Tetracycline antibiotic removal from aqueous solutions by MOF-5: Adsorption isotherm, kinetic and thermodynamic studies

Abstract

This study examines time-varying adsorption of aqueous tetracycline (TC) by metal-organic framework, MOF-5. The employed MOF-5 is firstly synthesized under room temperature condition. Its structural, chemical, and physical features are then determined applying FTIR, XRD, SEM, TGA, N2 adsorption, and TEM characterization techniques. Cubic arrangement, 84.3% crystallinity, up to 450 °C thermal stability and approximately 2510 m2/g BET surface area with the both micro- and meso-cavities are its revealed characteristics. The impacts of the operative factors (adsorbent dosage, contact time, initial TC concentration, initial pH and temperature) on TC removal efficiency are examined following a two-step experimental design procedure (two-level categorical screening followed by response surface methodology for correlative model development). Additionally, to define the most appropriate condition/conditions, model-based optimization is implemented and verified in practice (more than %96 TC removal is achieved). Further thermodynamic and kinetic assessments respectively signify the both physisorption (Langmuir adsorption isotherm with maximum capacity of 233 mg/g) and chemisorption (pseudo-second-order model) mechanisms in this adsorption system. To sum up, MOF-5 as a suitable adsorbing agent will possibly have significant effects on pharmaceutical wastewater treatment and can be considered for advanced studies as an appropriate candidate regarding practicable remediation techniques.