Facile preparation of sodium alginate-based gel spheres by droplet polymerization method for removal of levofloxacin from aqueous solution

The extensive use of fluoroquinolones antibiotics (FQs) makes great contributions to human society, but it also brings serious threats due to its stable chemical properties and difficulty in natural degradation. Since FQs can form stable chelates with polyvalent metal cations, the new adsorbents based on this chelating agent can not only remove FQs effectively, but also have the characteristics of selective identification on target pollutants. In this paper, novel sodium alginate-based gel spheres were prepared by droplet polymerization with sodium alginate (SA) as functional monomer, AlCl3/CaCl2 solutions and glutaraldehyde (GA) as crosslinking agents. The SA-Al/Ca gel spheres and GA (SA-Al/Ca) gel spheres were successively prepared for adsorption of levofloxacin (S-OFX) from aqueous solution. The results showed that after ion crosslinking with AlCl3/CaCl2 solutions and covalent crosslinking with GA, the prepared SA-Al/Ca and GA (SA-Al/Ca) gel spheres showed high adsorption capacity and good reusability, respectively. The equilibrium adsorption capacity of SA-Al/Ca gel spheres reached up to 176.26 mgL(-1) with the initial concentration of S-OFX as 100 mg.L-1. The maximum removal rate of SOFX was 92.10%. The GA (SA-Al/Ca) gel spheres had a certain degree of tolerance in temperature, pH, and ionic strength. The adsorption of S-OFX by both SA-Al/Ca and GA (SA-Al/Ca) gel spheres had fast kinetics. Moreover, the prepared GA (SA-Al/Ca) gel spheres also showed good reusability and stability.