You are trying to call append() on a ParticleEffect as though it were a Sequence, but it is not. Did you find example code that suggested this was possible?
Even if the append() worked, you call disable() right after you append(), so it would stop before it could actually run the Wait.
You might instead want to just start it, then start a separate Sequence that uses Func to call disable() after the Wait. Or, you could use taskMgr.doMethodLater to schedule a function to be run after that time to stop the particle system.