Effective adsorption of tetracycline on plasma-modified layered double hydroxides loaded carbon nanotubes

In this study, plasma was used to modify the composite adsorbent of layered double hydroxides (LDHs) and carbon nanotubes (CNT) to enhance the removal of tetracycline (TC) from wastewater. After plasma treatment, the morphology of composite adsorbent remained unchanged, and the plasma treatment created defects on the composite adsorbent and altered the surface functional groups. The kinetic data were well represented by the pseudo-second-order kinetics and the intra-particle diffusion model. The isothermal data were more accurately described by Generalized-Langmuir model, and the composite after 30 min plasm treatment has a higher adsorption capacity of 1150.35 mg/g. The theoretical analysis of site energy distribution indicated that after the plasma treatment, an increase in the number of available adsorption sites was produced and the calculated average site energies for samples are measured between 12.07 and 12.97 kJ/mol. The high-energy sites are formed on the surface of LDH@CNT after plasma treatment, enhancing the defect and oxygen-containing functional groups, thereby increasing the number of adsorption sites and improving the adsorption capacity for TC. The experiment of co-existing ions and pH shows that the removal efficiency remained around 80 % under different conditions. The recycling tests indicate that after four cycles of experimentation, the removal rate of TC remained above 65 %, demonstrating that the plasma-treated LDH@CNT exhibits adsorption stability in complex environments. This study highlights the plasma treatment of composite adsorbent as an effective technology for the removal of TC.