The prepared chitosan-coated diatomite (CCD) Was characterized using Fourier transform infrared spectroscopy and SEM techniques. The effects of pH, contact time, sorbent dosage, metal concentration, and temperature on the adsorption (%), of mercury (Hg(II)) from aqueous solution using the CCD sorbent were studied systemically. The monolayer sorption capacities of raw diatomite and CCD sorbents at pH 5 were found to be 68.1 and 116.2 mg/g, respectively. The mean adsorption energy (8.2 kJ/mol) calculated from the Dubinin-Radushkevich (D-R) model indicated that the sorption process occurred via chemisorption: The modified sorbent had good adsorption and desorption performance with respect to reusability after 10 repeated cycles. The thermodynamic calculations revealed that the:sorption was viable, spontaneous, and exothermic in nature under the conditions studied. The kinetic calculations indicated that the sorption mechanism Was Well-explained by a pseudo-second-order model. All results demonstrated that the prepared CCD is an effective serbent for the removal of Hg(II) from aqueous solution.