Recent trends of MnO<sub>2</sub>-derived adsorbents for water treatment: a review

Husnain, Syed M.; Asim, Umar; Yaqub, Azra; Shahzad, Faisal; Abbas, Naseem

doi:10.1039/c9nj06392g

Cited by 77 publications

(31 citation statements)

References 161 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Mn oxides have been attracting substantial attention for its potential application for oxidative removal of organic and inorganic pollutants, 68 in which Mn oxides are often partially reduced to Mn(II), and our findings help understand the stability of birnessite in such applications. For example, adsorption of oxidation products on birnessite helps explain the reluctance of birnessite transformation to other Mn phases during reduction by reducing oxyanions such as arsenite, 69,70 selenite, 71 and uraninite, 72 despite the accumulation of high levels of Mn(II,III) in the reaction system.…”

Section: ■ Results and Discussionmentioning

confidence: 89%

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Yang

Wen

Beyer

et al. 2021

Environ. Sci. Technol.

View full text Add to dashboard Cite

Layered manganese (Mn) oxides, such as birnessite, can reductively transform into other phases and thereby affect the environmental behavior of Mn oxides. Solution chemistry strongly influences the transformation, but the effects of oxyanions remain unknown. We determined the products and rates of Mn(II)-driven reductive transformation of δ-MnO2, a nanoparticulate hexagonal birnessite, in the presence of phosphate or silicate at pH 6–8 and a wide range of Mn(II)/MnO2 molar ratios. Without the oxyanions, δ-MnO2 transforms into triclinic birnessite (T-bir) and 4 × 4 tunneled Mn oxide (TMO) at low Mn(II)/MnO2 ratios (0.09 and 0.13) and into δ-MnOOH and Mn3O4 with minor poorly crystallized α- and γ-MnOOH at high Mn(II)/MnO2 ratios (0.5 and 1). The presence of phosphate or silicate substantially decreases the rate and extent of the above transformation, probably due to adsorption of the oxyanions on layer edges or the formation of Mn(II,III)-oxyanion ternary complexes on vacancies of δ-MnO2, adversely interfering with electron transfer, Mn(III) distribution, and structural rearrangements. The oxyanions also reduce the crystallinity and particle sizes of the transformation products, ascribed to adsorption of the oxyanions on the products, preventing their further particle growth. This study enriches our understanding of the solution chemistry control on redox-driven transformation of Mn oxides.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 89%

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Yang

Wen

Beyer

et al. 2021

Environ. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…19,20 Nanoscale confinement affects the interaction of guest ions/molecules to reactive surfaces, causing altered behaviors (e.g., accumulation, distribution, and binding) compared to that in the bulk phase and eventually altering the kinetics of various redox reactions. 21−24 Accordingly, we here hypothesize that manganese-based catalysis can be significantly improved by confining these reactions within nanoscale pores, thereby improving electrostatic interactions between negatively charged reactive sites (manganese oxide minerals have a point of zero charge <4.6) 25 and protons inside nanopores (i.e., key contributor for manganese-based oxidation). It has been suggested that the electrical potential extending from charged surfaces is significantly increased under nanoconfinement.…”

Section: ■ Introductionmentioning

confidence: 97%

Engineered Nanoconfinement Accelerating Spontaneous Manganese-Catalyzed Degradation of Organic Contaminants

Zhang

Hedtke

Wang

et al. 2021

Environ. Sci. Technol.

View full text Add to dashboard Cite

Manganese(III/IV) oxide minerals are known to spontaneously degrade organic pollutants in nature. However, the kinetics are too slow to be useful for engineered water treatment processes. Herein, we demonstrate that nanoscale Mn 3 O 4 particles under nanoscale spatial confinement (down to 3−5 nm) can significantly accelerate the kinetics of pollutant degradation, nearly 3 orders of magnitude faster compared to the same reaction in the unconfined bulk phase. We first employed an anodized aluminum oxide scaffold with uniform channel dimensions for experimental and computational studies. We found that the observed kinetic enhancement resulted from the increased surface area of catalysts exposed to the reaction, as well as the increased local proton concentration at the Mn 3 O 4 surface and subsequent acceleration of acid-catalyzed reactions even at neutral pH in bulk. We further demonstrate that a reactive Mn 3 O 4 -functionalized ceramic ultrafiltration membrane, a more suitable scaffold for realistic water treatment, achieved nearly complete removal of various phenolic and aniline pollutants, operated under a common ultrafiltration water flux. Our findings mark an important advance toward the development of catalytic membranes that can degrade pollutants in addition to their intrinsic function as a physical separation barrier, especially since they are based on accelerating natural catalytic pathways that do not require any chemical addition.

show abstract

“…In this regard, in past years, much encouraging experimental and computational developments on MnO 2 ‐based materials have been accomplished, providing a considerable approach for working on high‐efficiency environmental applications. Although there have been some reviews of MnO 2 ‐based materials on the topic of electrochemical energy storage and conversion applications, [ 43–49 ] electrocatalytic water oxidation, [ 50 ] wastewater remediation, [ 51,52 ] catalytic oxidation of airborne formaldehyde, [ 53,54 ] biosensing, biomedicine applications [ 55 ] as well as theranostic applications, [ 56,57 ] until now, there has been no target review summarizing their comprehensive environmental applications (water treatment, air purification, and MW adsorption). A systematic overview of frontier scientific research on the modulation of nanostructured MnO 2 ‐based materials for environmental application is urgent.…”

Section: Introductionmentioning

confidence: 99%

MnO₂‐Based Materials for Environmental Applications

et al. 2021

View full text Add to dashboard Cite

Manganese dioxide (MnO2) is a promising photo–thermo–electric‐responsive semiconductor material for environmental applications, owing to its various favorable properties. However, the unsatisfactory environmental purification efficiency of this material has limited its further applications. Fortunately, in the last few years, significant efforts have been undertaken for improving the environmental purification efficiency of this material and understanding its underlying mechanism. Here, the aim is to summarize the recent experimental and computational research progress in the modification of MnO2 single species by morphology control, structure construction, facet engineering, and element doping. Moreover, the design and fabrication of MnO2‐based composites via the construction of homojunctions and MnO2/semiconductor/conductor binary/ternary heterojunctions is discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave (MW) pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants (water and gas, organic and inorganic) are also highlighted. Finally, the research gaps are summarized and a perspective on the challenges and the direction of future research in nanostructured MnO2‐based materials in the field of environmental applications is presented. Therefore, basic guidance for rational design and fabrication of high‐efficiency MnO2‐based materials for comprehensive environmental applications is provided.

show abstract

Recent trends of MnO₂-derived adsorbents for water treatment: a review

Abstract: Over the years, manganese dioxide (MnO2) and its different allotropes have gained significant research attention in the field of wastewater treatment because of their exciting physicochemical properties.

Cited by 77 publications

References 161 publications

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Engineered Nanoconfinement Accelerating Spontaneous Manganese-Catalyzed Degradation of Organic Contaminants

MnO₂‐Based Materials for Environmental Applications

Contact Info

Product

Resources

About

Recent trends of MnO2-derived adsorbents for water treatment: a review

Abstract: Over the years, manganese dioxide (MnO2) and its different allotropes have gained significant research attention in the field of wastewater treatment because of their exciting physicochemical properties.

Cited by 77 publications

References 161 publications

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Inhibition of Oxyanions on Redox-driven Transformation of Layered Manganese Oxides

Engineered Nanoconfinement Accelerating Spontaneous Manganese-Catalyzed Degradation of Organic Contaminants

MnO2‐Based Materials for Environmental Applications

Contact Info

Product

Resources

About

Recent trends of MnO₂-derived adsorbents for water treatment: a review

MnO₂‐Based Materials for Environmental Applications