Novel EDTA-chitosan/alginate porous composite beads for the removal of Pb(ii) and methylene blue from aqueous solutions.

Wastewater containing heavy metals and organic dye pollutants discharged into receiving waters poses a serious environmental concern. Herein, a novel EDTA-chitosan/alginate porous composite bead adsorbent (EC-AB) was reported for the simultaneous removal of lead (Pb(ii)) and methyl blue (MB) complexes from wastewater. Characterization results showed that EC-AB contained plenty of oxygen/nitrogen functional groups. The effect of CaCO addition, pH of the initial solution, contact time, initial pollutant concentration, and ionic strength on EC-AB pollutant removal performance and the adsorption mechanism were systematically analyzed. These findings indicated that EC-AB exhibited high removal efficiency over a wide pH range and at high ionic strength. The maximum adsorption capacities of EC-AB for Pb(ii) and MB were 504.11 mg g and 660.76 mg g, respectively, at 298 K. Adsorption kinetics and isotherm studies indicated that the adsorption well fitted the pseudo-second-order kinetic model and the Langmuir isotherm. A possible adsorption mechanism involving electrostatic attraction, chelation, ion exchange, H-bonding and synergistic effects was proposed. Moreover, EC-AB showed superior stability and reusability, with removal efficiencies of 76.64% for Pb(ii) and 80.29% for MB after five continuous adsorption-desorption cycles for treating complex wastewater. In summary, this work provides a beneficial strategy for designing high-performance adsorbents for the treatment of wastewater.