An apparatus (10,110, 210, 310) for the separation and optional recovery of a first gas from a gas mixture containing said first gas and other gases, different from said first gas, by a cyclic adsorption/desorption process using a loose particulate sorbent for gas adsorption; wherein said sorbent is provided in a stack (22,122,222, 322) of at least two adjacent, parallel, spaced-apart layers (24,124, 224, 324) in a rigid vacuum chamber (12, 112, 212, 312) of said apparatus; wherein said layers (24,124, 224, 324) being provided in two or more, laterally-extending, axially spaced-apart, parallel stacks (22, 122, 222, 322); wherein each layer (24,124, 224, 324) comprises a flexible fabric enclosing said sorbent; wherein said fabric is permeable to said gas mixture but impermeable to said sorbent; wherein said fabric of each layer (24,124, 224, 324) is attached to, and enclosed by, a stiff frame (30,130) of said layer; wherein said vacuum chamber of said apparatus has an inlet (14,114, 214, 314) and outlet (16,116, 216, 316) for gases on axially opposite sides of said vacuum chamber of said apparatus; and wherein each of said layers (24,124, 214, 314) extends axially within said vacuum chamber of said apparatus and wherein said vacuum chamber of said apparatus is characterized by said layers (24,124, 224, 324) forming a serpentine flow path for gas through said vacuum chamber of said apparatus; wherein the vacuum chamber of said apparatus also has - pairs of axially-extending baffles and that are adjacent to, and on laterally opposite sides of said inlet (14,114, 214, 314) and outlet (16,116, 216, 316), respectively of said vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus and - pair of laterally- and vertically-extending baffles and between each stack (22, 122, 222, 322) on opposite lateral sides of the vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus to form the serpentine flow path. wherein each layer (24,124, 224, 324) comprises a flexible fabric enclosing said sorbent; wherein said fabric is permeable to said gas mixture but impermeable to said sorbent; wherein said fabric of each layer (24,124, 224, 324) is attached to, and enclosed by, a stiff frame (30,130) of said layer; wherein said vacuum chamber of said apparatus has an inlet (14,114, 214, 314) and outlet (16,116, 216, 316) for gases on axially opposite sides of said vacuum chamber of said apparatus; and wherein each of said layers (24,124, 214, 314) extends axially within said vacuum chamber of said apparatus and wherein said vacuum chamber of said apparatus is characterized by said layers (24,124, 224, 324) forming a serpentine flow path for gas through said vacuum chamber of said apparatus; wherein the vacuum chamber of said apparatus also has - pairs of axially-extending baffles and that are adjacent to, and on laterally opposite sides of said inlet (14,114, 214, 314) and outlet (16,116, 216, 316), respectively of said vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus and - pair of laterally- and vertically-extending baffles and between each stack (22, 122, 222, 322) on opposite lateral sides of the vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus to form the serpentine flow path. - pairs of axially-extending baffles and that are adjacent to, and on laterally opposite sides of said inlet (14,114, 214, 314) and outlet (16,116, 216, 316), respectively of said vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus and - pair of laterally- and vertically-extending baffles and between each stack (22, 122, 222, 322) on opposite lateral sides of the vacuum chamber of said apparatus and that extend vertically from a bottom wall to a top wall of said vacuum chamber of said apparatus to form the serpentine flow path.