If possible, try to work in an environment with minimal dust. The goal is to try to avoid dust from getting inside of the lens as much as possible.

Loosen the knob on the tripod mount.

Rotate the tripod mount counter-clockwise approximately 135 degrees.

Pull the tripod mount towards the rear of the lens. If it does not immediately come off, rotate the tripod mount back and forth slightly until it is in the correct position for the tripod mount to detach from the lens.