Minimizing the residual antimicrobial activity of tetracycline after adsorption into the montmorillonite: Effect of organic modification

Abstract

Variety of adsorbents have been developed and used for antibiotic separations (e.g. tetracycline), however, there is not enough information about the residual antimicrobial activity of adsorbed antibiotics. In this study, montmorillonite was modified using HDTMA and applied for adsorption of tetracycline in order to minimize the residual antimicrobial activity of tetracycline. Results revealed that despite the high adsorption capacity of the non-modified montmorillonite for tetracycline, high residual antimicrobial activity still remained which was probably correlated to the partial release of tetracycline from the montmorillonite structure. On the other hand, the adsorbed tetracycline onto HDTMA-modified montmorillonite had much weaker residual antimicrobial activity due to the strong attraction force between HDTMA and the tetracycline which minimize the chance of its desorption when releasing the complex in the environment. A series of changes on the HDTMA-modification process (by improvement of HDTMA arrangement in the interlayers of montmorillonite) enhanced the adsorption of tetracycline in the interlayer spaces of montmorillonite with the least residual antimicrobial activity of tetracycline and HDTMA-modified montmorillonite complex. Results of this study present a great enhancement in the adsorption of antibiotics to minimize the effect of antibiotics such as the development of antibiotic-resistant bacteria.