Longbo Jiang

Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction.

Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH2-MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH2-MIL-125(Ti) were well characterized by XRD, SEM, XPS, N2 adsorption-desorption measurements, thermogravimetric analysis and UV-vis diffuse reflectance spectra (DRS). It is revealed that the NH2-MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH2-MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti(3+)-Ti(4+) intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater.

Co-pelletization of sewage sludge and biomass: the density and hardness of pellet.

In the present study, the effects of process parameters on pellet properties were investigated for the co-pelletization of sludge and biomass materials. The relaxed pellet density and Meyer hardness of pellets were identified. Scanning electron microscopy, FT-IR spectra and chemical analysis were conducted to investigate the mechanisms of inter-particular adhesion bonding. Thermogravimetric analysis was applied to investigate the combustion characteristics. Results showed that the pellet density was increased with the parameters increasing, such as pressure, sludge ratio and temperature. High hardness pellets could be obtained at low pressure, temperature and biomass size. The optimal moisture content for co-pelletization was 10-15%. Moreover, the addition of sludge can reduce the diversity of pellet hardness caused by the heterogeneity of biomass. Increasing ratio of sludge in the pellet would slow down the release of volatile. Synergistic effects of protein and lignin can be the mechanism in the co-pelletization of sludge and biomass.

Photocatalytic Decontamination of Wastewater Containing Organic Dyes by Metal-Organic Frameworks and their Derivatives

Photoactive metal–organic frameworks (MOFs) have lately emerged as a class of crystalline porous materials, which provides an advanced platform to develop catalysts for the photocatalytic decolorization of wastewater. Controllable integration of pure MOFs into other active materials creates fabrication protocols for new multifunctional hybrids with superior photocatalytic properties for dye degradation into individual components, and the calcination of transition‐metal MOF precursors affords a convenient and practical route for preparation of nanosized photocatalysts with novel structures and good purity. Although the application of pure MOFs for organic pollutant decomposition has been reviewed previously, there have been significant advances in diverse MOF‐based composites and their derivatives for dye degradation, which have rarely been reviewed. This review aims to fill this gap and discuss the various influencing factors, the reaction kinetics, and mechanisms of dye degradation, considering the period from 2014 to 2016. Finally, the challenges and outlooks for dye decomposition by MOF‐based materials are suggested.

Chemical speciation, mobility and phyto-accessibility of heavy metals in fly ash and slag from combustion of pelletized municipal sewage sludge.

Combustion of pelletized municipal sewage sludge (MSS) can generate pestilent byproducts: fly ash and slag. Comparisons of heavy metal sequential extraction results among MSS, fly ash and slag showed that after combustion, the bioavailable heavy metal fractions (acid soluble/exchangeable, reducible and oxidizable fractions) were mostly transformed into the very stable heavy metal fractions (residual fractions). On the other hand, the results of toxicity characteristic leaching procedure (TCLP), diethylenetriamine pentaacetic acid and HCl extraction (phyto-accessibility assessment) demonstrated that the mobility and toxicity of heavy metals were greatly reduced. The direct and long-term bioavailability and eco-toxicity of heavy metals in fly ash and slag were relieved, which implied that combustion of pelletized MSS could be a promising and completely safe disposal technology for MSS treatment.

The comparison of the migration and transformation behavior of heavy metals during pyrolysis and liquefaction of municipal sewage sludge, paper mill sludge, and slaughterhouse sludge

Municipal sewage sludge, paper mill sludge, and slaughterhouse sludge were pyrolyzed and liquefied for the production of bio-char. The migration and transformation behavior of Cu, Cr, and Zn during pyrolysis and liquefaction of these sludges were studied. Pyrolysis and liquefaction promoted mobile fraction (F1 and F2) to stable fraction (F3 and F4). The results showed that pyrolysis and liquefaction largely affected the redistribution of Cu and Zn in raw materials. The environmental risk assessment results indicated that the environmental risk levels of Cu and Zn were significantly reduced in bio-char, and risk level of Cr was slightly decreased after pyrolysis or liquefaction. Both pyrolysis and liquefaction were promising detoxification technologies for the three sludges in terms of the mitigation of heavy metals toxicity. It was suggested that dewatered sludge could be reduced toxicity/risk before utilization by pyrolysis or liquefaction technology, especially for Cu and Zn in slaughterhouse sludge.

Complementary effects of torrefaction and co-pelletization: energy consumption and characteristics of pellets.

In this study, complementary of torrefaction and co-pelletization for biomass pellets production was investigated. Two kinds of biomass materials were torrefied and mixed with oil cake for co-pelletization. The energy consumption during pelletization and pellet characteristics including moisture absorption, pellet density, pellet strength and combustion characteristic, were evaluated. It was shown that torrefaction improved the characteristics of pellets with high heating values, low moisture absorption and well combustion characteristic. Furthermore, co-pelletization between torrefied biomass and cater bean cake can reduce several negative effects of torrefaction such as high energy consumption, low pellet density and strength. The optimal conditions for energy consumption and pellet strength were torrefied at 270°C and a blending with 15% castor bean cake for both biomass materials. The present study indicated that compelmentary performances of the torrefaction and co-pelletization with castor bean cake provide a promising alternative for fuel production from biomass and oil cake.

One-step calcination method for synthesis of mesoporous g-C3N4/NiTiO3 heterostructure photocatalyst with improved visible light photoactivity

A novel g-C3N4/NiTiO3 composite was fabricated by one-step calcination method using dicyandiamide, tetrabutyl titanate and nickel acetate as the precursors. The samples were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption/desorption isotherms, UV-vis diffuse reflection spectroscopy and photoluminescence spectroscopy. It was indicated that the hybrids owned a large surface area, mesoporous structure and improved visible light absorption. The optimal g-C3N4 content in the g-C3N4/NiTiO3 composite was 18.4 wt%, and the corresponding visible-light removal rate for nitrobenzene was 0.0132 min−1, about 1.6 times higher than that of pure NiTiO3. The enhanced photocatalytic activity may be attributed to the large surface area, stronger absorption in the visible region and efficient electron–hole separation.

Highly efficient visible-light-induced photoactivity of Z-scheme Ag2CO3/Ag/WO3 photocatalysts for organic pollutant degradation

Novel and efficient Z-scheme Ag2CO3/Ag/WO3 with excellent visible-light-driven photocatalytic performance was fabricated using a facile deposition and photochemical reduction process. Surface, morphological, and structural properties of the resulting materials were characterized using N2 sorption–desorption and Brunauer–Emmett–Teller (BET) surface area measurements, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis and photoluminescence spectroscopy. The photocatalytic performances of the Ag2CO3/Ag/WO3 composites were evaluated by the degradation of rhodamine B (RhB), methyl orange (MO), ciprofloxacin (CIP), and tetracycline hydrochloride (TC) under visible light irradiation. The results demonstrate that the novel Z-scheme Ag2CO3/Ag/WO3 composites exhibit higher photocatalytic activity than pure Ag2CO3 rods and WO3 nanoparticles. The enhanced photocatalytic activity of Ag2CO3/Ag/WO3 can be ascribed to the extended absorption in the visible light region caused by a surface plasmon resonance (SPR) effect, effective separation of photogenerated charges, and the formation of a Z-scheme system. In addition, the photocatalyst exhibits high stability and reusability. This work could offer a new insight into the design and fabrication of advanced materials with Z-scheme structures for photocatalytic applications for organic pollutants removal from wastewater.

Solvothermal synthesis of graphene/BiOCl0.75Br0.25 microspheres with excellent visible-light photocatalytic activity

Three-dimensional BiOCl0.75Br0.25/graphene (BG) microspheres have been synthesized via a facile solvothermal route. The as-prepared samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and Brunauer–Emmett–Teller (BET) area. The photocatalytic activities of the samples were evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. It was shown that the BG photocatalysts with 5.0 wt% graphene (BG5.0) exhibited the highest photocatalytic activity, which was almost up to 2.3 times than that of pure BiOCl0.75Br0.25. The enhanced photoactivity of BG5.0 was mainly attributed to the effective light absorption, the larger specific surface areas and the more efficient charge transportation and separation.

Highly efficient photocatalysis toward tetracycline of nitrogen doped carbon quantum dots sensitized bismuth tungstate based on interfacial charge transfer

In this study, a novel N-CQDs/Bi2WO6 was synthesized through a facile hydrothermal method. Multiple techniques were applied to investigate the structures, morphologies, optical and electronic properties and photocatalytic performance of as-prepared samples. The results indicated that the hybrid materials were formed with N-CQDs attached on the surface of sphere-like Bi2WO6. The photocatalytic activity of N-CQDs/Bi2WO6 materials was evaluated sufficiently by using tetracycline (TC) as target organic pollutant. N-CQDs/Bi2WO6-5 displayed superior photocatalytic efficiency with nearly 97% removal of TC in 25min and 86.37% mineralization in 90min. The degradation reaction coefficient (kobs) was approximately two times higher than pure Bi2WO6 as a result of the synergistic effects of N-CQDs and Bi2WO6. Increased light harvesting capacity, excellent electron transfer ability and improved molecular oxygen activation ability were obtained in N-CQDs/Bi2WO6 hybrid materials caused by N-CQDs. The present study demonstrated that N-CQDs modification was an effective way to improve photocatalytic efficiency, which can be extended to a general strategy for other semiconductors. The study indicated that novel N-CQDs/Bi2WO6 has a great potential for rapid and efficient treatment of organic pollutants in water.