"about their duties" is correct and commonly used in written English.
Example: The new employees were given a detailed orientation about their duties.
Tells about their duties.
Writer talked with some pilots, learned about their duties; how they feel about jet-flying, etc.
Staff stay admirably in character at all times and are resolutely depressed about their duties.
Not all the trackers, he said, are open about their duties.
If you want to hire people to run errands, do so and be candid about their duties.
In Norway, where the police normally go about their duties unarmed, there were public vows this week to preserve a peaceful and open society.
And I know for a fact every last one of them haven't given it a second thought, going about their duty with commitment and due attention.
Depending on the outcome of an ethics investigation, Mr. Silver may have to answer questions about his leadership and the other two officials about their duty to provide checks on legislative behavior.
"There are two alternatives: either the chief whip used appalling and offensive language to an officer going about their duty, or Mr Mitchell is saying the officer is lying.
The jury had resumed deliberations on Wednesday after reaching a "substantial disagreement" last week that led the judge to admonish them about their duty to try to reach a consensus.
