Adsorption behavior and mechanisms of the emerging antibiotic pollutant norfloxacin on eco-friendly and low-cost hydroxyapatite: Integrated experimental and response surface methodology optimized adsorption process

Abstract

In this study, hydroxyapatite derived from bovine bone (nat-HAp) was used to remove norfloxacin antibiotic (NOR) from an aqueous solution. The nat-HAp properties were interpreted by analysis of the structure, specific surface area, functional groups, morphology, and composition. The pseudo-second-order kinetic and Langmuir isotherm suit the experimental data on NOR adsorption very well. Maximum absorption was shown to be 166.01 mg g−1. Using a response surface methodology (RSM), the highest NOR elimination of 96.20 % was obtained under optimum conditions: NOR of 132.57 mg L–1, pH of 7.88, nat-HAp dose of 0.99 g L–1, and temperature of 25.06 °C. Thermodynamic studies demonstrated that the adsorption process was favorable, spontaneous, and exothermic. The value of standard enthalpy change (ΔH0) shows that physisorption controlled the adsorption, and for this purpose, a viable mechanism for the adsorption of NOR onto nat-HAp was suggested. Based on the reusability experiment, the nat-HAp remained stable after four cycling runs. These results show that nat-HAp effectively absorbed NOR and might be a cost-effective alternative adsorbent to eliminate fluoroquinolone antibiotics during wastewater treatment.