Lanthanum hydroxide: a highly efficient and selective adsorbent for arsenate removal from aqueous solution

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment

Background:

• Arsenic contamination in water poses significant health risks.
• Developing efficient and selective adsorbents for arsenic removal is crucial.
• Lanthanum-based materials show promise for water purification.

Purpose of the Study:

• To synthesize and characterize a lanthanum hydroxide adsorbent.
• To investigate its performance and mechanisms for arsenic removal.
• To evaluate selectivity between As(V) and As(III) and assess interference effects.

Main Methods:

• Batch adsorption experiments.
• Characterization using FESEM-EDX, BET, p-XRD, FTIR, and XPS.
• Isotherm studies to determine adsorption capacity.
• pH-dependent removal efficiency analysis.

Main Results:

• Lanthanum hydroxide effectively removes As(V) but shows low As(III) removal, indicating selectivity.
• Maximum As(V) adsorption capacities reached 299.4 mg/g at pH 5.0.
• Phosphate and natural organic acids significantly interfered with As(V) removal.
• Adsorption involves transformation to lanthanum arsenate and formation of inner-sphere surface complexes.

Conclusions:

• Lanthanum hydroxide is a highly effective adsorbent for selective As(V) removal.
• The adsorption mechanism is complex, involving ligand exchange and surface complexation.
• Further research is needed to fully elucidate the adsorption mechanisms and optimize performance in complex water matrices.