Nitrogen is separated from air through adsorption process using carbon molecular sieves as desiccant. The technology is known as PSA technology which means Pressure Swing Adsorption. 
The PSA Nitrogen gas plants are particularly used to produce Nitrogen gas of different purities ranging 95% to 99.99% directly through this technology, however if the gas is required to be further purified upto a level of 99.9999% then additional purification units are being attached to the system to deliver UHP nitrogen.