Adsorptive removal of sulfamethoxazole from water using carbon-mineral composites

The objective of this work was to synthesize new carbon-mineral composites and evaluate their ability to remove sulfamethoxazole from water. Carbon-halloysite (CHS1a,b, CHNT1a,b) and carbon-kaolinite (CKT1a,b) composites were prepared using fruit pomace waste as a carbon precursor. In addition, raw halloysite (HS), halloysite nanotubes (HNT), and kaolinite (KT) were used as templates in the carbonization process conducted under a nitrohen atmosphere at two temperature values: 500oC and 800oC. The morphology and structural characteristics of the obtained composites were investigated using SEM EDX, FT-IR, Raman spectroscopy, and low-temperature nitrogen adsorption methods. All the composites were mesoporous materials. SEM and FTIR results confirmed that the surfaces of HNT, HS, and KT were covered with carbon. The highest carbon content was observed in composites prepared with HNT, suggesting that the nanotube structure enhances carbon deposition. The adsorption of sulfomethoxazole on both the newly synthesized carbon-mineral composites and the unmodified minerals was also studied. The removal efficiency of sulfamethoxazole increased significantly for composites such as CHS1a, CHNT1a, and CKT1a obtained at 800oC, compared to the raw minerals. The optimal conditions for sulfamethoxazole removal, achieving a maximum efficiency of 84%, were found using CHS1a with a dosage of 6 g/dm3 and an initial antibiotic concentration of 20 mg/dm3. The adsorption kinetics of sulfamethoxazole on the most effective adsorbent, CHS1a, was described using the pseudo-second-order kinetic model and the multi-center Langmuir adsorption model. CHS1a composite can be considered a promising adsorbent for the removal of sulfamethoxazole from water.