Synthesis of an Mg–Fe–Al layered double oxide with a high arsenic anion adsorption capacity and the establishment of an arsenic anion desorption process

The removal of toxic anions from wastewater by layered double oxides (LDOs) is highly efficient and studies related to the synthesis of LDOs have been actively attempted. This paper reports the synthesis of a triatomic LDO consisting of Mg, Fe, and Al by a novel sol-gel synthesis process using organic chains (previously developed by our group). This adsorbent exhibited an excellent adsorption performance for the removal of arsenate anions with a maximum adsorption capacity calculated by the Langmuir equation of 304.6 mg/g and an absorbance density of 1.33 mg/m2. The Mg–Fe–Al LDO synthesized via the sol-gel method adsorbed arsenate anions better than an Mg–Al LDO prepared by the same method. Furthermore, a highly effective process for the desorption of arsenate from the adsorbent was investigated. The results revealed that the maximum arsenate anion desorption was achieved via an anion exchange with an NaHCO3 solution. Namely, we have succeeded in synthesizing a triatomic LDO of Mg, Fe, and Al by the sol-gel method that we established, and the adsorbent has excellent arsenate anion adsorption performance. [Display omitted] •The synthesis of a triatomic LDO consisting Mg, Fe and Al by this sol-gel process.•1.7 times increase in specific surface area compared to Mg–Al LDO (coprecipitation).•A maximum adsorption capacity and an absorbance density of Mg–Fe–Al LDO (sol-gel) are the highest compared to both Mg–Al LDO (coprecipitation) and Mg–Al LDO (sol-gel).•A highly effective process for desorption of arsenate anion has been established.