That Oatey sure vent is properly called an "Air Admittance Valve". The have a spring activated plate inside that is supposed to open to allow vent air to enter the drain, but close to prevent sewer gasses from escaping.

Such as is common to all things mechanical, they wear out or get gummed up with residue from soap and cooking grease.

The bottom end of the valve has a male pipe thread that threads into a female thread adapter on the drain line. To replace you simply unscrew and discard the defective AAV and screw a new one in its place.

That is a kitchen sink line so your AAV should be 1-1/2"

You can purchase a new one at any hardware store of home supply center for about $10 +/-