Adsorption properties of sugarcane bagasse and corn cob for the sulfamethoxazole removal in a fixed-bed column

Natural adsorbents are a good alternative to remove antibiotic residues from wastewater. In this study, the adsorption capacity of sulfamethoxazole (SMX) onto sugarcane bagasse (SB) and corn cob (CC) in a continuous fixed-bed was compared. Brunauer Emmett Teller, Fourier transform infrared (FTIR), Boehm titration, and point of zero charge (pH_pzc) were used to characterize both adsorbents. The adsorption capacity (q_e) and the removal percentage of SMX (% R) were investigated at different different flow rates (2, 5, and 7 mL min^{− 1}) and adsorbent masses (4 and 6.4 g), and a constant initial concentration of 5 mg L^{− 1}. The results of the characterization showed that SB has a morphology with more dispersed particles and a specific surface higher than CC (2.6 > 1.2 m² g^{− 1}). Boehm titration indicates that both the surface of SB and CC have a greater amount of acid groups, which is in agreement with FTIR and pH_pzc results. The continuous fixed-bed experiments showed that % R and q_e of SMX are higher with SB in all the tests. The highest q_e and maximum % R was 0.24 mg g^{− 1} and 74% with SB, and 0.15 mg g^{− 1} and 65% using CC. In most cases, the q_e of both adsorbents decreased with the increase of flow rate and bed height. An analysis suggests that hydrogen bonds could be the main factor favoring the SMX adsorption with SB. Finally, the intraparticle diffusion was the rate-controlling step, predominating the pore-volume diffusion resistance.