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High-efficiency, inexpensive, and simple preparation methods are the main features of future adsorption materials. To improve the adsorption efficiency of cadmium in micro-polluted water, natural zeolite was modified by high-temperature treatment combined with HCl-acidified to obtain activated zeolite. The structural characterizations were performed by X-ray powder diffractometer, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller surface area analysis. The characterization results confirmed that the internal structure of activated zeolite was dispersed and loose, the specific surface area, average pore diameter, and total pore volume increased, and the adsorption capacity was improved. Furthermore, adsorption isotherm, kinetics, and thermodynamics studies were further conducted to study the adsorption mechanisms. The kinetic studies demonstrated that the pseudo-second-order (R2 = 0.983) model described the adsorption of cadmium onto activated zeolite better than the pseudo-first-order (R2 =  0.934) and intra-particle diffusion model (R2 =  0.950), suggesting an equilibrium time of 180 min at 25°C. The Langmuir model, the Freundlich model, Temkin, and Redlich–Peterson adsorption isotherm equations were used to fit active zeolite adsorption Cd(II). The result showed that cadmium adsorption can be better described using the Langmuir model (R2 = 0.966), indicating that the process was single-molecular-layer adsorption. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, and was driven by the increase of entropy. Hence, this study demonstrated the adsorption capacity of activated zeolite was improved and activated zeolite was a promising adsorbent for the effective removal of cadmium from micro-polluted water. [ABSTRACT FROM AUTHOR]