Removal of As(V) from aqueous solutions using calcium-alginate microspheres with encapsulated iron nanoparticles

Abstract

This work investigated As(V) removal from aqueous solutions using calcium alginate microspheres with encapsulated iron nanoparticles (FeNPs) in batch systems. The kinetic, equilibrium, and thermodynamic parameters of the adsorption process were evaluated. Adsorbents were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Zeta Potential techniques. The FeNPs were obtained by a simple and low-cost method and they were successfully encapsulated and uniformly dispersed over the microspheres' surface. Significantly fast adsorption kinetic rates were observed due to microspheres' particle size and FeNPs encapsulation. The chemisorption mechanism was recognized in both adsorbate-adsorbent systems. The As(V) isotherms data suggested that the process is associated with heterogeneous adsorption. Available sorption sites with different adsorption energies were related to the functional groups involved in removing As(V), such as hydroxyl and carboxyl groups. Significantly high adsorption capacities were obtained for both materials, suggesting they can be competitive compared to conventional adsorbents, even at low FeNPs concentrations. Besides FeNPs encapsulation enhancing arsenate removal, higher adsorption was obtained at slightly acidic pH values and, together with their small particle size, suggests that the microspheres have a great potential to be used as arsenate adsorbents in the water treatment for human consumption.

Arsenate Adsorption from Aqueous Solutions Using Chitosan/Fe‐Nanoparticles Composite Microspheres

“…It facilitates the interaction between the functional groups of the adsorbent and the solute, hence promoting the coordination of ions with Fe(III) in the adsorbent. [66] The above corroborates that Fe-NPs enhance the performance of Ch-Fe for the removal of As(V).…”

“…However, at high temperatures (35 and 45 °C), this improvement is not significant compared to the Ch‐SD system. The calculated Qo values at high temperatures range from 42 mg/g to 150 mg/g, suggesting the high efficacy for As(V) removal using these composites and providing an advantage for applying such materials, particularly in the treatment of geothermal arsenic‐polluted waters [66] . The shape of the isotherms at high temperatures presents a steeper slope due to the effect of temperature on the adsorption capacity of the composite.…”

“…The calculated Qo values at high temperatures range from 42 mg/g to 150 mg/g, suggesting the high efficacy for As(V) removal using these composites and providing an advantage for applying such materials, particularly in the treatment of geothermal arsenic-polluted waters. [66] The shape of the isotherms at high temperatures presents a steeper slope due to the effect of temperature on the adsorption capacity of the composite. This fact indicates that the increase in the temperature of the aqueous solution greatly improves the removal of arsenates due to various factors related to the characteristics of the composite.…”