脱氧 is a separable verb (离合词) meaning 'to deoxidize' or 'to remove oxygen', commonly used in chemistry and industrial contexts. The verb 脱 and the object 氧 can be split when inserting measure words, duration, or other elements — for example, 脱了一次氧 ('deoxidized once'). You can also use it in compounds like 脱氧剂 ('deoxidizer').