Oil palm empty fruit bunch valorization for activated and non-activated carbon nanoparticles and its heavy-metal-removal efficiency oleh Salma Zubaidah, Adisti Permatasari Putri Hartoyo, Januard Kristian Sihombing, Elis Nina Herliyana, Saptadi Darmawan, Nela Rahmati Sari, Muhammad Naufal Ibrahim Prabowo, Imam Hermawan, Isna Maulida, Achmad Solikhin