Adsorption of sulfonamides by magnetic multiwall carbon nanotubes

Magnetic multiwall carbon nanotubes (MWCNTs) were prepared by soaking purified MWCNTs in a solution containing ammonium ferrous sulfate and ammonium ferric sulfatewith a pH of 11-12 at 50 ℃ for 30 min, and were used as an adsorbent for sulfonamides. Processing parameters affecting the adsorption efficiency were investigated, including the amount of adsorbent, pH value, adsorption time and the concentration of the sulfonamide solution. The removal of sulfonamides reached 85% when the ratio of the magnetic MWCNTs to the solution was 1 mg/mL, the pH value was 6 and the time of adsorption was 30 min. Adsorption kineticsfollowed apseudo-second order model and the Freundlich equation described the adsorption isotherm well. Desorption tests of the magnetic MWCNTs showed that the best elution was in ammonia-methanol (v/v, 5:95). The recovery of sulfonamides was more than 80% after ten desorption and adsorption cycles, indicating that the magnetic MWCNTs can be reused.