Activation and Zr precursor influence on UiO-66-NH₂ composites for efficient cationic and anionic dye removal

This study investigates the synthesis of UiO-66-NH₂@HTC composites, focusing on the control of surface charge, textural properties, and crystallinity. Surface charge modification was achieved through activation processes to enhance affinity for specific pollutants. By utilizing ZrCl₄ and ZrOCl₂⋅8H₂O precursors, the textural properties were optimized, leading to higher mesopore content and improved crystallinity with the ZrOCl₂⋅8H₂O precursor. The UiO-66-NH₂(ZrCl₄)@HTC composite exhibited a crystallinity of 51.7 %, with 40 % mesopores and 57 % micropores, while the UiO-66-NH₂(ZrOCl₂)@HTC composite showed a crystallinity of 60 %, consisting of 60 % mesopores and 37 % micropores. Adsorption followed the Langmuir isotherm model, with maximum adsorption capacities of 263.1 mg/g for methylene blue (MB) and 277.77 mg/g for Congo red (CR), driven by hydrogen bonding and electrostatic interactions. The activated UiO-66-NH₂@HTC composites demonstrated remarkable reusability. These findings emphasize the significant role of surface charge modification, pore structure optimization, and crystallinity enhancement in developing high-performance adsorbents.