Flexible core-shell/bead-like alginate@PEI with exceptional adsorption capacity, recycling performance toward batch and column sorption of Cr(VI)

A chemically modified alginate beads for heavy metal removal was prepared using polyethylenimine (PEI) as a modification reagent, which high density active sites were introduced favorably onto the surface by cross-linking reaction, leading to the designing of flexible core-shell/bead-like [email protected] sorbent and employed for the adsorption of Cr(VI) from aqueous solutions. This new sorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) etc. The results demonstrated that the optimized pH value was observed at 2.0. The adsorption processes fitted well with the pseudo-second-order kinetic model and the Freundlich isotherm in a batch system. The experimental maximum adsorption capacity for Cr(VI) was 431.6 mg/g under an optimal testing condition, which was much higher than that of sodium alginate (SA) (24.2 mg/g). Thomas and Bohart–Adams models were successfully fitted with breakthrough curves obtained under different experimental conditions in a continuous column process. More importantly, the adsorption capacity of the [email protected] only showed a slight loss after ten cycles of adsorption-desorption studies. Compared to other reported adsorptive materials, this core-shell/bead-like composite promises advantages of ultra-high adsorption capacity, low-cost, environmental friendliness and excellent recycling performance.