Novel Polycarboxylated Starch-Based Sorbents for Cu²⁺ Ions

In this article we report use of novel starch-based functional hydrogels as Cu 2+ ions sorbents. Starch was functionalized by acid hydrolysis and/or oxidized by nitrogen oxides to generate carboxylic groups at C-6. Sorption of Cu 2+ ions was studied as a function of hydrogel structure and environmental factors. Hydrogels exhibit structure−property relationship in the sorption of Cu 2+ ions. The hydrogel that exhibited the maximum ion uptake was used to investigate the effect of contact time, temperature, pH, and Cu 2+ ions concentration on the sorption capacity. The maximum sorption capacity of 128.26 mg g −1 was obtained in 2 h at 40 °C, 7.0 pH, and 50 ppm of Cu 2+ ions. Sorption data show good match both with Langmuir and Freundlich isotherms and obey pseudo-second-order kinetics. Cu 2+ ions bind to sorbents by chelation. Evidence of Cu 2+ uptake on hydrogels was obtained from FTIR spectrum of the ions-loaded hydrogel.