Hoppy was photographed at a café in New York City Thursday still wearing the band on his left ring finger
The couple have a 2½-year-old daughter, Bryn.
"It brings me great sadness to say that Jason and I are separating," Frankel, 42, said in a statement Sunday. "This was an extremely difficult decision that as a woman and a mother, I have to accept as the best choice for our family."
Earlier this year, the reality star revealed to PEOPLE that marriage didn't come easily to her.
"You have to fight for everything," she said. "Our core issues are wanting the other person to be somebody they are not."