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

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 25mgMgO/4g-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 25mgMgO/4g-drysample, the percentage of MgO used for As(V) sorption increased up to 35%, and correspondingly, the As(V) leaching level decreased to below 0.01mgAs/L at an MgO dosage of 75mgMgO/4g-drysample. Additionally, when the MgO dosage was 50mgMgO/4g-drysample or more, it was found that more than 40% of MgO remained as fresh MgO without undergoing chemical reactions.