TEMPO-oxidized cellulose hydrogel for efficient adsorption of Cu²⁺ and Pb²⁺ modified by polyethyleneimine

In this study, the hydrogel was prepared by dissolving and regenerating poplar cellulose in NaOH/urea/water system. The TEMPO-oxidized cellulose hydrogels (TCH) were prepared using microwave-assisted accelerated TEMPO-oxidation system. Polyethyleneimine (PEI) was grafted onto TCH with glutaraldehyde as a cross-linking agent and the products named as TCP. The hydrogels were characterized by SEM, FTIR, XPS, and elemental analyzer. The maximum adsorption capacities of Cu²⁺ and Pb²⁺ by TCP were 109.89 mg/g and 279.32 mg/g, respectively. TCP was a single molecule adsorption process with better fitting of the Langmuir model. Adsorption kinetics showed that the Pb²⁺ adsorption rate of TCP was higher than that for Cu²⁺. The Cu²⁺ affinity of TCP was higher than the Pb²⁺. The adsorption capacity of TCP for Cu²⁺ and Pb²⁺ was 58.26 mg/g and 91.96 mg/g, respectively, after five cycles. This study provided a promising option of preparing an efficient and recyclable adsorbent in treating wastewater containing heavy metal, such as Cu²⁺ and Pb²⁺.