Hydrous Manganese Dioxide Research Articles

Xylem-Inspired Hydrous Manganese Dioxide/Aluminum Oxide/Polyethersulfone Mixed Matrix Membrane for Oily Wastewater Treatment.

Ultrafiltration membrane has been widely used for oily wastewater treatment application attributed to its cost-efficiency, ease of operation, and high separation performance. To achieve high membrane flux, the pores of the membrane need to be wetted, which can be attained by using hydrophilic membrane. Nevertheless, conventional hydrophilic membrane suffered from inhomogeneous dispersion of nanofillers, causing a bottleneck in the membrane flux performance. This called for the need to enhance the dispersion of nanofillers within the polymeric matrix. In this work, in-house-fabricated hydrous manganese dioxide–aluminum oxide (HMO-Al2O3) was added into polyethersulfone (PES) dope solution to enhance the membrane flux through a xylem-inspired water transport mechanism on capillary action aided by cohesion force. Binary fillers HMO-Al2O3 loading was optimized at 0.5:0.5 in achieving 169 nm membrane mean pore size. Membrane morphology confirmed the formation of macro-void in membrane structure, and this was probably caused by the hydrophilic nanofiller interfacial stress released in PES matrix during the phase inversion process. The superhydrophilic properties of PES 3 in achieving 0° water contact angle was supported by the energy-dispersive X-ray analysis, where it achieved high O element, Mn element, and Al elements of 39.68%, 0.94%, and 5.35%, respectively, indicating that the nanofillers were more homogeneously dispersed in PES matrix. The superhydrophilic property of PES 3 was further supported by high pure water flux at 245.95 L/m2.h.bar, which was 3428.70% higher than the pristine PES membrane, 197.1% higher than PES 1 incorporated with HMO nanofiller, and 854.00% higher than PES 5 incorporated with Al2O3 nanofillers. Moreover, the excellent membrane separation performance of PES 3 was achieved without compromising the oil rejection capability (98.27% rejection) with 12 g/L (12,000 ppm) oily wastewater.

Potassium-doped hydrated manganese dioxide nanowires-carbon nanotubes on graphene for high-performance rechargeable zinc-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIB) are promising candidates for next-generation batteries because of their high safety, low cost, and relatively high capacity. In this study, we developed hydrated and potassium-doped manganese dioxide (MO) nanowires mixed with carbon nanotubes (CNT) on a graphene substrate (hydrated KMO-CNT/graphene) for ARZIB. A simple polyol process using poly(ethyl glycol), KMnO4, CNT, and graphene was utilized to fabricate hydrated KMO-CNT/graphene. MnO2 nanowires with diameters of 15–25 nm possess a high specific capacity with a short diffusion path. The intercalated K ions and hydrates in the layered MnO2 nanowires maintained the MO structure during the charge and discharge processes, whereas carbon nanomaterials (CNT and graphene) enhanced the conductivity of the material. Consequently, hydrated KMO-CNT/graphene demonstrated good ARZIB performance. A high capacity of 359.8 mAh g–1 at 0.1 A g–1, and at a high current density of 3.0 A g–1, a capacity of 129 mAh g–1 with 77% retention after 1000 cycles, were achieved.

Efficient oil/water separation using superhydrophilic polyethersulfone electrospun nanofibrous ultrafiltration membranes

This study reports the preparation and investigations of new ultrafiltration electrospun nanofibrous membranes (ENMs) incorporated with hydrous manganese dioxide (HMO) nanoparticles (NPs) for synthetic oily solution treatment. The mechanical strength and permeation properties of typical polyethersulfone (PES)-based ENMs were enhanced in three highly potential approaches. Firstly, a dimethylformamide (DMF) dope solution was prepared with n-methyl-pyrrolidinone (NMP) as the co-solvent to facilitate inter-fiber junctions. Secondly, HMO NPs were incorporated into the ENM dope solution to enhance water production and anti-fouling resistance against oil molecules. Lastly, the resultant ENMs were subjected to a hot pressing technique (HPT) to strengthen their structure and morphological properties. The results revealed that the ENMs incorporated with HMO NPs exhibited excellent oil rejection (95.42%) and promising water flux recovery (82.47%) upon exposure to a synthetic oily solution (12,000 ppm). The HMO-incorporated PES ENMs also demonstrated a high clean water productivity of over 3380 L/m2h without sacrificing oil removal rate. Furthermore, they exhibited a low degree of flux decline owing to the improved hydrophilicity and thus reducing oil contamination. This study may serve as a basis for manufacturing high-performance and robust nanocomposite ENMs for heavy wastewater treatment.

Removal of Cadmium(II) by hydrated manganese dioxide: behaviour and mechanism at different pH

ABSTRACT Homogeneous precipitation was proposed to prepare hydrated manganese dioxide (HMO) with KMnO4 as oxidant, NaCl as reductant and HNO3 as reaction auxiliary. HMO was applied to remove Cd(II) and the effect of contact time, initial concentration, adsorbent dose and pH value on adsorption efficiency were investigated. The removal mechanisms at various pH values were analysed in detail. Adsorption thermodynamics parameters were calculated as ΔG < 0, ΔH > 0 and ΔS > 0, which meant that the adsorption process was endothermic. The result of adsorption kinetics indicated the adsorption process conformed to pseudo-second-order kinetics. When adsorbing Cd(II) with initial concentration equaling 100 mg·L−1, the activation energy (Ea) was 62.740 kJ·mol−1. The Langmuir model could describe adsorption behaviour on HMO better than the Freundlich model, indicating that the adsorption sites of HMO were homogeneous and that single-layer adsorption was a dominant way in this process. The maximum adsorption capacity of Cd(II) on MnO2 calculated by the Langmuir model was 267 mg·g−1. The adsorbent HMO could be recycled and reused for several times with a high efficiency above 70% by adding HCl. SEM, EDS, FTIR and XPS were used to analyse the mechanisms of removal of Cd(II) at pH = 3,7 and 10. The mechanisms included electrostatic attraction, ion exchange and chemical precipitation. With pH increasing, the zeta potential decreased and the surface negative charge increased, promoting Cd(II) removal through enhanced electrostatic attraction. Meanwhile, ion exchange mechanisms including inner-sphere complexation and outer-sphere complexation occurred during adsorption process at different pH.

Effects of Mn(II) addition on Cd(II) removal by hydrated manganese dioxide.

In this study, the redox homogeneous precipitation method was applied to synthesize hydrated manganese dioxide (HMO) and to study the removal performance of Cd(II) from wastewater. Moreover, a small amount of Mn(II) could still combine with HMO without causing the desorption of Cd(II). A novel discovery was that the synergistic effect of KMnO4 and Mn(II) could directly regenerate MnO2 to deeply remove Cd(II), realizing the recycling of MnO2. The influence of Mn(II) addition on the adsorption behavior of Cd(II) was discussed in terms of pH, Mn(II) addition mode, initial concentration of Mn(II) or Cd(II), and contact time. The adsorption of Cd(II) on HMO could be better in line with the Langmuir model, while that of Mn(II) accorded with the Freundlich model. The pseudo-second-order kinetic fitting results indicated that the removal of Cd(II) and Mn(II) on HMO belonged to chemisorption. SEM, XRD, FTIR, and XPS analysis demonstrated that Cd(II) was trapped by forming an inner-sphere complex on HMO, and the added Mn(II) and KMnO4 could regenerate MnO2 through oxidation-reduction reaction, wrapping outside of Cd(II) for a purpose of deep removal of Cd(II). HIGHLIGHTS: 1)A small amount of Mn(II) can bind to HMO without causing Cd(II) desorption 2)A large amount of Mn(II) can cause partial desorption of Cd(II) 3)Large amount of Mn(II) will partially bind to the surface of HMO or Cd(II) complexes 4)Deeply remove Cd(II) without eluting and regenerating HMO.

Potassium-Doped Hydrated Manganese Dioxide Nanowires-Carbon Nanotube on Graphene for High Performance Rechargeable Zinc-Ion Battery

Potassium-Doped Hydrated Manganese Dioxide Nanowires-Carbon Nanotube on Graphene for High Performance Rechargeable Zinc-Ion Battery

The Preparation of 90Y Generator with Hydrated Manganese Dioxide

The Preparation of 90Y Generator with Hydrated Manganese Dioxide

WITHDRAWN: Potassium-doped hydrated manganese dioxide nanowires-carbon nanotube on graphene for high performance rechargeable zinc-ion battery

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The combination of KMnO4 with HMO for cyclic adsorption of heavy metal ions and regeneration of adsorbents.

In this experiment, three kinds of hydrous manganese dioxide (HMO) with different Zeta potentials were synthesized, and combined with KMnO4 for deep removal of Pb2+, Cd2+ and Ni2+. The competitive adsorption of three heavy metal ions was also investigated. The results indicated that the stronger the acidity, the higher the Zeta potential (-54.3) of the synthesized HMO. After regenerating HMO with acidic KMnO4 as eluent, the removal rates of Pb2+, Cd2+ and Ni2+ could still reach 79.25%, 80.13% and 60.43% after five cycles of adsorption. The promoting mechanism of KMnO4's effect on HMO was analyzed by SEM, TEM, EDS, FTIR, XRD, XPS, BET, and UV-vis. After absorbing heavy metal ions, HMO will release part of Mn (II), and the released Mn (II) reacts with KMnO4 to form a small amount of highly active in-situ HMO. The 'HMO + KMnO4' system can not only improve the removal rate of heavy metal ions by HMO, and reduce the amount of adsorbent, but also remove the released Mn (II). Because of its reproducibility, efficiency and simplicity, the research on water purification materials and technologies is of significance.

Hydrous manganese dioxide modified poly(sodium acrylate) hydrogel composite as a novel adsorbent for enhanced removal of tetracycline and lead from water

In this study, hydrous manganese dioxide (HMO) modified poly(sodium acrylate) (PSA) hydrogel was produced for the first time to remove tetracycline(TC) and lead(Pb(II)) from water. The as-prepared composite was characterized using various techniques, such as SEM-EDS, FTIR, XRD, BET, and XPS, to elucidate the successful loading of HMO and analyze subsequent sorption mechanisms. Different influencing parameters such as adsorbent dose, initial concentration of adsorbates, reaction time, solution pH, and temperature were also investigated. The adsorption kinetic studies of both TC and Pb(II) removal indicated that equilibrium was achieved within 12 h, with respective removal rates of 91.9 and 99.5%, and the corresponding adsorption data were fitted to the second-order kinetics model. According to the adsorption isotherm studies, the sorption data of TC best fitted to the Langmuir isotherm model while the adsorption data of Pb(II) were explained by the Freundlich isotherm model. The maximum adsorption capacities of both TC and Pb(II) were found to be 475.8 and 288.7 mg/g, respectively, demonstrating excellent performances of the adsorbent. The uptake capacity of PSA-HMO was significantly influenced by the level of solution pH, in which optimum adsorption amount was realized at pH 4.0 in the TC and Pb(II) systems, respectively. Thermodynamic studies showed the process of TC and Pb(II) adsorptions were endothermic and spontaneous. Overall this study elucidated that PSA-HMO composite can be a promising candidate for antibiotics and heavy metal removal in water treatment applications.

Effect of various oil/water emulsion concentration towards PVDF/HMO mixed matrix membrane performance

Meeting environmental quality standard for water and freshwater requires the use of innovative technologies, such as membrane technology for treating oily wastewater. Nevertheless, polymeric membrane require modification, as it is incapable of separating or removing oil molecules from oily wastewater. As such, this study incorporated the hydrous manganese dioxide (HMO) with polyvinylidene fluoride (PVDF) to attain mixed matrix membrane (MMM) for separation of various oil/water emulsion concentration feeds (50 ppm, 100 ppm, 500 ppm and 1000 ppm) by using lubricant oil. It was observed that the addition of HMO in MMM had altered the membrane surface morphology, as well as the wetting properties. The presence of HMO in the MMM had increased the membrane hydrophilicity, as it reduced the water contact angle value by up to 40%. Apart from that, the MMM was able to increase the oleophobicity of the membrane by increasing 35% of the oil contact angle value. Both pristine PVDF membrane and PVDF/HMO MMM showed a flux decline with increasing oil/water emulsion concentration but managed to achieve oil rejection percentage greater than 93%.

Evaluation of U(VI) adsorption from Ca2+ coexisted bicarbonate solution by synthetic inorganic and mineral materials

Abstract Part weakly alkaline natural uranium-containing water contains abundant Ca2+ and (bi)carbonate. Herein, two kinds of materials, namely mesoporous hydrous manganese dioxide (MHMO) and polyacrylonitrile (PAN)/dolomite composites were synthesized and characterized to evaluate their adsorption behaviors of U(VI) from Ca2+ coexisted bicarbonate solution. Characterization results showed that both samples exhibited good structural stability after U(VI) load. MHMO could coordinate U(VI) through the surface –OH sites, whereas an unfavorable U(VI) adsorption onto mineral composites was deduced. Adsorption tests indicated that increasing Ca2+ and (bi)carbonate amounts suppress U(VI) adsorption process, and ∼19.0 mg/g U adsorbed by MHMO could be obtained in solutions with 1 mmol/L [Ca2+], 5 mmol/L [CO3]T, 50 mg/L [U(VI)]initial at pH 8.0. Moreover, a heterogeneous surface chemical adsorption was verified through kinetics and isotherms study. Results from our study should be useful in exploring the adsorption behaviors and mechanisms of U(VI) on selected inorganic and mineral materials from natural uranium-containing water.

Facile Synthesis of Manganese Dioxide Nanoparticles for Efficient Removal of Aqueous As(III)

The development of highly efficient adsorbents for arsenic removal remains a challenge. In this paper, we propose the facile synthesis of hydrous manganese dioxide (HMO) and investigate its applica...

Hydrous Manganese Dioxide: Effect of KMnO4 on the Structure and Adsorption Behavior of Hydrous Manganese Dioxide Toward Pb(II) and Cd(II) (Crystal Research and Technology 9/2019)

Hydrous Manganese Dioxide: Effect of KMnO₄ on the Structure and Adsorption Behavior of Hydrous Manganese Dioxide Toward Pb(II) and Cd(II) (Crystal Research and Technology 9/2019)

Effect of KMnO4 on the Structure and Adsorption Behavior of Hydrous Manganese Dioxide Toward Pb(II) and Cd(II)

AbstractFour kinds of hydrous manganese dioxide (HMO) with different morphologies are synthesized by one‐pot method in this work. The effect of KMnO4 on structure and adsorption behavior of HMO has been thoroughly investigated by XRD, SEM, TEM, BET, and zeta potential analysis. The HMOs prepared are all δ‐MnO2, and a higher concentration of KMnO4 leads to a disordered, lower crystallinity structure, and higher absolute zeta potential values of HMO in the same condition, which exhibits a better adsorption capacity of 478.2 mg g−1 for Pb(II) and 135.2 mg g−1 for Cd(II). The addition of KMnO4 after reaction can also affect structure and adsorption capacity of HMO, it is characterized by higher crystallinity, fewer lattice defects, and higher adsorption capacity. The SEM and TEM analyses indicate that the possible formation is divided into two steps, involving the nucleation and shell growth, in a higher concentration of KMnO4: the first step is the reaction of KMnO4 and Mn2+, the second is KMnO4 decomposition with H+. In contrast, there is only the nucleation step in insufficient KMnO4. The addition of KMnO4 after reaction also involves two steps.

Removal of thorium and uranium from aqueous solution by adsorption on hydrated manganese dioxide

The hydrated manganese dioxide (HMO) was synthesized by hydrothermal process using MnSO4 and KMnO4. The adsorption of HMO for Th(IV) and U(VI) were investigated by batch static adsorption experiments. The HMO and MnO2 were characterized by FT-IR, XRD and SEM. At the same time, the adsorption mechanism is discussed. The adsorption process was in line with the pseudo-second-order kinetic model and Langmuir isothermal model. The maximum adsorption capacities were Th (T = 308 K, C0 = 200 mg L−1, qmax = 218.34 mg g−1) and U (T = 308 K, C0 = 200 mg L−1, qmax = 55.19 mg g−1).

The removal of Pb (II) and Cd (II) with hydrous manganese dioxide: mechanism on zeta potential and adsorption behavior

ABSTRACT In this study, the removal of Pb (II) and Cd (II) in aqueous solution by employing hydrous manganese dioxide (HMO) is investigated. The HMO synthesized was characterized by SEM, XRD, BET, FT-IR, and XPS. Simultaneously, the effect of Zeta potential (ZP), solution pH and contact time were discussed. The results reveal that at pH 5.0, 1-HMO (−51.7 mV) with the highest |ZP| value can reach equilibrium and reach 95.7% removal rate within 30 mins. The isotherm and kinetic data fitted Langmuir and pseudo-second-order models well. The maximum adsorption capacities calculated by Langmuir equation are 475.4 mg/g for Pb (II) and 140.3 mg/g for Cd (II) at 303.15 K, respectively. The binary experiment indicates the HMO showed a better affinity for Pb (II) than Cd (II). Thermodynamic studies (ΔG < 0, ΔH > 0, ΔS > 0) implies the both adsorptions are endothermic and spontaneous process. The intraparticle model analysis indicates that the film discussion controls the metal ions adsorption at the earlier stage and the intraparticle diffusion at the middle stage, while a chemical bonding process at the equilibrium stage. The FTIR and XPS analysis further proves Pb (II) and Cd (II) being adsorbed onto the surface of HMO as Pb-O and Cd-O, resulting from ion exchange and complexation. The reacted HMO could be recycled and reused for several times in a high efficiency above 90% by adding HCl or new HMO adsorbent. Simple preparation, low cost and remarkable removal efficiency make HMO a promising material in the treatment of heavy metal-contaminated water.

Cellulose acetate nanocomposite ultrafiltration membranes tailored with hydrous manganese dioxide nanoparticles for water treatment applications

Hydrous manganese dioxide (HMO) nanoparticles incorporated cellulose acetate (CA) composite ultrafiltration (UF) membranes are prepared with the aim of improving the water permeation and BSA contaminant removal. The HMO nanoparticles are synthesized from manganese ion and characterized by FT‐IR, XRD, and FESEM. The effect of variation of HMO on CA membranes is probed using FT‐IR, EDAX, contact angle, SEM, and AFM analysis to demonstrate their chemical functionality, hydrophilicity, and morphology. CA/HMO membranes are showing the enhancement in pure water flux (PWF), water uptake, porosity, hydrophilicity, fouling resistance, BSA rejection, and flux recovery ratio (FRR). CA‐1 membrane displayed higher PWF (143.6 Lm2h−1), BSA rejection (95.9%), irreversible fouling (93.3%), and FRR (93.3%). Overall results confirmed that the CA/HMO nanocomposite UF membranes overcome the bottlenecks and shows potential for water treatment applications.

Optimization of Dyeing Wastewater Treatment with New Eco-friendly Polysilicate Ferromanganese

To improve the efficiency of the removal of dye wastewater, a new type of coagulant "polysilicate ferromanganese (PSFM)" has been synthesized using sodium silicate, ferrous sulfate, and potassium permanganate. Three dyes (direct red, disperse blue, and active yellow) were used for the coagulation tests. The effects of the alkalinity and turbidity on the performance of PSFM were studied. The experimental results show that PSFM performs well with respect to the coagulation of the direct red and disperse blue dyes. The color and TOC removal efficiencies reach 99.2%, 95.4% and 98.5%, and 93.8%, respectively. The coagulation performance is better than that of the conventional coagulants polysilicate iron (PSF), Al2(SO4)3, and FeCl3. The color and TOC removal rates of PSFM for the active yellow dye reach 56% and 51%, respectively. Turbidity has no significant effect on the coagulation efficiency of PSFM. The purification efficiency and alkalinity depend on the amount of dye to be removed. The best alkalinity for the direct red, disperse blue, and active yellow dyes is 50 mg·L-1, 0 mg·L-1, and 75 mg·L-1, respectively. In addition, PSFM has been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The Zeta potentials of the mixed solutions and flocs during coagulation were also determined. The main indicators of PSFM coagulation are positively charged polynuclear complexes produced by hydrolysis of Fe+ and Mn+ and the bridging polymerization of polysilicon. The adsorption of hydrated manganese dioxide and hydroxyl oxide may also be included.

Fabrication of polyethersulfone electrospun nanofibrous membranes incorporated with hydrous manganese dioxide for enhanced ultrafiltration of oily solution

In this work, a new type of ultrafiltration (UF) electrospun nanofibrous membranes (ENMs) incorporating hydrous manganese dioxide (HMO) nanoparticles was fabricated with the objective of improving properties of polyethersulfone (PES)-based membrane for synthetic oily solution treatment. Two treatments were carried out to improve the mechanical property and hydrophilicity of the PES-based membrane without compromising its porosity and water permeance. The first treatment involved the use of mixed solvents – dimethylformamide and n-methyl-pyrrolidinone (DMF/NMP) in which NMP is a high vapor pressure component that could enhance the mechanical properties of the nanofibrous by improving solvent-induced fusion of inter-fiber junction points. The second treatment involved the incorporation of specific amount of HMO nanoparticles in PES dope solution to enhance membrane hydrophilicity. Heat treatment was also adopted as an effective approach to strengthen and prevent delamination of the nanofibrous mat during UF process. The HMO-incorporated ENMs exhibited an excellent oil rejection (97.98% and 94.04%) and a promising water flux recovery (89.29% and 71.10%) when used to treat a synthetic oily solution containing 5000 or 10,000 ppm oil, respectively. The best promising HMO-incorporated ENM exhibited much higher magnitude of water productivity (>7000 L/m2h) without sacrificing oil removal rate. Most importantly, this nanofillers-incorporated membrane showed significantly lower degree of flux decline as a result of improved surface resistance against oil fouling and is of potential for long-term operation with extended lifespan. The promising mechanical and anti-fouling properties of the ENMs is potentially applicable in the efficient industrial oily effluents treatment when challenged with oil-in-water emulsions.