The functionalization of surface charges on oil palm empty fruit bunch (EFB) fibers was modified by grafted carboxylic
acid and polymer amine groups. Single and binary adsorption of Cu(II), Ni(II), Mo(VI) and As(V) were investigated
by competitiveness in the adsorbents. The mechanism of each metal ion was deliberately studied on kinetics-diffusion
(intraparticle diffusion) and isotherm adsorption models (Langmuir and Freundlich). Competitiveness of metal ions was
found in the selectivity of Cu(II) > Ni(II) and Mo(VI) > As(V) in the binary solution. The regeneration of adsorbents
was performed up to five cycles of an adsorption/desorption process and the reduction of adsorption performance was
less than 14.5%. Therefore, this promises low-cost adsorbents for metal ion uptake, showing potential for removal and
recovery in industrial wastewater treatment.