Integrated experimental and theoretical insights for Malachite Green Dye adsorption from wastewater using low cost adsorbent

Water pollution is one of the problems that threaten humanity, and to confront it with only experimental procedures is not enough. It is necessary to integrate both practical methods and theoretical calculations to achieve decontamination with the most accurate interpretation. Hence, discussing the experimental mechanism study of MG dye adsorption with the help of the application of DFT calculations is the main goal of this article herein. The experimental results affirmed that the preparation of gamma-Al2O3 by precipitation method using (NH4)(2)CO3 improved the porosity, the surface capability, and the adsorbent capacities (q(max) = 210 mg/g) at optimum condition compared with the previous studies. Kinetic and equilibrium studies referred that the adsorption follows the pseudo-second order model and Freundlich isotherm model, respectively. Also, the calculated and observed thermodynamic parameters exerted positive values of (Delta H degrees) and (Delta S degrees) which translates into endothermic process with increasing disorder of the system. Theoretical calculations at DFT- B3LYP/6-31G (d,P) level of theory were calculated to show the selectivity of using the cationic form of the Malachite Green (MG) in the experimental measurements to find interaction mechanism. The electronic structure and intramolecular charge transfer of (MG), its cationic form and the complex of MG-Al were investigated theoretically at the B3LYP/6-31 G (d,p) level of theory. The equilibrium geometries of (MG), its cationic form and the complex of MG-Al were determined, and it was found that these geometries are non-planar. The E-HOMO and E-LUMO energies can be used to calculate the global properties; chemical hardness (eta), softness (S) and electronegativity (chi). The calculated nonlinear optical parameters (NLO) of the studied compounds; the electronic dipole moment (mu), first-order hyperpolarizability (beta), the hyper-Rayleigh scattering (beta(HRS)) and the depolarization ratio (DR)) showed promising optical properties. Finally, the computational and the experimental results indicated that the adsorption efficiency of MG from wastewater was directly associated with the dye electrophilicity power. HIGHLIGHTS Preparation of low cost adsorbent (gamma-Al2O3) with a success modify in its porosity. The efficiency for wastewater treatment of the as-prepared solid was examined by MG adsorption. Full kinetic and isotherm studies were done. The theoretical calculations at the DFT/B3LYP level of theory were performed. Mechanism of the MG adsorption was proposed depending on the integration of both experimental and theoretical results.