A study on membrane based absorption process has been done in order to better characterize mass transfer as a function of various parameters, such as membrane characteristic features, the shell side hydrodynamics conditions and the type of absorption taking place. The impact of these parameters on mass transfer has been experimentally investigated, analyzed, modeled and explained in this thesis.This is a two-part study. Part 1 deals with transient CO2 absorption using a flat sheet membrane module where the influence of membrane porosity on mass transfer has been presented. It further clarifies the seemingly conflicting viewpoints from other previous investigators as to whether the whole membrane area or the total area of the pores should be used for membrane based absorption mass transfer calculations. The results have indicated that depending on the rate of absorption process, whether physical or chemical,effective mass transfer area may not be the whole membrane area and nor the total area of the pores but somewhere in between.The second part explores the effect of shell side hydrodynamic conditions on steady-state mass transfer in a hollow fiber membrane. A mathematical model has rigorously been generated to predict the improved SO2 absorption performance due to an increased number of inlet channels into the shell side at various liquid velocities. In this model, a hollow fiber module has been treated as a cascade of numerous discrete stirred tank reactor (STR) cells. The model predictions reasonably agree with the experimentally determined mass transfer coefficients. Minor deviations have been attributed to complex combinedeffects of multi-inlet channels and the liquid flow velocity, which were no texplicitly incorporated into the model.Tracer experiments were also done to further validate the model. RTD curves became narrower and more symmetrically regular as the number of inlet channels increased. This also showed that flow maldistribution due to channeling, backmixing, and dead zones can further be eliminated at higher liquid flow velocity when the liquid stream is introduced into the shell side from three inlet channels.