Can I use an LM324 voltage follower with a single supply to rectify an AC signal?
This device can do what you are suggesting: -



As you can see it's an inverting unity gain amplifier that has a common mode input range that includes ground but, importantly it can stand an input voltage that falls up to -5V below ground. The other good thing about this circuit is that the 2M resistors are very good current limiters thus also protecting the chip.

Unfortunately the LM324 spec for negative voltage inputs is only -0.3 volts so your circuit will likely be destroyed. Maybe if you configured it like above it could work but given the input leakage current of the LM324 you may get some significant dc errors.

Also remember that the circuit above clips off the positive parts of the input because it is inverting. This may be OK but I can't tell if there is something inherently required in the positive half cycle in your application.