Construction of porous biochar decorated with NiS for the removal of ciprofloxacin antibiotic from pharmaceutical wastewaters

The employment of residual biomass to produce promising sorbents with highly adsorption characteristics and their successful application for the removal of antibiotics from wastewater has gained considerable interest because of their low production cost and sustainability. Herein, the banana peel waste (BP), its modified biochar (BC), and activated biochar decorated with NiS (BC-NiS) were assessed as renewable adsorbents for efficient removal of ciprofloxacin antibiotic (CIP) from wastewater. The modification of BP with H3PO4 followed by the carbonization process produced porous banana peel biochar (BC) with larger acidic functional groups that formed on the carbon surface. This activation facilitated the effective synthesis of biochar decorated with NiS (BC-NiS) using a facile hydrothermal approach. The samples were characterized by XRD, FE-SEM, EDX, HR-TEM, BET, FTIR, and XPS analysis. The influence of operating factors including pH, contact time, initial CIP concentration, adsorbents dose, interfering ions, and solution temperature on the removal of ciprofloxacin by banana peel waste and its porous biochar modified with NiS was also evaluated. The maximum adsorption capacity of the BC-NiS hybrid structure was found to be 41.66 mg/g, which was highly effective compared with BP (20.83 mg/g) and BC (35.71 mg/g) for CIP removal without pH adjustment. A good fit was observed by the pseudo-second-order model and the Langmuir adsorption isotherm. The values of △ H° and △G° indicated the endothermic and spontaneous character of the adsorption process. The adsorption mechanism has been comprehensively elucidated by electrostatic interaction, π-π stacking, coordination affinities, and pore-filling effect. Desorption and recycling studies of the BC-NiS hybrid structure were also carried out to investigate its stability, and the results showed that it can be recycled without a substantial loss in the adsorption process after three recycle runs.