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CuO was synthesized by a simple hydrothermal method and investigated as a heterogeneous activator of persulfate for the degradation of cephalexin and ofloxacin. X-ray photo-electron spectroscopy and hydrogen temperature-programmed reduction measurements reveal that CuO contains two types of Cu2+: one has more electron deficiency (named as Cu2+-h) and the other has relatively higher electron density (named as Cu2+-l). Electron paramagnetic resonance and radical scavenging experiments demonstrate that ·SO4− and ·O2− are responsible for the efficient degradation of cephalexin and ofloxacin, respectively. ·SO4− can be produced through the electron transfer from Cu2+-l to PS and the cleavage of peroxy bond, while ·O2− can be produced via the electron transfer from PS to Cu2+-h and the cleavage of S–O bond. Finally, the degradation intermediates were identified by liquid chromatograph–mass spectrometry. This study proposed a novel mechanism for the activation of persulfate with CuO, which is useful for the rational design of persulfate activator for controlling the production of active species.

Ag/NiOx-MnO2 was synthesized by redox and deposition-precipitation methods and its catalytic performance for o-xylene oxidation was investigated. It exhibited higher activity than NiOx-MnO2 and OMS-2. The T20, T50 and T100 values were 72, 145 and 190 °C, respectively (500 ppm o-xylene/humid air, GHSV = 6000 h−1). Moreover, it showed excellent water-resistance and stability, demonstrating its potential for practical application. Characterization results revealed that the introduction of Ni and Ag increased the catalyst reducibility, the amount of electrophilic oxygen species, and the ability for oxygen molecules activation, resulting in the superior performance at low temperatures. In situ DRIFT study indicated that aromatic ring could be directly oxidized into maleate by the electrophilic lattice oxygen of Ag/NiOx-MnO2 in the absence of oxygen molecules, and the formed maleate could be oxidized into formate and/or carbonate in the presence of oxygen molecules. Finally, the possible degradation pathway of o-xylene in the presence or absence gaseous oxygen was discussed.

A defective KR-OMS-2 catalyst was prepared by refluxing an OMS-2 precursor in KOH solution and investigated for the deep oxidation of o-xylene. The activity test results showed that the T100, T50 and T20 over KR-OMS-2 were 160, 146 and 132 °C, respectively, which were 20, 16 and 20 °C lower than that over unmodified OMS-2 (500 ppm o-xylene/air, W/F = 0.6 g s mL−1). The characterization results demonstrated the generation of Mn vacancies (VMn). K+ anchored to nearby VMn for charge balance and formed bonds with lattice oxygen, which deformed the OMS-2 structure and generated additional surface OH groups. As a result, surface active oxygen species increased, and the low-temperature reducibility of the catalyst and the replenishment capacity of molecular oxygen were improved. Moreover, the surface acid-base properties were modified to improve the desorption of carboxylate intermediates. In situ DRIFTS revealed that the synergistic effect of surface oxygen species and surface OH groups first induced the oxidation of aromatic rings to produce maleate. Then, gaseous oxygen formed highly-active oxygen species, oxidizing maleate to formate, and finally CO2 and H2O. This reaction pathway was more efficient. This study provides a useful method for BTX catalytic oxidation at low temperatures.

CuO is an efficient catalyst for persulfate (PS) activation. However, the leaching of Cu ions is usually serious and the improvement of CuO stability is highly desired for its practical application. Herein, CuO supported on Mg Al layered double hydroxide (LDH) and CuO-LDH composite were synthesized by two-step precipitation and co-precipitation methods, respectively. The leaching of Cu ions was avoided due to the high alkalinity and buffer capacity of LDH. CuO supported on LDH had larger surface area, higher alkalinity and more exposed CuO, thus exhibiting much higher activity than CuO-LDH composite. The sample with the Cu:Mg ratio of 1:1 (Cu4/LDH) exhibited the highest activity and could remove more than 99% of ciprofloxacin within 30 min at pH 4–10. The removal efficiency was still above 94% in the presence of various coexisting substances. Moreover, it showed good stability and reusability. Activated PS generated via the non-radical pathway and SO4−• generated via the radical pathway were the dominant reactive species for ciprofloxacin degradation. The results indicate that Cu4/LDH is a promising catalyst for the removal of organic pollutants with PS activation.

Ag or Cu doped manganese oxide octahedral molecular sieve (OMS-2) was prepared through the one-step reduction of KMnO 4 , Tollens’ reagent, or Fehling’ reagent with propionaldehyde. The influences of the dopants on the structure, redox ability and catalytic performance of OMS-2 were investigated. The results indicate that Ag-OMS-2 and Cu-OMS-2 exhibited relatively higher catalytic activity for o -xylene oxidation at higher (>185 °C) and lower temperatures (≤185 °C), respectively. This can be illustrated as follows. The doped Ag increased the content of surface absorbed oxygen and inhibited the adsorption of CO 2 . The doped Cu increased the content of lattice oxygen and the surface area of OMS-2, but increased its adsorption capacity toward CO 2 . In situ DRIFT study demonstrates that the oxidation of low molecular weight carboxylates (the stable intermediates in the oxidation of o -xylene) is the rate-determining step, which is closely related with the active oxygen species. The doped Ag increased the content of electrophilic oxygen (O 2 − , O − or O 2 2− ) and promoted the transformation of O 2 into nucleophilic oxygen (O 2− ), which facilitated the oxidation of benzene ring and small molecule carboxylate, respectively.

Amorphous Fe-Zn-oxide/hydrochar was prepared by a hydrothermal method and used as a heterogeneous photo-Fenton catalyst. The catalyst exhibited excellent activity for the degradation of various organic pollutants including Rhodamine B (RhB), methylene blue, antipyrine, and phenol at near neutral pH in the simultaneous presence of H 2 O 2 and visible light irradiation. The influences of pH on the degradation and adsorption of pollutants, and the formation of hydroxyl radical ( OH) were investigated. Meanwhile, the roles of surface Fe 2+ , dye photosensitization, OH, and photogenerated electrons in this photo-Fenton process were explored. The results indicate that the photogenerated electrons could accelerate the regeneration of surface Fe 2+ and the formation of OH. It was found that phenol was mostly degraded by OH in solution. Different from phenol, the degradation of RhB at pH 6.5 was mainly due to the reaction of excited RhB∗ with H 2 O 2 , while the contribution of OH increased significantly with decreasing pH. This study suggests the potential application of amorphous metal oxides/carbonaceous materials in catalytic degradation of organic pollutants.

Non-radical activation of persulfate (PS) is a promising technology for removing organic pollutants in water because of the higher selectivity and stability of activated PS than radicals. Hence, the development of effective catalyst for PS non-radical activation is highly desired. In this work, a series of Mn doped CuO samples were prepared and used for removing ofloxacin with PS activation. The correlation between their surface properties and catalytic performance was studied, and the key parameter affecting pollutant degradation was explored. The result indicates that the CM3 sample (Cu:Mn = 6:1) exhibited the highest activity for ofloxacin degradation at neutral pH due to its high adsorption capacity towards ofloxacin and high activity for non-radical activation of PS, which is beneficial for their surface reaction. The large surface area and uncharged surface of CM3 at neutral pH facilitate the adsorption of ofloxacin, while its surface Cu2+ with less electron deficiency might be responsible for the production of activated PS. Because ofloxacin was mainly degraded by the activated PS, the common ions in real water had little effect on this process. The toxicity assessment indicates that the treated ofloxacin solution was harmless. Finally, the reusability experiment demonstrates that CM3 is a stable and effective catalyst for non-radical activation of PS.

Amorphous silica–zirconium (SZx) has been synthesized via the sol–gel method accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). Herein x is the mol% of zirconium (Zr), i.e. 0, 1.5, 2.8, 5.6 and 8.9 mol%, respectively. 13% wt% cobalt-based SZx (Co/SZx) catalysts were prepared by an impregnation method. The Co/SZ catalysts were characterized by XRD, N2 adsorption–desorption, ESEM, H2-TPR and NH3-TPD. The catalytic behavior of Co/SZx was investigated for the Fischer–Tropsch (FT) reaction via a fixed-bed reactor under the conditions of 1.0 MPa, H2/CO = 2, W/F = 5.05 g h mol−1 and 235 °C. The results indicated that CO conversion followed the order of Co/SZ2.8 > Co/SZ1.5 > Co/SZ0 > Co/SZ5.6% > Co/SZ8.9. The activity differences for FT synthesis are mainly ascribed to the differences in SZx such as Zr dosage, pore structure and aggregation extent, which are also the direct reasons for the various Co dispersions on SZx. The existence of Zr in the Co/SZ catalysts leads to a decrement of the selectivity to CO2/C5+, and an increase of C2–C4 selectivity and N-p/O value. Overall, the Co/SZ2.8 catalyst exhibited the top FT reaction activity, top yield of C5+ and lowest selectivity to methane and C2–C4 among all the Co/SZ catalysts.

Er(3+)-singly doped and Er(3+)/Yb(3+)-codoped 50SiO2-(50-x)BaF2-xZnF2(SBZx) oxyfluoride glasses are prepared and the optical properties of Er(3+)-singly doped glasses are investigated by using the Judd-Ofelt theory. Bright green and red upconversion luminescence of Er(3+)/Yb(3+)-codoped glasses is obtained under 980nm excitation. Furthermore, factors affecting this phenomenon such as glass composition, doping concentration of Er(3+) and Yb(3+) ions, and pump power are discussed in details.

Manganese oxide supported on mesoporous ceria was prepared and used as catalyst for catalytic ozonation of sulfosalicylic acid (SA). Characterization results indicated that the manganese oxide was mostly incorporated into the pores of ceria. The synthesized catalyst exhibited high activity and stability for the mineralization of SA in aqueous solution by ozone, and more than 95% of total organic carbon was removed in 30 min under various conditions. Mechanism studies indicated that SA was mainly degraded by ozone molecules, and hydroxyl radical reaction played an important role for the degradation of its ozonation products (small molecular organic acids). The manganese oxide in the pores of CeO2 improved the adsorption of small molecular organic acids and the generation of hydroxyl radicals from ozone decomposition, resulting in high TOC removal efficiency.

In this work, FeCo2O4 was prepared by a simple coprecipitation method and investigated as a heterogeneous Fenton catalyst. The influences of sodium dodecyl sulfate (SDS) on the structure, surface charge, electron transfer ability, and catalytic activity of FeCo2O4 were investigated. FeCo2O4–S prepared with SDS exhibited much higher catalytic activity for the degradation of methylene blue (MB) in aqueous solution than pure FeCo2O4, which can be attributed to its higher electron transfer ability. The adsorbed SDS accelerated the reduction of surface Fe3+ to Fe2+ by H2O2 and •O2–. The high concentration of surface Fe2+ on FeCo2O4–S during the reaction promoted the decomposition of H2O2 into •OH, which was the main active specie for the degradation of MB. Furthermore, SDS increased the adsorption capacity of the catalyst toward MB, thus facilitating the reaction between adsorbed MB and •OH generated on the catalyst surface.

Manganese oxide supported on titanate nanotubes (TNT) was prepared by an impregnation method and used as a catalyst for ozonation of p-nitrophenol (PNP) in an aqueous solution. Characterization results indicated that the manganese oxide was highly dispersed on the surface of TNT. The synthesized catalyst exhibited high activity for the mineralization of PNP with ozone, and about 95% of the total organic carbon was removed at 45 min. The degradation of PNP was mainly due to the oxidative process in solution, and the hydroxyl radical reaction played an important role for the degradation of its ozonation products (formic acid and oxalic acid). The negatively charged surface and surface acid sites of the support favored the adsorption of ozone, while the highly dispersed MnOx accelerated the decomposition of adsorbed ozone into hydroxyl radicals. A possible mechanism for the catalytic ozonation of PNP was proposed.

MnO 2 materials with various structures and morphologies were prepared using KMnO 4 , and n-, i-, and t-butylamine (the 3 isomers of butylamine, that is, respectively, normal butylamine, isobutylamine and tert-butylamine) as precursors at the dichloromethane/water interface without any template. The relationship between the structure and morphology of the products and the polarity and steric hindrance of butylamine precursor was investigated by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the products synthesized by KMnO 4 /n-, i-,t-butylamine (the corresponding products were denoted as MnO 2 -n, MnO 2 -i and MnO 2 -t, respectively) were quasi-quadrangular α-MnO 2 , a mixture of α-MnO 2 and δ-MnO 2 with irregular structure and nano-spheres δ-MnO 2 , respectively. Nitrogen adsorption analysis showed that MnO 2 -n and MnO 2 -i had a mesoporous structure, while MnO 2 -t exhibited a macroporous structure. Their surface areas were calculated to be about 185, 65, and 15 m 2 g −1 correspondingly. In addition the obtained materials showed different catalytic abilities for the complete catalytic oxidation of a typical volatile organic compound (VOC), o -xylene.

CuO synthesized by a hydrothermal method was used to activate persulfate (PS) for removing ciprofloxacin (CIP) in water. The influences of reaction parameters and coexisting substances on this process were studied. Under the optimal conditions ([CuO]0 = 6.3 mmol L−1, [PS]0 = 1 mmol L−1, pH 8), CIP was completely degraded and the total organic carbon removal efficiency was 84.2%. Ca2+, Mg2+ and Cl− had little effect on CIP removal, while fulvic acid showed a slight inhibitory effect. By contrast, bicarbonate enhanced CIP degradation and significantly suppressed Cu leaching. Subsequently, the reactive species for CIP degradation were identified by electron paramagnetic resonance and radical scavenging experiments. Although the decomposition efficiency of PS was significantly accelerated by increasing pH, similar amounts of O2−, OH, SO4− and 1O2 were detected at different pH, suggesting the formation of more surface activated PS at higher pH. The reactive species for CIP degradation were found to be dependent on solution pH. CIP was mainly degraded by SO4− and 1O2 at acidic conditions. The activated PS might have high selectivity towards CIP and its amount might be higher than that of radicals at pH 8. In addition, the uncharged surface of CuO at pH 8 facilitated the adsorption of CIP, which is beneficial to the surface reaction between CIP and activated PS. Hence, the activated PS was the dominated species for CIP degradation at this pH.

Lignosulfonate modified titanate tubes (L-TNTs) were synthesized by a hydrothermal method. The influences of lignosulfonate on the structure and adsorption capacity of the product were investigated. The characterization results indicate that L-TNTs are layered titanates (NaxH2−xTi3O7·nH2O) with mesoporous structure, and the doped lignosulfonate increases the axial ratio and layer spacing of TNTs. The maximal adsorption capacities of L-TNTs are 740, 148 and 223 mg g−1 for Pb2+, Cu2+ and Cd2+, respectively, which are higher than those of TNTs. The results demonstrate that the lignosulfanate-assistant hydrothermal method is promising for improving the adsorption capacity of nanomaterial toward heavy metal ions.

Mesoporous composite metal oxides were prepared by an oxidation–precipitation method. The characterization studies indicated that the structure and surface property of the products could be controlled through simple manipulation of precursor composition. The activity of the synthesized catalysts for ozonation of p-nitrophenol (PNP) in aqueous solution was investigated. It was found that the negatively charged surface enhanced the adsorption and decomposition of ozone, but inhibited the adsorption of organic intermediates. This heterogeneous catalytic ozonation process should mainly follow a mechanism of surface reactions involving adsorbed ozone and organic molecules. Mn–Co–Fe exhibited the highest catalytic activity and stability for the mineralization of PNP due to its proper adsorption capacities for ozone and organic intermediates, which facilitated the surface reactions.

Mesoporous α -MnO 2 and β -MnO 2 were prepared using KMnO 4 and H 2 C 2 O 4 (Oxalate) as precursors via aqueous and hydrothermal routes respectively. The morphological and structural evolution of the MnO 2 materials were tracked by Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The preparation of MnO 2 materials was found to proceed through four steps: well-crystallized α -MnO 2 was formed first in aqueous solution, and then translated into microcrystalline α -MnO 2 microspheres consisting of nanoparticles and nanowires via a dissolution-recrystallization process. Subsequently, the microcrystalline α -MnO 2 microspheres collapsed, and γ -MnOOH nanowires were formed. Finally, β -MnO 2 nanowires were obtained after calcining the γ-MnOOH nanowires in air at 400 °C for 6 h. During the process, oxalate acted as an important reagent and played an important role for the structural and morphological evolution of MnO 2 . Nitrogen sorption analysis showed that the as-prepared α -MnO 2 and β -MnO 2 materials all exhibited type IV isotherms, indicating mesoporous characters. In addition, the performance of the MnO 2 materials as a catalyst was evaluated in the complete catalytic oxidation of a typical volatile organic compound (VOCs), o -xylene.

Optical properties of Tm3+-doped SiO2–BaF2–ZnF2 glasses have been investigated on the basis of the Judd–Ofelt theory. Judd–Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Tm3+/Yb3+-codoped SiO2–BaF2–ZnF2 glasses under 980 nm excitation. The effects of composition, concentration of the doping ions, temperature, and excitation pump power on the upconversion emissions were also systematically studied.

P-doped cryptomelane-type manganese oxide K-OMS-2 materials with three-dimensional structures were easily prepared using KMnO 4 and MnPO 4 as precursors via hydrothermal route. The scanning electron microscopy (SEM) and Energy dispersive X-ray spectra (EDS) results revealed that the morphology of P-doped K-OMS-2 transformed from hierarchical microspheres assembled from nanosheets and nanoneedles to nest-like structure with the increase of P/Mn molar ratio. Nitrogen sorption analysis showed that the isotherms of P-doped K-OMS-2 materials were typically type-IV with hysteresis loops, which meant that the samples had a mesoporous structure. The surface area and average pore diameter of the as-prepared K-OMS-2 materials were 138–153 m 2 g −1 and 18–56 nm respectively. In addition, the obtained materials showed good catalytic ability for the catalytic oxidation of a typical volatile organic compound (VOCs), o -xylene.

Magnetic core–shell nanocomposites were synthesized by an economical and environmentally friendly method. The shell materials with the desired composition can be obtained through simple manipulation of precursor adsorption, which can modify their performance for water treatment. The composite containing appropriate amounts of Fe, Mn, and Co oxides exhibits excellent adsorption capability and catalytic activity for removing heavy metal ions and organic pollutants in water. The results suggest that the chemical modification of the shell material is promising for the optimization of pollutants removal by core–shell nanocomposites.

Manganese oxide octahedral molecular sieve (OMS-2) with different microstructures were synthesized via simple wet chemical methods of KMnO4/benzyl alcohol and KMnO4/Mn(NO3)2 at room-temperature (the products were denoted as B-OMS-2 and N-OMS-2, respectively). The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene. It was found that B-OMS-2 presented a loose structure, and contained almost 100% Mn4+, while N-OMS-2 possessed a mixture of Mn4+ and Mn3+. H2-TPR and O2-TPO analyses showed that B-OMS-2 exhibited good low-temperature reducibility and high oxygen exchange ability with gas phase oxygen. The microstructure difference was caused by different reducing reagents used in the synthesis. Benzyl alcohol might adsorb on the surface of MnO2 nuclei acting as a ligand and/or structure-directing agent, and the desorption of the organic compound led to the formation of bulk oxygen vacancy in B-OMS-2. B-OMS-2 could convert 100% o-xylene into CO2 at 190 °C at a space velocity of 8000 h−1, 50 °C lower than N-OMS-2. The excellent catalytic performance of B-OMS-2 might be caused by its bulk oxygen vacancy, potent reducibility and high re-oxidation ability. It is believed that B-OMS-2 is a promising catalyst for the elimination of VOCs from air.

Highlights: ► Uniform mesoporous β-Ni(OH){sub 2} and NiO nanospheres with hierarchical structures were synthesized by a simple complexation–precipitation method. ► Both ammonia and citrate played an important role for the formation of mesoporous nanospheres. ► β-Ni(OH){sub 2} and NiO nanospheres showed excellent capacitive properties due to their mesoporous structures and larger surface areas. -- Abstract: Uniform mesoporous β-Ni(OH){sub 2} and NiO nanospheres with hierarchical structures were synthesized by a facile complexation–precipitation method. The effects of ammonia and citrate on the structure and morphology of the products were thoroughly investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements. The results indicated that ammonia played an important role for the formation of flowerlike spheres assembled from nanosheets. The addition of citrate could remarkably reduce the particle sizes and increase the specific surface areas of flowerlike spheres. A possible formation mechanism based on the experimental results was proposed to understand their growing procedures. β-Ni(OH){sub 2} and NiO nanospheres prepared with the addition of citrate showed excellent capacitive properties due to their mesoporous structures and large surface areas, suggesting the importance of controlled synthesis of hierarchical nanostructures for their applications.

Nickel hydroxide mesoporous structures are synthesized by a simple method in the presence of different additives (oxalic acid, aminoacetic acid, and sulfosalicylic acid). Structural characterizations reveal that the additives can affect the crystal structure, increase the specific surface area, and reduce the pore size of the products. The electrochemical properties of the synthesized Ni(OH)2 samples are dependent on their crystal phase, surface area, and pore size distribution. Mesoporous β-Ni(OH)2 with poor crystallinity shows high specific capacitances at different current densities and excellent cycling ability. A highest specific capacitance of 1,693 F g−1 can be achieved at a scan rate of 5 mV s−1. The results suggest its potential application in electrochemical supercapacitors.

Various MnO2 structures have been synthesized in this study by a facile method through the manipulation of KMnO4 concentration. The effect of KMnO4 concentration on the structure and morphology has been thoroughly investigated by X-ray powder diffraction, field-emission scanning electron microscopy, and nitrogen adsorption–desorption measurements. Birnessite-type MnO2 flower-like microsphere can be obtained at a lower concentration, while α-MnO2 nanorods can be obtained at a higher concentration. By increasing the KMnO4 concentration further, α-MnO2 nanorods can assemble into urchin-like microspheres and spherical aggregates. The possible formation mechanism based on the experimental results has been proposed to understand their growth procedures. The electrochemical properties of the synthesized materials evaluated by cyclic voltammetry and constant-current charge–discharge cycling techniques are dependent on their pore size distribution and nanostructures. Birnessite-type MnO2 microsphere showed excellent capacitive behavior with a maximum specific capacitance of 185 F g−1.

A series of alkali metal doped natural manganese ore (NMO) catalysts were prepared by an impregnation method, and tested for the complete catalytic oxidation of o -xylene. The effects of alkali metal on the catalytic performance and structural properties of NMO were examined. Alkali metals were found to enhance the activity of NMO in the following order: Li o -xylene (0.055 vol.%) into CO 2 and H 2 O at 240 °C, which was 60 °C lower than that of NMO. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) measurements revealed that the primary component of NMO and NMO-K-0.07 were MnO 2. It was found that K 2 O was highly dispersed onto the NMO surface. The addition of K 2 O did not increase the BET surface area of the NMO. However, it resulted in the binding energy of the Mn 2p of NMO-K-0.07 shifted to a lower value. The results suggested that alkali metals act as electronic promoters, indicating that alkali metal doped NMO are promising catalyst candidates for the catalytic oxidation of VOCs.

A magnetic core/shell Fe3O4/FeMnOx catalyst was prepared by a simple oxidation–precipitation method. The catalyst was characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. The characterization studies verified that Fe3O4 core was coated with a layer of Fe–Mn oxide. The Fe3O4/FeMnOx was found to be an effective and stable heterogeneous catalyst for the discoloration of methylene blue (MB) in aqueous solution by H2O2. The high catalytic activity is due to the FeMnOx shell, which not only increased the surface hydroxyl groups, but also enhanced the interfacial electron transfer. The discoloration of MB could be due to the decomposition of H2O2 into OH and the adsorption of MB on Fe3O4/FeMnOx.

A series of Mn–Ce oxides were prepared using a redox-precipitation method and the complete catalytic oxidation of o -xylene was examined. Catalytic activity was evaluated in terms of both o -xylene conversion and CO 2 yield. The effects of the Mn at /Ce at atomic ratio and calcination temperature on the features of catalyst structure and catalytic behavior were examined. When the Mn at /Ce at ratio was 1.5 and the catalyst was calcined at 400 °C, the conversion of o -xylene was 100% and the CO 2 yield was 100% at 240 °C. X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature-programmed reduction (H 2 -TPR) studies revealed that the catalysts prepared via the redox-precipitation method possessed a homogenous dispersion of amorphous MnO 2 and CeO 2 nanoparticles; in the main active phase, MnO 2 provided available oxygen species and CeO 2 enhanced oxygen mobility. The synergistic effects between MnO 2 and CeO 2 potentiated the catalytic activity necessary for the complete catalytic oxidation of o -xylene.

The effects of the presence of α-MnO 2 , β-MnO 2 and δ-MnO 2 on the photocatalytic degradation of phenol by TiO 2 and ZnO have been investigated. Experiments were conducted in a batch reactor, at initial pH 6.0 and 25°C. The results showed that the TiO 2 -Photocatalytic degradation of phenol was inhibited completely in the first 20-60 min in the presence of three crystal types of MnO 2 whereas the ZnO-photocatalytic degradation of phenol only declined slightly. UV-vis diffuse reflectance spectroscopy (DRS) and surface photovoltage spectroscopy (SPS) analysis implied that the interaction of MnO 2 with TiO 2 and ZnO could change the energetic of these two photocatalysts.

Mn–Co oxide hierarchical structure assembled from nanosheets was prepared by a simple method. The structure, surface property and adsorption capacity of the product were investigated. The characterization results confirm that the Co ions are incorporated into the structure of MnO 2 . In comparison with MnO 2 , the obtained composite oxide has a more highly negatively charged surface in aqueous solution, thus enhancing its adsorption capacity for heavy metal ions. The maximal adsorption capacities of Mn–Co oxide are 656 and 762 mg g −1 for Pb 2+ and Cu 2+ , respectively. The results demonstrate that the Mn–Co oxide is a promising adsorbent for the removal of heavy metals from aqueous solution.

Mesoporous α-MnO2 nanorods were easily prepared using KMnO4 and MnCO3 as precursors via hydrothermal route without any template. The transmission electron microscopy (TEM) observations revealed that the obtained α-MnO2 had three-dimensional frameworks. Nitrogen sorption analysis showed that the α-MnO2 nanorods exhibited a type IV isotherm, indicating a mesoporous character with adsorption average pore diameter of 18.0 nm, mesoporous volume of 0.16 cm3 g−1, and Brunauer–Emmett–Teller specific surface area of 176 m2 g−1. The obtained nanorods showed superior catalytic ability for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene, which can be due to its mesoporous structure and large surface area.

The development of efficient magnetic adsorbents is highly desirable for water treatment. In this work, MnFe2O4 and Fe3O4 were prepared by a lignosulfonate-assisted hydrothermal method. The structure, surface property and adsorption capacity of the products were investigated. The obtained products have a small amount of carbonaceous materials, mesoporous structure and narrow pore size distribution. In comparison with the samples prepared without lignosulfonate, they have more surface hydroxyl groups and highly negatively charged surface in aqueous solution, which favor the adsorption of cations. Fe3O4 and especially MnFe2O4 exhibited high adsorption capacity towards Pb(II). The maximal removal efficiency of Pb(II) (50[Formula: see text]mg[Formula: see text]L[Formula: see text]) on MnFe2O4 was 100% at pH 6.2. The results demonstrate that this method is promising for the synthesis of magnetic adsorbent.

Mesoporous α-Ni(OH)2 was synthesized by a facile method and investigated as an electrochemical pseudocapacitor material. Structural characterizations reveal that the mesoporous α-Ni(OH)2 has a narrow pore size distribution of 16 nm and a large surface area of 349 m2 g− 1. The α-Ni(OH)2 sample exhibits excellent electrochemical performance at different current densities and good cycling ability, which can be due to its mesoporous structure and large surface area. A maximum specific capacitance of 1718 F g− 1 can be achieved at a scan rate of 5 mV s− 1. These results indicate that the mesoporous α-Ni(OH)2 is a promising candidate for the supercapacitor electrodes.

Mn 3 O 4 nanoparticles were prepared by a novel oxidation–precipitation method at a low temperature. The crystal phase, microstructure, surface area and electrochemical properties of the products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N 2 adsorption–desorption isotherms and cyclic voltammetry (CV). The results indicate that the addition of citric acid and tartaric acid remarkably reduced the particle size and increased the specific surface area of Mn 3 O 4 nanoparticles. The samples prepared by the addition of citric acid and tartaric acid have a narrow particle size distribution of 5–10 nm, a surface area of 119 and 122 m 2 /g, and a capacitance of 171 and 172 F g −1 , respectively.

Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused.

A novel redox-precipitation method was developed for the preparation of α-MnO 2 , where Mn(NO 3 ) 2 and KOH were titrated into excess KMnO 4 solution at pH 8. For comparison, MnO x was also prepared using a conventional precipitation method. These materials were characterized by XRD, BET, SEM/EDS, XPS, and H 2 -TPR techniques, and their catalytic activities were evaluated for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o -xylene. The novel method produced open porous hierarchically structured microcrystalline α-MnO 2 containing almost 100% Mn 4+ ion on its surface. Whereas, the conventional precipitation method produced a mixture of MnO 2 and Mn 3 O 4 with a closely packed spherical morphology containing only 31% Mn 4+ ion on its surface. It was found that α-MnO 2 exhibited good low-temperature reducibility, and that it could convert 100% o -xylene into CO 2 at 220 °C at a space velocity of 8000 h −1 , 50 °C lower than the MnO x prepared by the conventional method. The surface concentration of Mn 4+ ion in α-MnO 2 played a key role for its high catalytic activity for the complete oxidation of o -xylene. In addition, the open porous structure and the presence of small amount of potassium ion in the microcrystalline α-MnO 2 channel may also be responsible for its excellent catalytic performance. Effects of pH and calcination temperature on its catalytic activity were investigated, and optimal preparation conditions were found. Durability of the α-MnO 2 was also studied.

Various manganese oxides nano/micro-crystals, including Mn 3 O 4 octahedrons, hierarchical flower-like K -δ- MnO 2 microspheres, multi-branch and strip-shaped γ- MnOOH , have been prepared by a lignosulfanate (LSN)-mediated hydrothermal process. The effect of LSN on the structure and morphology has been thoroughly investigated by X-ray powder diffraction and scanning electron microscopy (SEM). The results indicated that stepwise reduction and Ostwald's ripening occurred simultaneously in this hydrothermal process, and LSN could serve as both reducing agent and growth modifier. The appropriate reducing capacity and selective absorption ability of LSN played an important role for the formation of various manganese oxides nano/micro-crystals. The catalytic performance of the products for the oxidation of o-xylene has been also investigated. The result showed that the MnO 2 crystals prepared with LSN exhibited the highest catalytic activity.

Complex MnO2 nanostructures were prepared through controlled precursor adsorption. The preferential adsorption of a precursor ion leads to the anisotropic growth of crystals, and even produces crystals of different crystal structures. The thus produced primary anisotropic crystals assemble into porous spherical hierarchical 3D architectures.