Mechanochemically Synthesized ZIF-67/PANI-SSA Composites as Superior Adsorbents for the Removal of Basic Fuchsin from Water

In the search for efficient adsorbents for pollutants removal from water, we prepared novel composites of the metal–organic framework ZIF-67 and conducting 1-D nanostructured polyaniline sulfosalicylate (PANI-SSA) in different weight ratios (20–75 wt.% ZIF-67) using a mechanochemical method. Composites were characterized by FAAS, SEM-EDX, TGA, FTIR and Raman spectroscopies, N2 sorption, electrical conductivity and zeta-potential measurements and explored as adsorbents for the removal of basic fuchsin (BF) dye from an aqueous medium. TGA revealed improved thermal stability of the composites compared to pure components, while FTIR and Raman indicated strong interactions between PANI-SSA and ZIF-67 causing partial dedoping of the polymer. Composites’ morphology depended on their composition, with 1-D nanostructures observed for lower ZIF-67 contents. All composites are excellent adsorbents for BF, having better adsorption performance than pristine PANI-SSA. The composite with 75 wt.% ZIF-67 exhibited the highest values of maximum adsorption capacity (910 mg g−1) and removal efficiency (97.2%), exceeding those for pure ZIF-67. Adsorption processes followed pseudo-second-order kinetics fitting the Langmuir–Freundlich isotherm, indicating monolayer adsorption on a heterogeneous surface. Composite adsorbent can be efficiently regenerated by washing with ethanol and reused. The results highlight the synergistic effects of combining PANI and ZIF-67 into advanced materials for wastewater treatment.