Preparation of green sodium alginate adsorption membrane and its high adsorption performance for fluoroquinolones antibiotics

Fluoroquinolones (FQs) were widely used in human and veterinary medicine, however, the presence of FQs at lower concentration in the environment could threaten to human health and agricultural production. In this research, the adsorption membranes were prepared based on sodium alginate (SA) crosslinking with multivalent metal ions. The SA-Al/Ca membranes and SA-Ca membrane were prepared by crosslinking with AlCl3/CaCl2 solutions and CaCl2 solutions, respectively. Comparing with SA-Ca membrane, the presence of Al3+ in crosslinking agent could produce a large number of adsorption sites on the surface of SA-Al/Ca membrane and remarkably improve the adsorption performance of SA-Al/Ca membrane. Effects of preparation conditions such as crosslinking ways, CaCl2 percentage in compound crosslinker, and crosslinking time on the adsorption performance of prepared SA-Al/Ca membrane were demonstrated. Moreover, the effects of the initial concentration of ciprofloxacin (CIP) and Levofloxacin (S-OFX), adsorption time, solution pH, ionic strength and adsorption temperature on the performance of SA-Al/Ca membrane were studied. The thermodynamics of the adsorption of CIP and S-OFX were well fitted with the Tempkin adsorption isotherm model (R2 = 0.9455) and D-R adsorption isotherm model (R2 = 0.9822), respectively. The maximum adsorption capacity of S-OFX and CIP using SA-Al/Ca membrane was 836.31 mg·g−1 and 858.94 mg·g−1. The results showed that SA-Al/Ca membranes with good adsorption capacity, low cost and high stability.