Humic acid adsorption onto cationic cellulose nanofibers for bioinspired removal of copper( ii ) and a positively charged dye

© The Royal Society of Chemistry. Waste pulp residues are herein exploited for the synthesis of a sorbent for humic acid (HA), which is a major water pollutant. Cellulose pulp was etherified with a quaternary ammonium salt in water thereby introducing positive charges onto the surface of the pulp fibers, and subsequently mechanically disintegrated into high surface area cellulose nanofibers (CNF). CNF with three different charge contents were produced and their adsorption capacity towards HA was investigated with UV-spectrophotometry, quartz crystal microbalance with dissipation, and ζ-potential measurements. Substantial coverage of the CNF surface with HA in a wide pH range led to a reversal of the positive ζ-potentials of CNF suspensions. The HA adsorption capacity and the kinetics of HA uptake were found to be promoted by both acidic pH conditions and the surface charge content of CNF. It is suggested that HA adsorption onto CNF depends on electrostatic interactions between the two components, as well as on the conformation of HA. At pH ∼ 6, up to 310 mg g of HA were adsorbed by the functionalized CNF, a substantially higher capacity than that of previously reported HA sorbents in the literature. It is further shown that CNF-HA complexes could be freeze-dried into "soil-mimicking" porous foams having good capacity to capture Cu(ii) ions and positive dyes from contaminated water. Thus, the most abundant natural polymer, i.e., cellulose could effectively bind the most abundant natural organic matter for environmental remediation purpose.

Sehaqui H, Perez de Larraya U, Tingaut P, Zimmermann T (2015) Humic acid adsorption onto cationic cellulose nanofibers for bioinspired removal of copper( ii ) and a positively charged dye . Soft Matter 11: 5294–5300. Available:

Esther Strub from EMPA is thanked for assistance in SEM characterization. Michael Sander, Antonius Armanious and Michael Zumstein from the University of Zürich are thanked for their assistance in QCM-D measurements and for fruitful discussions. Dr Jiang Wei from Alfa Laval and Dr Mohamed Eita from KAUST University are thanked for their advices. This work was supported by the European project NanoSelect, FP7 Collaborative project, grant agreement no. 280519.

Royal Society of Chemistry (RSC)

Soft Matter


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