Removal of Azo-dyes from wastewater by adsorption on the surface of Graphene Oxide nanosheet: Experimental and Computational approaches

Abstract

Azo dyes are a coloring agents having wide applications in various industries like paint, textile and paper industries. Azo dyes released as waste materials by textile industries during cleaning process have detrimental impacts on aquatic environment. Now a days heterogenous catalysis and adsorption studies have been gaining much popularity worldwide due to its versatility. Presently heterogenous adsorption mechanism of five novel azo dyes namely, Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-4- chlorobenzaldehyde, Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-p-anisaldehyde, Bis 3,3'-(4,4'- Diazenyldiphenylmethane)-naphthaldehyde, Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-salicylaldehyde, Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-2,4-dihydroxybenzaldehyde with Graphene Oxide (GO) was probed to determine adsorption prosperity on basis of experimental and computational kinetics and thermodynamic parameters. Experimental Langmuir adsorption constant (KL) determined by UV-Vis spectroscopy was found to be highest for Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-salicylaldehyde i.e., 3.76×109 as compared to other four azo-dyes and having more negative free energy value -54.62 kJ/mol. Calculated electronic (EHOMO, ELUMO), kinetic (Kad), and thermodynamic parameters (ΔG, ΔH, and ΔS) based on quantum chemical DFT approach also revealed highest adsorption of Bis 3,3'-(4,4'- Diazenyldiphenylmethane)-salicylaldehyde with Graphene oxide (GO) due to strong deactivating –OH, -CHO group on aromatic ring of azo-dye. Based on quantum chemical findings calculated adsorption constant (Kad) of Bis 3,3'-(4,4'-Diazenyldiphenylmethane)-salicylaldehyde was also highest 1.93×1010 and free energy (ΔG) was -58.69 kJ/mol. It was observed that experimental results are complying with computational results. Current research would have tremendous impact in the area of water purification and desalination using Graphene oxide (GO) molecular sieve.