X-ray molecular structure characterization of a hexamethylenetetramine zinc(II) porphyrin complex, catalytic degradation of toluidine blue dye, experimental and statistical studies of adsorption isotherms

Abstract

In this work, we report the single crystal X-ray molecular structure of the pentacoordinate zinc(II) porphyrin coordination compound [Zn(TFMPP)(HMTA)] (complex (I)), where TFMPP = meso-tetrakis[(para-tetratrifluoromethylphenyl]porphyrinato and HMTA = hexamethylenetetramine. The 3D Hirshfeld surfaces and the 2D fingerprint maps have been employed to investigate the intermolecular interactions in the crystal lattice of complex (I). The main part of this paper is devoted to the use of the free base porphyrin H2TFMPP and the metalled zinc(II)-HMTA-porphyrin derivative (I) as adsorbents for the toluidine blue (BT) dye. The kinetic of the adsorption process for both H2TFMPP and complex (I) fitted well with the Pseudo-Second-Order kinetic model and the adsorption isotherms were well described by the Langmuir model. The advanced statistical physics models were used to provide good interpretations of the adsorption of the BT dye. Furthermore, complex (I) was found to be a good catalyst for the removal of this cationic dye in 30% aqueous hydrogen peroxide solution.The theoretical thermodynamic analyses performed on the free base porphyrin H2TFMPP and complex (I) show that the adsorption of the BT pollutant on these porphyrin compounds is not only possible but also spontaneous.