The natural mother has no capacity to give a child in adoption without the consent of the  biological father  if he is alive  except in cases where the biological father is dead or has completely and finally renounced the world or has ceased to be a Hindu or is  declared by  the court that he is of unsound mind. 

it is not possible, u have to take ur ex husbands permission for this,  IF i u have got divorce on the grounds of  insanity FROM UR HUSBAND and court had declare so  then u can give adoption.The mother may give the child in adoption if the father is dead or has completely and finally renounced the world or has ceased to be a Hindu or has been declared by a court of competent jurisdiction to be of unsound mindd so, u can do it on ur own

No it can't be done without the consent of the biological father unless he is no more in this world or is declared to be of unsound mind to take a decision on his own.