Abstract: A heat and mass exchanger including a plurality of vertical plates that are spaced apart from one another by gaps so as to allow a first gas to flow between the plates. Each plate includes a front wall that defines a front surface of the plate, a back wall that defines a back surface of the plate, and separate, parallel channels disposed between the front and back walls. The parallel channels include a first set of parallel channels, a first liquid flowing within the first set of channels and over one of the front or back surfaces of the plate, the first liquid having a bulk composition comprising one or more constituents, the first gas having at least one constituent in common with the first liquid, and a second set of parallel channels, a first fluid flowing within the second set of channels.