Synthesis and selenate removal of magnesium–aluminum-layered double hydroxide particle using magnesium oxide

K. Tsuchiya, Shigeshi Fuchida, C. Tokoro*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

High levels of selenium (Se) sometimes exist in wastewater from coal-fired power plants and mining operations; however, reduction of the Se level to the effluent standard (10 µg dm−3, Japan) is difficult to achieve. Magnesium (Mg)–aluminum (Al)-layered double hydroxides (Mg–Al LDHs) are good adsorbents for hexavalent selenium (Se(VI)), but they tend to have low sedimentation rates. Here, we evaluated the Se(VI)-removal performance (1–50 mg dm−3) and sedimentation rate of a LDH produced from magnesium oxide (MgO) and aluminum (Al) (MgO–Al LDH). To investigate the best conditions for LDH synthesis, three MgO–Al LDHs were compared: MOAL-1 produced by simultaneously mixing MgO and Al in the solution; MOAL-2 produced by adding MgO to the solution and then mixing Al with the suspension after 20–120 min; and MOAL-3 produced by adding MgO to the solution, adding Al to the suspension after 60 min, and then reacting for a further 1–48 h. Morphological analysis showed that the MgO–Al LDH particles were larger (10–250 µm) than general Mg–Al LDH secondary particle aggregates (1–10 µm), which resulted in 8.6–11 times higher sedimentation rate. In addition, the sedimentation rate of MOAL-2 was higher than that of MOAL-1. This could result from the lower amount of fine Mg–Al LDH secondary particle aggregates in MOAL-2 (13%) than in MOAL-1 (28%), which could prevent sedimentation. For MOAL-3, the sedimentation rate gradually increased with increasing reaction time after Al addition, and most of the particles were sedimented within 30 min after reaction for 48 h. X-ray diffraction and pore-size distribution analysis indicated that this could be because of increased crystallization and aggregation during the extended reaction. In conclusion, extending the MgO hydration time and/or MgO–Al reaction time during Mg–Al LDH synthesis is expected to produce Mg–Al LDHs with good Se(VI)-removal performance. Graphical Abstract: [Figure not available: see fulltext.]

Original languageEnglish
JournalInternational Journal of Environmental Science and Technology
DOIs
Publication statusAccepted/In press - 2022

Keywords

  • Layered double hydroxide
  • Magnesium–aluminum-layered double hydroxide
  • Sedimentation
  • Selenate
  • Wastewater treatment

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Agricultural and Biological Sciences(all)

Fingerprint

Dive into the research topics of 'Synthesis and selenate removal of magnesium–aluminum-layered double hydroxide particle using magnesium oxide'. Together they form a unique fingerprint.

Cite this