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Abstract To availably utilize opal-palygorskite clay, dry beneficiation technique was applied to separate opal and palygorskite clay. Based on separated opal from opal-palygorskite clay, 4A zeolite was successfully synthesized by using a hydrothermal method. Box-Behnken was used to optimize Na 2 O/SiO 2 , H 2 O/Na 2 O and SiO 2 /Al 2 O 3 with cation exchange capacity (CEC) as the response value. The optimum parameters was determined to be Na 2 O/SiO 2 = 1.0, H 2 O/Na 2 O = 40, and SiO 2 /Al 2 O 3 = 2.0, and CEC got the maximum of 2.99 mmol/(g·dry zeolite) under the conditions. The as-obtained 4A zeolite was characterized by using X-ray diffraction (XRD), thermo gravimetric analysis (TG), acid-base titration, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and then was applied to remove Hg2+ from aqueous solution. The maximum removal capacity of Hg2+ was 41.99 mg/g and adsorption equilibrium was obtained with contact time of 2 h. Effects of pH, ionic strength, temperatures, metal cations, strippant kinds and cycle times on removal behaviors of Hg2+ onto 4A zeolite were investigated by batch experiments. The kinetics and isotherms of Hg2+ adsorption fitted well by pseudo-second kinetic and Langmuir models. When Hg2+-adsorbed 4A zeolite was desorbed using 1 mol/L NaNO 3 solution, the adsorption efficiency was maintained about 70% after four cycles. Highlights • Opal-palygorskite clay was separated by dry beneficiation technique. • 4A zeolite was synthesized successfully based on the separated opal. • The synthetic conditions of the 4A zeolite were optimized. • The performance of the 4A zeolite on removal of Hg2+ was evaluated. • The isotherms, kinetics, selectivity and effect of water chemistry were investigated. [ABSTRACT FROM AUTHOR]