In this work, iron terephthalate metal–organic framework (MOF-235) as an efficient adsorbent has been synthesized and employed for toluidine blue (TB) removal in a batch system. The adsorbent was characterized by Fourier-transform infrared, scanning electron microscopy, and powder X-ray diffraction. The effects of operational parameters including pH, initial dye concentration (Cd), and the adsorbent dosage (m) on the TB adsorption were studied. A Box–Behnken design (BBD) was applied to identify the effective factors on the removal efficiency (R%) of toluidine blue. The optimal conditions were as follows: m = 0.02 g, Cd = 100 mg L−1, and pH = 4.5. The equilibrium adsorption isotherms and kinetic models were also studied. Since the results of the Langmuir model fitted well to all the experimental data (R2 = 0.9972), the maximum monolayer adsorption of TB was 180.4 mg g−1. Furthermore, the pseudo-second-order model describes well the process. Iron terephthalate metal–organic framework (MOF-235) shows a great potential to remove TB from aqueous solution.
