Iron/nickel decorated palygorskite-sodium alginate beads for tetracycline removal

Sodium alginate composite beads were synthesized using iron/nickel decorated palygorskite as filler by calcium chloride crosslink and applied to remove tetracycline (TC) from water efficiently. The beads were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The results suggested that the synergistic effect of nano iron/nickel and palygorskite could improve the adsorption performance of the beads for TC greatly. Batch adsorption experiments showed that the adsorption process fitted the Sips model and the maximum adsorption capacity of TC could reach 189.86 mg/g at 298 K, which was 31.6 times than that of pure sodium alginate and 4 times than that of palygorskite. The beads could be easily separated from water after adsorption using a mesh sieve. The adsorption mechanisms were mainly contributed to electrostatic attraction , π-π accumulation, hydrogen bond, silicate bond, chelation and ion exchange. In addition, the site energy distribution found that the surface of the adsorbents showed more heterogeneity at higher temperatures. The prepared beads could thus be used as a promising adsorbent for TC from water.