Sorption of Heavy Metal Ions by the “Cellulose–Carbon Nanotubes” Biocomposite

This paper presents the development of a composite sorbent based on cellulose and carbon nanotubes and its sorption properties towards Cu(II) ions. Carbon nanotubes were sequentially modified with concentrated sulfuric acid, thionyl chloride, and ethylenediamine, and subsequently attached to cellulose pretreated with citric acid. The formation of new functional groups on the surface of the composite cellulose sorbent was confirmed through FTIR spectroscopy. Scanning electron microscopy revealed differences in the surface structure of cellulose-based sorbents before and after modification. The kinetics and equilibrium of Cu(II) ion sorption were investigated in a heterogeneous “aqueous solution–modified sorbent” system. The kinetic data were more accurately described using the pseudo-second-order kinetic model. Analysis of sorption isotherms using the Langmuir equation allowed determination of the maximum sorption capacity of the original sorbent and its composite derivative. It was found that the sorption capacity of the composite sorbent is approximately six times greater than that of unmodified cellulose.