The Gunners lost 3-1 away to Sevilla after Eduardo gave the Premiership leaders an early lead.
Arsenal boss Arsene Wenger was ordered to leave the technical area just before Kanoute scored on a penalty for the hosts.
Wenger said: “I had no exchanges with the referee.
“I don’t know why I was sent off, I was really surprised.
“The fourth official was really difficult for the whole game, I said to the referee ‘will you explain to me why I have been sent off?’.”
