Release characteristics of heavy metals from electrolytic manganese residue under varying environmental factors.

High levels of manganese (Mn) and other heavy metals from electrolytic manganese residue (EMR) stockpiled would be released into the environment under natural conditions. A batch-leaching test was carried out to investigate the release characteristics of heavy metals from EMR with different storage times under simulated environmental conditions such as acid rain with different pH (3.0, 4.5, 5.6, and 7.0) at contact times of 1, 2, 4, 6, and 12 h; liquid to solid ratio (L/S) (5:1, 10:1, 20:1, and 30:1); and temperature (15, 25, 35, and 45 °C). The results showed that low pH (3.0 and 4.5) and high temperature (35 and 45 °C) could significantly promote heavy metal leaching from EMRs and increasing the L/S ratio above 20:1 mL/g significantly decreased heavy metal leachate concentrations due to dilution effect. Cr, Mn, and Pb concentrations in leachate increased almost continuously throughout the leaching process, while Zn decreased slightly at the 12th hour. Meanwhile, heavy metal concentrations in EMR1 (fresh EMR) were higher than in EMR2 (out stockpiled for more than 3 months). The concentrations of Mn, Pb, and Zn in leachates from EMRs at pH 3.0 and 4.5 leaching far exceeded the allowable maximum discharge concentrations for pollutants of the integrated wastewater discharge standard in China (GB8978-1996) by 57.5-59.0, 1.3-4.3, and 1.1-1.8 and 53.5-56.0, 3.04-7.25, and 1.0-1.91 times, respectively. Additionally, the Mn concentrations from both EMR leachates at pH 7.0 were above the national safe emission threshold. The morphological structure of EMRs changed after leaching, and XRD analysis showed the disappearance of MnO2, SiO2, FeS2, and CaSO4. The XPS revealed that Cr, Mn, Pb, and Zn existed as Cr3+, MnO, PbSO4, and ZnSiO3, respectively, after leaching. The study concluded that Mn, Pb, and Zn from EMRS leached by acid rain might pose a high potential environmental risk. Therefore, developing appropriate disposal techniques for EMR is necessary to prevent heavy metal pollution.

Pedological data for the study of soils developed over a limestone bed in a humid tropical environment.

Lithological characteristics interact with other factors of soil formation to define soil genesis. This becomes more interesting as data on the mineral and elemental oxide components of soils developed from limestone are rarely available in the humid tropical environment. The present study investigated the elemental oxide content, forms of sesquioxides, and clay mineral species in some limestone soils. Soil samples were obtained from three (3) crestal soil profile pits and analyzed for elemental content by the use of an X-ray fluorescence spectrometer, and sesquioxide forms by inductively coupled plasma-mass spectrometer. Analyses were done in triplicates. The mineralogy of the clay fraction was determined on the A, B, and C horizon samples using an X-ray diffraction technique. The occurrence of SiO2 (203-277 g/kg), Al2O3 (65-105 g/kg), and Fe2O3 (14-95 g/kg) in substantial amounts over MnO2, ZrO2, and TiO2 with negligible quantities of CaO suggested comparatively more developed soils in the Agoi Ibami and Mfamosing tropical rainforests. Crystalline form of Fe was dominant over amorphous form, with indications of the co-migration of dithionite Fe with clay to the B horizons of the soils. Quartz, kaolinite, montmorillonite, and chlorite-vermiculite-montmorillonite interlayered minerals dominated the clay mineralogy of the studied soils. Mineral transformation places the soils at the transitory stage from the intermediate to the complete stage of soil development. The expanding clay minerals are most likely to increase plant nutrient adsorption and soil fertility status to accommodate the cultivation of a wider range of crops.

Iron and manganese mobilisation due to dam height increase for a tropical reservoir in South East Asia.

The aim of this research was the analysis of the effect of a dam height raise on the water quality of a tropical reservoir used for drinking water purposes in South East Asia. Analyses of iron, manganese, pH and ammonia were performed over a 5-year period from daily water sampling at the reservoir. In addition, high-frequency monitoring data of nitrate, ammonium, pH and blue-green algae were obtained using a monitoring probe. The results showed that due to the raising of the reservoir water level, previously oxic sediments became submerged, triggering an increase in iron and manganese in particular due to the establishment of reducing conditions. Manganese concentrations with values up to 4 mg L-1 are now exceeding guideline values. The analysis strongly indicated that both iron and manganese have a seasonal component with higher iron and manganese concentrations during the wet season. Over a three-year period afterwards, concentrations did not go back to pre-raise levels. The change in water quality was accompanied by a change in pH from previous values of around 5 to pH values of around 6.5. Geochemical simulations confirmed the theory that the increasing concentrations of iron and manganese are due to the dissolution of MnO2 and ferric oxyhydroxides oxidising organic matter in the process. This study showed that changes in reservoir water levels with the establishment of reducing conditions can have long-term effects on the water quality of a reservoir.

Community structure of bacterioplankton and its relationship with environmental factors in the upper reaches of the Heihe River in Qinghai Plateau.

Planktonic microorganisms play a key role in the biogeochemical processes of the aquatic system, and they may be affected by many factors. High-throughput sequencing technology was used in this study to investigate and study the bacterioplankton community of water bodies in the upper reaches of the Heihe River Basin in Qinghai Plateau. Results showed that Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria are the predominant phyla in this river section, while the main genera are Thiomonas, Acidibacillus, Acidocella, Rhodanobacter, Acidithiobacter and Gallionella, which are autochthonous in the acid-mine drainage. Additionally, total nitrogen, total phosphorus, permanganate index and pH are significantly correlated with the bacterioplankton abundance and are the main limiting factors for the spatial distribution of the bacterioplankton. PICRUSt inferred that the mainstream microbial assemblages had a higher abundance of KOs belong to metabolism of terpenoids and polyketides, while the tributary had higher abundance of KOs belong to the immune system. The relationship between bacterioplankton community composition and environmental factors in the Heihe River basin was discussed for the first time in this study, which provides a theoretical basis for the healthy, orderly development of the water environment in the Heihe River Basin.

Geothermobacter hydrogeniphilus sp. nov., a mesophilic, iron(III)-reducing bacterium from seafloor/subseafloor environments in the Pacific Ocean, and emended description of the genus Geothermobacter.

A novel mesophilic, anaerobic, mixotrophic bacterium, with designated strains EPR-MT and HR-1, was isolated from a semi-extinct hydrothermal vent at the East Pacific Rise and from an Fe-mat at Lo'ihi Seamount, respectively. The cells were Gram-negative, pleomorphic rods of about 2.0 µm in length and 0.5 µm in width. Strain EPR-MT grew between 25 and 45 °C (optimum, 37.5-40 °C), 10 and 50 g l-1 NaCl (optimum, 15-20 g l-1) and pH 5.5 and 8.6 (optimum, pH 6.4). Strain HR-1 grew between 20 and 45 °C (optimum, 37.5-40 °C), 10 and 50 g l-1 NaCl (optimum, 15-25 g l-1) and pH 5.5 and 8.6 (optimum, pH 6.4). Shortest generation times with H2 as the primary electron donor, CO2 as the carbon source and ferric citrate as terminal electron acceptor were 6.7 and 5.5 h for EPR-MT and HR-1, respectively. Fe(OH)3, MnO2, AsO4 3-, SO4 2-, SeO4 2-, S2O3 2-, S0 and NO3 - were also used as terminal electron acceptors. Acetate, yeast extract, formate, lactate, tryptone and Casamino acids also served as both electron donors and carbon sources. G+C content of the genomic DNA was 59.4 mol% for strain EPR-MT and 59.2 mol% for strain HR-1. Phylogenetic and phylogenomic analyses indicated that both strains were closely related to each other and to Geothermobacter ehrlichii, within the class δ-Proteobacteria (now within the class Desulfuromonadia). Based on phylogenetic and phylogenomic analyses in addition to physiological and biochemical characteristics, both strains were found to represent a novel species within the genus Geothermobacter, for which the name Geothermobacter hydrogeniphilus sp. nov. is proposed. Geothermobacter hydrogeniphilus is represented by type strain EPR-MT (=JCM 32109T=KCTC 15831T=ATCC TSD-173T) and strain HR-1 (=JCM 32110=KCTC 15832).

Bright Mn-doped carbon dots for the determination of permanganate and L-ascorbic acid by a fluorescence on-off-on strategy.

A one-pot hydrothermal synthesis of manganese-doped carbon dots (Mn-CDs) is reported for fluorescent "on-off-on" determination of Mn(VII) and L-ascorbic acid (L-AA) in aqueous solution and living cells. Mn-CDs were prepared by using sulfanilic acid, tetrakis(hydroxymethyl)phosphonium chloride, and Mn(II) chloride as precursors. Mn-CDs were characterized by several spectroscopic methods and microscopic techniques. Mn-CDs show distinctly long fluorescence lifetime (12.39 ± 0.07 ns) and high absolute fluorescence quantum yield (around 37%) with excitation and emission wavelengths of 362 and 500 nm, respectively. Mn-CDs exhibit no significant cytotoxicity to human cervical carcinoma HeLa cells and human embryonic kidney HEK-293T cells at 200 µg mL-1 level after 48 h incubation. The fluorescence of Mn-CDs at 500 nm (excited at 362 nm) is quenched efficiently by Mn(VII) and can be further recovered after the addition of L-AA, resulting in a fluorescent "on-off-on" assay for the determination of Mn(VII) and L-AA. Under optimal experimental conditions, the linear response covers the 3 to 150 µM Mn(VII) concentration range and the 3 to 140 µM L-AA concentration range. This method offers relatively low detection limits of 0.66 µM for Mn(VII) and 0.90 µM for L-AA. This strategy was applied to visual determination of Mn(VII) and L-AA in living HeLa cells with satisfying results. Graphical abstract Schematic presentation of bright Mn-CD-based fluorescence "on-off-on" assay for both Mn(VII) and L-AA. This fluorescent assay possessed low detection limit of 0.66 µM for Mn(VII) and 0.90 µM for L-AA. This strategy was applied for visual determination of Mn(VII) and L-AA in living HeLa cells with satisfying results.

Facile Preparation of Boron and Nitrogen Codoped Green Emission Carbon Quantum Dots for Detection of Permanganate and Captopril.

A hydrothermal strategy for preparing boron and nitrogen codoped carbon quantum dots was studied using the precursors of p-amino salicylic acid, boric acid and ethylene glycol dimethacrylate. The boron and nitrogen codoped carbon quantum dots have high fluorescence intensity, good monodispersity, high stability, superior water solubility, and a fluorescence quantum yield of 19.6%. Their average size is 5 nm. Their maximum excitation and emission wavelengths are 380 and 520 nm, respectively. Permanganate (MnO4-) quenched boron and nitrogen codoped carbon quantum dots fluorescence through inner filter effect and static quenching effects. The linear relation between quenching efficiency and MnO4- concentration ranged from 0.05 to 60 µmol/L with a detection limit of 13 nmol/L. In the presence of captopril, MnO4- was reduced to Mn2+ and the fluorescence of boron and nitrogen codoped carbon quantum dots was recovered. The linear range between recovery and captopril concentration was from 0.1 to 60 µmol/L. The limit of detection was 0.03 µmol/L. The developed method can be employed as a sensitive fluorescence sensing platform for MnO4-. It has been successfully used for captopril detection in mouse plasma.

T1-Mediated Nanosensor for Immunoassay Based on an Activatable MnO2 Nanoassembly.

Current magnetic relaxation switching (MRS) sensors for detection of trace targets in complex samples still suffer from limitations in terms of relatively low sensitivity and poor stability. To meet this challenge, we develop a longitudinal relaxation time (T1)-based nanosensor by using Mn2+ released from the reduction of a MnO2 nanoassembly that can induce the change of T1, and thus can greatly improve the sensitivity and overcome the "hook effect" of conventional MRS. Through the specific interaction between antigen and the antibody-functionalized MnO2 nanoassembly, the T1 signal of Mn2+ released from the nanoassembly is quantitatively determined by the antigen, which allows for highly sensitive and straightforward detection of targets. This approach broadens the applicability of magnetic biosensors and has great potential for applications in early diagnosis of disease biomarkers.

Structure and properties of Co-doped cryptomelane and its enhanced removal of Pb²âº and Cr³âº from wastewater.

Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure spectroscopy, and its performances for removal of Pb(2+) and Cr(3+) from aqueous solutions were investigated. Co doping has a negligible effect on the structure and morphology of cryptomelane but increases the specific surface area and Mn average oxidation state. Mn and Co K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that Co barely affects the atomic coordination environments of Mn, and distances of edge- and corner-sharing Co-Me (MeCo, Mn) pairs are shorter than those of the corresponding Mn-Me pairs, implying the replacement of framework Mn(III) by Co(III). These Co-doped cryptomelanes can quickly oxidize Cr(3+) to be HCrO4(-) and remove 45%-66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb(2+) adsorption capacities. Thus these materials are promising adsorbents for heavy metal remediation. The results demonstrate the design and modification of environmental friendly Mn oxide materials and can help us understand the interaction mechanisms of transition metals with Mn oxides.

Uncovering the origin of the black stains in Lascaux Cave in France.

Lascaux Cave in France was discovered in 1940. Since being opened to visitors the cave has suffered three major microbial outbreaks. The current problem is the fast dissemination of black stains which are threatening the Palaeolithic paintings. Previous data pointed to the involvement of new fungal species in the formation of black stains on the rock walls and ceiling. However, it appears that there could be other reasons for the formation of different and extensive black stains coating the surface of the clayey sediments. Our analyses reveal that black stains on clayey sediments are mainly produced by Acremonium nepalense, a manganese oxide-depositing fungus, widely distributed in the cave. Thus, in Lascaux Cave, the black stains have a dual origin: on limestone rocks they are mainly produced by the accumulation of fungal melanins, and on clayey sediments by the biogenic deposition of black manganese oxides.

Quantification of rapid environmental redox processes with quick-scanning x-ray absorption spectroscopy (Q-XAS).

Quantification of the initial rates of environmental reactions at the mineral/water interface is a fundamental prerequisite to determining reaction mechanisms and contaminant transport modeling and predicting environmental risk. Until recently, experimental techniques with adequate time resolution and elemental sensitivity to measure initial rates of the wide variety of environmental reactions were quite limited. Techniques such as electron paramagnetic resonance and Fourier transform infrared spectroscopies suffer from limited elemental specificity and poor sensitivity to inorganic elements, respectively. Ex situ analysis of batch and stirred-flow systems provides high elemental sensitivity; however, their time resolution is inadequate to characterize rapid environmental reactions. Here we apply quick-scanning x-ray absorption spectroscopy (Q-XAS), at sub-second time-scales, to measure the initial oxidation rate of As(III) to As(V) by hydrous manganese(IV) oxide. Using Q-XAS, As(III) and As(V) concentrations were determined every 0.98 s in batch reactions. The initial apparent As(III) depletion rate constants (t < 30 s) measured with Q-XAS are nearly twice as large as rate constants measured with traditional analytical techniques. Our results demonstrate the importance of developing analytical techniques capable of analyzing environmental reactions on the same time scale as they occur. Given the high sensitivity, elemental specificity, and time resolution of Q-XAS, it has many potential applications. They could include measuring not only redox reactions but also dissolution/precipitation reactions, such as the formation and/or reductive dissolution of Fe(III) (hydr)oxides, solid-phase transformations (i.e., formation of layered-double hydroxide minerals), or almost any other reaction occurring in aqueous media that can be measured using x-ray absorption spectroscopy.

Mesoporous silica-coated hollow manganese oxide nanoparticles as positive T1 contrast agents for labeling and MRI tracking of adipose-derived mesenchymal stem cells.

Mesoporous silica-coated hollow manganese oxide (HMnO@mSiO(2)) nanoparticles were developed as a novel T(1) magnetic resonance imaging (MRI) contrast agent. We hypothesized that the mesoporous structure of the nanoparticle shell enables optimal access of water molecules to the magnetic core, and consequently, an effective longitudinal (R(1)) relaxation enhancement of water protons, which value was measured to be 0.99 (mM(-1)s(-1)) at 11.7 T. Adipose-derived mesenchymal stem cells (MSCs) were efficiently labeled using electroporation, with much shorter T(1) values as compared to direct incubation without electroporation, which was also evidenced by signal enhancement on T(1)-weighted MR images in vitro. Intracranial grafting of HMnO@mSiO(2)-labeled MSCs enabled serial MR monitoring of cell transplants over 14 days. These novel nanoparticles may extend the arsenal of currently available nanoparticle MR contrast agents by providing positive contrast on T(1)-weighted images at high magnetic field strengths.

Arsenic-enriched groundwaters of India, Bangladesh and Taiwan--comparison of hydrochemical characteristics and mobility constraints.

Arsenic (As) enrichment in groundwater has become a major global environmental disaster. Groundwater samples were collected from 64 sites located in the districts of 24-Parganas (S), and Nadia in West Bengal, India (Bhagirathi sub-basin), and 51 sites located in the districts of Comilla, Noakhali, Magura, Brahman baria, Laxmipur, Munshiganj, Faridpur and Jhenaida in Bangladesh (Padma-Meghna sub-basin). Groundwater samples were also collected from two As-affected areas (Chianan and Lanyang plains) of Taiwan (n = 26). The concentrations of major solutes in groundwater of the Padma-Meghna sub-basin are more variable than the Bhagirathi sub-basin, suggesting variations in the depositional and hydrological settings. Arsenic concentrations in groundwaters of the studied areas showed large variations, with mean As concentrations of 125 µg/L (range: 0.20 to 1,301 µg/L) in Bhagirathi sub-basin, 145 µg/L (range: 0.20 to 891 µg/L) in Padma-Meghna sub-basin, 209 µg/L (range: 1.3 to 575 µg/L) in Chianan plain, and 102 µg/L (range: 2.5 to 348 µg/L) in Lanyang plain groundwater. The concentrations of Fe, and Mn are also highly variable, and are mostly above the WHO-recommended guideline values and local (Indian and Bangladeshi) drinking water standard. Piper plot shows that groundwaters of both Bhagirathi and Padma-Meghna sub-basins are of Ca-HCO(3) type. The Chianan plain groundwaters are of Na-Cl type, suggesting seawater intrusion, whereas Lanyang plain groundwaters are mostly of Na-HCO(3) type. The study shows that reductive dissolution of Fe(III)-oxyhydroxides is the dominant geochemical process releasing As from sediment to groundwater in all studied areas.

Medium optimization for production of gamma-aminobutyric acid by Lactobacillus brevis NCL912.

Production of gamma-aminobutyric acid (GABA) was carried out in Erlenmeyer flasks by Lactobacillus brevis NCL912. Traditional methods were first adopted to select the key factors that impact the GABA production to preliminarily determine the suitable concentration ranges of the key factors. It was found that glucose, soya peptone, Tween-80 and MnSO(4).4H(2)O were the key factors affecting GABA production. Then, response surface methodology was applied to analyze the optimum contents of the four key factors in the medium, and the production of GABA was predicted as 349.69 mM under the optimized conditions with this model. Afterward, the experiment was performed under the optimized conditions, and the yield of GABA reached 345.83 mM, which was 130% higher than the initial medium. The results showed that experimental yield and predicted values of GABA yield were in good agreement.

Manganese bioconcentration in aquatic insects: Mn oxide coatings, molting loss, and Mn(II) thiol scavenging.

Streams below mountaintop removal-valley fill coal mining operations often have elevated Mn concentrations, but it remains unclear if Mn plays a role in biodiversity reduction. We examined various aspects of aqueous Mn interactions with aquatic insects exposed to environmentally relevant Mn concentrations, revealing complex behavior. First, Mn accumulation rates varied widely among 9 species. A significant percentage of total Mn accrued (mean 74%, range 24-95%) was associated with the cuticle, predominantly in the form of Mn-oxides, and to a lesser degree Mn(II). Mn II is also absorbed into tissues, possibly through calcium transporters. Increased ambient calcium concentrations decreased both adsorbed and absorbed Mn accumulation from solution. Though species showed similar Mn efflux rate constants (0.032-0.072 d(-1)), the primary mode of Mn loss was through molting. Both adsorbed and absorbed Mn is lost during the molt. Subcellular compartmentalization studies revealed an overwhelming tendency for internalized Mn to associate with the heat stable cytosolic protein fraction. After short dissolved Mn exposures, intracellular glutathione and cysteine levels were markedly reduced relative to controls. These findings suggest that Mn exposure results in transient physiological stress in aquatic insects which is likely relieved, in part, during the molting process.

Inhalation of an essential metal: development of reference exposure levels for manganese.

Exposures to high levels of manganese by ingestion or inhalation can damage the central nervous system. However, the capacity of environmental manganese to cause neurotoxicity is of most concern following inhalation exposure. Reference exposure levels (RELs) are values developed by California EPA's Office of Environmental Health Hazard Assessment (OEHHA) to protect the general public from periodic and continual exposures to airborne toxicants. The recently revised guidelines for the development of noncancer RELs encourage the use of benchmark dose methodology where appropriate, and explicitly address the potential susceptibilities associated with early-life exposures (OEHHA, 2008). This paper describes the application of those guidelines to the derivation of RELs to protect the general public from routine 8h and chronic exposures to airborne manganese. The data were amenable to benchmark analysis and the RELs derived reflect the mounting evidence that children represent a population that is differentially susceptible to manganese toxicity.

Degradation kinetics and estrogenic activity of 17beta-estradiol removal by aqueous manganese dioxide.

Natural and synthetic hormones have emerged as a new group of contaminants in soil and water systems. To better understand the processes affecting these compounds in soils and sediments, the kinetics of 17beta-estradiol (E2) transformation by hydrous manganese oxide (delta-MnO(2) were investigated as a function of reactant concentration, MnO(2) concentration, pH and the presence of co-solutes. The reaction of E2 degradation by delta-MnO(2) did not exhibit simple pseudo-first-order kinetics, although a good linear fit (R(2) = 0.97) was obtained during the first 30 min, which was indicative of pseudo-first-order reaction kinetics in the first stage. The initial reaction rate (r(init)) values of E2 degradation were enhanced with increasing E2, MnO(2) and H(+) concentration. The reaction orders for E2, MnO(2) and H(+) concentrations were 0.80, 0.72 and 0.07, respectively. The presence of metal ions and carboxylic acids had an inhibitory effect on r(init) as a result of the decreased number of active surface sites in the presence of co-solutes. The same inhibitory effect on r(init) was also observed in wastewater. Furthermore, the results showed that delta-MnO(2) not only degraded E2 but also removed 62% and 48% of the estrogenic activity originating from E2 in ultrapure water and wastewater, respectively. This study demonstrated that natural manganese oxides in soils and sediments are likely to promote appreciable degradation of E2, and that reaction rates are strongly dependent on solution conditions. However, a combination of methods should be adopted in order to completely remove the estrogenic activity of E2.

Enhanced mineralization of 2,4-dichlorophenol by ozone in the presence of trace permanganate: effect of pH.

Ozonation of 2,4-dichlorophenol (DCP) in the presence of permanganate has been investigated at various levels of pH. Compared with only 40% in single ozonation, by catalytic ozonation the total organic carbon removal efficiency reached almost 95%. It has been shown that the addition of 0.5 mg L(-1) MnO4- (based on manganese content) greatly accelerated the mineralization of DCP when the initial pH was below 8.5. Under these conditions MnO4- was reduced to Mn2+, which enabled homogeneous catalysis to take place. When the initial pH was above 10.1, the MnO4- was reduced to MnO2, which did not promote mineralization of DCP by ozone under either neutral or alkaline conditions. Under acidic conditions, however, the addition of MnO2 greatly enhanced DCP mineralization, the mechanism being that MnO2 was reduced to Mn2+ which is a highly effective homogeneous catalyst for ozonation.

Catalytic removal of toluene over manganese oxide-based catalysts: a review.

It is necessary to control the emissions of toluene, which is hazardous to both human health and the atmosphere environment and has been classified as a priority pollutant. Manganese oxide-based (Mn-based) catalysts have received increased attention due to their high catalytic performance, good physicochemical characteristic, availability in various crystal structures and morphologies, and being environmentally friendly and low cost. These catalysts can be classified into five categories, namely single manganese oxide, Mn-based composite oxides, Mn-based special oxides, supported Mn-based oxides, and Mn-based monoliths. This review focused on the recent progress on the five types of Mn-based catalysts for catalytic removal of toluene at low temperature and further systematically summarized the strategies improving catalysts, including improving synthetic methods, incorporating MnOx with other metal oxides, depositing Mn-based oxides on proper supports, and tuning the supports. Moreover, the effect of coexisting components, the reaction kinetics, and the oxidation mechanisms toward the removal of toluene were also discussed. Finally, the future research direction of this field was presented.

Safranin O-functionalized cuboid mesoporous silica material for fluorescent sensing and adsorption of permanganate.

Incorporation of dual functions, i.e., sensing and adsorption, into one single organic-inorganic hybrid material for the detection and removal of toxic permanganate (MnO4-) ions is of great importance, representing a challenging and new task in the design and application of new functional materials. However, most of the reported materials display only one function as either sensing probes or adsorbents. In this work, a fluorescent cuboid mesoporous silica-based hybrid material (SiO2@SFNO) is first prepared by the covalent coupling of a new safranin O-based fluorophore (2,8-dimethyl-5-phenyl-3,7-bis(3-(3-(triethoxysilyl)propyl)ureido)phenazin-5-ium chloride) (SFNO) and newly-made cuboid mesoporous silica, which showed selective dual-functional activities towards MnO4- and green emission at 575 nm with a long-range excitation wavelength that is suitable for bio-imaging application. The design of this SiO2@SFNO material is based on the position of -NHCONH- groups, which are mainly responsible for the strong and selective coordination with MnO4-. SiO2@SFNO is responsive to MnO4- at parts per billion (67 ppb) level; it also displays high adsorption ability (292 mg g-1) to MnO4- in aqueous solutions. The fluorescence responses of MnO4-in vivo (limnodrilus claparedianus and zebrafish) demonstrate the possibility of further application in biology. Interestingly, this SiO2@SFNO material is also capable of monitoring trace amounts of Hg2+ and Cu2+ in living organisms, holding great potential in bio-related applications.