Removal of cefixime from aqueous solutions by the biosorbent prepared from pine cones: kinetic and isotherm studies

The bio-char prepared from pine cones was used to remove cefixime (CFX) from aqueous solutions. The influence of some parameters including pH (2-12), contact time (0 to 120 min), initial concentration of CFX (10, 50, and 100 mg L-1), adsorbent dose (0.1 to 2.5 g L-1), temperature (10 degrees C to 50 degrees C) was evaluated. The pine cones pieces were washed with the distilled water, dried, crushed, and sieved to provide a particle size of 100-250 nm. For carbonization, the dried raw material was put into a stainless steel reactor and heated in an electrical furnace at 20 degrees C per min and maintained at 460 degrees C for 2 h. After carbonization, the samples were washed with distilled water and then dried at 105 degrees C for 12 h, and were used as adsorbent. The specific surface area, total pore volume, and mean pore diameter of the biosorbent were determined to be 789 m(2) g(-1), 0.373 cm(3) g(-1), and 1.89 nm, respectively. In the optimum conditions (pH = 6.3, initial concentration of CFX = 50 mg L-1, contact time = 90 min, and adsorbent dose = 2 g L-1), the removal efficiency was 92%. The adsorption isotherm of CFX follows the Langmuir model. The kinetic study confirmed that the adsorption process fits with the pseudo-second-order reaction. The thermodynamic study indicated that the adsorption of CFX by the bio-char is feasible, spontaneous, and exothermic. This study represents that the biosorbent prepared from the pine cones can be used as an appropriate and cost-effective adsorbent for the removal of CFX from aqueous solutions and hospital wastewater.