Ciprofloxacin, ranitidine, and chlorphenamine removal from aqueous solution by adsorption. Mechanistic and regeneration analysis

Several studies have reported the presence of pharmaceuticals in freshwater bodies all around the world. For this investigation, the removal of the pharmaceuticals ciprofloxacin (CIP) ranitidine (RNT), and chlorphenamine (CPM) using lignocellulose-derived granular activated carbon (GAC) was analyzed, and the physicochemical mechanisms of removal were elucidated. Additionally, the textural and surface properties of the GAC were evaluated, the concentrations of the contaminants were monitored with UV-Vis Spectrophotometry. The results revealed that GAC is a mesoporous material with a surface area of 940 m(2)/g and an acidic character with a point of zero charge (pH (PZC)) around 2. The adsorption isotherms showed a consistent behavior with the Prausnitz-Radke model, reporting adsorption capacities of 668, 521, and 582 mu mol/g (221, 173 and 193 mg/g), at an equilibrium concentration of 50 mu mol/L, pH 7 and 25 degrees C for CIP, RNT and CPM, respectively. Moreover, studies at different pH levels, temperature, and reversibility suggested that adsorption obeys physical mechanisms, which led to the proposal of a chemical regeneration process with organic (ethanol and methanol) and inorganic (NaOH and HCl) diluents. Better results were obtained using the inorganic diluents, ranging between 44 and 73% thermodynamic desorption. Additionally, three reuse cycles were successfully performed at the best conditions, with a regeneration efficiency in the range of 68%-98% for each of the pharmaceuticals. The results demonstrate the viability of the use of GAC for the removal of drugs with different characteristics in scenarios that are very close to the real ones. (C) 2021 The Author(s). Published by Elsevier B.V.