Two adsorption-based separation processes not considered in this chapter because of lack of significant commercial application are (1) parametric pumping, first conceived by R.H. Wilhelm in the early 1960s, and (2) cycling-zone adsorption, invented by R.L. Pigford and co-workers in the late 1960s. The status of and future for these two processes was assessed by Sweed in 1984 [AIChE Symp. Series, 80 (233), 44-53 (1984)]. Describe in detail each of these processes. Can either be used for both gas-phase and liquid-phase adsorption?