MPX is part of Batista's EBX Group, a conglomerate that also includes logistics and mining firms.
The company said in a statement that former board vice chairman Jorgen Kildahl has been named interim chairman.
Kildahl is also a member of the board of management of E.ON the German utility that has a 36 percent stake in MPX. The statement also says that MPX's board of directors approved a capital increase of 800 million reals (USD 356 million) at 6.45 reals (USD 2.96) per share.