Filtration and adsorption of tetracycline in aqueous solution by copper alginate-carbon nanotubes membrane which has the muscle-skeleton structure

Abstract

Recently, removal of antibiotic contaminants such as tetracycline (TC) from wastewater has been widely studied. In this study, we innovatively used copper alginate as the substrate and carbon nanotubes (CNTs) as the framework to obtain copper alginate-carbon nanotubes (CA-CNTs) composite membrane which has the “muscle-skeleton” structure after vacuum freeze-drying, cross-linking reaction and natural drying. Its performance on TC removal was verified from both filtration and adsorption. As shown by various analytical methods, the prepared composite membranes have good filtration and adsorption performance, with a maximum filtration removal rate of 95.03 % and a maximal adsorption capacity of 230.17 mg·g−1 at 318 K. The adsorption equilibrium data were well in accordance with the Langmuir isothermal model and the pseudo-second-order kinetic model. In addition, the thermodynamic analysis showed that the adsorption action of TC by CA-CNTs membranes was spontaneous and endothermic. In terms of principle and mechanism, copper alginate (CA) and CNTs were mainly bonded by hydrogen bonds, and the adsorption of TC was mainly accomplished by hydrogen bonds, cation bonding bridges and n-π EDA interactions. Meanwhile, it still had good adsorption performance after five regeneration cycles. Therefore, the prepared composite membrane has a good prospect in the application of TC removal.