Concentration of a Traditional Chinese Medicine extract by direct contact membrane distillation

A study of the concentration of a Traditional Chinese Medicine extract by direct contact membrane distillation has been carried out in order to determine the reason why the trans-membrane water flux declined during the concentration process. The effects of varying the extraction temperature and the flow velocity in the membrane module were investigated. It was found that during the concentration process, the flux reduction was mainly caused by membrane fouling in the earlier stages of lower extract concentration (i.e. when the concentration was increased by a factor of 4.0). In the latter stages of extract concentration (i.e. when the concentration was from increased from 4.0 to 16.0 times its initial value), the reduction in water vapor pressure also contributed significantly to the decline in flux. It was also found that when the extraction temperature and velocity were increased from 46°C to 60°C and from 0.074 m/s to 0.130 m/s respectively, the trans-membrane water flux increased from 13.88 kg/(m2·h) to 30.82 kg/(m2·h) and from 24.14 kg/(m2·h) to 31.22 kg/(m2·h) respectively.