Deep eutectic solvent functionalized rice husk ash for effective adsorption of ofloxacin from aqueous environment

Abstract

Deep eutectic solvents (DESs) have achieved the rising attention of the scientific community because of their distinctive physicochemical properties and variety of applications. Herein, DES composed of choline chloride as hydrogen bond acceptor (HBA) and glycolic acid as hydrogen bond donor (HBD) was synthesized. Next, the prepared DES was examined as a functionalization agent for rice husk ash (RHA) to form a novel adsorbent (DES-RHA). To ensure the formation of DES and to recognize the modifications occurred due to the functionalization process, a comprehensive characterization study was performed using ¹HNMR, FTIR spectroscopy, TGA, XRD, FESEM, HR-TEM and BET surface area. Potential of the prepared DES-RHA was investigated for the uptake of ofloxacin (OFL) from an aqueous environment. The impact of relevant process parameters was evaluated under optimum conditions, and the data were examined applying various kinetic and isotherm models. As per the regression findings, adsorption kinetics data were well described by pseudo-second-order model, and the isotherm data were in good agreement with Langmuir, Temkin, RP and Freundlich isotherm models. Further, the adsorption procedure was endothermic and spontaneous. The high regeneration and adsorption capacity of DES-RHA than untreated RHA adds a promising approach to eliminate emerging pollutants present in effluent sites.

Keywords: Adsorption isotherms; DES functionalized RHA; Kinetics; Ofloxacin; Rice husk ash.