Adsorption properties of methylene blue and Cu(II) on magnetically oxidized tannic acid cross-linked carboxymethyl chitosan gels
Xubing Sun, Shiyu Yin, Zhao Li, Wenhua Yang, Yaohui You
Abstract
In this work, tannic acid was selected as a green cross-linking agent to cross-link carboxymethyl chitosan to prepare a magnetic adsorbent (CC-OTA@Fe 3 O 4 ), which was used to remove methylene blue (MB) and Cu 2+ . CC-OTA@Fe 3 O 4 was characterized by FTIR , 13 C NMR, XRD , VSM , TGA , BET and SEM. The adsorption behavior was studied using various parameters such as pH value, contact time, initial concentration of MB and Cu 2+ , and temperature. The results showed that adsorption of MB and Cu 2+ followed the pseudo-second-order model and the Sips model. The maximum adsorption capacities were determined to be 560.92 and 104.25 mg/g MB and Cu 2+ at 298 K, respectively. Thermodynamic analysis showed that the adsorption is spontaneous and endothermic in nature. According to the results of FTIR and XPS analyses , the electrostatic interaction was accompanied by π–π interaction and hydrogen bonding for MB adsorption, while complexation and electrostatic interaction were the predominant mechanism for Cu 2+ adsorption. Furthermore, CC-OTA@Fe 3 O 4 displayed remarkable stability in 0.1 M HNO 3 , exhibited promising recyclability, and could be easily separated from aqueous solutions in the magnetic field . This study demonstrates the potential of CC-OTA@Fe 3 O 4 as an adsorbent for the removal of cationic dyes and heavy metals from wastewater.