voltage measurement ic
Normally, the rectified mean value is a usual parameter in AC measurement. Using a rectifier with a capacitor as in a power supply, you rather measure a peak than a mean value, which would be unwanted, I think. A suitable selection of time constant is another question, it has to be answered according to your application. To reduce mean value ripple, a higher order low-pass can be used.
To my opinion, an OP full-wave rectifier circuit, as shown in any circuit design text book or OP manufacturer application notes, followed by a 2nd or 3rd order low-pass should work. Another option to remove the ripple is synchronize the ADC sampling with mains frequency.