A novel green synthesis of MnO2-Coal composite for rapid removal of silver and lead from wastewater.

The presence of Ag(I) and Pb(II) ions in wastewater poses a significant threat to human health in contemporary times. This study aims to explore the development of a novel and economical adsorbent by grafting MnO2 particles onto low-rank coal, providing an innovative solution for the remediation of water contaminated with silver and lead. The synthesized nanocomposites, referred to as MnO2-Coal, underwent thorough characterization using FTIR, XRD, BET, and SEM to highlight the feasibility of in-situ surface modification of coal with MnO2 nanoparticles. The adsorption of Ag(I) and Pb(II) from their respective aqueous solution onto MnO2-Coal was systematically investigated, with optimization of key parameters such as pH, temperature, initial concentration, contact time, ionic strength, and competing ions. Remarkably adsorption equilibrium was achieved within a 10 min, resulting in impressive removal rates of 80-90 % for both Ag(I) and Pb(II) at pH 6. The experimental data were evaluated using Langmuir, Freundlich, and Temkin isotherm models. The Langmuir isotherm model proved to be more accurate in representing the adsorption of Ag(I) and Pb(II) ions onto MnO2-Coal, exhibiting high regression coefficients (R2 = 0.99) and maximum adsorption capacities of 93.57 and 61.98 mg/g, along with partition coefficients of 4.53 and 71.92 L/g for Ag(I) and Pb(II), respectively, at 293 K. Kinetic assessments employing PFO, PSO, Elovich, and IPD models indicated that the PFO and PSO models were most suitable for adsorption mechanism of Pb(II) and Ag(I) on MnO2-Coal composites, respectively. Moreover, thermodynamic evaluation revealed the spontaneous and endothermic adsorption process for Ag(I), while exothermic behavior for adsorption of Pb(II). Importantly, this approach not only demonstrates cost-effectiveness but also environmental friendliness in treating heavy metal-contamination in water. The research suggests the potential of MnO2-Coal composites as efficient and sustainable adsorbents for water purification applications.

Biocompatibility assessment of bovine serum albumin conjugated manganese dioxide nanoparticle and their therapeutic role against microwave radiation induced haematological toxicity in male Wistar rats.

Microwave (MW) radiations are widely used in communications, radar and medical treatment and thus human exposure to MW radiations have increased tremendously, raising health concerns as MW has been implicated in induction of oxidative stress condition in our body. Few metallic nanoparticles (NPs) have been shown to mimic the activity of antioxidant enzymes and hence can be applied for the modulation of adverse effects caused by MW. Present study aimed to assess the biocompatibility of Bovine serum albumin (BSA) conjugated manganese dioxide nanoparticles (MNP*) and to counteract the impact of MW on the haematological system of male Wistar rats. Experiments were conducted in two sets. Set I involved biodistribution and antioxidant activity evaluation of MNP* at different doses. Results showed a dose-dependent increase in antioxidant potential and significant biodistribution in the liver, spleen, kidney, and testis, with no organ damage, indicating its biocompatibility. Experiment set II constituted the study of separate and combined effects of MW and MNP* on haematological parameters, oxidative status, and genotoxic study in the blood of rats. MW exposure significantly altered red blood cell count, hemoglobin, packed cell volume percentage, monocyte percentage, aspartate aminotransferase, Alanine aminotransferase and uric acid. MW also induced significant DNA damage in the blood. A significant increase in lipid peroxidation and a decrease in antioxidant enzyme superoxide dismutase was also observed in MW exposed group. However, these alterations were reduced significantly when MNP* was administered. Thus, MNP* showed biocompatibility and modulatory effects against MW-induced alterations in the haematological system of rats.

Hybrid radical coupling during MnO2-mediated transformation of a mixture of organic UV filters: Chemistry and toxicity assessment.

Manganese oxide (MnO2) is one of the most abundant metal oxides, and it is renowned for its ability to degrade various phenolic micropollutants. However, under MnO2-mediated transformation, BP-3 transforms into 12 different radical-coupled transformation products (TPs) out of 15 identified TPs. These radical-coupled TPs are reported with adverse environmental impacts. This study explored the effects of MnO2 on organic UV filter mixtures and different water constituents (i.e., bicarbonate ion (HCO3-), humic acid (HA) and halide ions) in terms of degradation efficiency and transformation chemistry. When a mixture of benzophenone-3 (BP-3) and avobenzone (AVO) underwent transformation by MnO2, hybrid radical-coupled TPs derived from both organic UV filters were generated. These hybrid radical-coupled TPs were evaluated by an in silico prediction tool and Vibrio fischeri bioluminescence inhibition assay (VFBIA). Results showed that these TPs were potentially toxic to aquatic organisms, even more so than their parent compounds. The higher the concentration of HCO3-, HA, chloride ion (Cl-) and bromide ion (Br-), the greater the reduction in the efficiencies of degrading BP-3 and AVO. Contrastingly, in the presence of iodide ion (I-), degradation efficiencies of BP-3 and AVO were enhanced; however, iodinated TPs and iodinated radical-coupled TPs were formed, with questionable toxicity. This study has revealed the environmental risks of hybrid radical-coupled TPs, iodinated TPs and iodinated radical-coupled TPs when the organic UV filters BP-3 and AVO are transformed by MnO2.

Electrochemical Nanosensors for Sensitization of Sweat Metabolites: From Concept Mapping to Personalized Health Monitoring.

Sweat contains a broad range of important biomarkers, which may be beneficial for acquiring non-invasive biochemical information on human health status. Therefore, highly selective and sensitive electrochemical nanosensors for the non-invasive detection of sweat metabolites have turned into a flourishing contender in the frontier of disease diagnosis. A large surface area, excellent electrocatalytic behavior and conductive properties make nanomaterials promising sensor materials for target-specific detection. Carbon-based nanomaterials (e.g., CNT, carbon quantum dots, and graphene), noble metals (e.g., Au and Pt), and metal oxide nanomaterials (e.g., ZnO, MnO2, and NiO) are widely used for modifying the working electrodes of electrochemical sensors, which may then be further functionalized with requisite enzymes for targeted detection. In the present review, recent developments (2018-2022) of electrochemical nanosensors by both enzymatic as well as non-enzymatic sensors for the effectual detection of sweat metabolites (e.g., glucose, ascorbic acid, lactate, urea/uric acid, ethanol and drug metabolites) have been comprehensively reviewed. Along with this, electrochemical sensing principles, including potentiometry, amperometry, CV, DPV, SWV and EIS have been briefly presented in the present review for a conceptual understanding of the sensing mechanisms. The detection thresholds (in the range of mM-nM), sensitivities, linear dynamic ranges and sensing modalities have also been properly addressed for a systematic understanding of the judicious design of more effective sensors. One step ahead, in the present review, current trends of flexible wearable electrochemical sensors in the form of eyeglasses, tattoos, gloves, patches, headbands, wrist bands, etc., have also been briefly summarized, which are beneficial for on-body in situ measurement of the targeted sweat metabolites. On-body monitoring of sweat metabolites via wireless data transmission has also been addressed. Finally, the gaps in the ongoing research endeavors, unmet challenges, outlooks and future prospects have also been discussed for the development of advanced non-invasive self-health-care-monitoring devices in the near future.

Removal of bisphenol A and methylene blue through persulfate activation by calcinated α-MnO2 nanorods: effect of ultrasonic assistance and toxicity assessment.

This work investigates the efficacy of α-MnO2 nanorods for persulfate-mediated degradation of bisphenol A (BPA) and methylene blue (MB), in silent and ultrasonic-assisted systems. The conversion of α-MnO2 nanoparticle flakes to nanorods occurs upon calcination at a temperature of 400 °C for 3 h under the ramping conditions. The comparative characterization of nanomaterials pre- and post-calcination reveals better physical, chemical, and thermal properties of α-MnO2 nanorods. The impact of various operational parameters such as pH, dosage of nanorods, persulfate dose, selected contaminant concentration, ultrasound frequency and power, scavengers, and landfill leachate medium on the degradation of pollutants is also assessed. The ultrasonic assistance yields higher removal for both BPA and MB than the silent system. This may be attributed to the generation of more radicals as ultrasound activates persulfate. This can be due to acoustic cavitation, which leads to better solute dissociation and excited state. The results obtained through scavenger tests reveal that both OH• and SO4•- can contribute to degradation, but the role of SO4•- is found dominant. Significant removal of BPA and MB ((BPA)silent, 87.12%; (MB)silent, 96.54%; (BPA)ultrasonic, 88.75%; (MB)ultrasonic, 93.86%)) is observed in landfill leachate medium. The degradation pathway for pollutants is also proposed. The toxicity of pollutants and their degradation intermediates are evaluated using Ecological Structure Activity Relationships (ECOSAR) program. The results indicate reduced toxicity of BPA intermediates, while most MB degradation intermediates show higher toxicity. Therefore, it can be affirmed that removing pollutants does not ensure a completely non-toxic process. However, the study proposes a comprehensive toxicity evaluation and eliminating toxic intermediates for completely harmless wastewater treatment.

Adsorption of Fluoride onto Acid-Modified Low-Cost Pyrolusite Ore: Adsorption Characteristics and Efficiencies.

Fluoride concentrations in the groundwater continue to be a major cause for concern in Thailand, particularly in the country's north and west. The process of removing fluoride through adsorption has captured the attention of the abundance of ore in the mining industry. For the purpose of this investigation, the utilization of the adsorbent pyrolusite, which is a manganese mineral largely composed of MnO2, was a major component. Lab-scale experiments were conducted to investigate the efficacy of original pyrolusite ore (PA-1) and acid-modification PA (PA-2) created as low-cost adsorption materials for fluoride removal. The results of the adsorption rate in both PAs showed a fast rate of adsorption within 60 min of reaching equilibrium. According to the results of the adsorption capacity (qe) tests, PA that had been treated with an acid solution (PA-2) had the capacity to contain more fluoride (qe = 0.58 mg/g) than the PA that had been used initially (PA-1) (qe = 0.11 mg/g). According to the findings of an isotherm, primary adsorption behavior is determined by the effect that surface components and chemical composition have on porous materials. This is the first current study that provides a comparison between pyrolusite from Thailand's mining industry and basic modified pyrolusite regarding their ability to remove a fluoride contaminant in synthetic groundwater by an adsorption process. Such an approach will be able to be used in the future to protect the community from excessive fluoride concentrations in household and drinking water treatment technology.

Investigation and risk assessment of dibutyl phthalate in a typical region by a high-throughput dual-signal immunoassay.

The systematic investigation and risk assessment of dibutyl phthalate (DBP) were performed using an ultrasensitive dual-signal immunoassay in Zhenjiang, Jiangsu Province. In this study, C-dots@H-MnO2 nanohybrid were synthesized and labelled on the secondary antibody to generate fluorometric and colorimetric signals. Attributed to the efficient catalysis of carbon dots (C-dots) and the high C-dots loading of hollow manganese (IV) oxide (H-MnO2), the excellent sensitivity and low detection limits (0.243 and 0.692 µg/L respectively) were produced. Based on the proposed method, 25 water and 119 beverage samples were investigated. DBP was found in all water samples and 65.5% of beverage samples, with the concentrations varying in 16.5-32.1 µg/L and 0-553 µg/L, respectively. In addition, the mean concentration (22.9 µg/L) in waters was decreased significantly compared with that detected in 2016 (43.5 µg/L) by our Lab. For beverages, a similar phenomenon was observed by the measured concentrations from coffee. Furthermore, the potential ecological risks of DBP were evaluated, the results indicated that human activities had caused serious pollution and high risks to the local aquatic ecosystem. On the other hand, the results of health risk assessment suggested that DBP in beverages might not cause obvious side effects to local residents.

Brønsted-acid sites promoted degradation of phthalate esters over MnO2: Mineralization enhancement and aquatic toxicity assessment.

Advanced oxidation processes (AOPs) are important technologies for aqueous organics removal. Despite organic pollutants can be degraded via AOPs generally, high mineralization of them is hard to achieve. Herein, we synthesized a manganese oxide nanomaterial (H2-OMS-2) with abundant Brønsted-acid sites via ion-exchange of cryptomelane-type MnO2 (OMS-2), and tested its catalytic performance for the degradation of phthalate esters via peroxymonosulfate (PMS) activation. About 99% of dimethyl phthalate (DMP) at a concentration of 20 mg/L could be degraded within 90 min and 82% of it could be mineralized within 180 min over 0.6 g/L of catalyst and 1.8 g/L of PMS. The catalyst could activate PMS to generate SO4-˙ and ·OH as the dominant reactive oxygen species to reach complete degradation of DMP. Especially, the higher TOC removal rate was obtained due to the rich Brønsted-acid sites and surface oxygen vacancies on the catalyst. Kinetics and mechanism study showed that MnII/MnIII might work as the active sites during the catalytic process with a lower reaction energy barrier of 55.61 kJ/mol. Furthermore, the catalyst could be reused for many times through the regeneration of the catalytic ability. The degradation and TOC removal efficiencies were still above 98% and 65% after seven consecutive cycles, respectively. Finally, H2-OMS-2-catalyzed AOPs significantly reduced the organismal developmental toxicity of the DMP wastewater through the investigation of zebrafish model system. The present work, for the first time, provides an idea for promoting the oxidative degradation and mineralization efficiencies of aqueous organic pollutants by surface acid-modification on the catalysts.

Phosphate-triggered ratiometric fluoroimmunoassay based on nanobody-alkaline phosphatase fusion for sensitive detection of 1-naphthol for the exposure assessment of pesticide carbaryl.

The excessive use of carbaryl has resulted in the risk of its exposure. In this study, we isolated six nanobodies (Nbs) from a camelid phage display library against the biomarker of carbaryl, 1-naphthol (1-NAP). Owing to its characteristics of easy genetic modifications, we produced a nanobody-alkaline phosphatase (Nb-CC4-ALP) fusion protein with good stability. A dual-emission system based ratiometric fluoroimmunoassay (RFIA) for quick and highly sensitive determination of 1-NAP was developed. Silicon nanoparticles (SiNPs) was used as an internal reference and for aggregation-induced emission enhancement (AIEE) of gold nanoclusters (AuNCs), while AuNCs could be quenched by MnO2 via oxidation. In the presence of ALP, ascorbic acid phosphate (AAP) can be transformed into ascorbic acid (AA), the later can etch MnO2 to recover the fluorescence of the AuNCs. Based on optimal conditions, the proposed assay showed 220-fold sensitivity improvement in comparison with conventional monoclonal antibody-based ELISA. The recovery test of urine samples and the validation by standard HPLC-FLD demonstrated the proposed assay was an ideal tool for screening 1-NAP and provided technical support for the monitoring of carbaryl exposure.

Phosphate removal from wastewater using novel renewable resource-based, cerium/manganese oxide-based nanocomposites.

Nanocomposites containing mixed metal oxides show excellent phosphate removal results and are better compared to individual metal oxides. In this research, cerium/manganese oxide nanocomposites, embedded on the surface of modified cellulose pine wood shaving, were synthesized by a simple technique that is both eco-friendly and economically feasible. No toxic or petroleum chemicals were employed during preparation. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface area analysis, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy were performed to study the shape and size of nanocomposites as well as composition of elements present on the surface of the nanocomposites. Adsorption isotherm (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and kinetic studies (pseudo first and second-order, Elovich and Weber-Morris) were carried out to determine the adsorption mechanism for phosphate removal from contaminated water. The maximum adsorption capacity of nanocomposites was found to be 204.09 mg/g, 174.42 mg/g, and 249.33 mg/g for 100 mg, 300 mg, and 500 mg, respectively. The results indicate that the nanocomposites were able to decrease the phosphorus concentration from 10 to 0.01 ppm, below the threshold limit required by EPA guidelines in the USA. We also demonstrated that the media could be regenerated and reused five times without loss of performance.

An innovative method for manganese (Mn2+) and ammonia nitrogen (NH4+-N) stabilization/solidification in electrolytic manganese residue by basic burning raw material.

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue (EMR) have seriously hindered the sustainable development of electrolytic manganese industry. In this study, an innovative basic burning raw material (BRM) was used to stabilize/solidify Mn2+ and NH4+-N in EMR. The characteristics of EMR and BRM, stabilize mechanism of NH4+-N and Mn2+, and leaching test were investigated. The concentrations of NH4+-N and Mn2+ were 12.8 mg/L and 0.1 mg/L, respectively, when the solid liquid ratio was 1.5:1, and the mass ratio of EMR and BRM was 100:10, at the temperature of 20 °C reacting for 12 h Mn2+ was mostly solidified as bustamite ((Mn,Ca)Si2O6), groutite (MnOOH) and ramsdellite (MnO2). NH4+-N was mostly recycled by (NH4)2SO4 and (NH4)3H(SO4)2. Leaching test results indicated that the concentrations of heavy metals were within the permitted level for the integrated wastewater discharge standard (GB8978-1996). Economic evaluation revealed that the cost of EMR treatment was $ 10.15/t by BRM. This study provided a new research idea for EMR harmless disposal.

Chemical and Colloidal Dynamics of MnO2 Nanosheets in Biological Media Relevant for Nanosafety Assessment.

Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are manganese dioxide (MnO2 ) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO2 is its sensitivity to chemical reduction leading to dissolution and Mn2+ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO2 biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO2 nanosheets in biological media for environmental and human health risk assessment. MnO2 nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO2 internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn2+ release. The results are used to classify MnO2 nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO2 transformations for nanotoxicity testing and nanosafety assessment are discussed.

The first and low cost copper Schiff base/manganese oxide bio nanocomposite from unwanted plants as a robust industrial catalyst.

In this paper, the first bio-nano colloid including manganese oxide nanoparticles and copper nanocomplex in the presence of Amaranthus spinosus as one unwanted plant was prepared (Mn3O4/CuL bio-nanocolloid). As-prepared bio nanocolloid was analysed completely by different techniques such as FT-IR, ICP-AES, SEM, EDX, TEM and elemental analysis to have the size, structure, morphology and elements in this compound. This bio-nanocolloid showed high catalytic activity towards green oxidation reactions of alcohols using hydrogen peroxide under solvent free conditions. The longevity, easy and practical recoverability of the solid catalyst was also confirmed for six times. The natural starting material for a long-term stability catalyst preparation, using ideal oxidant (H2O2), solventless and easy work up show the great potential in scalability for actual industries applications.

Assessment of the manganese cluster's oxidation state via photoactivation of photosystem II microcrystals.

Knowledge of the manganese oxidation states of the oxygen-evolving Mn4CaO5 cluster in photosystem II (PSII) is crucial toward understanding the mechanism of biological water oxidation. There is a 4 decade long debate on this topic that historically originates from the observation of a multiline electron paramagnetic resonance (EPR) signal with effective total spin of S = 1/2 in the singly oxidized S2 state of this cluster. This signal implies an overall oxidation state of either Mn(III)3Mn(IV) or Mn(III)Mn(IV)3 for the S2 state. These 2 competing assignments are commonly known as "low oxidation (LO)" and "high oxidation (HO)" models of the Mn4CaO5 cluster. Recent advanced EPR and Mn K-edge X-ray spectroscopy studies converge upon the HO model. However, doubts about these assignments have been voiced, fueled especially by studies counting the number of flash-driven electron removals required for the assembly of an active Mn4CaO5 cluster starting from Mn(II) and Mn-free PSII. This process, known as photoactivation, appeared to support the LO model since the first oxygen is reported to evolve already after 7 flashes. In this study, we improved the quantum yield and sensitivity of the photoactivation experiment by employing PSII microcrystals that retained all protein subunits after complete manganese removal and by oxygen detection via a custom built thin-layer cell connected to a membrane inlet mass spectrometer. We demonstrate that 9 flashes by a nanosecond laser are required for the production of the first oxygen, which proves that the HO model provides the correct description of the Mn4CaO5 cluster's oxidation states.

A novel smartphone-based CD-spectrometer for high sensitive and cost-effective colorimetric detection of ascorbic acid.

As a powerful tool for medical diagnosis and bioanalysis, conventional optical spectrometers are generally expensive, bulky and always require an accompanying data processing device. In this work, we developed a novel smartphone-based CD-spectrometer (SCDS) for high sensitive and ultra-portable colorimetric analysis, with the advantage of cost-effective and simplicity. The distance between the light source and slit, the structure of SCDS and the parameters of camera in the smartphone were all optimized to ensure the best analytical performance. Besides, the SCDS employed HSV color model and utilized the overall intensity calculated by summing V-value of adjacent position for the absorbance measurement. In this way the errors caused by the low resolution of CD-grating can effectively be eliminated to promote the sensitivity of the SCDS. The performance of the SCDS was first validated for colorimetric detection of BSA with a detection limit of 0.0073 mg/mL, which is superior compared to that of the microtiter plate reader (MTPR). Moreover, by combining with 3,3',5,5'-tetramethylbenzidine-manganese dioxide (TMB-MnO2) nanosheets reaction, a high sensitive and specific system for ascorbic acid detection was established. The SCDS gives a detection range from 0.6250 µM to 40 µM with a detection limit of 0.4946 µM for AA detection. Compared to other studies, the SCDS features wide detection range and very low detection limit with low cost instrument. Therefore, the SCDS will be an ideal and promising colorimetric system for point-of-care (POC) application in food security, disease diagnosis and environmental monitoring.

Transformation of m-aminophenol by birnessite (δ-MnO2) mediated oxidative processes: Reaction kinetics, pathways and toxicity assessment.

The m-aminophenol (m-AP) is a widely used industrial chemical, which enters water, soils, and sediments with waste emissions. A common soil metal oxide, birnessite (δ-MnO2), was found to mediate the transformation of m-AP with fast rates under acidic conditions. Because of the highly complexity of the m-AP transformation, mechanism-based models were taken to fit the transformation kinetic process of m-AP. The results indicated that the transformation of m-AP with δ-MnO2 could be described by precursor complex formation rate-limiting model. The oxidative transformation of m-AP on the surface of δ-MnO2 was highly dependent on reactant concentrations, pH, temperature, and other co-solutes. The UV-VIS absorbance and mass spectra analysis indicated that the pathway leading to m-AP transformation may be the polymerization through the coupling reaction. The m-AP radicals were likely to be coupled by the covalent bonding between unsubstituted C2, C4 or C6 atoms in the m-AP aromatic rings to form oligomers as revealed by the results of activation energy and mass spectra. Furthermore, the toxicity assessment of the transformation productions indicated that the toxicity of m-AP to the E. coli K-12 could be reduced by MnO2 mediated transformation. The results are helpful for understanding the environmental behavior and potential risk of m-AP in natural environment.

Synthesis of modified amorphous manganese oxide using low-cost sugars and biochars: Material characterization and metal(loid) sorption properties.

In this study, amorphous Mn oxides (AMOs) and their composites with biochar (BC) were synthesized using different sugars (glucose, sucrose, and molasses), and their sorption efficiency toward Zn(II), Cd(II), and As(V) was tested. Additionally, detailed characterization of synthesized materials using various solid-state analysis methods (e.g. XRD, FTIR-ATR, and/or SEM-EDX) was also performed. Despite glucose-based AMOs presented higher sorption efficiency for As(V), i.e., 0.73 mmol g-1 (glucose) > 0.27 mmol g-1 (sucrose and molasses), similar sorption efficiency toward Zn(II), i.e., 0.80 mmol g-1 (glucose and molasses) > 0.66 (sucrose) and Cd(II) (0.71-0.74 mmol g-1 (sucrose and molasses) > 0.36 mmol g-1 (glucose), was observed for sucrose- and molasses-based AMOs under the given conditions. Next, the sorption efficiency of all AMO/BC composites was proportional to their AMO content. Finally, Mn(II) leaching from the structure of the new AMOs was negligible compared to that observed for the glucose-based AMOs, in this study as well as in other similar studies. Moreover, using molasses as reducing agent during AMO synthesis dramatically decreased the total cost of the final materials, which suggested that these new AMOs could represent interesting alternatives for standard remediation technologies. The AMOs synthesized using low-cost sugars could, therefore, be promising materials for real field applications, since the main disadvantages of using standard AMOs are mitigated. Nevertheless, the efficiency and stability of these composites under real-life conditions must be tested prior to their direct application for remediation technologies.

Simultaneous optimizing removal of manganese and ammonia nitrogen from electrolytic metal manganese residue leachate using chemical equilibrium model.

Electrolytic metal manganese residue leachate (EMMRL) was produced from long-term deposition of electrolytic metal manganese residue. EMMRL contains huge amount of manganese and ammonia nitrogen which could seriously damage the ecological environment. In this study, a chemical equilibrium model-Visual MINTEQ was used to simultaneously optimize removal of manganese and ammonia nitrogen from EMMRL with chemical precipitation methods. In the laboratory experiment, the effect of different N: P ratios and pH were investigated, and the characterization of the precipitates was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results showed that over 99.9% manganese and 96.2% ammonia nitrogen were simultaneously removed, respectively, when molar ratio of N:P was 1:1.15 at pH 9.5. Moreover, the experimental results corresponded well with the model outputs with respect to ammonia nitrogen and manganese removal. Manganese was mainly removed in the form of MnHPO4·3H2O and manganite, and ammonia nitrogen was mainly removed in the form of struvite. Economic evaluation indicated the chemical precipitation methods can be applied in the factory when the price of precipitation was higher than 0.295 $/kg.

High resolution spatiotemporal sampling as a tool for comprehensive assessment of zinc mobility and pollution in sediments of a eutrophic lake.

To assess zinc (Zn) pollution risk from sediments, this study investigated the monthly changes of dissolved Zn and labile Zn in sediment-overlying water profiles in a eutrophic bay (Meiliang Bay) of Lake Taihu (China) using high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) at a 4 mm vertical resolution. In February and March, Mn oxides reduction caused high concentrations of DGT-labile Zn (14 ∼ 235 µg L-1), as evidenced by the significant correlation between DGT-labile Zn and DGT-labile Mn in sediments. In June and July, algal blooms reduced concentrations of dissolved Zn via algal assimilation. From August through October, concentrations of dissolved Zn in overlying water (338 ∼ 1023 µg L-1) exceeded the water quality limit for fisheries in China (100 µg L-1). This was attributed to reductive dissolution of Mn oxides in sediments caused by algal degradation followed by complexation of dissolved organic matter (DOM), which was identified in a simulated algal bloom experiment. In the winter, decreased Zn mobility was mainly attributed to adsorption by Mn oxides. It was concluded that enhanced Zn pollution risk from sediments is worthy of concern especially during algal degradation in eutrophic lakes.

The residual tetracycline in pharmaceutical wastewater was effectively removed by using MnO2/graphene nanocomposite.

The object of this study was to remove the tetracycline (TC) residue in pharmaceutical wastewater after flocculation treatment. MnO2/graphene nanocomposite was synthesized by an in situ hydrothermal method and its TC removal rate was up to 99.4%. This nanocomposite had excellent water solubility. More importantly, the introduction of MnO2 nanorods allowed the avoidance of excessive stacking of treated graphene sheets during the adsorption process, which made the TC molecules to have more opportunities to make contact with the adsorbents. In order to eliminate the interference factors, the adsorption isotherm, kinetics, thermodynamics and mechanism were all studied in TC aqueous solution. The influence of solution pH, contact time, MnO2 loading amount, temperature and solution concentration on the adsorption process were also assessed. The main adsorption mechanism contributed to the complexation of Mn(IV) and π-π interactions of the benzene ring structure on treated graphene sheets with TC molecules.