Adsorption Properties of a Magnetite Composite with Coffee Waste

Magnetic composite sorbent consisting of a synthetic magnetite and ground coffee waste is produced and characterized. The point of zero charge is determined. The presence of carbonyl and carboxyl groups on the sorbent surface is established. The sorbent's sorption capacity toward methylene blue dye is determined. The adsorption kinetic curves are analyzed using models of diffusion and chemical kinetics. It is shown that adsorption proceeds in the mixed diffusion regime and can be described by pseudo second-order kinetics. The correlation between the adsorption isotherms and the Langmuir and Freundlich models is evaluated. The possibility of sorbent regeneration is demonstrated. It is concluded that the proposed composite magnetic sorbent has high efficiency and can be used to purify water of organic dyes.