Phosphate removal from polluted waters is one of the most important environmental problems. This study aimed to remove phosphate from municipal wastewater by a ternary composite of shrimp shell- chitosan/activated carbon/iron nanoparticles synthesized via the sonochemical method. Chitosan was synthesized from shrimp shell via sonochemical method and then modified using orange peel-activated carbon via synthesis of a ternary composite of chitosan/activated carbon/iron nanoparticles (CACIC). Identification of the composite functional groups, the morphology of its surface and pores, and porosity properties were investigated by FTIR, SEM, and BET techniques. The effect of solution pH (1-6), adsorbent amount (0.05-0.15 g), and pollutant concentration (20-100 mg/L) on the adsorption operation was investigated and the optimal operating conditions were determined using the Central Composite Design (CCD). Pseudo-first-degree, pseudo-second-degree, intra-particle diffusion, and Boyd kinetic patterns were utilized to portray the kinetic data, as well as the Langmuir, Freundlich, and Dubinin-Radushkevitch isotherms to describe the adsorption equilibrium data. The results offered that the adsorption confirmed the pseudo-second-degree kinetics (R2=1). Also, among the studied isotherms, the Langmuir pattern described well the phosphate adsorption upon the composite (R2=0.9996) and the maximum adsorption valence was 312.5 mg of phosphate /g composite. The optimum pH of phosphate uptake was 5.92. The amount of phosphate adsorbed by CACIC under optimal conditions was 97.05 mg/g. In general, it can be said that the composite of chitosan/orange peel-activated carbon/iron nanoparticles performs well in the process of phosphate ion adsorption in discontinuous adsorption.