Nanosized Manganese Dioxide Research Articles

Facile Fabrication of Manganese Dioxide Composite Incorporated Aluminium Rich Alloy Metal Matrix as Efficient Sacrificial Anodes

Nanosized manganese dioxide was prepared by anodic electro deposition method under standardized experimental conditions. Aluminum-zinc alloy sacrificial anodes incorporated with MnO2 nanoparticles were fabricated for cathodic protection of steel. The physico-chemical properties of anodes were enhanced by uniform dispersion and infiltration of the nano-MnO2 particles into the Al-Zn matrix. Such effective and uniform presence of nano-MnO2 inside the interior mass of the anodes was characterized by electrochemical techniques. The anodes exhibited stable potential in open circuit, small polarization and significant rate of depletion in self-corrosion in the course of galvanic immersion studies. The existence of nanocomposite particles in the anode matrix caused effective destruction of the passive aluminia film, which facilitated enrichment of galvanic performance of anode. The anode had better endurance against biofouling also.

Green synthesis of nanosized manganese dioxide as positive electrode for lithium-ion batteries using lemon juice and citrus peel

Nanosized MnO2 powders were grown using a green synthesis based on citrates via redox reaction between KMnO4 and natural reducing agents, i.e. lemon juice and peel extracts, without generating hazardous waste. X-ray diffraction (XRD) and Raman studies show that the samples grow as cryptomelane polymorph, α-MnO2, crystallized with the tetragonal cryptomelane structure. Both J-MnO2 prepared from lemon juice and P-MnO2 prepared from citrus peel consist of nanosized particles as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) confirms the typical thermal decomposition of MnO2 at temperatures of up to 500 °C. Improved electrochemical properties are obtained and discussed for P-MnO2, with a reversible capacity that reaches 160 mAh g−1 (initial capacity of 212 mAh g−1) at a current density of 10 mA g−1 and a good rate capability.

Effective removal of trace thallium from surface water by nanosized manganese dioxide enhanced quartz sand filtration

Thallium (Tl) has drawn wide concern due to its high toxicity even at extremely low concentrations, as well as its tendency for significant accumulation in the human body and other organisms. The need to develop effective strategies for trace Tl removal from drinking water is urgent. In this study, the removal of trace Tl (0.5 μg L−1) by conventional quartz sand filtration enhanced by nanosized manganese dioxide (nMnO2) has been investigated using typical surface water obtained from northeast China. The results indicate that nMnO2 enhanced quartz sand filtration could remove trace Tl(I) and Tl(III) efficiently through the adsorption of Tl onto nMnO2 added to a water matrix and onto nMnO2 attached on quartz sand surfaces. Tl(III)-HA complexes might be responsible for higher residual Tl(III) in the effluent compared to residual Tl(I). Competitive Ca2+ cations inhibit Tl removal to a certain extent because the Ca2+ ions will occupy the Tl adsorption site on nMnO2. Moreover, high concentrations of HA (10 mgTOC L−1), which notably complexes with and dissolves nMnO2 (more than 78%), resulted in higher residual Tl(I) and Tl(III). Tl(III)-HA complexes might also enhance Tl(III) penetration to a certain extent. Additionally, a higher pH level could enhance the removal of trace Tl from surface water. Finally, a slight increase of residual Tl was observed after backwash, followed by the reduction of the Tl concentration in the effluent to a “steady” state again. The knowledge obtained here may provide a potential strategy for drinking water treatment plants threatened by trace Tl.

Significantly improving trace thallium removal from surface waters during coagulation enhanced by nanosized manganese dioxide

Thallium (Tl) is an element of high toxicity and significant accumulation in human body. There is an urgent need for the development of appropriate strategies for trace Tl removal in drinking water treatment plants. In this study, the efficiency and mechanism of trace Tl (0.5 μg/L) removal by conventional coagulation enhanced by nanosized manganese dioxide (nMnO2) were explored in simulated water and two representative surface waters (a river water and a reservoir water obtained from Northeast China). Experimental results showed that nMnO2 significantly improve Tl(I) removal from selected waters. The removal efficiency was dramatically higher in the simulated water, demonstrating by less than 0.1 μg/L Tl residual. The enhancement of trace Tl removal in the surface waters decreased to a certain extent. Both adjusting water pH to alkaline condition and preoxidation of Tl(I) to Tl(III) benefit trace Tl removal from surface waters. Data also indicated that competitive cation of Ca2+ decreased the efficiency of trace Tl removal, resulting from the reduction of Tl adsorption on nMnO2. Humic acid could largely low Tl removal efficiency during nMnO2 enhanced coagulation processes. Trace elemental Tl firstly adsorbed on nMnO2 and then removed accompanying with nMnO2 settling. The information obtained in the present study may provide a potential strategy for drinking water treatment plants threatened by trace Tl.

Degradation of bisphenol A by nano-sized manganese dioxide synthesized using montmorillonite as templates

A new method was developed to synthesize nanoscale manganese dioxide (MnO2) using natural montmorillonite as the template. When the exchangeable Mn2+ cations reacted with KMnO4, the unique structure of montmorillonite effectively prevented the agglomeration of MnO2 resulting in the formation of nano-sized MnO2 particles. The clay mineral-templated MnO2 showed higher reactivity compared to nano-MnO2 prepared by conventional method as indicated by the oxidation of bisphenol A (BPA). Over 90% of BPA could be degraded within 10min at pH4.0 containing 250mgL−1 montmorillonite (109μM MnO2) and 21.9μM BPA. The presence of humic acid showed significant enhancement on BPA removal under acidic condition, while slight inhibition under alkaline condition. Due to the ubiquitous distribution of montmorillonite in natural environment, montmorillonite templated MnO2 would offer the potential for in situ remediation of many organic contaminants.

Adsorption and Oxidation of Thallium(I) by a Nanosized Manganese Dioxide

The adsorption and oxidation of thallium(I) by nanosized manganese dioxide (nMnO2) may have an impact on the removal of Tl from waters in engineered applications, as well as the fate and transport of Tl in natural waters. The fundamental data on the adsorption and oxidation of Tl(I) by nMnO2 were obtained here. The results show that Tl was adsorbed by nMnO2 within 15 min at pH 7.0. Moreover, Langmuir fitting indicated a maximum adsorption capacity of ∼58.48 mg/mmol (i.e., ∼672 mgTl/gMnO2). The presence of Ca2+, Mg2+, SiO32−, PO43−, and CO32−decreased the removal of Tl(I) to a certain extent; however, it was increased by a pH from 4.0 to 9.0. The oxidation of Tl(I) was proposed at pH 4.0 based on the observation of Mn release and nMnO2 aggregation, while the oxidation of Tl(I) might not be favored at neutral and basic conditions. The presence of 3 mg/L humic acid hindered the adsorption of Tl(I) on nMnO2. These results indicate that nMnO2 could help to remove Tl from water in engineered applications and might deepen our understanding of the transport of Tl in natural waters.

Effect of thermal annealing on the structural, morphological and super capacitor behavior of MnO2 nanocrystals

Precursors of nanosized manganese dioxide were prepared through a chemical precipitation method. The synthesized precursors of MnO2 were subjected to thermo gravimetric analysis. The thermal analysis results showed the MnO2 formation at 500°C. To study the effect of thermal treatments on the capacitive behavior of MnO2, the precursors were annealed at different temperatures (300, 400 and 500°C). The annealed products were characterized by X-ray diffraction (XRD), Fourier transforms infra-red spectroscopy (FT-IR) and cyclic Voltammetry (CV) analysis. Among the annealed products, MnO2 annealed at 400°C exhibits high specific capacitance. The morphologies of the products annealed at 400 and 500°C were analyzed by a scanning electron microscope (SEM) and atomic force microscopy (AFM). The sample annealed at 500°C shows spherical morphology with the inclusion of nanorods. To confirm the morphology of the annealed products, field emission transmission electron microscope (FE-TEM) measurements were carried out.

Preconcentration and determination of lead and cadmium in water samples with a MnO 2 coated carbon nanotubes by using ETAAS

A procedure for separation and preconcentration trace amount of Pb(II) and Cd (II) by nano-sized manganese dioxide functionalized multi-wall carbon nanotubes (MnO 2/MWCNTs) packed column has been proposed. Various influencing parameters on the separation and preconcentration of trace metals, such as pH, flow rate, concentration of eluent, sample volume and interference ions, were studied. Under the optimized conditions (pH 6, flow rate 2.5 mL min − 1 ), Pb(II) and Cd (II) were retained on the column, then quantitatively eluted by 1.5 mL 1.5 mol L − 1 nitric acid solution and determined by electrothermal atomic absorption spectroscopy (ETAAS). The detection Limits of Pb(II) and Cd(II) for an extraction of 5.0 mL water sample were 4.4 and 1.5 ng L − 1 , respectively. The relative standard deviations (R.S.D.) were 3.2% and 2.5% for Pb(II) and Cd(II), respectively. The optimized method was successfully applied to the determination of Pb(II) and Cd(II) in certified reference materials and real water samples.

XAFS Study of Reaction Mechanism of Nano-sized Manganese Dioxide as Cathode Materials for Lithium-ion Batteries

XAFS Study of Reaction Mechanism of Nano-sized Manganese Dioxide as Cathode Materials for Lithium-ion Batteries