In this study, a new composite resin, based on the triple structure of bentonite clay, magnetite, and polyacrylonitrile, was synthesized, characterized, and applied for the removal of water hardness. The composite resins were characterized by Fourier-transform infrared, X-ray diffraction, and scanning electron microscope. The performance toward water hardness removal was evaluated using different approaches of batch and column experiments, using the ethylenediaminetetraacetic acid (EDTA) method, to determine different hardness levels of diverse water samples, which included synthetic and natural water samples. Different parameters were investigated that include contact time, resin dose, initial concentration, and the flow rate in the column process. The results showed an increase in the hardness removal with contact time. A batch process recorded 100% removal of water hardness by an equilibration time of about 60 min with a minimum of 3 g L-1. The adsorption results were found to be successfully fitted with the pseudo-second-order kinetic model and were better described with the Freundlich isotherm model. Furthermore, column studies revealed the effects of several operating parameters on the breakthrough profiles. Remarkably, the experimental results using the column approach revealed a high removal efficiency of 88-100% for the natural water samples, employing a 5 g packed column with a 2 mL min(-1) flow rate for hard water that ranged from 237 to 680 mg CaCO3/L. The results illustrate the potential of this polymeric composite resin as an alternative to conventional softening treatment techniques in terms of low cost and high performance.