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

Abstract

In this work, a novel composite material based on β-cyclodextrin-immobilized sodium alginate aerogel (β-CD/NaAlg) was developed utilizing cross-linker of epichlorohydrin and applied as an adsorbent to remove tetracycline antibiotics from reclaimed wastewater. A series of characterizations were utilized to confirm the successful synthesis of the adsorbent and this β-CD/NaAlg presented a three-dimensional network at the nano or micro scale. Under optimal conditions (pH=4, t=8 h, β-CD: NaAlg=9, adsorbent dosage=1.5 g·L–1), the maximum removal rate of β-CD/NaAlg to tetracycline was 70%. The adsorption behavior of tetracycline on β-CD/NaAlg conformed to the Freundlich isotherm model (R2=0.9977) and the pseudo-second-order kinetic model (R2=0.9993). Moreover, the adsorbent still removed 55.3% of tetracycline after 5 cycles. Specially, the adsorbent was integrated with ultrafiltration to adsorb tetracycline antibiotics from simulated reclaimed wastewater, and the removal rate of tetracycline reached 78.9% within 2 hours. The existence of Cr (VI) had a negligible impact on tetracycline removal, while the presence of humic acid exhibited a promoting effect. The possible adsorption mechanisms were also elucidated through X-ray photoelectron spectroscopy and density functional theory analysis. In summary, β-CD/NaAlg represents an environmentally friendly, efficient, and sustainable adsorbent for removing tetracycline antibiotics from reclaimed water.