Investigation of sorption mechanism of methylene blue, congo red and tannic acid from aqueous solutions onto magnetic composite sorbent obtained from alkaline pretreated spent coffee grounds

Abstract

In this article, a novel magnetic composite material obtained from alkaline pretreated spent coffee grounds was used for investigating of the sorption mechanism of methylene blue, congo red and tannic acid from aqueous solutions. In order to clarify mechanisms were analyzed the adsorption kinetics models (external and internal diffusion; chemical kinetics (pseudo-first order, pseudo-second order); intraparticle diffusion) and the adsorption thermodynamics. The results showed that the sorption of all studied sorbates was controlled by a mixed diffusion model and a pseudo-second order and diffusion rate revealed three stage of the mass transfer. The adsorption process of methylene blue, congo red and tannic acid onto Fe3O4/PVA/APSCGs sorbent was spontaneous and endothermic. Based on the results, it was concluded that the mechanism for removal of the studied sorbates by adsorption onto Fe3O4/PVA/APSCGs sorbent may be assumed both physisorption and chemisorption.