Chemical oxidation of arsenic in the environment and its application in remediation: A mini review

doi:10.1016/j.pedsph.2022.06.033

Pedosphere

Volume 33, Issue 1, February 2023, Pages 185-193

https://doi.org/10.1016/j.pedsph.2022.06.033 Get rights and content

Abstract

Arsenic (As) contamination in soil and water poses a serious threat to the ecosystem health and human beings, and is of widespread concern. The main As species found in soil and water are arsenite As(III) and arsenate As(V). Because As(III) is more toxic and often more mobile than As(V), many remediation strategies aim to oxidize As(III) to As(V). In the environment, the reduction of As(V) under anaerobic conditions is mainly mediated by microorganisms, but the oxidation of As(III) under aerobic conditions can be mediated primarily by chemical processes. This article first reviews the existing knowledge on chemical oxidation of As(III) in the environment, with an emphasis on the roles of iron (Fe) and manganese (Mn) oxides. The application of Fe and Mn oxides for the remediation of As-contaminated soil and water is then summarized. The oxidation of As(III) by oxygen is very slow in the absence of catalysts. Many Mn oxides, on the other hand, can efficiently oxidize As(III). Although the oxidation of As(III) by Fe(III) is also slow, this process can be accelerated by light or Fe(II). Iron and Mn oxides are widely used for the remediation of As-contaminated soil and water, with Fe oxides generally acting as absorbents while Mn oxides as oxidants. To better understand and regulate As transformation and transport in the environment, further study is needed on the mechanisms and influencing factors of As(III) oxidation by Fe and Mn oxides, and the development of innovative methods and materials based on Fe and Mn oxides are desired.

Section snippets

INTRODUCTION

Arsenic (As) is a toxic metalloid that is ubiquitous in the environment, and the International Agency for Research on Cancer classifies As as a Class I carcinogen (Chen and Costa, 2021). It can cause acute poisoning and chronic diseases, including many types of cancer, as well as skin lesions, endemic peripheral vascular disorders (e.g., black foot disease), hypertension, ischemia, arteriosclerosis, diabetes, and neuropathies (Argos et al., 2010; Martinez et al., 2011).

Arsenic in soil and water

ARSENIC CONTAMINATION OF SOIL AND WATER

Despite its relatively low concentration in the Earth's crust (approximately 1.8 mg kg^–1), As is widely distributed in the environment (Kabata-Pendias, 2011). It mainly occurs in minerals such as arsenopyrite (FeAsS), orpiment (As₂S₃), realgar (AsS), and arsenolite (As₂O₃) (Oremland and Stolz, 2003; Kabata-Pendias, 2011). In uncontaminated soil, As concentration generally does not exceed 10 mg kg^–1 (Kabata-Pendias, 2011). Natural processes such as rock weathering and volcanic eruptions can

ARSENIC TRANSFORMATION IN THE ENVIRONMENT

Arsenic in soil and water occurs mainly as inorganic species As(V) and As(III) (Wenzel et al., 2001; Meharg and Zhao, 2012; Podgorski and Berg, 2020). In soil, As is mainly associated with Fe oxides (Wenzel et al., 2001; Meharg and Zhao, 2012). Redox potential (Eh) and pH are the primary factors controlling As speciation (Fig. 1). In soil pore water, when the Eh is 200–500 mV, As(V) accounts for 65%–98% of the total As, but when the Eh is –200–0 mV, As(III) becomes the dominant form (

ARSENIC OXIDATION IN THE ENVIRONMENT

Some microorganisms can oxidize As(III) (Silver and Phung, 2005; Zhu et al., 2017). The oxidation of As(III) by heterotrophic microorganisms is a detoxification mechanism. On the other hand, chemoautotrophic As-oxidizing microorganisms oxidize As(III) using oxygen (O₂) (under aerobic conditions) or nitrate (under anaerobic conditions) as terminal electron acceptors to support cell growth (Rhine et al., 2006; Zhang J et al., 2015).

Despite the contribution of microorganisms, As(III) oxidation in

APPLICATION OF CHEMICAL OXIDATION OF AS IN ENVIRONMENTAL REMEDIATION

Arsenic is often chemically oxidized in remediation practices (Guan et al., 2012; Wan et al., 2020). Compared to As(III), As(V) can be more strongly adsorbed by most metal (hydr)oxides and clay minerals, so the oxidation of As(III) to As(V) leads to the immobilization of As in soil (Inskeep et al., 2002; Meharg and Zhao, 2012; Wan et al., 2020). In addition, As(III) is difficult to be removed from water using most techniques, so the processes for removing As from water, such as adsorption,

CONCLUSIONS AND FURTHER RESEARCH

Arsenic contamination is a global environmental challenge. Because As(III) is more toxic and generally more mobile than As(V), for remediation purposes, As(III) often needs to be oxidized to As(V). The generated As(V) can subsequently be stabilized or removed by adsorption. Arsenic(III) oxidation in the environment may be a primarily chemical process, although microorganisms can play a considerable role. Many Mn oxides are effective oxidants of As(III), whereas O₂ and Fe oxides can only oxidize

ACKNOWLEDGEMENTS

This work was supported by the National Natural Science Foundation of China (Nos. 41977273 and U21A20291), the National Key Research and Development Program of China (No. 2018YFC1800702), and the Major Research Plan of the Shandong Science Foundation, China (No. ZR2020ZD19). Jiangrong Chen also acknowledges funding from the Special Fund for Basic Scientific Research Business of Central Public Research Institutes, China (No. K-JBYWF-2019-T04).

References (94)

A Amirbahman et al.
Kinetics of sorption and abiotic oxidation of arsenic(III) by aquifer materials
Geochim Cosmochim Acta
(2006)
R Antonelli et al.
AS3MT, GSTO, and PNP polymorphisms: Impact on arsenic methylation and implications for disease susceptibility
Environ Res
(2014)
M Argos et al.
Arsenic exposure from drinking water, and all-cause and chronic-disease mortalities in Bangladesh (HEALS): A prospective cohort study
Lancet
(2010)
M H Cao et al.
Remediation of arsenic contaminated soil by coupling oxalate washing with subsequent ZVI/Air treatment
Chemosphere
(2016)
J Chen et al.
The arsenic methylation cycle: How microbial communities adapted methylarsenicals for use as weapons in the continuing war for dominance
Front Environ Sci
(2020)
W Ding et al.
Photooxidation of arsenic(III) to arsenic(V) on the surface of kaolinite clay
J Environ Sci
(2015)
Y H Duan et al.
Arsenic speciation in aquifer sediment under varying groundwater regime and redox conditions at Jianghan Plain of central China
Sci Total Environ
(2017)
J E Greenleaf et al.
Abiotic As(III) oxidation by hydrated Fe(III) oxide (HFO) microparticles in a plug flow columnar configuration
Process Saf Environ Prot
(2003)
X H Guan et al.
Application of titanium dioxide in arsenic removal from water: A review
J Hazard Mater
(2012)
W Hartley et al.
Arsenic and heavy metal mobility in iron oxide-amended contaminated soils as evaluated by short- and long-term leaching tests
Environ Pollut
(2004)

M J Kim et al.

Oxidation of arsenite in groundwater using ozone and oxygen

Sci Total Environ

(2000)

M Komárek et al.

Chemical stabilization of metals and arsenic in contaminated soils using oxides—A review

Environ Pollut

(2013)

P Kumarathilaka et al.

Arsenic speciation dynamics in paddy rice soil-water environment: Sources, physico-chemical, and biological factors—A review

Water Res

(2018)

B Y Li et al.

Mitigating arsenic accumulation in rice (Oryza sativa L.) from typical arsenic contaminated paddy soil of southern China using nanostructured α-MnO₂: Pot experiment and field application

Sci Total Environ

(2019)

Z X Lin et al.

Potential indicators for the assessment of arsenic natural attenuation in the subsurface

Adv Environ Res

(2003)

X B Luo et al.

Adsorption of As(III) and As(V) from water using magnetite Fe₃O₄ -reduced graphite oxide–MnO₂ nanocomposites

Chem Eng J

(2012)

I Machado et al.

Total arsenic and inorganic arsenic speciation in groundwater intended for human consumption in Uruguay: Correlation with fluoride, iron, manganese and sulfate

Sci Total Environ

(2019)

P Mondal et al.

Remediation of inorganic arsenic in groundwater for safe water supply: A critical assessment of technological solutions

Chemosphere

(2013)

H W Nesbitt et al.

XPS study of reductive dissolution of 7Å-birnessite by H₃AsO₃, with constraints on reaction mechanism

Geochim Cosmochim Acta

(1998)

K F Pi et al.

Remediation of arsenic-contaminated groundwater by in-situ stimulating biogenic precipitation of iron sulfides

Water Res

(2017)

S Ploychompoo et al.

Fast and efficient aqueous arsenic removal by functionalized MIL-100(Fe)/rGO/δ-MnO₂ ternary composites: Adsorption performance and mechanism

J Environ Sci

(2020)

S I Siddiqui et al.

Iron oxide and its modified forms as an adsorbent for arsenic removal: A comprehensive recent advancement

Process Saf Environ Prot

(2017)

P L Smedley et al.

A review of the source, behaviour and distribution of arsenic in natural waters

Appl Geochem

(2002)

A Suda et al.

Functional effects of manganese and iron oxides on the dynamics of trace elements in soils with a special focus on arsenic and cadmium: A review

Geoderma

(2016)

L Wang et al.

Effects of pH, dissolved oxygen, and aqueous ferrous iron on the adsorption of arsenic to lepidocrocite

J Colloid Interface Sci

(2015)

Y J Wang et al.

Natural montmorillonite induced photooxidation of As(III) in aqueous suspensions: Roles and sources of hydroxyl and hydroperoxyl/superoxide radicals

J Hazard Mater

(2013)

Y L Wang et al.

Simultaneous removal and oxidation of arsenic from water by δ-MnO₂ modified activated carbon

J Environ Sci

(2020)

Z G Wei et al.

Adsorption and oxidation of arsenic by two kinds of β-MnO₂

J Hazard Mater

(2019)

Z P Wen et al.

Redox transformation of arsenic by magnetic thin-film MnO₂ nanosheet-coated flowerlike Fe₃O₄ nanocomposites

Chem Eng J

(2017)

W W Wenzel et al.

Arsenic fractionation in soils using an improved sequential extraction procedure

Anal Chim Acta

(2001)

F Wu et al.

Photochemical formation of hydroxyl radicals catalyzed by montmorillonite

Chemosphere

(2008)

X J Xie et al.

In situ treatment of arsenic contaminated groundwater by aquifer iron coating: Experimental study

Sci Total Environ

(2015)

X W Xu et al.

Control of arsenic mobilization in paddy soils by manganese and iron oxides

Environ Pollut

(2017)

L Yang et al.

In situ chemical fixation of arsenic-contaminated soils: An experimental study

Sci Total Environ

(2007)

H Afroz et al.

Inhibition of microbial methylation via arsM in the rhizosphere: Arsenic speciation in the soil to plant continuum

Environ Sci Technol

(2019)

American Water Works Association (AWWA) Staff

AWWA Manual M21: Groundwater

(2003)

K Amstaetter et al.

Redox transformation of arsenic by Fe(II)-activated goethite (α-FeOOH)

Environ Sci Technol

(2010)

S Ashraf et al.

Titanium-based nanocomposite materials for arsenic removal from water: A review

Heliyon

(2019)

J D Ayotte et al.

Estimating the high-arsenic domestic-well population in the conterminous United States

Environ Sci Technol

(2017)

A Basu et al.

A review on sources, toxicity and remediation technologies for removing arsenic from drinking water

Res Chem Intermed

(2014)

H Basu et al.

Graphene oxide-MnO₂-goethite microsphere impregnated alginate: A novel hybrid nanosorbent for As(III) and As(V) removal from groundwater

J Water Process Eng

(2021)

N Bhandari et al.

Photoinduced oxidation of arsenite to arsenate on ferrihydrite

Environ Sci Technol

(2011)

N Bhandari et al.

Photoinduced oxidation of arsenite to arsenate in the presence of goethite

Environ Sci Technol

(2012)

M Bissen et al.

Arsenic—A review. Part II: Oxidation of arsenic and its removal in water treatment

Acta Hydrochim Hydrobiol

(2003)

Q Y Chen et al.

Arsenic: A global environmental challenge

Annu Rev Pharmacol Toxicol

(2021)

C Claudio et al.

Iron oxide nanoparticles in soils: Environmental and agronomic importance

J Nanosci Nanotechnol

(2017)

D V Cuong et al.

Active MnO₂/biochar composite for efficient As(III) removal: Insight into the mechanisms of redox transformation and adsorption

Water Res

(2021)

Cited by (10)

Sulfur enhances iron plaque formation and stress resistance to reduce the transfer of Cd and As in the soil-rice system
2024, Science of the Total Environment
Sulfur plays an essential role in agricultural production, but few studies have been reported on how sulfur simultaneously impacts the transformation of cadmium (Cd) and arsenic (As) in the soil-rice system. This research selected two soils co-contaminated with both Cd and As, varying in acidity and alkalinity levels, to study the impacts of elemental sulfur (S) and calcium sulfate (CaSO₄) on the migration and accumulation of Cd and As by rice. Results indicated that two types of sulfur had a substantial (P < 0.05) impact on decreasing the contents of Cd (28.3–50.4 %) and As (20.1–38.6 %) in brown rice in acidic and alkaline soils. They also increased rice biomass (29.3–112.8 %) and reduced Cd transport coefficient (27.2–45.6 %) significantly (P < 0.05). Notably, sulfur augmented the generation of iron plaque on rice root surfaces, which increased the fixation of Cd (17.6–61.0 %) and As (14.0–45.9 %). SEM-EDS results also indicated that the rice root surface exhibited significant enrichment of Fe, Cd, and As. The mechanism of simultaneous Cd and As immobilization by sulfur application was mainly ascribed to the contribution of iron plaque. Additionally, sulfur reduced the contents of Cd and As in soil porewater and promoted the transformation of As(III) to As(V) to reduce the toxicity of As. The K-edge XAFS of As in iron plaque also confirmed that sulfur application significantly promoted As(III) oxidation. Sulfur also promoted the activities of antioxidant enzymes and the contents of NPT, GSH, and PCs in rice plants. In general, this study establishes a foundation for sulfur to lower As and Cd bioavailability in paddy soils, enhance iron plaque and rice resistance, and reduce heavy metal accumulation.
Microbial consortia-mediated arsenic bioremediation in agricultural soils: Current status, challenges, and solutions
2024, Science of the Total Environment
Arsenic poisoning in agricultural soil is caused by both natural and man-made processes, and it poses a major risk to crop production and human health. Soil quality, agricultural production, runoff, ingestion, leaching, and absorption by plants are all influenced by these processes. Microbial consortia have become a feasible bioremediation technique in response to the urgent need for appropriate remediation solutions. These diverse microbial populations collaborate to combat arsenic poisoning in soil by facilitating mechanisms including oxidation-reduction, methylation-demethylation, volatilization, immobilization, and arsenic mobilization. The current state, problems, and remedies for employing microbial consortia in arsenic bioremediation in agricultural soils are examined in this review. Among the elements affecting their success include diversity, activity, community organization, and environmental conditions. Also, we emphasize the sensitivity and accuracy limits of existing assessment techniques. While earlier reviews have addressed a variety of arsenic remediation options, this study stands out by concentrating on microbial consortia as a viable strategy for arsenic removal and presents performance evaluation and technical problems. This work gives vital insights for tackling the major issue of arsenic pollution in agricultural soils by explaining the potential methods and components involved in microbial consortium-mediated arsenic bioremediation.
Simultaneous suppression of As mobilization and N<inf>2</inf>O emission from NH<inf>4</inf><sup>+</sup>/As-rich paddy soils by combined nitrate and birnessite amendment
2024, Journal of Hazardous Materials
The environmental impacts of As mobilization and nitrous oxide (N₂O) emission in flooded paddy soils are serious issues for food safety and agricultural greenhouse gas emissions. Several As immobilization strategies utilizing microbially-mediated nitrate reducing-As(III) oxidation (NRAO) and birnessite (δ-MnO₂)-induced oxidation/adsorption have proven effective for mitigating As bioavailability in flooded paddy soils. However, several inefficiency and unsustainability issues still exist in these remediation approaches. In this study, the effects of a combined treatment of nitrate and birnessite were assessed for the simultaneous suppression of As(III) mobilization and N₂O emission from flooded paddy soils. Microcosm incubations confirmed that the combined treatment achieved an effective suppression of As(III) mobilization and N₂O emission, with virtually no As(T) released and at least a 87% decrease in N₂O emission compared to nitrate treatment alone after incubating for 8 days. When nitrate and birnessite are co-amended to flooded paddy soils, the activities of denitrifying enzymes within the denitrification electron transport pathway were suppressed by MnO₂. As a result, the majority of applied nitrate participated in nitrate-dependent microbial Mn(II) oxidation. The regenerated biogenetic MnO₂ was available to facilitate subsequent cycles of As(III) immobilization and concomitant N₂O emission suppression, sustainable remediation strategy. Moreover, the combined nitrate-birnessite amendment promoted the enrichment of Pseudomonas, Achromobacter and Cupriavidu, which are known to participate in the oxidation of As(III)/Mn(II). Our findings document strong efficacy for the combined nitrate/birnessite treatment as a remediation strategy to simultaneously mitigate As-pollution and N₂O emission, thereby improving food safety and reducing greenhouse gas emissions from flooded paddy soils enriched with NH₄⁺ and As.
Mechanism of sulfite enhanced As(III) oxidation in the As(III)-Fe minerals under ambient conditions
2024, Journal of Hazardous Materials
Iron (Fe) minerals are known to be effective adsorbents for arsenic (As). However, the effects of sulfur species formed from the reductive dissolution of Fe minerals on the transformation of As(III) during the redox fluctuations processes under ambient conditions were poorly understood. Herein, we synthesized the As(III)-Fe minerals using sodium arsenite and ferric nitrate to investigate the effects of sulfur species on As(III) transformation in the As(III)-Fe minerals. Experimental results showed that sulfite rather than elemental sulfur and thiosulfate significantly accelerated As(III) oxidation. The oxidation rate of As(III) increased markedly from 0.0050 to 0.0168 min⁻¹ with the increase of sulfite concentration from 0.5 to 2.0 mM. Sulfate radicals (SO₄^•−) and hydroxyl radicals (^•OH) were identified as the dominant reactive species for As(III) oxidation. Besides, the underlying mechanism of Fe(II)/Fe(III) cycling for enhancing As(III) oxidation was further explored in the homogeneous Fe(II)/sulfite systems. Finally, interactions between sulfite and soil components induced radical formation, leading to As(III) oxidation in the soil environments. This study gives new insights into As(III) transformation co-existed with Fe minerals and sulfur species, which shed light on developing remediation strategies for regulating As contamination in temporarily flooded soils.
“New Insights into the Mechanism of Sulfur Species Induced As(III) Oxidation in the As-Fe Minerals”
This study systematically explored the coupled effects between sulfur species and Fe minerals on As(III) transformation in the As-Fe-minerals under oxic conditions, which showed that sulfite significantly accelerated As(III) oxidation to As(V) via the enhanced formation reactive oxygen species (e.g., SO₄^•− and ^•OH). This study shed light on the development of remediation strategies in the contaminated soils with toxic pollutants via introducing sulfur species. We strongly believe this study is of great interest to environmental scientists and chemical engineers, especially those who works on the remediation of contaminated sites and wish to explore the high-efficiency strategies for the control of toxic pollutants like As.
Illuminated fulvic acid stimulates denitrification and As(III) immobilization in flooded paddy soils via an enhanced biophotoelectrochemical pathway
2024, Science of the Total Environment
Fulvic acid (FA) is a representative photosensitive dissolved organic matter (DOM) compound that occurs naturally in paddy soils. In this study, the effect of a FA + nitrate treatment (0, 4 and 8 mg/L FA + 20 mmol/L nitrate) on denitrification and As(III) immobilization in flooded paddy soils was assessed under dark and intermittently illuminated conditions (12 h light+12 h dark). The FA input stimulated denitrification in illuminated soils (~100 % of nitrate removal within 6 days) compared to dark conditions (~92 % nitrate removal after 6 days). Meanwhile, As(III) (initial concentration of 0.1 mmol/L) was nearly completely immobilized (~100 %) under illuminated conditions after 4 days for the FA + nitrate treatment compared to 90– 93 % retention in the dark. Denitrification and As immobilization were positively related to the FA dosage in the illuminated assays. The stronger denitrification in illuminated soils was ascribed to denitrifiers harvesting photoelectrons from photosensitive substrates/semiconducting minerals. FA addition also increased the activities of denitrifying enzymes (e.g., NAR, NIR and NOR) and the denitrification electron transport system by nearly 0.6–0.7 and 1.5–1.8 times that of the nitrate-alone treatment under illuminated and dark conditions, thereby fostering stronger denitrification. Upon irradiation, As(III) immobilization was not only stimulated by the interactions with the denitrification pathway whereby As(III) acts as an electron donor for denitrifiers, but was also modulated by Fe(III)/oxidative reactive species-derived photooxidation of As(III). Moreover, the FA + nitrate treatment promoted the enrichment of metal-oxidizing bacteria (e.g., Stenotrophomonas and Acidovorax) that are responsible for nitrate-dependent As(III)/Fe(II) oxidation. The results of this study enhance our understanding of interactions among the biogeochemical cycles of As, Fe, N and C, which are intricately linked by a biophotoelectrochemical pathway in flooded paddy soils.
A combined strategy to mitigate the accumulation of arsenic and cadmium in rice (Oryza sativa L.)
2023, Science of the Total Environment
Arsenic and cadmium in rice grain are of growing concern in the global food supply chain. Paradoxically, the two elements have contrasting behaviors in soils, making it difficult to develop a strategy that can concurrently reduce their uptake and accumulation by rice plant. This study examined the combined impacts of watering (irrigation) schemes, different fertilizers and microbial populations on the bioaccumulation of arsenic and cadmium by rice as well as on rice grain yield. Compared to drain-flood and flood-drain treatments, continuously flooded condition significantly reduced the accumulation of cadmium in rice plant but the level of arsenic in rice grain remained above 0.2 mg/kg, which exceeded the China national food safety standard. Application of different fertilizers under continuously flooded condition showed that compared to inorganic fertilizer and biochar, manure addition effectively reduced the accumulation of arsenic over three to four times in rice grain and both elements were below the food safety standard (0.2 mg/kg) while significantly increasing the rice yield. Soil Eh was the critical factor in the bioavailability of cadmium, while the behavior of arsenic in rhizosphere was associated with the iron cycle. The results of the multi-parametric experiments can be used as a roadmap for low-cost and in-situ approach for producing safe rice without compromising the yield.

View all citing articles on Scopus

View full text

Chemical oxidation of arsenic in the environment and its application in remediation: A mini review

Abstract

Section snippets

INTRODUCTION

ARSENIC CONTAMINATION OF SOIL AND WATER

ARSENIC TRANSFORMATION IN THE ENVIRONMENT

ARSENIC OXIDATION IN THE ENVIRONMENT

APPLICATION OF CHEMICAL OXIDATION OF AS IN ENVIRONMENTAL REMEDIATION

CONCLUSIONS AND FURTHER RESEARCH

ACKNOWLEDGEMENTS

Geochim Cosmochim Acta

Environ Res

Lancet

Chemosphere

Front Environ Sci

J Environ Sci

Sci Total Environ

Process Saf Environ Prot

J Hazard Mater

Environ Pollut

Sci Total Environ

Environ Pollut

Water Res

Sci Total Environ

Adv Environ Res

Chem Eng J

Sci Total Environ

Chemosphere

Geochim Cosmochim Acta

Water Res

J Environ Sci

Process Saf Environ Prot

Appl Geochem

Geoderma

J Colloid Interface Sci

J Hazard Mater

J Environ Sci

J Hazard Mater

Chem Eng J

Anal Chim Acta

Chemosphere

Sci Total Environ

Environ Pollut

Sci Total Environ

Inhibition of microbial methylation via arsM in the rhizosphere: Arsenic speciation in the soil to plant continuum

Environ Sci Technol

AWWA Manual M21: Groundwater

Redox transformation of arsenic by Fe(II)-activated goethite (α-FeOOH)

Environ Sci Technol

Titanium-based nanocomposite materials for arsenic removal from water: A review

Heliyon

Estimating the high-arsenic domestic-well population in the conterminous United States

Environ Sci Technol

A review on sources, toxicity and remediation technologies for removing arsenic from drinking water

Res Chem Intermed

Graphene oxide-MnO2-goethite microsphere impregnated alginate: A novel hybrid nanosorbent for As(III) and As(V) removal from groundwater

J Water Process Eng

Photoinduced oxidation of arsenite to arsenate on ferrihydrite

Environ Sci Technol

Photoinduced oxidation of arsenite to arsenate in the presence of goethite

Environ Sci Technol

Arsenic—A review. Part II: Oxidation of arsenic and its removal in water treatment

Acta Hydrochim Hydrobiol

Arsenic: A global environmental challenge

Annu Rev Pharmacol Toxicol

Iron oxide nanoparticles in soils: Environmental and agronomic importance

J Nanosci Nanotechnol

Active MnO2/biochar composite for efficient As(III) removal: Insight into the mechanisms of redox transformation and adsorption

Water Res

Graphene oxide-MnO₂-goethite microsphere impregnated alginate: A novel hybrid nanosorbent for As(III) and As(V) removal from groundwater

Active MnO₂/biochar composite for efficient As(III) removal: Insight into the mechanisms of redox transformation and adsorption