Intercalation of organosilane in clay mineral for the removal of Procion red MX-5B: Investigational and theoretical studies

Abstract

Finding new materials with specific characteristics such as eco-friendly, low-cost, sustainable, and efficient in wastewater treatment is still challenging. Thus, the present work combines the surface modification and intercalation of [3-(2-aminoethylamino)propyl]trimethoxysilane (TMSPEDA) of natural montmorillonite (Mmt) and its adsorption performance in the removal of Procion red MX-5B from aqueous solution. The modified clay (Mmt@SPEDA; the hybrid of montmorillonite-[3-(2-aminoethylamino)propyl] silane) was also characterised using XRD, FESEM, EDS, pHpzc, FTIR, N2-adsorption/desorption analyses, elemental analysis, TGA/DTG, hydrophobicity-hydrophilicity balance (HI). In order to improve the comprehension of the process intercalation and adsorption mechanism between Procion red MX-5B and Mmt@SPEDA adsorbent, a theoretical analysis of the adsorption phenomenon was performed based on DFT calculation. As a result, the interlamellar spacing of natural clay increased more than 1.50 times after the intercalation process, corresponding to a 50.33 % expansion. The final geometry of the intercalation process reveals that SPEDA molecules are perpendicular to the surface of montmorillonite with a specific orientation interaction between the oxygen atoms of the silanol group of the intercalating molecules and the atoms on the surface of montmorillonite. These interactions are likely electrostatic or correspond to van der Waals forces and hydrogen bonds. The characterisation data confirms the grafting of SPEDA groups on the clay. The positive adsorption energies indicate the endothermic nature of the adsorption process, suggesting that the system absorbs energy during the adsorption of PRMX-5B dye. The Liu's Qmax values for PRMX-5B dye varied from 171.4 and 318.6 mg g−1 for temperatures ranging from 10°–45 °C, demonstrating the excellent properties of the Mmt@SPEDA hybrid adsorbent.