Comparative assessment of cellulose nanofibers and calcium alginate beads for continuous Cu(II) adsorption in packed columns: the influence of water and surface hydrophobicity
2021
Fiol, Núria | Tarrés, Quim | Vásquez, Matías G. | Pereira, Miguel A. | Mendonça, Regis Teixeira | Mutjé, Pere | Delgado-Aguilar, Marc
While water is indispensable for life, around 785 million people do not have access to basic drinking water. Heavy metals present high toxicity at low concentrations, are non-biodegradable and easy to accumulate in living organisms such as human body, causing serious diseases or even death. Copper is usually found at high concentrations in wastewater due to its extensive use in several industrial applications, and effective copper removal systems must be developed. The present work aims at developing effective TEMPO-oxidized cellulose nanofibers (CNFs) based systems able to adsorb Cu(II) in adsorption columns. CNFs were partially modified with alkyl ketene dimer (AKD) to avoid regelation during flowing through the column, as it was experienced for those unmodified. Calcium alginate beads were used as reference, as there is extensive literature on their use as Cu(II) adsorbent. Breakthrough curves were obtained and modelled according to Bohart-Adams, Yoon-Nelson and Thomas models, concluding that the adsorption rate of CNFs was significantly higher than in the case of calcium alginate beads due to the negative effects of highly charged water and diffusion through the beads. In addition, CNF-based adsorption systems demonstrated to be effective, especially at the beginning of the tests, as they exhibited a well-defined sigmoidal behavior, which was not observed in the case of the calcium alginate beads. On the contrary, the adsorption capacity was higher in the case of the alginate-based system, mainly due to the higher carboxyl content and ion exchange capacity. Overall, the present work shows the feasibility of using a high-performance bio-based and nanostructured cellulose material as Cu(II) adsorbent by means of a fast, simple, and effective chemical modification based on surface esterification.
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