Models based on the film, penetration and surface renewal theories were developed for predicting the local, dynamic behavior of liquid-solid mass transfer in a fixed bed. The influence of velocity pulses of frequency less than 1 Hz in the range 0.005-0.03 m/s has been studied. A model based on the surface renewal theory estimates the local instantaneous mass transfer coefficient from the instantaneous velocity. Experimental validation is provided. Potential applications are the determination of local transient velocity in fixed beds from mass or heat transfer measurements and the assessment of mass transfer enhancement in pulsating systems.