Removal of Typical Organic Contaminants with a Recyclable Calcined Chitosan-Supported Layered Double Hydroxide Adsorbent: Kinetics and Equilibrium Isotherms

In this work, the calcined chitosan (CS)-supported layered double hydroxides were prepared, characterized, and further applied to remove organic contaminants in aqueous solution. The chitosan-supported layered double hydroxide calcined at 400 degrees C (CSLDO400) was found to be effective for the adsorption of azo dye and antibiotic. CSLDO400 showed excellent adsorption performance at a wide pH range from 5 to 9 for methyl orange (MO) while the adsorption of tetracycline (TC) Was most efficient at a pH of 9, and the optimal CSLDO400 dosages were 0.175 g L-1 for MO and 0.375 g L-1 for TC. The divalent and trivalent anions have a great effect on removal efficiency of MO and TC, while the effect of monovalent anions adsorption can be neglected. The adsorption kinetics indicated that the MO and TC removal followed the pseudo-second-order model. In addition, it can be fitted well with both the Langmuir and Freundlich model for MO and TC at 298 K, respectively. The adsorptions of MO and TC on CSLDO400 were both spontaneous and endothermic. After five adsorption-desorption cycles, CSLDO400 still showed high efficiency with an adsorption capacity of 60.72 mg g(-1) for MO and 21.92 mg g(-1) for TC. Therefore, the CSLDO400 are promising for use in the treatment of drinking water and wastewater contaminanted by organic matters.