Derivation and Discussion of Diffusion Dialysis Overall Mass Transfer Coefficient

A new equation is derived to calculate overall mass transfer coefficient,K of diffusion dialysis with large membrane areas.The equation consists of two parts,K_C,and K_W.K_C is the mass transfer coefficient,owing to solute concentration gradient without solution volume change caused by water osmosis,and K_W is the mass transfer coefficient,owing to solution volume change caused by water osmosis.Besides,effect of flow rate,Q on two kinds of mass transfer coefficient,K_C,K_W and overall mass transfer coefficient K,is also qualitatively investigated in continuous spring wound diffusion dialysis with large membrane areas.The results show that Kc is the key factor of mass transfer during diffusion dialysis,however,K_C gradually decreases,and K_W gradually increases,so that overall mass transfer coefficient,K firstly increases and then decreases,within the flow rate,Q range of 100～300 mL/min; reaches is the maximum when flow rate,Q is 200 mL/min.