High-efficiency HFSLM for silver-ion pertraction from pharmaceutical wastewater and mass-transport models

Abstract

Hollow fiber supported liquid membrane (HFSLM) is a favorable technique for the pertraction of metal ions, especially at very low metal concentration. In this work, the pertraction of silver ions from acidic pharmaceutical wastewater via HFSLM was investigated. Pharmaceutical wastewater containing 30mg/dm3 of silver ions and 120mg/dm3 of ferric ions was subjected to HFSLM as a feed solution. LIX 84-I dissolved in organic solvent together with Na2S2O35H2O solution was selected for use as a liquid membrane and a receiving solution, respectively. The influence of ferric ions on the pertraction of silver ions was studied firstly using wastewater with normal ferric ion concentration and secondly using wastewater with ferric ion precipitation by phosphoric acid solution. The highest pertraction of silver ions was achieved by using 0.1M of LIX 84-I and 0.5M of Na2S2O3·5H2O solution at pH of feed and receiving solutions of 3.5 and 2. The flow rates of feed and receiving solutions were 0.2dm3/min. 0.6mg/dm3 of silver ions that remained in the wastewater was below the mandatory discharge limit. No effect of normal ferric ion concentration in the wastewater on silver ion pertraction was observed. The crucial parameters were defined to confirm the efficiency and reliability of the system. Finally, the controlling transport regime of silver ion pertraction across HFSLM was determined by the diffusion flux and reaction flux models.