Adsorption modelling on the removal of ciprofloxacin antibiotic from aqueous solution by acid-modified corn cob

Abstract

ABSTRACT The removal of emergent contaminants like ciprofloxacin (CIP) from effluents discharged from pharmaceutical industries is important for water purification. An environmental and eco-friendly nitric acid modified adsorbent produced from corn cob containing cellulosic materials was used for the sequestration of ciprofloxacin antibiotic from aqueous media. The adsorbent was characterised using SEM, FTIR, BET, EDX, and TGA techniques. The results of the characterisations depicted enrichment of the adsorbent porosity, surface functional groups and surface area (156.39 m2/g) of the agro-waste precursor after pretreatment. The effects of various adsorption parameters, including adsorbent dosage, initial concentration, pH, contact time, and temperature, were investigated, with an optimal pH value of 7 being determined. The maximum monolayer adsorption capacity for the CIP drug was found to be 51.55 mg/g. The Freundlich isotherm successfully explained the generated experimental results indicating a heterogeneous surface for the physisorption process. The rate-determining step of the reaction was predominately dominated by intraparticle diffusion, and the kinetic models were represented by pseudo-second-order processes that suggested chemisorption. The analysis of thermodynamics revealed that the adsorption process was endothermic (∆Ho < 0), and spontaneous (∆Go < 0) with an increasing degree of randomness (∆So < 0). Finally, it should be noted that CIP loaded on the adsorbent could be easily desorbed with 0.1 mol L−1 HNO3 and the adsorbent showed good reusability for adsorption of the studied drug. Therefore, this study proposed the viability of acid-pretreated corn cob for economically effective treatment of ciprofloxacin in water or similar pharmaceutical-laden wastewater.