Chitosan was dispersed on bentonite for the preparation of a Cd2+ adsorbent. The adsorption process followed a Freundlich isotherm, and the experimental adsorption capacity was determined. For understanding the adsorption mechanism, the pristine and Cd-doped adsorbents were analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. A red shift of the band corresponding to amino groups was observed, while the Cd 3d binding energy declined. Furthermore, density functional theory calculation results indicated that Cd2+ bonded with amino and hydroxyl groups in chitosan. The zeta potential of the adsorbent was lower than that of the support bentonite, improving the electrostatic affinity for Cd2+. The synergy between electrostatic and coordination interactions contributed to the adsorption capacity.