Influence of anionic, cationic and nonionic surfactants on adsorption and desorption of oxytetracycline by ultrasonically treated and non-treated multiwalled carbon nanotubes

High adsorption capacity of carbon nanotubes (CNTs) may greatly determine the bioavailability and mobility of organic contaminants. The fate of contaminants adsorbed by CNTs may be substantially influenced by surfactants used both in the synthesis and dispersion of CNTs. The aim of this research was to determine the influence of surfactants (nonionic - TX100, cationic - CTAB and anionic - SDBS) on adsorption and desorption of oxytetracycline (OTC) by multiwalled carbon nanotubes (MWCNTs). The surfactants used had a substantial influence on both adsorption and desorption of OTC. The direction of changes depended clearly on the type of surfactant. In case of anionic SDBS, increased adsorption of OTC by MWCNTs was observed. The presence of TX100 and CTAB decreased the adsorption of OTC by MWCNTs significantly. The increase of OTC adsorption after ultrasonic treatment was observed in case of MWCNTs alone and MWCNTs with SDBS and TX100. However, ultrasonic treatment caused OTC adsorption decrease in the presence of CTAB. The change of pH had also an important effect on OTC adsorption in the presence of surfactants. Depending on the surfactant and pH, an increase or decrease of OTC adsorption was observed. The presence of surfactants increased OTC desorption from MWCNTs significantly as follows: SDBS = CTAB < TX100. The results obtained suggest new potential threats and constitute a basis for further research considering the bioavailability and toxicity of antibiotics in the presence of MWCNTs and surfactants.