Promotion of clinoptilolite adsorption for azithromycin antibiotic by Tween 80 and Triton X-100 surface modifiers under batch and fixed-bed processes

Abstract

In this study, azithromycin (AZT) adsorbed on natural clinoptilolite (NC) modified by Triton X-100 (NC-Triton) and Tween 80 (NC-Tween) surfactants. The effect of pH, contact time, adsorbent dose, and temperature on the adsorption was investigated. For NC, the Temkin isotherm and for NC-Tween and NC-Triton, Langmuir isotherm fitted the experimental data well. The maximum adsorption capacity value of NC, NC-Tween, and NC-Triton was 28.011, 36.764, and 44.642 mg/g, respectively. Fixed-bed experiments were performed under different conditions to predict breakthrough curve. For NC and NC-Tween, the intra-particle diffusion kinetic model and for NC-Triton, fractional power model were the best investigated models. The thermodynamic parameters of Gibbs free energy$\mathrm{}(\mathrm{\Delta }\mathrm{G}°=-13.042\mathrm{}\mathrm{to}-17.214\mathrm{kJ}/\mathrm{mol})\mathrm{}$ for NC, $\mathrm{\Delta }\mathrm{G}°=-13.838\text{to}-18.090\mathrm{kJ}/\mathrm{mol}$ for NC-Tween, $\mathrm{\Delta }\mathrm{G}°=-14.570\text{to}-18.683\mathrm{kJ}/\mathrm{mol}\mathrm{}$ for NC-Triton in 20-35 °C, enthalpy $(\mathrm{\Delta }\mathrm{H}°=68.440\mathrm{kJ}/\mathrm{mol}),$ and entropy $(\mathrm{\Delta }\mathrm{S}°=278.194\mathrm{J}/\text{mol K})\mathrm{}$ changes for NC, $\mathrm{\Delta }\mathrm{H}°=69.227\mathrm{kJ}/\mathrm{mol},$ and $\mathrm{\Delta }\mathrm{S}°=283.590\mathrm{J}/\text{mol K}$ for NC-Tween,$\text{ΔH}°=69.286\mathrm{kJ}/\mathrm{mol},$ and $\mathrm{\Delta }\mathrm{S}°=286.292\mathrm{J}/\text{mol K}$ for NC-Triton were determined.

Keywords:

• Adsorption
• azithromycin
• batch studies
• fixed-bed column
• natural clinoptilolite Tween 80
• Triton X-100