Single-step removal of arsenite ions from water through oxidation-coupled adsorption using Mn/Mg/Fe layered double hydroxide as catalyst and adsorbent

Thi Hai Nguyen; Hai Nguyen Tran; Tien Vinh Nguyen; Saravanamuthu Vigneswaran; Van Tuyen Trinh; Thanh Dong Nguyen; Thi Hoang Ha Nguyen; Trong Nhuan Mai; Huan-Ping Chao

doi:10.1016/j.chemosphere.2021.133370

Single-step removal of arsenite ions from water through oxidation-coupled adsorption using Mn/Mg/Fe layered double hydroxide as catalyst and adsorbent

Chemosphere. 2022 May:295:133370. doi: 10.1016/j.chemosphere.2021.133370. Epub 2021 Dec 29.

Authors

Thi Hai Nguyen¹, Hai Nguyen Tran², Tien Vinh Nguyen³, Saravanamuthu Vigneswaran¹, Van Tuyen Trinh⁴, Thanh Dong Nguyen⁴, Thi Hoang Ha Nguyen⁵, Trong Nhuan Mai⁵, Huan-Ping Chao⁶

Affiliations

¹ Faculty of Engineering and IT, University of Technology Sydney (UTS), Sydney, Australia.
² Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh, 700000, Viet Nam; Faculty of Environmental and Chemical Engineering, Duy Tan University, Da Nang, 550000, Viet Nam. Electronic address: trannguyenhai@duytan.edu.vn.
³ Faculty of Engineering and IT, University of Technology Sydney (UTS), Sydney, Australia. Electronic address: Tien.Nguyen@uts.edu.au.
⁴ Institute of Environmental Technology, Vietnam Academy of Science and Technology, Hanoi, Viet Nam.
⁵ VNU University of Science, Vietnam National University, Hanoi, Viet Nam.
⁶ Department of Environmental Engineering and R&D Center for Membrane Technology, Chung Yuan Christian University, Taoyuan, 32023, Taiwan.

PMID: 34973248
DOI: 10.1016/j.chemosphere.2021.133370

Abstract

This study developed a layered double hydroxides (Mn/Mg/Fe-LDH) material through a simple co-precipitation method. The Mn/Mg/Fe-LDH oxidized arsenite [As(III)] ions into arsenate [As(V)] anions. The As(III) and oxidized As(V) were then adsorbed onto Mn/Mg/Fe-LDH. The adsorption process of arseniate [As(V)] oxyanions by Mn/Mg/Fe-LDH was simultaneously conducted for comparison. Characterization results indicated that (i) the best Mg/Mn/Fe molar ratio was 1/1/1, (ii) Mn/Mg/Fe-LDH structure was similar to that of hydrotalcite, (iii) Mn/Mg/Fe-LDH possessed a positively charged surface (pH_IEP of 10.15) and low Brunauer-Emmett-Teller surface area (S_BET = 75.2 m²/g), and (iv) Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺/Mn⁴⁺ coexisted in Mn/Mg/Fe-LDH. The As(III) adsorption process by Mn/Mg/Fe-LDH was similar to that of As(V) under different experimental conditions (initial solutions pH, coexisting foreign anions, contact times, initial As concentrations, temperatures, and desorbing agents). The Langmuir maximum adsorption capacity of Mn/Mg/Fe-LDH to As(III) (56.1 mg/g) was higher than that of As(V) (32.2 mg/g) at pH 7.0 and 25 °C. X-ray photoelectron spectroscopy was applied to identify the oxidation states of As in laden Mn/Mg/Fe-LDH. The key removal mechanism of As(III) by Mn/Mg/Fe-LDH was oxidation-coupled adsorption, and that of As(V) was reduction-coupled adsorption. The As(V) mechanism adsorption mainly involved: (1) the inner-sphere and outer-sphere complexation with OH groups of Mn/Mg/Fe-LDH and (2) anion exchange with host anions (NO₃^-) in its interlayer. The primary mechanism adsorption of As(III) was the inner-sphere complexation. The redox reactions made Mn/Mg/Fe-LDH lose its original layer structure after adsorbing As(V) or As(III). The adsorption process was highly irreversible. Mn/Mg/Fe-LDH can decontaminate As from real groundwater samples from 45-92 ppb to 0.35-7.9 ppb (using 1.0 g/L). Therefore, Mn/Mg/Fe-LDH has great potential as a material for removing As.

Keywords: Arsenic removal; Layer double hydroxides; Oxidation-coupled adsorption; Redox reaction; Reduction-coupled adsorption; Water treatment.

MeSH terms

Adsorption
Arsenites*
Hydrogen-Ion Concentration
Hydroxides / chemistry
Oxidation-Reduction
Water
Water Pollutants, Chemical* / chemistry

Substances

Arsenites
Hydroxides
Water Pollutants, Chemical
Water