Nanostructured CaCO3 modified sewage sludge biochar (CMSSB) was successfully fabricated for efficient removal of Cd(II) from aqueous solutions. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicated that the loaded CaCO3 mainly existed in the form of dispersive calcite nanoparticles, and the loading of calcite nanoparticles had a slight effect on the morphology of the sewage sludge biochar (SSB). The adsorption capacity of the obtained CMSSB for Cd(II) based on the Langmuir model is 36.5 mg g−1, which was nearly three times higher than that of the pristine SSB. The adsorption process can be well described by the Elovich model, and the initial adsorption rate of the CMSSB is faster than that of the SSB. The Cd(II) adsorption mechanism on the CMSSB involves ion-exchange and precipitation reactions between heavy metal ions and calcite nanoparticles and biochar. The present results suggested that the as-prepared CMSSB is an efficient and economic adsorbent for environmental heavy metal remediation.

•Functional NZVI coupled with ultrasound as a novel and green system was proposed.•The functional NZVI was fabricated via a facile, one-step and eco-friendly method.•The new system achieved a significant synergy in decolorization of cationic dyes.•As reductant, dispersant and capping agent, tea polyphenol is eco-friendly.•The findings offer insight into nanoremediation with practical green approach.For the first time, an integrated green technology by coupling functional nanoscale zero-valent iron (NZVI) with ultrasound (US) was innovatively developed for the enhanced decolorization of malachite green (MG) and methylene blue (MB). The functional NZVI (TP-Fe) was successfully fabricated via a facile, one-step and environmentally-benign approach by directly introducing high pure tea polyphenol (TP), where TP contenting abundant epicatechin was employed as reductant, dispersant and capping agent. Note that neither additional extraction procedure nor protection gas was needed during the entire synthesis process. Affecting factors (including US frequency, initial pH, dye concentration, and reaction temperature) were investigated. Results show that TP-Fe exhibited enhanced activity, antioxidizability and stability over the reaction course, which could be attributed to the functionalization of TP on NZVI and the invigorating effect of US (i.e., improving the mass transfer rate, breaking up the aggregates of TP-Fe nanoparticles, and maintaining the TP-Fe surface activity). The kinetics for MG and MB decolorization by the TP-Fe/US system could be well described by a two-parameter pseudo-first-order decay model, and the activation energies of MG and MB decolorization in this new system were determined to be 21 kJ mol−1 and 24 kJ mol−1, respectively. In addition, according to the identified reaction products, a possible mechanism associated with MG and MB decolorization with the TP-Fe/US system was proposed.Download high-res image (246KB)Download full-size image

A general and facile hydrothermal method was developed to improve carbon coating formation on the surface of magnetic nanoparticles from sucrose and hindering growth of pure carbon spheres by using ammonium acetate (CH3COONH4) as a structure guiding agent. The thickness of the carbon coating could be easily realized by adjusting the reaction time.A facile hydrothermal method was developed to improve carbon coating formation on the surface of magnetic nanoparticles from sucrose by using CH3COONH4 as a structure guiding agent.

The hydrothermally synthesized layered chalcogenide, K2xMnxSn3−xS6 (x = 0.5–0.95) (KMS-1), was applied to remove ciprofloxacin from aqueous solution. Kinetic data showed the removal reaction followed a pseudo-second-order kinetic model and the rate controlling step was both through external film and intraparticle diffusion. The adsorption of CIP by KMS-1 is endothermic and the maximum adsorption capacity of KMS-1 was 199.6, 230.9 and 269.5 mg/g at temperature of 10, 25 and 40 °C, respectively. The heavy metal ions had great effect on the removal efficiency of CIP and the degree of inhibition followed the order: Pb2+ > Zn2+ > Cd2+ > Ni2+. The shift of Bragg peaks from XRD at various pH accompanying CIP removal and FE-SEM images confirmed that cation exchange is the major mechanism for the adsorption of CIP by KMS-1. In the pH range of 4.0–7.0, the intercalation of cationic CIP adopted a titled orientation of di-molecular CIP in KMS-1 with the titling angle of 68° and 42°, respectively. A vertical arrangement of the zwitterionic CIP adsorbed on the surface of KMS-1 was also confirmed. These results suggested that KMS-1 is an effective adsorbent to remove CIP from water.

A novel KMS-1/PAN composite was successfully and simply fabricated by combining KMS-1 with PAN. The KMS-1/PAN combines the efficient, rapid adsorption of Cs+ by KMS-1 with granulation for easy separation after adsorption. The maximum Cs+ adsorption capacity of KMS-1/PAN was estimated to be 72.00 mg g−1 according to the Langmuir model.

The evolution of antibiotic resistance and the potential impact on human health of chloramphenicol (CAP) have made it an environmental pollutant requiring urgent action. In this study, Au–Pd bimetallic nanoparticles (BNPs) were first synthesized and then successfully loaded on Amberlite 717 to form an Amberlite 717 supported Au–Pd BNP catalytic system (717@Au–Pd) with the mass fraction of Au–Pd at about 4.5%. The as-synthesized catalytic system was used to degrade CAP in water under a H2 atmosphere at room temperature. When 0.5 g of 717@Au–Pd was added into the CAP solution (50 mg L−1, 50 mL, pH 7), about 60% of CAP was absorbed on the 717@Au–Pd in the first 10 h and then all of CAP can be completely removed in the following 3 h under a H2 atmosphere. The degradation process of the reaction can be fitted with a first-order kinetics equation with the kinetics constant of 4.3 h−1 ± 0.009. The degradation products and mechanism were studied using LC/MSD Trap-XCT. The results showed that CAP was removed by the 717@Au–Pd via cleaving the carbon–halogen bond of CAP while keeping the nitro-group unaffected and this made the degradation products less environmentally toxic. The recycled experiments showed that the removal rate of CAP can still be maintained at 99% even after 5 cycles. The study indicated that 717@Au–Pd is a promising catalyst for removing environmental pollutants such as CAP containing carbon–halogen bonds.

•Hybrid γ-Fe2O3/C hollow spheres were successfully synthesized by one step hydrothermal method.•The hollow spheres contain a preferred orientation (1 1 1) plane in γ-Fe2O3.•The hollow spheres contain rich oxygen-containing groups on carbon.•The γ-Fe2O3/C hollow spheres exhibit remarkably high capacity for heavy metal removal.One-step hydrothermal method was developed to prepare hybrid γ-Fe2O3/carbon hollow spheres with a predominant orientation (1 1 1) plane of γ-Fe2O3 and rich oxygen-containing functional groups on carbon. The resulting functional hybrid exhibited extremely high adsorption capacities for toxic Pb(II) and Cr(VI) ions in solutions with easy magnetic separation. The ease of synthesis and low cost, coupled with the efficient and rapid removal of toxic heavy metal ions, make hybrid γ-Fe2O3/carbon hollow spheres an attractive adsorbent for the purification of waste and contaminated water.Graphical abstract

Three-dimensional core–shell structured Fe3O4@α-MnO2 microspheres were successfully fabricated by a two-step hydrothermal method. The obtained magnetic microspheres exhibit excellent ability to activate persulfate for catalytic degradation of ciprofloxacin in wastewater with easy magnetic separation.

Three-dimensional porous Mn doped α-Fe2O3 nanostructures are successfully fabricated by calcined carbon spheres containing Fe(II) and Mn(II) ions, which were obtained by hydrothermal treatment of glucose, Fe(II), and Mn(II) mixed solutions. The obtained nanostructures exhibit excellent abilities for the removal of Pb(II), Cr(VI), and As(III) ions from wastewater with easy magnetic separation.

Anatase TiO2 with exposed {001} facets has been deepgoingly studied for optimizing its photocatalytic activity. In this study, we synthesized N-doped TiO2 nanocrystals with exposed {001} facets by sol–gel method and solvothermal method, respectively. The physical and chemical properties of as-synthesized samples, such as morphology, crystal phase, surface elements composition, porous structure, specific surface area, and optical response, were characterized in detail. The photocatalytic performances of all samples were evaluated by photocatalytic decoloration of methylene blue under visible-light irradiation (λ > 420 nm). The results showed that the as-prepared samples present high visible-light photocatalytic performances, which can be ascribed to the excellent crystallization, the enhancement of absorbance in the visible-light region, and the strong adsorption performance, and calcination treatment is helpful to further improve the visible-light photocatalytic performance of N-doped TiO2 nanocrystals with exposed {001} facets.

•N-doped TiO2 plates with dominant {0 0 1} facets were synthesized by one-pot method.•Microstructure and property evolution were successfully captured.•N-doped TiO2 plates presented higher visible-light induced photocatalytic activity.•The photocatalytic activity was decided by the synergic effects of many factors.Nitrogen doped TiO2 plates with dominant {0 0 1} facets were successfully synthesized by one-pot hydrothermal method. The dependence of microstructure and property evolution, such as crystal phase, morphology, N-doping and optical response property, on the hydrothermal time was investigated systematically, and their photocatalytic activities for the degradation of methylene blue are evaluated under visible light irradiation. The results showed that the structure of cubic TiN with the morphology of irregular bulk gradually collapses to form the structure of anatase TiO2 with the morphology of well-defined plate during the hydrothermal process with the extension of hydrothermal time. The bonds of TiN in TiN are gradually replaced by OTiN and TiON due to the oxidation effect, which realizes the N-doping of TiO2 plates. The as-prepared N-doped TiO2 plates with dominant {0 0 1} facets demonstrate photocatalytic activity under visible light irradiation (λ > 420 nm), and their photocatalytic activities are decided by the synergistic effects of many factors, such as crystal phase, morphology, nitrogen doping, optical response, in which morphology and nitrogen doping are more significant factors in comparison with crystal phase and optical response.

Two kinds of porous magnetic ferrite nanowires containing manganese (MnFe2O4 and Mn doped Fe3O4) have been successfully synthesized by thermal decomposition of organometallic compounds, using nitrilotriacetic acid (NA) as a chelating agent to coordinate with various ratios of Fe(II) and Mn(II) ions. The resultant MnFe2O4 and Mn doped Fe3O4 nanostructures are superparamagnetic, and have magnetization saturation values of about 45.9 and 48.7 emu g−1 for MnFe2O4 and Mn doped Fe3O4, respectively. The Brunauer–Emmett–Teller specific surface areas of the MnFe2O4 and Mn doped Fe3O4 are 37.8 and 45.4 m2 g−1, respectively. The as-prepared porous MnFe2O4 and Mn doped Fe3O4 nanowires exhibit excellent ability to remove heavy metal ions and organic pollutant in waste water. In addition, these porous magnetic ferrites may be useful in other fields such as biomedicine and Li-ion batteries.

•Hybrid metal oxide quantum dots, CuxO and FexO, were anchored on rutile TiO2.•“Hybrid” refers to that Cu and Fe were in mixed valence state.•Composites were prepared by a facile, low-cost and large scale reflux method.•CuxO/TiO2 and FexO/TiO2 showed much higher activity than TiO2 itself.•The mechanisms of photocatalysis on CuxO/TiO2 and FexO/TiO2 were proposed.Two kinds of hybrid metal oxide quantum dots, CuxO and FexO, were successfully anchored on TiO2 blocks by a facile, low-cost and large scale reflux method. The resultant photocatalysts (CuxO/TiO2 and FexO/TiO2) were characterized by transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectrum, and their photocatalytic performances were evaluated by photocatalytic decoloration of methylene blue (MB) solution under simulated sunlight and visible light (λ > 420 nm) irradiation. The results showed that hybrid metal oxide quantum dots CuxO (or FexO) were dispersed uniformly on TiO2 blocks. Both Cu and Fe are in mixed valences state (Cu+ and Cu2 +, Fe2 + and Fe3 +, respectively). CuxO/TiO2 and FexO/TiO2 demonstrated high photocatalytic ability whether they were under simulated sunlight or under visible light (λ > 420 nm) irradiation, which can be confirmed from the measurement of the amount of hydroxyl radicals (OH). Based on the above results, the mechanisms of enhanced photocatalysis on CuxO/TiO2 and FexO/TiO2 under simulated sunlight and visible light were proposed.

•Ozonation was effective to degrade MIB and GSM in the synthetic water.•Ozonation of Lyngbya kuetzingii led to the damage of algae cells.•Ozonation caused the release of cellular cytoplasm from cells.•Possible degradation pathways for the ozonation of MIB and GSM were proposed.2-Methylisoborneol (MIB) and geosmin (GSM) are taste and odor compounds produced as secondary metabolites by some cyanobacteria and actinomycetes, and thus they can be present in some drinking water sources. The removal efficiency, intermediate by-products, and degradation pathway of MIB and GSM in synthetic water by ozonation were studied. The results show that ozone is efficient in removing MIB and GSM from an aqueous solution, depending on pH and the initial MIB and GSM concentration. Ozonation of algal suspension was also studied and the removal efficiency of GSM mainly produced by Lyngbya kuetzingii can reach 99.91% although the ozonation could damage the algal cells and release the intracellular organic compounds. The degradation by-products of MIB or GSM were identified by gas chromatography–mass spectrometry and dehydration and open ring compounds are the main by-products. Possible degradation pathways for the ozonation of MIB and GSM were proposed.

Magnetic cryptomelane-type manganese oxide (OMS-2) nanotubes were successfully prepared by grafting Fe3O4 nanoparticles onto the OMS-2 nanotubes. SEM and HRTEM images show that the prepared magnetic OMS-2 nanotubes exhibited diameters of 100 nm, lengths less than 3.0 μm, and the diameters of the Fe3O4 nanoparticles are less than 10 nm. The synthesized material exhibits excellent magnetic separation and catalytic properties for the degradation of methylene blue (MB) by a Fenton-like reaction.

A facile one-pot reflux method was explored for large-scale preparation of todorokite-type manganese oxide octahedral molecular sieves (OMS-1) composed of hierarchical nanoplate microspheres. The diameters of the microspheres are usually 1.5–2.5 μm, and the thickness of the nanoplate is approximately 10 nm.

Bi–N–TiO2 nanoparticles were synthesized via anneal after a simple sol-gel combined hydrothermal method. X-ray diffraction (XRD), UV–Visible diffuse reflectance spectra, Scanning Electron Microscope (SEM) and X-ray photoelectron spectra (XPS) confirm that the grain sizes are almost uniform diameters of about 11 nm, the response to light extends to visible region, the doped ions substitute some of the lattice titanium atoms, and furthermore Bi3+ and Bi4+ ions coexist. The photodegradation of acid orange 7 (AO7) is used to evaluate the photocatalytic activity of the prepared Bi–N–TiO2 nanoparticles. The experiments indicated that Bi–N–TiO2 showed higher photocatalytic activity than that of P25, TiO2, N–TiO2 and Bi–TiO2 in the visible light area and ultraviolet light. The improvement of photocatalytic activity of Bi–N–TiO2 is more likely because the N doping causes the visible light response and improves the quantum yield and photocatalytic activity of TiO2, and Bi doping causes the enhancement of the separation of photogenerated charges.

Biochar amendments can alter phosphorus (P) availability in soils, though the influencing mechanisms are not yet fully understood. This work investigated the adsorption and desorption of P on ferrihydrite (F, a Fe-oxide widely distributed in surface environments) in order to evaluate the interactions between P and Fe-oxide in the absence or presence of biochar (F or ferrihydrite–biochar (F–B) interaction) in soils.Biochar was produced by pyrolysis of rice straw at 600°C in steel ring furnaces. Two-line ferrihydrite was synthesized by dropwise addition of 1 mol L−1 KOH into Fe(NO3)3 solution until the pH reached 7–8 while stirring vigorously. An F–B complex was prepared under similar conditions, except that a mixture of 10 g biochar and the Fe(NO3)3 solution was used as the starting material instead of Fe(NO3)3 alone. A batch equilibration method was used to determine sorption or desorption of P. The mechanisms of P adsorption on F and F–B complex materials were discussed.Adsorption of P on F decreased as the pH was increased from 3.0 to 10, but the adsorption capacity of F decreased by about 30–40% in the presence of biochar. The P chemisorption rates on F also decreased in the presence of biochar. The Freundlich model showed that the active adsorption sites on the surface of the F–B complex were energetically heterogeneous. The desorbability of adsorbed P on F was enhanced by combination with biochar. The mechanisms of P adsorption on F and F–B complex materials are different.The results showed that the amount and rate of P adsorption on the surface of ferrihydrite decreased with the presence of biochar, and the desorbability of adsorbed P on ferrihydrite can be enhanced when combined with biochar. Thus, the presence of biochar can decrease P adsorption on the Fe-oxides and enhance P availability in soils.

Single-crystalline β-MnO2 nanorods were successfully synthesized through facile reflux treatment of KMnO4 and MnSO4 in HNO3 solution. TEM and SEM images show that the synthesized β-MnO2 nanorods exhibited diameters of 20–50 nm, and lengths that ranged from approximately 0.5 to 2.0 μm with decreasing HNO3 concentrations from 0.8 to 0.1 mol/L. The β-MnO2 nanorods underwent three primary evolutionary stages over time. They exhibited excellent catalytic properties for the degradation of methylene blue (MB) by a Fenton-like reaction.Single-crystalline β-MnO2 nanorods with different size were successfully synthesized through a facile reflux treatment of KMnO4 and MnSO4 in acid solutions by adjusting the HNO3 concentrations. The products revealed remarkable catalysis for the degradation of methylene blue (MB) in the presence of H2O2, which can be potential application in the waste water.Download full-size imageHighlights► Single-crystalline β-MnO2 nanorods were successfully prepared through a facile refluxing route. ► The size of the synthesized β-MnO2 nanorods can be controlled by adjusting HNO3 concentrations. ► The products were shown to be an efficient catalyst for the degradation of methylene blue.

A facile one-pot reflux method was explored for large-scale preparation of todorokite-type manganese oxide octahedral molecular sieves (OMS-1) composed of hierarchical nanoplate microspheres. The diameters of the microspheres are usually 1.5–2.5 μm, and the thickness of the nanoplate is approximately 10 nm.

Two kinds of porous magnetic ferrite nanowires containing manganese (MnFe2O4 and Mn doped Fe3O4) have been successfully synthesized by thermal decomposition of organometallic compounds, using nitrilotriacetic acid (NA) as a chelating agent to coordinate with various ratios of Fe(II) and Mn(II) ions. The resultant MnFe2O4 and Mn doped Fe3O4 nanostructures are superparamagnetic, and have magnetization saturation values of about 45.9 and 48.7 emu g−1 for MnFe2O4 and Mn doped Fe3O4, respectively. The Brunauer–Emmett–Teller specific surface areas of the MnFe2O4 and Mn doped Fe3O4 are 37.8 and 45.4 m2 g−1, respectively. The as-prepared porous MnFe2O4 and Mn doped Fe3O4 nanowires exhibit excellent ability to remove heavy metal ions and organic pollutant in waste water. In addition, these porous magnetic ferrites may be useful in other fields such as biomedicine and Li-ion batteries.