Synthesis and arsenic adsorption performances of ferric-based layered double hydroxide with α-alanine intercalation

• Ferric-based layered double hydroxide intercalated with α-alanine was synthesized.
• Mg-Fe-Ala-LDH showed much higher adsorption capacity for As(III) than for As(V).
• Desorption experiments indicated As(III) had stronger affinity to Mg-Fe-Ala-LDH.
• The obtained Mg-Fe-Ala-LDHs is a potential efficient adsorbent for arsenic removal.

In order to obtain a highly efficient functional material for As(III) removal, a ferric-based layered double hydroxide intercalated with α-alanine (denoted as Mg-Fe-Ala-LDH) was synthesized by a co-precipitation method. The adsorption performances for arsenite and arsenate species in aqueous solutions were studied with the obtained Mg-Fe-Ala-LDH material by batch experiments. The effects of various factors, such as solution pH, adsorbent dosage, competing anions, contact time and initial arsenic concentrations, have been investigated. The results showed that the adsorption isotherm of both As(III) and As(V) onto this Mg-Fe-Ala-LDH material can be well described by the Langmuir model, and the adsorption process followed the pseudo-second-order model. It was found that the maximum adsorption capacity for As(III) was 49.8 mg·g−1, which is significantly higher than that for As(V). Desorption experiments also indicated that arsenite species showed stronger affinity to this Mg-Fe-Ala-LDH than arsenate. This interesting result is closely related to the characteristics of the intercalation species, such as α-alanine in layered double hydroxide materials. It was demonstrated that the synthesized Mg-Fe-Ala-LDH material might be a potential efficient adsorbent for As(III) removal in water.

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