ABSTRACT This study investigated the effectiveness of the clinoptilolite (Na@CPT) surface as an adsorbent for removing anionic dyes. The Na@CPT surface was modified using hexadecyltrimethylammonium bromide (NaCPT@HDTMA) to improve its ability to remove Reactive Blue 171 (RB171) from water. A thorough study was conducted to analyze the adsorption isotherms, kinetics, temperature, and pH effects of RB171 onto Na@CPT and NaCPT@HDTMA. A pH of 1.0 was found to be the optimum value for adsorbents. Kinetic studies revealed that both adsorbents followed the pseudo-second-order kinetic model, with NaCPT@HDTMA exhibiting a faster adsorption process and quickly reaching equilibrium with increasing temperature. The adsorption efficiency of RB171 was found to improve by 83.56% after the modification at 50°C. The equilibrium data showed that the adsorption of RB171 on Na@CPT and NaCPT@HDTMA fit the Freundlich and Langmuir isotherm models, respectively. The thermodynamic parameters showed that the overall adsorption process of both adsorbents was endothermic and spontaneous. NaCPT@HDTMA is a highly effective adsorbent for removing RB171 from aqueous solution due to its low cost and abundant presence in nature.