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Linear driving force (LDF) model is widely used in a diffusion process. However thismodel has inherent weakness. When the dimensionless time is less than 0.1, its relativeerror is up to 95%. In this paper a new concentration profile is proposed, and then a newmodified LDF model (MLDF) is deduced. Compared with the exact solution ofintraparticle diffusion equation, the transient volume-average amount adsorbedcalculated from the MLDF is more accurate than that calculaled from the LDF modeL .Ifone takes ±10% relative error for the limit of validity of approximation, the new model isvalid when the dimensionless time is just larger than 0. 0002, while the LDF model is notvalid until the dimension time is large than 0.05. The new model is superior to the LDFmodel. The new concentration profiles corresponding to the MLDF model are much closeto the exact concentration profiles within a particle than the parabolic propescorresponding to the LDF model.