Tailoring Natural and Fly Ash-Based Zeolites Surfaces for Efficient 2,4-D Herbicide Adsorption: The Role of Hexadecyltrimethylammonium Bromide Modification

Global development has led to the generation of substantial levels of hazardous contaminants, including pesticides, which pose significant environmental risks. Effective elimination of these pollutants is essential, and innovative materials and techniques offer promising solutions. This study examines the modification of natural zeolite (clinoptilolite) and fly ash-based NaA and NaX zeolites with hexadecyltrimethylammonium bromide (CTAB) to create inexpensive adsorbents for removing 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide from water. Detailed characterization of these materials was performed, along with an evaluation of the effects of pH, contact time, temperature, and initial 2,4-D concentration on their sorption capacities. The modified samples exhibited significant changes in elemental composition (e.g., reduced SiO2 and Al2O3 content, presence of Br) and textural properties. The adsorption of the pesticide was found to be an exothermic, spontaneous process of pseudo-second-order kinetics and was consistent with the Langmuir model. The highest sorption capacities were observed for samples modified with 0.05 mol L−1 CTAB, particularly for CliCTAB-0.05.