KMnO4 Solution Research Articles

Anode Glow Discharge Electrolysis Synthesis of Flower-Like α-MnO2 Nanospheres: Structure, Formation Mechanism, and Supercapacitor Performance.

A novel green synthesis strategy-anode glow discharge electrolysis (AGDE) was employed for one-step preparation of α-MnO2 in 2 g L-1 KMnO4 solution, in which Pt needle and carbon rod were regarded as anode and cathode, respectively. The optimal preparation condition is 400 V for 60 min and the power consumption is below 45 W. The XRD, Raman spectra, XPS and EPR proved that α-MnO2 with structural defects (oxygen vacancies) is obtained. SEM and TEM revealed that α-MnO2 shows a flower-like nanospheres with a diameter of 165 nm, which is assembled by many nanosheets. A possible formation mechanism is that the MnO2 is generated via the reduction of MnO4 - by H⋅ and eaq - in plasma-liquid interface. Electrochemical test found that MnO2 nanospheres exhibit a specific capacitance of 365 F g-1 at 1 A g-1, and capacity retention of 79.8 % after 10,000 cycles at 5 A g-1. The assembled asymmetric supercapacitor shows the maximum energy density of 23.1 Wh kg-1 at power density of 1.89 kW kg-1. In brief, AGDE is a simple, facile and green technique for the synthesis of α-MnO2 without adding extra chemicals, and prepared α-MnO2 can be considered as an excellent candidate of electrode materials for supercapacitor.

A portable dual-mode colorimetric and fluorescence sensing platform for RGB detection in liquid solutions

The color of liquids is crucial in food safety, pharmaceuticals, cosmetics, and environmental monitoring. Traditional color measurement methods typically require expensive spectrophotometers, limiting their utility in rapid testing and cost-effective applications. This study developed a cost-effective, portable dual-mode colorimetric and fluorescence sensing platform with using the TCS230 sensor and STM32F103ZET6 microcontroller for real-time RGB color detection. Equipped with built-in white and ultraviolet light sources, the platform operates reliably across different environmental conditions, aided by its darkroom design and white balance calibration strategy to minimize ambient light interference. Tests with fluorescent and dye solutions show stability and reliability of the platform. The relationship between color saturation and concentration under different concentrations showed the excellent correlation coefficients above 0.99 for CuSO4 and KMnO4 solutions. The measurement deviations of 1.93% to 3.41%, render it an efficient tool for on-site and multiple-mode color testing.

Effect of Carbon Nanotubes Functionalization on the Chemical Composition and Electrochemical Characteristics of Composites with Layered Potassium Manganese Oxide

The influence of pretreatment of multiwalled carbon nanotubes (MWCNTs) in oxidizers (solutions of H2O2 and HNO3) on the structure and electrochemical properties of composites with layered potassium-manganese oxide (KxMnO2) was studied. Composites were obtained by soaking carbon nanotubes in an aqueous solution of KMnO4 at 60 °C. The electrochemical performance of the composites was evaluated by cyclic voltammetry and galvanostatic charge‒discharge methods. It has been established that stronger oxidation of the MWCNTs surface at the functionalization stage leads to a noticeable increase in the reaction rate as well as the optimal potassium content in the KxMnO2 composition, which provides higher capacitive characteristics of the composite (a maximum specific capacitance of 150 F g−1 and a rate capability of 43% with increasing density current from 0.1 to 2.0 A g−1). The resulting composites are promising active components for increasing the capacitive characteristics of conductive carbon black (CB). Compared with an electrode based only on CB, electrodes based on a combination of the composite and CB at a mass ratio of 1:1 showed specific capacitance values approximately 1.5 to 3 times greater, as well as a twofold increase in rate capability (from 35 to 70%) in the range of discharge current density 0.1 to 2.0 A g−1.

Modification of morphological, structural and optical properties of graphene oxide by alteration molarity of aqueous KMnO4 solution

This work reports a nontraditional modified Hummer’s method to synthesize graphene oxide (GO) nanosheets by adjusting the oxidation process via a different-molarity potassium permanganate (KMnO4) solution instead of utilizing its powder. The effect of KMnO4 concentrations on the structural and morphological properties of GO nanosheets was studied. Oxidant solutions of 0.5 M, 1 M and 1.5 M were experimented to control the properties of the GO layers. Then, the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), Raman and ultraviolet-visible (UV–Vis) spectroscopes. Finally, oxidant concentration was optimized at 1 M by which thinner, high-quality crystalline GO layers and wider bandgap energy ( E g ) were obtained. It is thus confirmed that such a modification in the oxidation is a pioneering process to improve the GO properties.

Study on the effect of wet scrubbing technique on emissions in a dual fuel engine operating with diesel and hydrogen.

Reducing emissions from internal combustion (IC) engines is a crucial goal, encompassing nitrogen oxide (NO), hydrocarbon (HC), carbon monoxide (CO), and smoke. To enhance both performance and emissions, contemporary IC engines have turned to alternative gases such as hydrogen (H2) and exhaust after-treatment systems. A promising method to effectively decrease exhaust emissions entails the application of the scrubber technique as an exhaust gas after-treatment. This study's objective is to explore two avenues for curtailing exhaust emissions. The first involves substituting traditional fuels in IC engines with hydrogen gas (H2) at a flow rate of 6 LPM. The second entails integrating a liquid chemical solution into the scrubber technique. Notably, the utilization of KMnO4 solutions exhibits an appreciable reduction in NO and CO emissions compared to solutions containing NaOH. The experimental process included two aspects: investigating hydrogen fuel (H2) as an alternative fuel for IC engines and incorporating a scrubber technique using both KMnO4 and NaOH solutions. These experiments were conducted using a single-cylinder engine with a power output of 5.2 kW, cooled by water. The engine underwent tests under various load conditions, spanning from minimal to maximal loads. The findings revealed that employing KMnO4 solutions within the scrubber technique led to reductions of 25% and 40% in NO and CO emissions, respectively, in contrast to the utilization of NaOH solutions. Similarly, introduction hydrogen gas also has a significant effect on emission reduction.

Laboratory-scale characterization of slow-release permanganate gel (SRP-G) for the in-situ treatment of chlorinated-solvent groundwater plumes

Significant challenges remain for the remediation of chlorinated-solvent plumes in groundwater, such as trichloroethene (TCE) and tetrachloroethene (PCE). A novel slow-release permanganate gel (SRP-G) technique may show promise for the in-situ treatment (remediation) of chlorinated contaminant plumes in groundwater. A series of laboratory experiments were conducted to characterize the primary physical factors that influence SRP-G gelation processes to optimize SRP-G performance for plume treatment. Specifically, experiments were conducted to quantify gel zeta potential, particle size distribution, and viscosity to determine SRP-G gelation characteristics and processes. These experiments tested various concentrations of two SRP-G amendment solutions (NaMnO4 and KMnO4) prepared with 30-wt.% and 50-wt.% colloidal silica to determine such influences on zeta potential, particle size distribution, and viscosity. The results of this study show that SRP-G solutions with low zeta potential and relatively high pH favor more rapid SRP-G gelation. The concomitant interaction of the predominantly negatively charged colloidal silica particles and the positively charged dissociated cations (Na+ and K+) in the SRP-G solution had the effect of stabilizing charge imbalance via attraction of particles and thereby inducing a greater influence on the gelation process. Gel particle size distribution and changes in viscosity had a significant influence on SRP-G solution gelation. The addition of permanganate (NaMnO4 or KMnO4) increased the average particle size distribution and the viscosity of the SRP-G solution and decreased the overall gelation time. SRP-G amendments (NaMnO4 or KMnO4) prepared with 50-wt.% colloidal silica showed more effective gelation (and reduced gelation time) compared to SRP-G amendments prepared with 30-wt.% colloidal silica. Under the conditions of these experiments, it was determined that both the 7-wt.% NaMnO4 solution and 90 mg/L KMnO4 solution using 50-wt.% colloidal silica would be the optimal injection SRP-G solution concentrations for this in-situ treatment technique.

Spontaneous Multi-scale Supramolecular Assembly Driven by Noncovalent Interactions Coupled with the Continuous Marangoni Effect.

Reported herein is the multi-scale supramolecular assembly (MSSA) process along with redox reactions driven by supramolecular interactions coupled with the spontaneous Marangoni effect in ionic liquid (IL)-based extraction systems. The black powder, the single sphere with a black exterior, and the single colorless sphere were formed step by step at the interface when an aqueous solution of KMnO4 was mixed with the IL phase 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (C2OHmimNTf2) bearing octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO). The mechanism of the whole process was studied systematically. The phenomena were related closely to the change in the valence state of Mn. The MnO4- ion could be reduced quickly to δ-MnO2 and further to Mn2+ slowly by the hydroxyl-functionalized IL C2OHmimNTf2. Based on Mn2+, Mn(CMPO)32+, elementary building blocks (EBBs), and [EBB]n clusters were generated step by step. The [EBB]n clusters with the large enough size that were transferred to the interface, together with the remaining δ-MnO2, assembled into the single sphere with a black exterior, driven by supramolecular interactions coupled with the spontaneous Marangoni effect. When the remaining δ-MnO2 was used up, the mixed single sphere turned completely colorless. It was found that the reaction site of C2OHmim+ with Mn(VII) and Mn(IV) was distributed mainly at the side chain with a hydroxyl group. The MSSA process presents unique spontaneous phase changes. This work paves the way for the practical application of the MSSA-based separation method developed recently. The process also provides a convenient way to observe in situ and characterize directly the continuous Marangoni effect.

Mineral Contents in Some Wild Neglected Leafy Vegetables

Most of the iron for our body requirements can be obtained from green leafy vegetables and nutritional anemia can be easily cured by green leafy vegetables. The iron in the ash solution was determined colorimetrically by first converting the iron into ferric form using oxidizing agent potassium persulphate and the converting the ferric into red ferric thiocynate complex [Fe (SCN)6]3- exhibiting λmax at 480 nm by treatment with potassium thiocynate reagent. The calcium is essential for strong bones and teeth while iron which along with above vegetables also present in sufficient quantity in carrot, bitter gourd, onions and tomatoes is essential constituent of hemoglobin which helps to carry oxygen to cell in various parts of the body. Calcium was determined by oxalate precipitation method, and then titrated in hot condition against 0.01 M KMnO4 solution till permanent pink colour is obtained. Keywords: Iron, Thiocynate complex, colorimetrically, Calcium, Oxalate precipitation, KMnO4

Study on Varied Bagasse Fiber and Epoxy Resin Compositions with Rice Bran Filler to Biocomposite Characteristics

<p>Natural fibers, with environmental, economic, and cost advantages, are highly sought-after for biocomposite materials. In the present study, the biocomposite samples of epoxy resin (as a matrix), bagasse fiber (as reinforcement), and rice bran (as a filler) were prepared. Tensile strength, strain, and Young's modulus will be the parameters concerning which the quality of the biocomposite can be tested. On the one hand, bagasse fiber is to be a strength enhancer in the resulting biocomposite. On the other hand, rice bran may increase the biocomposite's density. The process research comprises fiber yarn from milled bagasse, alkalized fiber with KMnO4, specimen printing process, and analysis. All the fibers were treated by soaking them in 3 grams of KMnO4 solution for 30 and 45 minutes. The fiber is drained in an oven at 50 °C for ±1.5 hours. The printed fiber onto a specimen mold was printed with a mixture of epoxy resin and rice bran (1:1 w/w) and left for one day. Variation in the fiber mass was at 3, 4, and 5 grams. The sizes of the specimens were similar to the size of the mold according to ASTM D-638 type IV. Then, the fibers were removed from the mold and tested for tensile strength, strain, and Young's modulus. The results show that the greater the fiber mass, the greater the tensile strength value. These findings indicate that the tensile strength was optimized after soaking for 45 minutes with 5-gram fiber weight, which resulted in the tensile strength of 26.32±0.25 MPa, strain of 9.65±0.14%, Young's Modulus of 3.29±0.05 MPa, and water absorption of 41.99%.</p>

Advances in making Mn oxide‐coated sands

AbstractManganese (Mn) oxide‐coated sand has been suggested as an amendment for scrubbing metals in water filtration beds and also as a less concentrated medium for uniformly amending soils with Mn oxides in mesocosm scale studies. Earlier work at the lab bench scale, using potassium permanganate (KMnO4) solutions that were reduced with sodium (Na) lactate, resulted in sands coated with about 0.13% Mn. The goal of this project was to increase the amount of Mn oxide that could be coated on sand to make it a more useful amendment and also to attempt to scale up the procedure to produce larger (kg) quantities of coated sand. Titration experiments examined the effects of (1) varying the molar ratio of Na lactate to KMnO4, (2) varying the rate at which the titration was accomplished, and (3) varying the concentration (molarity) of the original KMnO4 solution. The results of this work led to an optimal approach utilizing 0.32 M KMnO4 solution that was titrated to a final lactate:permanganate ratio of ∼1.1 with 10% of the lactate being added every 10 min while the suspension was being stirred. The proportion of sand to an initial solution was also increased 5–20 fold to between 50 and 200 g per 100 mL of solution. Applying this method and using a large 20‐ to 30‐L reaction vessel yields sands coated with up to 0.7% Mn in batches 5–10 kg is size, which could be useful as an amendment in mesocosm scale studies, or as a component of treatment filter beds. The examination of various size fractions of the coated sands demonstrated that more Mn was coated on finer sand fractions, which appears to be a function of the particle surface area available for the coating of Mn oxides, and at a rate of 0.3–0.5 µg Mn mm−2 of the particle surface.

Lemna minor in studying the combined effects of Mn7+ and pyrocatechol

The work investigated the combined effect of pyrocatechol (0.001n and 0.1n) with KMnO4 (0.001n and 0.01n) on the Lemna minor. The range of ratios of equivalent concentrations of metal ion and pyrocatechol was from 1:100 to 10:1. It was shown that individual solutions of pyrocatechol exhibited a pronounced damaging effect towards L. minor starting from a concentration of 0.1n, and KMnO4 – from 0.01n. It was revealed that the toxic effect of a 0.1n solution of pyrocatechol decreased with the addition of 0.01n and, to a greater extent, 0.001n solutions of KMnO4. A significant reduction in the damaging effect of 0.01n KMnO4 solution was established when adding 0.001n pyrocatechol to a 10-fold excess of the equivalent concentration of potassium permanganate (2.0-2.4 times). On the contrary, the yield of electrolytes increased in equinormal 0.001 n mixtures of solutions of pyrocatechol and a metal compared to individual solutions. Based on the toxicological data, analysis of UV-VIS spectra, an attempt was made to explain the mechanisms of interaction between pyrocatechol and KMnO4 during their action on plant. The data can be useful for understanding the processes of self-purification of water bodies, be of interest when using plants to clean water bodies, predicting environmental risks.

Extraction and Characterization of Chitosan from Eco-Green <i>Hermetia Illucens</i> for Application in Dentistry

Chitosan can be extracted from the hermetia illucens chitin. It has excellent biocompatibility, non-toxic, bioresorbable, anti-inflammatory and wound healing properties. It can be formed into a gel, granules, sheet/film, porous structure, or scaffold in dental medications. Hermetia illucens cocoons were collected and extracted from the by-product of organic waste management in Bandung City. The samples were dried in the oven at 105°C for 48h and grounded in the powder grinder and sieved. Demineralization proces were done by immersed samples in 1 M HCl for 6h. The powder then deproteinized using 1 M NaOH solution for 8h at 80 oC, filtrated, and washed with distilled water. Then, the samples were immersed in 1% KMnO4 solution for 1h, and cleaned the residue with an oxalic acid solution. Samples obtained were dried in the oven at 60 oC for 48h before deacetylated with deionized water. Characterization were done by Fourier Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM). IR spectra showed disctinctive OH bond at 3253.62 cm-1 and amide I band at 1616.98 cm-1. Degree of deacylated were calculated using infrared spectra data and resulting 77.372% indicating good character of chitosan. The result SEM were inducated typical pattern of chitosan. Further study is to fabricate the medical-grade chitosan for dental material. The chitosan from the hermetia illucens is a promising natural biopolymer for dental applications and organic waste management solutions.

Free‐standing δ‐MnO2 atomic sheets

Abstractδ‐Manganese dioxide (δ‐MnO2) is a 2D material which possesses distinct properties and features due to its unique atomic structure and has already been utilized in numerous disciplines recently, especially in the field of magnetism, energy storage, magnetic resonance imaging, biocatalysts, and fluorescence sensing. Keeping an eye on the huge potential of this 2D material, we report our recent discovery of single‐step synthesis of MnO2 nanosheets via bottom‐up laser crystallization (of aqueous KMnO4 solution) and top‐down sonochemical exfoliation of bulk MnO2 powder. The successful synthesis of δ‐MnO2 nanosheets has been proved through the observation of characteristic Raman peaks at 173 and 634 cm−1 and characteristic X‐ray diffraction peaks. The optical band gap was found to be 1.64 and 1.45 eV for both methods. We also demonstrated that 2D‐MnO2 is a prominent candidate material for ammonia sensing and strain sensing. δ‐MnO2 powder, when employed as cathode material in Li‐ion batteries, results in a stable voltage of ˜0.5 V and in contrast, gives ˜1 V when used in Li‐S batteries and the attained voltage is stable even for >5 h. New methods of synthesis of δ‐MnO2 and its hybrids with graphene will lead to future generation devices, it is expected.

Conformal Coverage of ZnO Nanowire Arrays by ZnMnO3 : Room-temperature Photodeposition from Aqueous Solution.

Compositionally and structurally complex semiconductor oxide nanostructures gain importance in many energy-related applications. Simple and robust synthesis routes ideally complying with the principles of modern green chemistry are therefore urgently needed. Here we report on the one-step, room-temperature synthesis of a crystalline-amorphous biphasic ternary metal oxide at the ZnO surface using aqueous precursor solutions. More specifically, conformal and porous ZnMnO3 shells are photodeposited from KMnO4 solution onto immobilized ZnO nanowires acting not only as the substrate but also as the Zn precursor. This water-based, low temperature process yields ZnMnO3 /ZnO composite electrodes featuring in 1 M Na2 SO4 aqueous solution capacitance values of 80-160 F g-1 (as referred to the total mass of the porous film i. e. the electroactive ZnMnO3 phase and the ZnO nanowire array). Our results highlight the suitability of photodeposition as a simple and green route towards complex functional materials.

Влияние стимуляторов на всхожесть семян и рост сеянцев сосны обыкновенной (Pinus sylvestris L.)

Scots pine (Pinus sylvestris L.) is a potential introduced plant that can be used for reforestation in the southern part of Primorsky Krai. This plant is valuable for water regulation and mountain strengthening. It is widely used in the national economy. However, the growing area of the stands reduces with logging. It is possible to speed up the regeneration process by applying growth stimulants. The purpose of this study is to investigate the impact of natural (Zircon, Ekopin, Ribav-Extra) and synthetic (Krezatzin, Epin-Extra) growth stimulants on seed germination and biometric parameters of annual and biennial Scots pine seedlings (height, root collar diameter, length of root lobes, and biomass). Before cultivation, the seeds were soaked for 1 hour in a solution of KMnO4 (0.5 %) followed by 20 hours in growth stimulant solutions with concentrations 1.4·10–3 ml/l. The control group was presented with seeds without stimulant treatment. The soil germination was controlled on day 15. It was also determined the effectiveness of the stimulants as root top dressing for annual and biennial seedlings. The concentrations of the solutions were 0.2 and 0.1 ml/l with water as a solvent. The referentce group was seedlings without fertilization. Krezatzin, Ribav-Extra, and Ecopin had a significant impact on seed germination (92.7–94.0 %), exceeding the control group by 5.7–7.2 %. Krezatzin, Ribav-Extra, Zircon and Ecopin were most effective for Scots pine seedlings. In the first year of growth, seedling height increased by 20.3–43.5 %, root collar diameter by 22.2–38.9 %, root lobe length by 23.5–52.9 %. In the second year, these indicators exceeded the control group by 18.4–75.5, 2.9–11.8 and 15.0–36.1 %, respectively. The biomass of biennial seedlings increased by 63.7–185.2 % compared to the control group with the use of these stimulants. The solution concentration of 0.1 ml/l was more effective. The biennial seedlings grown using the stimulants as root top dressing according to biometric indicators meet the requirements of the Reforestation Regulations 2020, significantly exceeding the values specified in them. These seedlings can be used for planting woodlands and landscaping in populated areas. For citation: Ostroshenko V.Yu., Ostroshenko L.Yu. Influence of Growth Stimulants on Seed Germination and Seedlings Growth of Scots Pine (Pinus sylvestris L.). Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 93–104. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-93-104

Green synthesis of Plectranthus amboinicus leaf extract incorporated fine-tuned manganese dioxide nanoparticles: Antimicrobial and antioxidant activity

Plectranthus amboinicus Manganese dioxide (PA-MnO2) nanoparticles were synthesized by the reduction of potassium permanganate (KMnO4) using Plectranthus amboinicus (P. amboinicus) leaf extract at room temperature. A dark brown colour appeared after the addition of leaf extract to the solution of KMnO4. PA-MnO2 nanoparticles showed absorbance maximum at 324 nm. Scanning Electron Microscopy (SEM) study of particle size and morphology revealed that PA-MnO2 nanoparticles have spherical structures in shape. The electron dispersive X-ray spectroscopy confirmed the presence of Mn and O in the sample. Fourier Transforms infrared spectra of PA-MnO2 nanoparticles show the occurrence of O-Mn-O vibrational mode at around 515 cm-1. Based on the spectral and morphological data confirms the prepared compounds are nanometer in size. The structural investigation of MnO2 nanoparticles using the powder X-ray diffraction method reveals that the nanoparticles have a tetragonal configuration. Powder X-ray diffraction measurements were used to estimate crystallite grain diameter. The size of the crystalline grains is 7.5 nm. The PA-MnO2 nanoparticles demonstrated enhanced antibacterial activity against various gram positive bacteria like as S. aureus, S. pneumoniae, Stap. Pneumoniae and B. subtilis and various gram negative bacterial strains like as E. coli, K. pneumoniae, p. mirabilis and P. aeruginosa than standard drug ciprofloxacin. Antifungal activity of PA-MnO2 nanoparticles exhibited abnormal character against various fungal strains such as A. niger, C. albicans, C. tropicalis and M. campestris than the standard drug nystatin. Free radical scavenging study by DPPH assay showed enhanced activity by increasing the concentration of PA-MnO2. This study shows simple and eco-friendly synthesis of PA-MnO2 nanoparticles by plant extract. PA-MnO2 nanoparticles by green approach have potential to resolve emerging drug resistance against pathogenic diseases.

Study on the effect of KMnO4−modified humic acid residues on the removal of Hg(Ⅱ)/Pb(Ⅱ) from solution

As a solid waste, a coal−based humic acid residue (HAS) is less researched for its resource utilization. HAS is advantageous to the adsorption of heavy metals in water bodies because of its high adsorption capacity and low cost. In this study, HAS was modified using KMnO4 solution to improve the adsorption of Hg(Ⅱ)/Pb(Ⅱ), while the modification process was optimised by response surface methodology (RSM) and named K−HAS. The Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X − ray photoelectron spectroscopy (XPS) and X − ray diffraction (XRD) were jointly adopted to characterize the HAS and K−HAS. The batch sorption experiments were used to study the adsorption characteristics of external factors such as initial concentration, pH, and reaction time on the adsorption of Hg(Ⅱ)/Pb(Ⅱ) by K−HAS, and the isothermal adsorption model and kinetic model were used to fit the behavior of Hg(Ⅱ)/Pb(Ⅱ) adsorption by K−HAS. The results show that the pseudo−second−order model and the Langmuir adsorption isotherm model can better describe the adsorption behavior of K−HAS on Hg(Ⅱ)/Pb(Ⅱ), with the maximum adsorption amounts of 128.40 and 342.43 mg·g−1, respectively; there is competitive adsorption between Hg(Ⅱ) and Pb(Ⅱ), and Pb(Ⅱ) has a stronger competitive ability, as the concentration of Hg(II) increased, the adsorption of Pb(II) by K-HAS decreased by 20.29% and the adsorption of Hg by K-HAS decreased by 22.77% as the concentration of Pb(II) increased; the thermodynamic parameters indicate that the adsorption of Hg(Ⅱ)/Pb(Ⅱ) by K−HAS is a spontaneous heat absorption reaction. The adsorption mechanism of K−HAS for Hg(Ⅱ)/Pb(Ⅱ) mainly consisted of precipitation and complexation, which contributed 58.7% and 20.6% to Hg(Ⅱ) and 50.7% and 27.5% to Pb(Ⅱ), respectively. In addition, the site energy distribution (SED) shows that Hg(Ⅱ)/Pb(Ⅱ) preferentially occupy the high−energy adsorption sites and then gradually occupies the low−energy sites and that the K−HAS surface becomes more and more inhomogeneous as the solution temperature increases. The experiments demonstrate that K−HAS is effective in the adsorption of Hg(Ⅱ)/Pb(Ⅱ), and the investigation of the adsorption mechanism can be useful for further studies.

In-situ growth of homogeneous δ-MnO2 within lignin based porous carbon to reassemble uniform mesoporous crosslinked 3D-network structure for supercapacitors

In order to enhance the electrochemical performances of lignin based porous carbon (LPC), a feasible strategy is to incorporate homogeneous δ-MnO2 nanosheets within the LPC substrate via in-situ redox deposition. This work clarified the effects of different LPC supports and KMnO4 solution concentration on in-situ growth of MnO2 and the electrochemical performances of MnO2/LPC composite. The surface topography of δ-MnO2 significantly depends upon the pores feature of LPC. In-situ growth of δ-MnO2 embedded within LPC nanostructure also has a similar type of N2 adsorption-desorption isotherms of nanopores with the original LPC, belong to the type-IV isotherm with a hysteresis loop of H4 type. Moreover, as the KMnO4 solution concentration increases from 1 to 6 mM, the crystal form of δ-MnO2 within LPC maintains, while the electrochemical performances of MnO2/LPC can be improved. Such a uniform 3D-interlinked mesoporous nanostructure of Mn-4/LPC-CO composite electrode exhibits the highest specific capacitance of 198 F g−1 at 1 A g−1, much higher 190% than that of LPC (104 F g−1). Furthermore, the assembled symmetrical supercapacitor by using as-prepared Mn-4/LPC-CO composite exhibits a high energy density of 3.82 Wh kg−1 at the power density of 125 W kg−1 in voltage range of 0–1 V. This study offers a facile and low-cost approach for fabrication of biomass-based functional nanomaterials that can be used in energy storage devices.

Immobilization of polypyrrole on waste face masks using a novel in-situ-surface polymerization method: removal of Cr(VI) from electroplating wastewater

ABSTRACT In this work, polypyrrole (PPy) was synthesized on the surface of waste surgical face masks (SFM) with a novel environmentally-friendly in-situ-surface polymerization approach and used as an adsorbent for removing hexavalent chromium (Cr(VI)). In this method, the SFM surface was activated using KMnO4, resulting in the immobilization of porous MnO2, on which pyrrole can be polymerized efficiently. The novelty of this method is the presence of the oxidant on the surface before the polymerization step, which results in a better surface modification with polypyrrole. This method provides adsorbents with higher adsorption capacity compared to the conventional polymerization method with ammonium persulfate (APS). The adsorbent prepared at the mass ratios of 1.0 and 2.0; respectively, for KMnO4/SFM and pyrrole/SFM showed the highest performance. The adsorbent characterization revealed the successful polymerization of pyrrole on the surface of SFM. Reusability of the KMnO4 and pyrrole solutions were successful with remarkable results, showing the advantage of this technique compared to the conventional polymerization method with APS. The effect of different factors on the adsorption process was investigated. The removal rate was around 98% under the optimum conditions (pH, 2; adsorbent dosage, 3 g L−1; contact time, 60 min). The equilibrium data were well fitted by Langmuir isotherm (R2 = 0.9999). Kinetic investigations revealed that the adsorption process fitted well with the pseudo-second-order model. The adsorbent was regenerated for up to five cycles. One of the most important advantages of the proposed method compared to other methods is the reduction of wastewater during the synthesis process.

Wastewater Treatment and Electricity Generation with Different Cathode Solutions in MFC

A microbial fuel cell (MFC) with cathode and anode chambers was utilized to generate power while simultaneously removing COD from wastewater. By utilizing various oxidant solutions, it is possible to increase the generated voltage. The anode chamber was used for anaerobic treatment of synthetic wastewater (approximately 1000 mg/L), whereas the cathode chamber contained various oxidant solutions such as dilute hydrogen peroxide (300 mg/L), KMnO4 (300 mg/L), K2Cr2O7 (300 mg/L) and Fenton reagent (H2O2/Fe(II), 300/20 mg/L). Aerobic wastewater treatment and intermittent ozonation were also tested in the cathode chamber. With intermittent ozonation of the cathode chamber, the highest power output (382 mW/m2) was obtained. At the conclusion of the operation period, the COD concentration in the anode chamber decreased from 1170 mg/L to 650 mg/L, resulting in nearly 45% COD removal. In the cathode chamber, the use of diluted KMnO4 and H2O2 solutions produced high power densities of 35 and 23 W/m2, respectively, while the other oxidants produced low power densities. At the end of 72 hours, the COD content of the anaerobic chamber decreased from 800 mg/L to nearly 333 mg/L, resulting in nearly 59% COD removal for the KMnO4 solution. Considering the high cost of ozonation, it is recommended that either aerobic wastewater treatment or dilute KMnO4/H2O2 solutions should be used in the cathode chamber for high power generation.