Comparative adsorption study related to benefits of parent media size, i.e. microfibrillated cellulose (MC) versus nanocellulose (NC) support, for the preparation of magnetite (MG) based high performance adsorbent for arsenic removal was conducted. Precipitation of MG on amino terminal branched organic structure, L, either linked by maleic acid residue on NC surface (NC-MA/L) or linked by oxalyl bridge on MC surface (MC-O/L) produced NC-MA/L-MG and MC-O/L-MG adsorbents, respectively. Precipitation of nanosized MG on amino functionalized NC-MA/L and MC-O/L, performed according to optimized procedure, contributed to improved textural properties and adsorptive/kinetic performances of novel adsorbents. Adsorption capacity of arsenate, As(V), was in favor of NC-MA/L-MG (85.3 versus 18.5 mg g−1) while MC-O/L-MG exhibited faster kinetics (0.541 versus 0.189 g mg−1 min−1). Lower capacity of arsenite, As(III), removal, 68.3 mg g−1 for NC-MA/L-MG and 17.8 mg g−1 for MC-O/L-MG, were obtained. Calculated activation energies, 13.28 and 10.87 kJ mol−1 for NC-MA/L-MG and MC-O/L-MG with respect to As(V), respectively, suggest, in accordance with results of Weber-Morris fitting, that internal mass transfer controls adsorption process. Model free adsorption kinetics confirmed beneficial uses of MC-O/L-MG due to low activation energy dependence on the extent of adsorption