Adsorption and oxidation of arsenic by two kinds of β-MnO2
Graphical abstract
Introduction
Arsenic is a toxic element that is widely distributed in water, soil and rock. Increasingly, highly populated Asian countries, such as China, Bangladesh, Vietnam and India, have reported that the concentration of arsenic is higher than the World Health Organization (WHO) recommended concentration of 10 μg/L [1,2]. In nature, arsenic exhibits four major oxidation states: -3, 0, +3 and +5. The toxicity of arsenic depends strongly on its chemical form [3,4]. As(III) is more toxic and more difficult to remove than As(V), so there have been many publications reporting how to transform As(III) into As(V) [[5], [6], [7]]. Among the treatments for removing arsenic from drinking water, adsorption and/or oxidation processes are the most useful methods.
As a nontoxic and inexpensive material, differently structured manganese oxides (MnO2) have been extensively used for arsenic removal due to their adsorption and oxidation capacities [[8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]]. As is commonly known, β-MnO2 is widespread and stable in nature. However, only a limited amount of data is available on arsenic adsorption and oxidation by β-MnO2 because β-MnO2, with a low specific surface area (SBET), did not show an excellent ability to decrease arsenic in water [15,16]. In 2012, we reported a kind of β-MnO2, namely, column β-MnO2 (CM), with the main facet of {110} [25]. In 2014, we reported another kind of β-MnO2, namely, pincer β-MnO2 (PM), with the facets of {110} and {101} [26]. These two kinds of β-MnO2, with large SBET values, exhibit high capacities to remove arsenic. To the best of our knowledge, no papers presenting the adsorption kinetics of arsenic on β-MnO2 surfaces are available in the literature. In the present paper, both adsorption and oxidation are investigated in detail. Based on the adsorption and oxidation experimental results under different conditions, CM and PM present different tendencies especially for the pH effect. In the present study, it is shown that the oxidation of As(III) is related to the concentration of O2.
Section snippets
Preparation of β-MnO2
Column β-MnO2 (CM) has been prepared with the following method [25]: 7 mmol KClO3, 4 mmol MnSO4·H2O and 69.6 mmol CH3COOH were dissolved in 60 mL distilled water with magnetic stirring. Transferring the solution into a Teflon-lined stainless steel autoclave of 100 mL after the solution became clear and kept it at 433.15 K for 12 h. After the reaction, the precipitates were washed and filtered with distilled water, then CM was obtained from the Buchner funnel. At last, CM was dried at 333.15 K
Morphology and structure
The crystallinity and surface of CM and PM are obtained by XRD, as shown in Fig. 1. The patterns fit well with the standard β-MnO2 (JCPDS 24–0735). The peaks for CM and PM are narrow and sharp, indicating that both compounds have good crystallinities, and the crystallinity of PM is better than that of CM. It is worth noting that the peak of the {101} facet for PM is high, which implies a large {101} surface area for the crystal. The FT-IR spectra of CM and PM at room temperature are shown in
Conclusion
Systemic experiments have been carried out to investigate the absorption and oxidation abilities of CM and PM. The pseudo second-order kinetic model is more suitable to describe the adsorption kinetics, and the Langmuir model is better to describe the adsorption isotherms. The adsorption orders of As(III) and As(V) for CM are pH 4 < pH 7 < pH 9 and pH 4 > pH 7 > pH 9, respectively. However, for PM the adsorption orders of As(III) and As(V) are pH 4 > pH 7 > pH 9 and pH 4 < pH 7 < pH 9,
Acknowledgements
The financial supports of this work are the National Natural Science Foundation of China (21373104, 21173022, 20803014), the National Natural Science Foundation of Guangdong Province (2016A030313704), and the Guangdong University funding program (xj201611845170, xj201711845034).
References (37)
- et al.
Arsenic round the world: a review
Talanta
(2002) - et al.
Arsenic geochemistry and health
Environ. Int.
(2005) - et al.
A review of the source, behaviour and distribution of arsenic in natural waters
Appl. Geochem.
(2002) - et al.
Application of titanium dioxide in arsenic removal from water: a review
J. Hazard. Mater.
(2012) - et al.
Adsorption studies of arsenic on Mn-substituted iron oxyhydroxide
J. Colloid Interface Sci.
(2006) - et al.
Sorption and desorption of arsenate and arsenite on calcite
Geochim. Cosmochim. Acta
(2008) - et al.
The oxidative transformation of sodium arsenite at the interface of alpha-MnO2 and water
J. Hazard. Mater.
(2010) - et al.
X-ray absorption fine structure study of As(V) and Se(IV) sorption complexes on hydrous Mn oxides
Geochim. Cosmochim. Acta
(2003) - et al.
Development of a scalable model for predicting arsenic transport coupled with oxidation and adsorption reactions
J. Contam. Hydrol.
(2008) - et al.
Synthesis, characterization and study of arsenate adsorption from aqueous solution by α- and δ-phase manganese dioxide nanoadsorbents
J. Solid State Chem.
(2010)
Arsenic adsorption on α-MnO2 nanofibers and the significance of (1 0 0) facet as compared with (1 1 0)
Chem. Eng. J.
Differences in Sb(V) and As(V) adsorption onto a poorly crystalline phyllomanganate (delta-MnO2): adsorption kinetics, isotherms, and mechanisms
Process Saf. Environ.
The effects of iron(II) on the kinetics of arsenic oxidation and sorption on manganese oxides
J. Colloid Interface Sci.
Manganese oxides with different crystalline structures: facile hydrothermal synthesis and catalytic activities
Mater. Lett.
A facile one-pot hydrothermal synthesis of β-MnO2 nanopincers and their catalytic degradation of methylene blue
J. Solid State Chem.
A rapid colorimetric method for measuring arsenic concentrations in groundwater
Anal. Chim. Acta
Compilation of PZC and IEP of sparingly soluble metal oxides and hydroxides from literature
Adv. Colloid Interface Sci.
Adsorption of As (III) and As (V) from water using magnetite Fe3O4-reduced graphite oxide–MnO2 nanocomposites
Chem. Eng. J.
Cited by (46)
A critical review on arsenic and antimony adsorption and transformation on mineral facets
2024, Journal of Environmental Sciences (China)Construction of hollow mesoporous zirconia nanospheres with controllable particle size: Synthesis, characterization and adsorption performance
2023, Journal of Environmental Chemical EngineeringA review on multi-synergistic transition metal oxide systems towards arsenic treatment: Near molecular analysis of surface-complexation (synchrotron studies/modeling tools)
2023, Advances in Colloid and Interface Science