I had a similar situation with a coworker- but the ranting maniac was the RN, I was the CNA.
This guy was *notorious* on the unit for being grouchy and mean to anyone except the handful of people he liked (maybe 5 of them). He was always trying to tell the doctors what to do (and I don't mean helpful suggestions based on good nursing observations, but order-barking). An attending once walked in on one of these rants (directed at a group of residents) and said, 'wow, jim, you're an MD now! congratulations!'
this guy, for whatever reason, hated me. no idea why. He'd report me for 'not following orders' all the time, but wouldn't give specific examples (I'd never refused to do anything I was asked to do, unless I was already assisting with another patient, and I would explain I'd help them ASAP). He would yell at me, bark orders, and demean me for absolutely no reason. Apparently (and this was the general consensus on the unit), he wanted people to bow down to his mighty intellect. He was smart, but an a**.
Anyway, I was 15 minutes late one morning because of ice on my street that i literally couldn't cross (sat there spinning tires the whole time). I'd called the charge and she knew about it. (The unit secretary, meanwhile, was pregnant and said the was late because she didn't want to slip on ice and fall and hurt her baby...she was 3 HOURS late.) When telling another coworker about the ice, 'jim' said, quite loudly, 'there wasn't ice at my house. I don't believe you. You're a liar.'
(for the record, he lived an hour away from me, so how the heck did he know?)
I said, 'i've put up with your intimidation and attitude long enough. When you can speak to me respectfully, like an adult, let me know. because I'm done listening to this.' I walked away and continued with my day.
For months, we would work together and he would only say the minimum he absolutely had to communicate to me. After 4 months or so, he started, slowly, showing me respect and pointing out learning opportunities for me with his patients. We were never buddies, but he eventually found some civility somewhere.
I've never understood bullies (and I believe this PCA is definitely bullying you). My mother would smack me silly if she saw me pitch a fit like that in a public place- let alone at WORK!