Unveiling the Remarkable Potential of Geopolymer-Based Materials by Harnessing Manganese Dioxide Incorporation.

Thermoelectric (TE) building materials have the potential to revolutionize sustainable architecture by converting temperature differences into electrical energy. This study introduces geopolymeric TE materials enhanced with manganese dioxide (MnO2 ) as a modifying agent. Calorimetric experiments examine the impact of MnO2 on geopolymerization. Mechanical tests show that adding MnO2 (up to 5% by weight) improves the geopolymer composite's strength, achieving a peak compressive strength of 36.8 MPa. The Seebeck effect of the MnO2 -modified geopolymeric composite is also studied. The inclusion of MnO2 boosts the Seebeck coefficient of the geopolymer, reaching a notable 4273 µV C-1 at a 5% MnO2 dosage. This enhancement is attributed to an increase in the density of states (DOS) and a reduction in relaxation time. However, excessive MnO2 or high alkali levels may adversely affect the Seebeck coefficient by lengthening the relaxation time.

Self-Assembled Layer of Organic Phosphonic Acid Enables Highly Stable MnO2 Cathode for Aqueous Znic Batteries.

Manganese dioxide (MnO2) is an attractive cathode material for aqueous zinc batteries (AZBs) owing to its environmental benignity, low cost, high operating voltage, and high theoretical capacity. However, the severe dissolution of Mn2+ leads to rapid capacity decay. Herein, a self-assembled layer of amino-propyl phosphonic acid (AEPA) on the MnO2 surface, which significantly improves its cycle performance is successfully modified. Specifically, AEPA can be firmly attached to MnO2 through a strong chemical bond, forming a hydrophobic, and uniform organic coating layer with a few nanometers thickness. This coating layer can significantly inhibit the dissolution of Mn2+ by avoiding the direct contact between the electrolyte and cathode, thus enhancing the structural integrity and redox reversibility of MnO2. As a result, the MnO2@AEPA cathode achieves a high reversible capacity of 223 mAh g-1 at 0.5 A g-1 and a high capacity retention of 97% after 1700 cycles at 1 A g-1. This work provides new insights in developing stable Mn-based cathodes for aqueous batteries.

Suppressing Formation of Zn─Mn─O Phases by In Situ Ti Decoration of MnO2 for Long Lifespan MnO2-Zn Battery.

Mildly-acidic MnO2-Zn batteries are considered as a promising alternative for large-scale energy storage systems for their low toxicity, high safety, and low cost. Though, the degradation of MnO2 with cycling still hinders the further development of the batteries. In this study, it is observed that the decrease in available capacity of MnO2 with charge and discharge is accompanied by a structural transformation with the emergence of Zn─Mn─O phases. An electrodeposition test indicates that the Zn─Mn─O phase is formed from a co-precipitation of Zn and Mn during the charge process. Further, the structural change of MnO2 is suppressed and its cycle stability is improved with the addition of TiOSO4 as a facile electrolyte additive. As a result, under a current of 1200 mA g-1, the MnO2 electrode still gives a capacity of 230 mAh g-1 for over 1500 cycles. Capacity retention is 75% after 10 000 cycles under a current rate of 4800 mA g-1. These findings provide fundamental insights on the degradation mechanism of MnO2 and a new strategy to improve the electrochemical performance of aqueous MnO2-Zn batteries.

Smartphone-enabled colorimetric immunoassay for deoxynivalenol based on Mn2+-mediated aggregation of AuNPs.

Deoxynivalenol (DON) is a common mycotoxin in food that mainly pollutes grain crops and feeds, such as barley, wheat and corn. DON has caused widespread concern in the field of food and feed safety. In this study, a colorimetric immunoassay was proposed based on the aggregation of gold nanoparticles (AuNPs) due to the decomposition of Mn2+ from gold-coated manganese dioxide (AuNP@MnO2) nanosheets. In this study, 2-(dihydrogen phosphate)-l-ascorbic acid (AAP) was hydrolyzed by alkaline phosphatase (ALP) and converted to ascorbic acid (AA). Then, AuNP@MnO2 was reduced to Mn2+ and AuNPs aggregation occurred. Using the unique optical characteristics of AuNPs and AuNP@MnO2, visible color changes realized simple detection of DON with high sensitivity and portability. With increasing DON content, the color changed more obviously. To quantitatively detect DON, pictures can be taken and the blue value can be read by a smartphone. The detection limit (Ic10) of this method was 0.098 ng mL-1, which was 326 times higher than that of traditional competitive ELISA, and the detection range was 0.177-6.073 ng mL-1. This method exhibited high specificity with no cross-reaction in other structural analogs. The average recovery rate of DON in corn flour samples was 89.1 %-110.2 %, demonstrating the high accuracy and stability of this assay in actual sample detection. Therefore, the colorimetric immunoassay can be used for DON-related food safety monitoring.

Characteristics of humification, functional enzymes and bacterial community metabolism during manganese dioxide-added composting of municipal sludge.

The aim of this study was to assess effects of MnO2 addition (CK-0%, T1-2% and T2-5%) on humification and bacterial community during municipal sludge (MS) composting. The results suggested that MnO2 addition inhibited the growth of Nitrospira but stimulated Nonomuraea, Actinomadura, Streptomyces and Thermopolyspora, facilitating the lignocellulose degradation and humification with the increase in organic matter degradation by 13.8%-19.2% and humic acid content by 10.9%-20.6%. Compared to CK, the abundances of exoglucanase (EC:3.2.1.91), endo-1,4-beta-xylanase (EC:3.2.1.136) and endomannanase (EC:3.2.1.78) increased by 88-99, 52-66 and 4-15 folds, respectively. However, 5%-MnO2 induced the enrichment of Mizugakiibacter that harms the environment of agricultural production. The addition of 2%-MnO2 was recommended for MS composting. Furthermore, metabolic function analysis indicated that MnO2 addition altered amino acid and carbohydrate metabolism, especially enhancing propanoate metabolism and butanoate metabolism but inhibiting citrate cycle. Structural equation modeling revealed that Nonomuraea and Actinomadura were the main drivers for lignocellulose degradation. This study provided theoretical guidance in regulating humification via MnO2 for MS composting.

Manganese dioxide decorated kiwi peel powder for efficient removal of lead from aqueous solutions, blood and Traditional Chinese Medicine extracts.

For human health and environment safety, it is of great significance to develop novel materials with high effectiveness for removal of lead from not only aqueous solutions but also human body and traditional Chinese medicines. Here, functional kiwi peel composite, manganese dioxide decorated kiwi peel powder (MKPP), is proposed for the removal of Pb2+ effectively. The adsorption of Pb2+ in aqueous solution is a highly selective and endothermic process and kinetically follows a pseudo-second-order model, which can reach equilibrium with the capacity of 192.7 mg/g within 10 min. Comprehensive factors of hydration energy, charge-to-radius ratio and softness of Pb2+ make a stronger affinity between MKPP and Pb2+. The possible adsorption mechanism involves covalent bond, electrostatic force and chelation, etc. MKPP can be efficiently regenerated and reused with high adsorption efficiency after five cycles. Besides, MKPP can remove over 97% of Pb2+ from real water samples. MKPP can also alleviate lead poisoning to a certain extent and make the Pb level of TCM extract meet the safety standard. This work highlights that MKPP is a promising adsorbent for the removal of Pb2+ and provides an efficient strategy for reusing kiwi peel as well as dealing with the problem of Pb pollution.

Manganese dioxide nanoparticles provoke inflammatory damage in BV2 microglial cells via increasing reactive oxygen species to activate the p38 MAPK pathway.

With the widespread use of manganese dioxide nanoparticles (nano MnO2), health hazards have also emerged. The inflammatory damage of brain tissues could result from nano MnO2, in which the underlying mechanism is still unclear. During this study, we aimed to investigate the role of ROS-mediated p38 MAPK pathway in nano MnO2-induced inflammatory response in BV2 microglial cells. The inflammatory injury model was established by treating BV2 cells with 2.5, 5.0, and 10.0 µg/mL nano MnO2 suspensions for 12 h. Then, the reactive oxygen species (ROS) scavenger (20 nM N-acetylcysteine, NAC) and the p38 MAPK pathway inhibitor (10 µM SB203580) were used to clarify the role of ROS and the p38 MAPK pathway in nano MnO2-induced inflammatory lesions in BV2 cells. The results indicated that nano MnO2 enhanced the expression of pro-inflammatory cytokines IL-1ß and TNF-α, elevated intracellular ROS levels and activated the p38 MAPK pathway in BV2 cells. Controlling intracellular ROS levels with NAC inhibited p38 MAPK pathway activation and attenuated the inflammatory response induced by nano MnO2. Furthermore, inhibition of the p38 MAPK pathway with SB203580 led to a decrease in the production of inflammatory factors (IL-1ß and TNF-α) in BV2 cells. In summary, nano MnO2 can induce inflammatory damage by increasing intracellular ROS levels and further activating the p38 MAPK pathway in BV2 microglial cells.

Composite of KLVFF-Transthyretin-Penetratin and Manganese Dioxide Nanoclusters: A Multifunctional Agent against Alzheimer's ß-Amyloid Fibrillogenesis.

Design of amyloid ß-protein (Aß) inhibitors is considered an effective strategy for the prevention and treatment of Alzheimer's disease (AD). However, the limited blood-brain barrier (BBB) penetration and poor Aß-targeting capability restricts the therapeutic efficiency of candidate drugs. Herein, we have proposed to engineer transthyretin (TTR) by fusion of the Aß-targeting peptide KLVFF and cell-penetrating peptide Penetratin to TTR, and derived a fusion protein, KLVFF-TTR-Penetratin (KTP). Moreover, to introduce the scavenging activity for reactive oxygen species (ROS), a nanocomposite of KTP and manganese dioxide nanoclusters (KTP@MnO2) was fabricated by biomineralization. Results revealed that KTP@MnO2 demonstrated significantly enhanced inhibition on Aß aggregation as compared to TTR. The inhibitory effect was increased from 18%, 33%, and 49% (10, 25, and 50 µg/mL TTR, respectively) to 52%, 81%, and 100% (10, 25, and 50 µg/mL KTP@MnO2). In addition, KTP@MnO2 could penetrate the BBB and target amyloid plaques. Moreover, multiple ROS, including hydroxyl radicals, superoxide radicals, hydrogen peroxide, and Aß-induced-ROS, which cannot be scavenged by TTR, were scavenged by KTP@MnO2, thus resulting in the mitigation of cellular oxidative damages. More importantly, cell culture and in vivo experiments with AD nematodes indicated that KTP@MnO2 at 50 µg/mL increased the viability of Aß-treated cells from 66% to more than 95%, and completely cleared amyloid plaques in AD nematodes and extended their lifespan by 7 d. Overall, despite critical aspects such as the stability, metabolic distribution, long-term biotoxicity, and immunogenicity of the nanocomposites in mammalian models remaining to be investigated, this work has demonstrated the multifunctionality of KTP@MnO2 for targeting Aß in vivo, and provided new insights into the design of multifunctional nanocomposites of protein-metal clusters against AD.

Achieving Ultralong-Cycle Zinc-Ion Battery via Synergistically Electronic and Structural Regulation of a MnO2 Nanocrystal-Carbon Hybrid Framework.

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted burgeoning interests owing to the prospect in large-scale and safe energy storage application. Although manganese oxides are one of the typical cathodes of ZIBs, their practical usage is still hindered by poor service life and rate performance. Here, a MnO2 -carbon hybrid framework is reported, which is obtained in a reaction between the dimethylimidazole ligand from a rational designed MOF array and potassium permanganate, achieving ultralong-cycle-life ZIBs. The unique structural feature of uniform MnO2 nanocrystals which are well-distributed in the carbon matrix leads to a 90.4% capacity retention after 50 000 cycles. In situ characterization and theoretical calculations verify the co-ions intercalation with boosted reaction kinetics. The hybridization between MnO2 and carbon endows the hybrid with enhanced electrons/ions transport kinetics and robust structural stability. This work provides a facile strategy to enhance the battery performance of manganese oxide-based ZIBs.

Layered K0.37MnO2·0.25H2O as cathode material for potassium ion batteries.

Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K+(1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K0.37MnO2·0.25H2O (KMO) cathode, comprising alternately connected MnO6octahedra with a large interlayer spacing (0.71 nm) to accommodate the migration and transport of K+ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g-1at current densities of 60 mA g-1and 1 A g-1, respectively. The storage mechanism of K+ions in PIBs was demonstratedex situusing x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.

In Situ Regulation of MnO2 Structural Characteristics by Oxyanions to Boost Permanganate Autocatalysis for Phenol Removal.

Oxyanions, a class of constituents naturally occurring in water, have been widely demonstrated to enhance permanganate (Mn(VII)) decontamination efficiency. However, the detailed mechanism remains ambiguous, mainly because the role of oxyanions in regulating the structural parameters of colloidal MnO2 to control the autocatalytic activity of Mn(VII) has received little attention. Herein, the origin of oxyanion-induced enhancement is systematically studied using theoretical calculations, electrochemical tests, and structure-activity relation analysis. Using bicarbonate (HCO3-) as an example, the results indicate that HCO3- can accelerate the degradation of phenol by Mn(VII) by improving its autocatalytic process. Specifically, HCO3- plays a significant role in regulating the structure of in situ produced MnO2 colloids, i.e., increasing the surface Mn(III)s content and restricting particle growth. These structural changes in MnO2 facilitate its strong binding to Mn(VII), thereby triggering interfacial electron transfer. The resultant surface-activated Mn(VII)* complexes demonstrate excellent degrading activity via directly seizing one electron from phenol. Further, other oxyanions with appropriate ionic potentials (i.e., borate, acetate, metasilicate, molybdate, and phosphate) exhibit favorable influences on the oxidative capability of Mn(VII) through an activation mechanism similar to that of HCO3-. These findings considerably improve our fundamental understanding of the oxidation behavior of Mn(VII) in actual water environments and provide a theoretical foundation for designing autocatalytically boosted Mn(VII) oxidation systems.

Redox-Induced In Situ Growth of MnO2 with Rich Oxygen Vacancies over Monolithic Copper Foam for Boosting Toluene Combustion.

Catalytic combustion has been known to be an effective technique in volatile organic compound (VOC) abatement. Developing monolithic catalysts with high activity at low temperatures is vital yet challenging in industrial applications. Herein, monolithic MnO2-Ov/CF catalysts were fabricated via the in situ growth of K2CuFe(CN)6 (CuFePBA, a family of metal-organic frames) over copper foam (CF) followed by a redox-etching route. The as-synthesized monolith MnO2-Ov-0.04/CF catalyst displays a superior low-temperature activity (T90% = 215 °C) and robust durability for toluene elimination even in the presence of 5 vol % water. Experimental results reveal that the CuFePBA template not only guides the in situ growth of δ-MnO2 with high loading over CF but also acts as a source of dopant to create more oxygen vacancies and weaken the strength of the Mn-O bond, which considerably improves the oxygen activation ability of δ-MnO2 and consequently boosts the low-temperature catalytic activity of the monolith MnO2-Ov-0.04/CF toward toluene oxidation. In addition, the reaction intermediate and proposed mechanism in the MnO2-Ov-0.04/CF mediated catalytic oxidation process were investigated. This study provides new insights into the development of highly active monolithic catalysts for the low-temperature oxidation of VOCs.

MnO2-Induced Oxidation of Iodide in Frozen Solution.

Metal oxides play a critical role in the abiotic transformation of iodine species in natural environments. In this study, we investigated iodide oxidation by manganese dioxides (ß-MnO2, γ-MnO2, and δ-MnO2) in frozen and aqueous solutions. The heterogeneous reaction produced reactive iodine (RI) in the frozen phase, and the subsequent thawing of the frozen sample induced the gradual transformation of in situ-formed RI to iodate or iodide, depending on the types of manganese dioxides. The freezing-enhanced production of RI was observed over the pH range of 5.0-9.0, but it decreased with increasing pH. Fulvic acid (FA) can be iodinated by I-/MnO2 in aqueous and frozen solutions. About 0.8-8.4% of iodide was transformed to organoiodine compounds (OICs) at pH 6.0-7.8 in aqueous solution, while higher yields (10.4-17.8%) of OICs were obtained in frozen solution. Most OICs generated in the frozen phase contained one iodine atom and were lignin-like compounds according to Fourier transform ion cyclotron resonance/mass spectrometry analysis. This study uncovers a previously unrecognized production pathway of OICs under neutral conditions in frozen environments.

Hollow manganese dioxide-chitosan hydrogel for the treatment of atopic dermatitis through inflammation-suppression and ROS scavenging.

Atopic dermatitis (AD) is a chronic inflammatory disease associated with immune dysfunction. High levels of reactive oxygen species (ROS) can lead to oxidative stress, release of pro-inflammatory cytokines, and T-cell differentiation, thereby promoting the onset and worsening of AD. In this study, we innovatively used quaternary ammonium chitosan (QCS) and tannic acid (TA) as raw materials to design and prepare a therapeutic hydrogel(H-MnO2-Gel) loaded with hollow manganese dioxide nanoparticles (H-MnO2 NPs). In this system, the hydrogel is mainly cross-linked by dynamic ion and hydrogen bonding between QCS and TA, resulting in excellent moisture retention properties. Moreover, due to the inherent antioxidant properties of QCS/TA, as well as the outstanding H2O2 scavenging ability of H-MnO2 NPs, the hydrogel exhibits significant ROS scavenging capability. In vitro experiments have shown that H-MnO2-Gel exhibits good cellular biocompatibility. Importantly, in an AD-induced mouse model, H-MnO2-Gel significantly enhanced therapeutic effects by reducing epidermal thickness, mast cell number, and IgE antibodies. These findings suggest that H-MnO2-Gel, by effectively clearing ROS and regulating the inflammatory microenvironment, provides a promising approach for the treatment of AD.

Preparation of MnO2@poly-(DMAEMA-co-IA)-conjugated methotrexate nano-complex for MRI and radiotherapy of breast cancer application.

OBJECTIVE: A novel efficient pH-sensitive targeted magnetic resonance imaging (MRI) contrast agent and innovative radio-sensitizing system were synthesized based on MnO2 NPs coated with biocompatible poly-dimethyl-amino-ethyl methacrylate-Co-itaconic acid, (DMAEMA-Co-IA) and targeted with methotrexate (MTX). MATERIALS AND METHODS: The as-established NPs were fully characterized and evaluated for MRI signal enhancement, relaxivity, in vitro cell targeting, cell toxicity, blood compatibility, and radiotherapy (RT) efficacy. RESULTS: The targeted NPs MnO2@Poly(DMAEMA-Co-IA) and MTX-loaded NPs inhibited MCF-7 cell viability more effectively than free MTX after 24 and 48 h, respectively, with no noticeable toxicity. Additionally, the insignificant hemolytic activity demonstrated their proper hemo-compatibility. T1-weighted magnetic resonance imaging was used to distinguish the differential uptake of the produced MnO2@Poly(DMAEMA-Co-IA)-MTX NPs in malignant cells compared to normal ones in the presence of high and low MTX receptor cells (MCF-7 and MCF-10A, respectively). In MRI, the produced theranostic NPs displayed pH-responsive contrast enhancement. As shown by in vitro assays, treatment of cells with MnO2@Poly(DMAEMA-Co-IA)-MTX NPs prior to radiotherapy in hypoxic conditions significantly enhanced therapeutic efficacy. CONCLUSION: We draw the conclusion that using MnO2@Poly(DMAEMA-Co-IA)-MTX NPs in MR imaging and combination radiotherapy may be a successful method for imaging and radiation therapy of hypoxia cells.

Colorimetric and visual determination of uric acid based on decolorization of manganese dioxide nanosheet dispersions.

Serum levels of uric acid (UA) play an important role in the prevention of diseases. Developing a rapid and accurate way to detect UA is still a meaningful task. Hence, positively charged manganese dioxide nanosheets (MnO2NSs) with an average latter size of 100 nm and an ultra-thin thickness of below 1 nm have been prepared. They can be well dispersed in water and form stable yellow-brown solutions. The MnO2NSs can be decomposed by UA via redox reaction, leading to a decline of a characteristic absorption peak (374 nm) and a color fading of MnO2NSs solution. On this basis, an enzyme-free colorimetric sensing system for the detection of UA has been developed. The sensing system shows many advantages, including a wide linear range of 0.10-50.0 µmol/L, a limit of quantitation (LOQ) of 0.10 µmol/L, a low limit of detection (LOD) of 0.047 µmol/L (3σ/m), and rapid response without need of strict time control. Moreover, a simple and convenient visual sensor for UA detection has also been developed by adding an appropriate amount of phthalocyanine to provide a blue background color, which helps to increase visual discrimination. Finally, the strategy has been successfully applied to detect UA in human serum and urine samples.

Multi-target responsive nanoprobe with cellular-level accuracy for spatiotemporally selective photodynamic therapy.

Photodynamic therapy is known for its non-invasiveness to significantly reduce undesired side effects on patients. However, the infiltration and invasiveness of tumor growth are still beyond the specificity of traditional light-controlled photodynamic therapy (PDT), which lacks cellular-level accuracy to tumor cells, possibly leading to "off-target" damage to healthy tissues such as the skin or immune cells infiltrated. Here, upconversion nanoparticles (UCNPs) were co-encapsulated with manganese dioxide (MnO2) by amphiphilic polymers poly(styrene-co-methyl acrylate) (PSMA) and further coated with photosensitizer (riboflavin)-loaded mesoporous silica (C@S/V). The C@S/V nanoprobes exhibited shielded upconversion luminescence in normal conditions (pH 7.4, no hydroperoxide (H2O2)) under 980-nm irradiation and thus minimal reactive oxygen production from riboflavin. However, the excess H2O2 (1 mM) and acidic environment (pH 5.5) could decompose the MnO2 within the C@S/V, resulting in remarkable enhancement of upconversion luminescence and a favorable hypoxia-relieving condition for PDT, providing a spatiotemporal signal for therapy initiation. The C@S/V nanoprobes were applied to the co-culture of normal cells (HEK293) and pancreatic cancer cells (Panc02) and performed a selective killing on Panc02 under the 980-nm irradiation. By using the "double-safety" strategy, a responsive C@S/V nanoprobe was designed by the selective activation of acidic and H2O2-rich conditions and 980-nm irradiation for spatiotemporally selective photodynamic therapy with cellular-level accuracy.

Preparation of Biocompatible Manganese Selenium-Based Nanoparticles with Antioxidant and Catalytic Functions.

The specificity of the tumor microenvironment (TME) severely limits the effectiveness of tumor treatment. In this study, we prepared a composite nanoparticle of manganese dioxide and selenite by a one-step redox method, and their stability under physiological conditions was improved with a bovine serum protein modification to obtain MnO2/Se-BSA nanoparticles (SMB NPs). In the SMB NPs, manganese dioxide and selenite endowed the SMB NPs with acid-responsive and catalytic, and antioxidant properties, respectively. The weak acid response, catalytic activity, and antioxidant properties of composite nanoparticles were verified experimentally. Moreover, in an in vitro hemolysis assay, different concentrations of nanoparticles were incubated with mouse erythrocytes, and the hemolysis ratio was less than 5%. In the cell safety assay, the cell survival ratio was as high as 95.97% after the co-culture with L929 cells at different concentrations for 24 h. In addition, the good biosafety of composite nanoparticles was verified at the animal level. Thus, this study helps to design high-performance and comprehensive therapeutic reagents that are responsive to the hypoxia, weak acidity, hydrogen peroxide overexpression nature of TME and overcome the limitations of TME.

The Expanded Vermiculite Was Quickly Prepared by the Catalytic Action of Manganese Dioxide on Hydrogen Peroxide and Its Adsorption Properties to Cd.

The structure and activity of vermiculite can be maintained by expanding vermiculite (Vrm) with hydrogen peroxide. However, it is time-consuming. In past studies, little attention has been paid to the catalytic properties of manganese dioxide on hydrogen peroxide to improve the swelling efficiency of vermiculite. In this experiment, this catalytic effect was utilized to swell Vrm in a short time. The samples were then used to adsorb Cd from the solution. Through a series of characterization tests. The results showed that the exothermic rate was 1960.42-2089.164 J/min and the total exothermic heat was 39,208.4-41,783.28 J when expanding 10 gVrm, which could have a good expansion effect. The expansion was completed in about 40 min. Compared with Vrm, the adsorption of Cd is enhanced by about 30%. It is consistent with the proposed secondary kinetic adsorption model. This study provides a new perspective and theoretical guidance for improving the efficiency of Vrm stripping by hydrogen peroxide. A kind of expanded Vrm with better Cd adsorption efficiency was also prepared.

Peroxymonosulfate Activation by Facile Fabrication of α-MnO2 for Rhodamine B Degradation: Reaction Kinetics and Mechanism.

The persulfate-based advanced oxidation process has been an effective method for refractory organic pollutants' degradation in aqueous phase. Herein, α-MnO2 with nanowire morphology was facially fabricated via a one-step hydrothermal method and successfully activated peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. Influencing factors, including the hydrothermal parameter, PMS concentration, α-MnO2 dosage, RhB concentration, initial pH, and anions, were systematically investigated. The corresponding reaction kinetics were further fitted by the pseudo-first-order kinetic. The RhB degradation mechanism via α-MnO2 activating PMS was proposed according to a series of quenching experiments and the UV-vis scanning spectrum. Results showed that α-MnO2 could effectively activate PMS to degrade RhB and has good repeatability. The catalytic RhB degradation reaction was accelerated by increasing the catalyst dosage and the PMS concentration. The effective RhB degradation performance can be attributed to the high content of surface hydroxyl groups and the greater reducibility of α-MnO2, and the contribution of different ROS (reactive oxygen species) was 1O2 > O2·- > SO4·- > ·OH.