Mechanistic investigations on sorption of ciprofloxacin from water using groundnut shell derived biochar

• Groundnut shell biochar, synthesized at 3 different temperatures, was used for removal of ciprofloxacin in water • Maximum efficiency of 99% could be achieved at neutral pH in room temperature conditions. • Reaction followed pseudo second order kinetics and Langmuir isotherm. . Increasing problem of antimicrobial resistance and mismanagement of waste have led to serious repercussions for the environment. Therefore, in this study, development and optimization of groundnut shell (GNS)-derived biochars were carried out for the removal of ciprofloxacin (CIP) from water. The GNS-derived biochars were prepared at varying temperatures (500-900°C) under controlled conditions and their physico-chemical properties were characterized. The effect of operating parameters on CIP removal was systematically studied. The removal efficiency varied in the range of 56-99% using various adsorbents under different conditions. The maximum removal efficiency was ∼99% using biochar synthesized at 700°C (GNS700) at neutral pH in room-temperature conditions. Four isotherm models were employed to study the removal of CIP. Notably, adsorption capacity for CIP was significantly higher for GNS700 (22.1 mg·g −1 ) compared to other adsorbents (2.3-6.4 mg·g −1 ), evaluated using Langmuir isotherm. Batch adsorption of CIP is governed by Langmuir, Freundlich, and Temkin models, confirming multiple mechanisms, as monolayer, multilayer, and surface adsorption. Kinetic study revealed the dominance of physical, chemical, and film diffusion for GNS700 and GNS900 biochar. Presence of –OH functional group and Si on biochar surface supposedly promoted the removal of CIP using GNS-derived biochars. Further, high surface area (276.6 m 2 ·g −1 ) and pore volume (0.26 cc·g −1 ) aided in better adsorption. Thermodynamic analysis proves that reaction is endothermic and proceeds spontaneously for sorption of CIP. This study demonstrated the potential of waste-biomass for removing emerging contaminants and provides valuable insights towards achieving Sustainable Development Goals of ‘Good Health and Well-being (SDG #3)’ and ‘Clean Water and Sanitation (SDG #6)’. .