Abstract

Mineral pumice as an adsorbent was explored for tetracycline (TC) removal from water. Pumice was characterized by X-ray diffraction, X-ray fluorescence and Fourier transform infrared spectroscopy. Batch and column studies were conducted to investigate the adsorbability of pumice towards TC. Results showed that the TC adsorption amount declined as the pH increased from 3 to 9 and was strongly dependent on ionic strength. Adsorption kinetic data fitted to the pseudo-first-order, pseudo-second-order and Elovich model very well (R2 > 0.9). Intraparticle diffusion was the main rate controlling step during TC adsorption. The Langmuir and Freundlich models were utilized to simulate isotherm data (10–30°C). The obtained Langmuir uptake amount (20°C) was 3.345 mg/g. Thermodynamic analyses showed that the TC uptake amount increased with the temperature rising, suggesting its endothermic nature. At pH 6 and 8, both Pb2+ and Cu2+ significantly promoted the TC removal (>25%) via ion bridging action. Adsorption mechanisms mainly involved physisorption (Van der Waals & electrostatic forces) and chemisorption via the formation of inner-sphere complexes. Column tests showed that the exhausted column could be effectively regenerated using alkaline EDTA solution. Current results suggest that pumice is a promising adsorbent for TC removal from aqueous solutions.

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