11/13/2014 04:05 EST | Updated 01/13/2015 05:59 EST

Quebecer pleads guilty after throwing acid in then-girlfriend's face in 2012

LONGUEUIL, Que. - A Quebec man has pleaded guilty to aggravated assault after throwing acid in the face of his then-girlfriend in 2012.

Nikolas Stefanatos entered the plea in a Montreal-area courtroom today, three weeks before his trial was set to begin.

The assault against Tanya St-Arnauld occurred in August 2012 with what police described as concrete cleaner.

Sentencing arguments have been set for Dec. 3.

St-Arnauld suffered serious burns to her head and upper body and was in a medically induced coma for days. She later required skin grafts.

She appeared on Anderson Cooper's "Anderson Live'' in January 2013, where she received news that a Miami-based dermatologist would fly her down for treatment.