The rates of the sorption of zinc ions from aqueous sulfate solutions with di(2-ethylhexyl) phosphoric acid-impregnated Amberlite XAD macroporous resins were measured in finite bath by a batch-contact time method. The sorption process was initially found to be controlled by a combined chemical reaction and particle diffusion process using a provable modified shrinking,core model. A more rigorous model based on Fick’s law was then developed to elucidate the sorption mechanism, and a procedure was suggested to simultaneously determine the reaction rate constant and effective particle diffusivity.