Kinetics and Adsorption Investigation of Malachite Green onto Thiolated Graphene Oxide Nanostructures

Abstract

Release of dye-containing wastewater into ecosystems has posed serious risks to the environment and aquatic life because of toxicity and adverse effects on the water bodies. Malachite green is a basic dye that has very wide industrial applications, especially in the aquaculture industry. This study was carried out in order to remove the malachite green from aqueous solutions by thiolated graphene oxide in batch system. In the present work, the effects of experimental parameters such as adsorbent dosage, solution pH, initial dye concentration, thermodynamics and adsorption mechanism were comprehensively studied in batch system. In order to characterize the physical and chemical properties of the synthetized nanostructure and also to confirm the functionalization steps, different analyses including SEM and FT-IR were used. Batch studies showed that the experimental data fitted logically to applied isotherms, namely Langmuir (R2=0.991) and Freundlich (R2=0.983) models. Kinetic calculations confirmed that malachite green adsorption was described more accurately by pseudo-second order model compared to the pseudo-first order model. The study showed that thiolated graphene oxide is an effective adsorbent for malachite green removal from aqueous solution. Under controlled reaction conditions, Gibbs free energy (ΔG) varied from -1.46 to -3.25 kJ/mol, besides, the resulting ΔH° and ΔS° values were obtained 0.059 kJ/mol and 15.67 kJ/mol.K, respectively. So, it can be considered that the adsorption of malachite green onto the thiolated graphene oxide nanostructure is a physico-chemical and spontaneous process.