BOSTON — Three college friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev were arrested and accused Wednesday of removing a backpack containing fireworks emptied of gunpowder from Tsarnaev’s dorm room three days after the attack to try to keep him from getting into trouble.In court papers, the FBI said one of them threw the backpack in the garbage — it was later found in a landfill by law enforcement officers — after they concluded from news reports that Tsarnaev was one of the bombers. Azamat Tazhayakov and Dias Kadyrbayev were charged with conspiring to obstruct justice by concealing and destroying evidence. A third man, Robel Phillipos, was charged with lying to investigators about the visit to Tsarnaev’s room.A court appearance for the three was scheduled for Wednesday afternoon. Their lawyers refused to comment ahead of the hearing.Three people were killed and more than 260 injured on April 15 when two bombs exploded near the finish line. Tamerlan Tsarnaev died after a gunfight with police days later. His younger brother, Dzhokhar Tsarnaev, a 19-year-old sophomore at the University of Massachusetts at Dartmouth, was captured and lies in a prison hospital.Tazhayakov and Kadyrbayev, who are from Kazakhstan, have been held in jail for more than a week on allegations that they violated their student visas by not regularly going to class at UMass. All three men charged Wednesday began attending UMass with Tsarnaev at the same time in 2011, according to the FBI.