(II) separation and stripping from relatively low-level lead-containing synthetic solutions through a hollow fiber supported liquid membrane (HFSLM) by using di-2-ethylhexyl phosphoric acid (D2EHPA) in toluene as an extractant or carrier. The separation was studied on several variables: concentration of D2EHPA, types of stripping solutions (distilled water, HNO3, H2SO4 and HCl), concentration of the selected stripping solution, flow patterns of feed and stripping solutions, types of lead-containing solutions (Pb(NO3)2 and PbCl2), and flow rates of feed and stripping solutions. The results remarkably showed that HFSLM could successfully reduce a very low concentration of Pb(II) in feed solution to less than the regulatory discharge limit of 0.2 mg/L issued by the Ministry of Industry and the Ministry of Natural Resource Environment, Thailand. The highest extraction and stripping results were achieved by using 0.03 M D2EHPA, 0.9 M HCl at equal flow rates of feed and stripping solutions of 100 mL/min using a single-pass of feed solution and circulating of stripping solution. High percentages of extraction and stripping were observed from both Pb(NO3)2 and PbCl2 solutions. The kinetics of Pb(NO3)2 and PbCl2 separation were corresponded to second-order reaction with the rate constants of 1.49 and 1.51 L/mg min, respectively. The prediction of Pb(II) concentrations in the outlet Pb(NO3)2 and PbCl2 feed solutions obtaining from mathematical model were in good agreement with the experimental results at the average percent deviations of 4% for Pb(NO3)2 solution and 8% for PbCl2 solution.

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► HFSLM system can reduce a very low concentration of Pb(II) to less than the regulatory discharge limit.
► 0.03 M D2EHPA, 0.9 M HCl, flow rates of 100 mL/min are optimum conditions.
► The highest percentages of extraction about 97% from Pb(NO3)2 and 96% from PbCl2 solutions were observed.
► The kinetics of Pb(NO3)2 and PbCl2 separation corresponded to second-order reaction with the rate constants of 1.49 and 1.51 L/mg min.
► The modeled results were in good agreement with the experimental results.