Selective adsorption of tetracycline by β-CD-immobilizing sodium alginate aerogel coupled with ultrafiltration for reclaimed water

Abstract

Abstract β-CD-immobilizing sodium alginate aerogel (β-CD/NaAlg) was fabricated using β-cyclodextrin (β-CD) as a modification reagent to eliminate tetracycline antibiotics from wastewater. β-CD/NaAlg aerogel with the β-CD/NaAlg molar ratio of 9 achieved the maximum removal rate of more than 70% for tetracycline in 8 h, 1.5 g/L of adsorbent dosage, and pH of 4. Tetracycline adsorption on β-CD/NaAlg aerogel was aligned with the Freundlich and pseudo-second-order model, showing that this process was mostly controlled by chemisorption. According to XPS analyses and DFT simulations, the tetracycline adsorption mechanism via β-CD/NaAlg aerogel is ascribed to electrostatic attraction through carboxyl groups and amido groups, hydrogen bonds connecting hydroxyl groups, as well as van der Waals forces. Besides, the as-prepared aerogel had a good reusability with the removal efficiencies of 55.3% for tetracycline even after repeating five times. Additionally, the couple of β-CD/NaAlg aerogel greatly improved selective separation performance for tetracycline antibiotics of the ultrafiltration membrane. In general, the synthesized β-CD/NaAlg aerogel is constructive for strategies to develop novel green, metal-free and stable adsorbent materials.