A split king can absolutely help keep your partner quiet at night. When you sleep, the muscles in your throat relax, allowing your soft tissues to rattle around inside your airways. This is the mechanism that causes snoring. Elevating the head can allow gravity to hold the soft tissues in the throat in place. This can reduce or even eliminate snoring entirely.
Keep in mind that an adjustable bed alone may not be sufficient if your partner's snoring issue is actually caused by obstructive sleep apnea. If the snoring is extremely loud, or if breathing regularly ceases during sleep, it's best to see a sleep specialist.