Removal and removing mechanism of tetracycline residue from aqueous solution by using Cu-13X

In order to improve the removal efficiency of the reported adsorbents via freely physical adsorption, a novel adsorbent, Cu-13X, was applied to remove tetracycline (TC) residue from aqueous solution due to the chemically selective adsorption. The removal behaviors, adsorption kinetics, adsorption isotherm, adsorption thermodynamics of TC on synthesized Cu-13X were studied in batch experiments under different conditions. It was found that the adsorption capability of Cu-13X increased greatly after exchanging. The amount of Cu(II) cation in Cu-13X and the pH value were important factors. At pH 7.0 and the maximum exchange amount of Cu(II), the maximum adsorption capacity of Cu-13X for TC residue reached about 2400 mg g−1. The adsorption isotherms were fitted well by the Langmuir model. The adsorption kinetics was described well by pseudo-second order equation, simultaneously was described well by the intra-particle diffusion model at high initial concentration of TC. The data calculated by adsorption thermodynamics of TC on Cu-13X showed it was exothermic and spontaneous. The probable adsorption mechanism was proposed by Fourier transform infrared (FTIR) analysis, which showed that the adsorbing TC residue on Cu-13X depended on the strong complexation of Cu(II) with NH2 radical of amide group of TC.