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Comparative adsorption of ciprofloxacin on sugarcane bagasse from Ecuador and on commercial powdered activated carbon

Abstract:

This work examined the adsorption capacity of sugarcane bagasse (SB) for the removal of ciprofloxacin (CPX) from water using batch experiments and a fixed bed column and compared its adsorption performance with a powdered activated commercial carbon (PAC). Both adsorbents achieved a similar percentage removal of about 78% with doses of 3 g L−1 of SB and 0.3 g L−1 of PAC (20 mg L−1 initial CPX concentration at 30 °C). The maximum removal was obtained at a pH between 6 and 8. SB adsorption isotherms were fitted to the Langmuir, BET and Freundlich models showing a maximum adsorption capacity of 13.6 mg g−1. The kinetic data for both SB and PAC fitted the pseudo second-order model (R2 = 0.99). The adsorption process was faster on the SB (65% of elimination in the first 5 min) than on the PAC. The study of the adsorbent properties shows that SB is a macroporous solid with a specific surface area 250 times smaller than PAC. The thermodynamic results show that SB adsorption was physical and exothermic. The main suggested interactions between CPX and SB are electrostatic attraction, hydrogen bonding and dipole-dipole interactions. The experiments carried out in a fixed bed show that the adsorption capacity at breakthrough increases with the bed height. The adsorption capacity at saturation time was 9.47 mg g−1 at a flow rate of 3 mL min−1, a bed height of 14 cm, and a diameter of 1.5 cm. The experimental data were fitted to the Bohart-Adams model (R2 = 0.98). These results highlight the capacity of sugarcane bagasse to adsorb ciprofloxacin from water, illustrating its potential as a low-cost adsorbent.