HIGH COLLECTION RATE OF PD IN HYDROCHLORIC-ACID MEDIUM USING CHELATING MICROPOROUS MEMBRANE

An iminodiacetate (IDA) group was introduced onto a microporous hollow -fiber membrane while maintaining the permeation flux of the original membrane. A 20 g/m3 Pd/palladium chloride solution, with pH ranging fr om 0.5 to 4 with hydrochloric acid addition, was forced to permeate th rough the chelating microporous hollow-fiber membrane with a thickness of 0.9 mm. The higher permeation rate of the Pd solution led to a hig her sorption rate because of negligible diffusional mass-transfer resi stance. In the subsequent elution of Pd sorbed onto the membrane, the convective transport of Pd ions due to permeation of HCl as an eluent produced a lower degree of tailing in the elution curve, resulting in a higher enrichment of Pd. For comparison, a similar procedure was per formed with a bed charged with the IDA-group-containing beads. Convect ion-aided separation using the chelating microporous membrane was supe rior to diffusion-limited separation using the chelating-bead-packed b ed with respect to sorption and elution rates.