Preparation, characterization and application of sulphuric acid-treated soursop (annona muricata l.) seeds powder in the adsorption of cu(ii) ions by Megat Hanafiah, Megat Ahmad Kamal, Abu Bakar, Nurul Amira, Al-Amrani, Waheeba A., Ibrahim, Shariff, Nik Malek, Nik Ahmad Nizam, Jawad, Ali H.