iPhone recognized by itunes but wont power on

This is one of @refectio 's excellent answers:

Do not put your phone in rice! The rice myth kills too many phones...

The water is inside the phone, on the logic board and under the shields, even under the IC's. The rice is nowhere near where the water is. So while it ‘’may’’ soak up some water vapour, the real problem is the corrosion that is taking place as the water evaporates. Powering on the phone accelerates the process. The longer you let a phone sit in rice, the more time you are giving corrosion to damage your logic board. The saltier or harder the water is, the more damage will occur.

Open your phone and remove the logic board (follow this guide)

Inspect the logic board, especially around the connectors and look for corrosion.

Inspect both sides of the board. Unfortunately, 80% of the board is covered in shields. That's usually where the damage is occurring.

Put your board in a container with >90% isopropyl alcohol and let it sit for a while.

Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.

Rinse in alcohol and repeat.

Let it air dry for a day.

Re-assemble and hope for the best.

Use a tool like 3uTools to flash the firmware as it may be corrupted.

You should also consider getting a new battery

A professional repair shop that does water damage repair may be able to recover your phone or the data because they have access to pro-level ultrasonic baths and specialized cleaners as well as the skills to troubleshoot your board. Many shops have a no fix/no fee policy so you don't have to spend money to find out if the phone is fixable or not.