Lanthanum-iron incorporated chitosan beads for adsorption of phosphate and cadmium from aqueous solutions

Abstract

Excessive emissions of phosphate and cadmium have posed great risks to human health and the environment. To explore cost-effective approaches for simultaneous uptake of phosphate and cadmium remain a challenge. Herein, novel nanocomposite adsorbents were prepared by La-Fe incorporated chitosan beads (LaFe@CS), and were examined on the adsorption performance for phosphate or cadmium or both from aqueous solutions via batch experiments. Results showed that the maximum adsorption capacity reached 35.5 mg/g of cadmium or 52.0 mg/g of phosphate (calculated in P) at pH 6.5 according to the Langmuir model. In the phosphate-cadmium binary system, the presence of phosphate could extend the duration of cadmium adsorption, and enhance the adsorption capacity of cadmium due to the formation of phosphate-bridged ternary complexes. The coexisting cadmium affected negligibly on phosphate adsorption at low Cd(II) concentration (0.2 mg/L and 1 mg/L). The adsorption capacities remained approximate 80% after four cycles of adsorption. Electrostatic attraction, ligand exchange as well as the formation of phosphate-bridged ternary complexes affected the adsorption behaviors. This adsorbent could be a cost-effective material for the simultaneous removal of phosphate and cadmium from polluted water.