Immobilization of arsenate in kaolinite by the addition of magnesium oxide: An experimental and modeling investigation

Tasuma Suzuki; Fumiya Nakahara; Takakuni Kawamoto; Masakazu Niinae

doi:10.1016/j.jhazmat.2015.07.072

Immobilization of arsenate in kaolinite by the addition of magnesium oxide: An experimental and modeling investigation

J Hazard Mater. 2015 Dec 30:300:680-687. doi: 10.1016/j.jhazmat.2015.07.072. Epub 2015 Jul 31.

Authors

Tasuma Suzuki¹, Fumiya Nakahara², Takakuni Kawamoto³, Masakazu Niinae⁴

Affiliations

¹ Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan. Electronic address: tsuzuki@yamaguchi-u.ac.jp.
² Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan. Electronic address: nkhr0310@gmail.com.
³ Department of Sustainable Environmental Engineering, Faculty of Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan. Electronic address: r011fj@yamaguchi-u.ac.jp.
⁴ Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan. Electronic address: niinae@yamaguchi-u.ac.jp.

PMID: 26292055
DOI: 10.1016/j.jhazmat.2015.07.072

Abstract

MgO was chosen as an As(V) immobilization agent and a series of immobilization experiments was performed to obtain insights into the behavior of As(V) and MgO during leaching tests. Our experimental and modeling results demonstrated that As(V) immobilization by MgO consists of the following steps: (i) an increase in sample pH, (ii) desorption of As(V) from the samples, and (iii) the re-immobilization of As(V) by MgO/Mg(OH)2 particles. Regarding the behavior of MgO, the modeling results showed that when the MgO dosage was 25 mgMgO/4 g-drysample or less, the majority of MgO was used to increase pH, and less than 1% of MgO was used to sorb As(V), which was consistent with the result of leaching tests showing that a high level of As(V) was leached at the MgO dosages. On the other hand, when the MgO dosage was above 25 mgMgO/4 g-drysample, the percentage of MgO used for As(V) sorption increased up to 35%, and correspondingly, the As(V) leaching level decreased to below 0.01 mgAs/L at an MgO dosage of 75 mgMgO/4 g-drysample. Additionally, when the MgO dosage was 50 mgMgO/4 g-drysample or more, it was found that more than 40% of MgO remained as fresh MgO without undergoing chemical reactions.

Keywords: Arsenate; Immobilization; Kaolinite; Magnesium oxide.