Chitosan was cross-linked using glutaraldehyde in the presence of magnetite. The resin obtained was chemically modified through the reaction with tetraethylenepentamine ligand. The obtained resin was loaded with Mo(VI) and investigated. The adsorption characteristics of the obtained resin toward As(V) at different experimental conditions were investigated by means of batch and column methods. The resin showed high affinity and fast kinetics for the adsorption of As(V) where an uptake value of 1.30 mmol g−1 was reported in 6 min at 25 °C. Various parameters such as pH, agitation time, As(V) concentration and temperature had been studied. The kinetics and thermodynamic behavior of the adsorption reaction were defined. These data indicated an endothermic and spontaneous adsorption process and kinetically followed pseudo-second-order model, Fickian diffusion low and Elovich equation. Breakthrough curves for the removal of As(V) were studied at different flow rates and bed heights. The critical bed height for the studied resin column was found to be 0.656 cm at flow rate of 4 mL min−1. The mechanism of interaction between As(V) and resin’s active sites was discussed. Regeneration and durability of the loaded resin toward the successive cycles were also clarified.