Fluid-flow models operating on linear algebra for extraction and stripping of silver ions from pharmaceutical wastewater by HFSLM

The extraction and stripping of silver ions by hollow fiber supported liquid membrane (HFSLM) was examined. Pharmaceutical wastewater containing 30 mg/dm3 of silver ions was used as the feed solution. LIX 84-I dissolved in kerosene, and sodium thiosulfate pentahydrate solution were used as the liquid membrane and stripping solution, respectively. The influences of several variables on the extraction and stripping of silver ions were investigated. Fluid-flow models for greater accuracy in describing the transport of silver ions from feed phase to stripping phase were developed. The models were calculated by linear algebra. The investigated parameters in the models were axial convections and axial diffusions on both sides, chemical reactions at the feed-liquid membrane and liquid membrane-stripping interfaces as well as the accumulation of silver ions in the system. The mass transfer coefficient in the liquid membrane (km) was determined for use in the models. The final predicted concentrations of silver ions in feed and stripping phases were successfully in agreement with the experimental data. It indicates that the fluid-flow model can accurately estimate the transport of silver ions inside and outside the hollow fibers corresponding to the axial convections, axial diffusions, reactions at the feed-liquid membrane and liquid membrane-stripping interfaces. In accordance with this investigation, the HFSLM shows a practical implication for the use in pharmaceutical wastewater treatment.

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► HFSLM reduced silver ions at ppm level to less than the mandatory discharge limit.
► The highest extraction and stripping of silver ions as 98% and 85% were observed.
► Fluid-flow models were described Ag(I) transports inside and outside hollow fibers.
► The modeling results were in good agreement with the experimental results.
► The Ag(I) transports corresponded to fluxes of convection, diffusion and reactions.