Prediction the effect of the most efficient factors on the adsorption process of some azo dyes compounds on carbon surface using quantum mechanical methods

Abstract

This work includes the adsorption study of four azo dyes. The used dyes are p-COOH RD, m-NO₂ RD, p-Br RD, and p-NH₂ RD. The study aims to determine the most efficient sites of the dyes that connect to the surface of the adsorbent to understand the mechanism of removing these dyes from contaminated water. The calculations have been achieved using quantum mechanics methods including two semiempirical methods AM1, PM3, and Ab initio (HF). The total energy of the molecule 18.167 kcal., the energies of HOMO -3.060 ev and LUMO -5.357 ev, the energy gap between them, hardness, and atomic charges have been calculated. The obtained results show that the nitrogen atoms in the azo dyes are the most influencing factor affect the adsorption process. By comparing the practical results with the theoretical ones, it was found that the azo group the most efficient group on the stability of these compounds and responsible for the adsorption of the studied compounds.