Simultaneous Removal of Arsenate and Fluoride Using Magnesium-Based Adsorbents

Abstract

In this study, arsenate, As(V), and fluoride (F) were simultaneously removed from contaminated water using MgO, Mg(OH)2, and MgCO3 as Mg-based adsorbents, as existing studies only focus on their individual removal. The removal performance of As(V) and F followed the order MgCO3 < Mg(OH)2 < MgO. Under the test conditions, MgO and Mg(OH)2 met the environmental standards for As and F (0.01 and 0.8 mg/L, respectively), but MgCO3 did not. The As(V) removal performance was not significantly affected by an increase in the initial F concentration. It was concluded that As(V) was adsorbed and removed more preferentially than F by Mg-based adsorbents because a considerable amount of F remained even when the majority of As(V) was removed. Most arsenic (As)-adsorption data for MgO fit the Langmuir and Freundlich models, whereas those for Mg(OH)2 did not fit either model well. Additionally, the As-adsorption data for MgCO3 fit the Freundlich model but not the Langmuir model. Most of the F-adsorption data for the Mg-based adsorbents fit the Langmuir and Freundlich models. The removal mechanisms of As(V) and F using Mg-based adsorbents were assumed to be predominantly caused by ion-exchange and chemical-adsorption reactions on the adsorbent surface because no magnesium arsenate, magnesium fluoride, or magnesium hydroxide fluoride species were observed in the X-ray diffraction analysis. This research advances the sustainable As–F simultaneous treatment method using inexpensive adsorbents.