Abstract
Abstract Commercial antiseptic solutions containing a mixture of antibacterial agents such as, chlorhexidine gluconate, in presence of a cationic surfactant like cetrimide, are commonly used as floor, toilet and kitchen cleaning agents. Although a specific composition may be beneficial for disinfecting human beings, these are toxic to aquatic organisms, the plant biota and useful microorganisms present in soil and in municipal sewer pipes. In this study, functional modification of granular activated carbon (GAC) is carried out with hydrochloric and hydrofluoric acids in order to enhance the adsorption capacity of GAC for simultaneous removal of both chlorhexidine gluconate and cetrimide. Hydrofluoric acid functionalized activated carbon shows highest removal of both cetrimide and chlorhexidine gluconate (maximum adsorption capacitypure component chlorhexidine gluconate =349.0 g/g; maximum adsorption capacitypure component cetrimide =23.0 g/g). Average removal of cetrimide by GAC, FAC-HCl and FAC-HF are 36.64 %, 47.09 % and 75.74 % respectively. Surface charge of modified activated carbons is significantly altered as compared to unmodified GAC which provided an enhanced net available driving potential for the positive cetrimonium ions to reach the surface much faster as compared to the bulky chlorhexidine gluconate molecules. Cetrimide then undergoes pure physical adsorption through pore diffusion. However, chlorhexidine gluconate forms surface complexes with the functional groups as confirmed by the relative quantities of oxygenated surface functional groups and Fourier Transform Infrared (FT-IR) analysis. Intraparticle diffusion and Boyd plots show that film diffusion and not intraparticle diffusion is the rate controlling step.
Published Version
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