Enhanced adsorption for the removal of antibiotics by carbon nanotubes/graphene oxide/sodium alginate triple-network nanocomposite hydrogels in aqueous solutions.

Large-scale abuse of antibiotics has led to serious environmental problems. Some conventional adsorbents such as several biopolymer gels have poor adsorption performance and inadequate mechanical properties. In this paper, carbon nanotubes (CNTs) and graphene oxide (GO), were combined with sodium alginate (SA) to improve the adsorption performance and other properties of traditional adsorbents. With the help of hydrogen peroxide and l-cysteine (L-cys), carbon nanotubes/l-cysteine@graphene oxide/sodium alginate (CNTs/L-cys@GO/SA) triple-network composite hydrogels were prepared. Compared with traditional hydrogels and the double-network hydrogels that are currently being developed, these triple-network composite hydrogels can exploit their three-dimensional structure to improve their adsorption capacity. The independent triple-network structure increases the three-dimensional space, so there are more pores and pollutant adsorption sites to achieve the high-efficient removal of ciprofloxacin. And the adsorption capacity of CNTs/L-cys@GO/SA hydrogels can reach 181 mg g-1 and 200 mg g-1 at 25 °C and 15 °C respectively in weak acidity environment. In fact, CNTs/L-cys@GO/SA hydrogels show better property at low temperature. In addition, the thermal stability, mechanical properties and swelling ability of the triple-network hydrogels have also been improved. The independent multilayer network can retain the excellent properties of the original materials and make the internal space of hydrogels larger. These multinetwork hydrogels have great potential for removing pollutants from wastewater. In addition, the CNTs/L-cys@GO/SA hydrogels show the higher adsorption capacity of ciprofloxacin under the conditions of weak acidity, low temperature and low inorganic salt concentration, so the removal of ciprofloxacin by hydrogels can also be promoted by changing environmental conditions.