Arsenate Removal from Aqueous Media Using Chitosan-Magnetite Hydrogel by Batch and Fixed-Bed Columns

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Arsenate contamination in water poses significant health risks.
• Effective removal of arsenate at near-neutral pH is challenging.
• Chitosan-magnetite (ChM) hydrogels show promise as adsorbents.

Purpose of the Study:

• To investigate the efficacy of chitosan-magnetite (ChM) hydrogel beads for arsenate ion removal from aqueous solutions.
• To analyze the equilibrium and kinetic behavior of arsenate adsorption onto ChM.
• To evaluate the performance of ChM in a fixed-bed column system.

Main Methods:

• Batch adsorption experiments were conducted at near-neutral pH.
• Equilibrium data were fitted to isotherm models (e.g., Langmuir).
• Kinetic data were analyzed using kinetic models (e.g., pseudo-first order).
• X-ray Photoelectron Spectroscopy (XPS) was used to study ChM-arsenate interactions.
• Fixed-bed column studies were performed to assess ChM performance.

Main Results:

• The Langmuir model best described equilibrium data, yielding a maximum adsorption capacity of 66.9 mg As/g at pH 7.0.
• The pseudo-first order kinetic model accurately represented the adsorption kinetics.
• Solution pH increased with contact time due to amine group protonation, enhancing active sites.
• Fixed-bed column performance was non-ideal, influenced by effluent pH increase.

Conclusions:

• Chitosan-magnetite hydrogel beads are effective adsorbents for arsenate removal, particularly at near-neutral pH.
• The adsorption process is governed by Langmuir isotherm and pseudo-first order kinetics.
• Protonation of functional groups is a critical factor enhancing adsorption capacity.
• Further optimization is needed for fixed-bed applications, considering pH effects.