Development of Mn-PBA on GO sheets for adsorptive removal of ciprofloxacin from water: Kinetics, isothermal, thermodynamic and mechanistic studies

Water as a universal solvent has well-documented for its ability to dissolve various substances leading to water pollution. Metal organic frameworks (MOFs) have been proved to have interesting properties for the adsorptive removal of pollutants from water. In this work, Mn-PBA (Mn[Fe(CN)(6)]) and Mn-PBA/GO composite have been developed using simple and facile method for the adsorption of ciprofloxacin (CIP). The adsorption kinetic performance of as-synthesized composite for CIP is justified by applying pseudo-second order (R-2 = 0.99638) and liquid-film diffusion model (R-2 = 0.91603), whereas for the Mn-PBA, pseudo-second order (R-2 = 0.99951) and intra-particle model (R-2 = 0.80577) is well-fitted. The adsorption isotherm data of Mn-PBA/GO composite for CIP is fitted using Langmuir model (R-2 = 0.99994) and adsorption capacity (1826.64 mg/g) is observed higher than previous reports. The relative correlation coefficient value is calculated by using Tampkin model (R-2 = 0.62798), which indicated electrostatic relationship between Mn-PBA/GO and ciprofloxacin (CIP). Adsorption of CIP on the Mn-PBA/GO takes place according to endothermic and spontaneous processes (Delta H = +16.94 kj/mol, Delta G = -9.25 kj/mol). The composite has well retained its reusability and the removal efficiency is reduced only 5% after several cycles. Further, the influence of various factors (pH, contact time, adsorbent dose, adsorbate quantity, temperature and ionic strength) on adsorptive removal of CIP is also discussed.