Effective sequestration of tetracycline and ciprofloxacin from aqueous solutions by Al-based metal organic framework and reduced graphene oxide immobilized alginate biosorbents

Abstract

Antibiotics are chemical compounds commonly used to treat bacterial infections in humans and animals and can easily enter aquatic environments as a result of human activities. Tetracycline (TC) and ciprofloxacin (CIP) are two of the most common antibiotics found in water bodies. Aluminium-based metal organic framework (MOF) and reduced graphene oxide (rGO) were used as supporting materials in Alg hydrogel beads (Alg@MOF-rGO) in batch and column experiments to enhance the removal efficiency of TC and CIP. The as-prepared Alg@MOF-rGO hydrogel beads were effective in eliminating pharmaceutical residues from aquatic media. The physicochemical properties of the hydrogel were thoroughly characterized, and various key parameters, such as contact time, solution pH, adsorbent dose, temperature, co-existing ions, and different flow rates were studied to determine the maximum adsorption efficiency of the prepared hydrogel beads. The Alg@MOF-rGO beads showed the highest adsorption capacity to eliminate TC and CIP (qm = 43.76 and 40.76 mg/g for TC and CIP, respectively) during reaction time of 12 h compared to the other forms of hydrogel beads, and the adsorption of TC and CIP followed the Langmuir isotherm and pseudo-second-order (PSO) kinetic models. According to the pH and temperature study, the maximum adsorption capacity were attained at neutral pH (pH 7) and temperature of 40 °C. The continuous column studies showed that the Thomas, Adams-Bohart, and Yoon-Nelson models fit well for eliminating TC and CIP on the prepared Alg@MOF-rGO beads. Several attractive forces such as electrostatic interaction, pore filling, hydrogen bonding, and π-π attraction were the major forces responsible for the uptake of TC and CIP on Alg@MOF-rGO beads from the aquatic environment.