Removal of Norfloxacin from aqueous solution by clay-biochar composite prepared from potato stem and natural attapulgite

Abstract The objective of this study was to determine the feasibility of using a novel low-cost clay-biochar (APB) composite with potato stem and natural attapulgite to enhance removal efficiency of Norfloxacin from aqueous solution. A small amount of natural attapulgite was loaded onto biomass with a weight ratio of 1:5 and then pyrolyzed at 500 °C for 6 h in a muffle furnace. Biochar samples were characterized by Fourier transform infrared (FTIR), X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM). Characterization experiments suggested that the clay-biochar surface was covered with attapulgite particles. Batch sorption experiment indicated that NOR was adsorbed to the clay-biochar strongly with maximum sorption capacities of 5.24 mg/g, which was about 1.68 times higher than the pristine biochar (PB). The adsorption data of NOR was analyzed by Langmuir and Freundlich model, and the better correlation was achieved by the Langmuir isotherm. The kinetic data of the adsorption process showed that it followed closely the pseudo-second order model. The results of thermodynamic study about clay-biochar composite revealed that adsorption was a spontaneous and endothermic. In comparison to the pristine biochar, likely because the attapulgite particles on the carbon surface served as sorption sites and was bound with NOR through electrostatic interactions. The APB was successfully applied for the removal of NOR in tap water and Yellow River samples corresponding to the spiked samples. The APB was shown to be highly regenerable over several iterations. These results implied that attapulgite modified biochar had potential as a green cost-effective adsorbent for remediating NOR contaminated water environment.