Phosphorus- and sulfur-codoped graphitic carbon nitride has been successfully synthesized by in situ thermal copolymerization of hexachlorocyclotriphosphazene and thiourea. The phosphorus doping, together with the sulfur doping, would enhance light trapping, surface area, and charge separation, making it serve as a more efficient photocatalyst than its pure g-C3N4 and single-doped g-C3N4 counterpart for the removal of tetracycline (TC) and methyl orange (MO). The optimum photocatalytic activities of a P-, S-codoped g-C3N4 sample for the degradation of TC and MO were about 5.9 times and 7.1 times higher than that of individual g-C3N4, respectively. Furthermore, the optimum TOC removal reached 70.33% and 55.37% for TC and MO within 120 min, respectively. The introduction of a P atom and S atom could significantly change the electronic property of g-C3N4 and suppress the recombination of photogenerated charges. Moreover, the defects in the framework of samples caused by the doping of P and S could serve as centers to trap the photoinduced electrons, thus inhibiting the charge recombination and improving its photocatalytic performance.Keywords: Codoping; g-C3N4; Methyl orange; Tetracycline; Visible light photocatalysis;

•Element doped g-C3N4 for improved photocatalytic activity is summarized.•Band gap engineering regarding the catalytic activity improvement is explicated.•Metal doping, nonmetal doping, co-doping and heterojunction design are explored.•Increased light absorption and improved charge separation rate are obtained.•The crystallographic, textural and electronic structures are synergistically tuned.As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has been the hotspot in the materials science as a metal-free and visible-light-responsive photocatalyst. Pure g-C3N4 suffers from the insufficient sunlight absorption, low surface area and the fast recombination of photo-induced electron-hole pairs, resulting in low photocatalytic activity. Element doping is known to be an efficient method to tune the unique electronic structure and band gap of g-C3N4, which considerably broaden the light responsive range and enhance the charge separation. This review summarizes the recent progress in the development of efficient and low cost doped g-C3N4 systems in various realms such as photocatalytic hydrogen evolution, reduction of carbon dioxide, photocatalytic removal of contaminants in wastewater and gas phase. Typically, metal doping, nonmetal doping, co-doping and heterojunction based on doped g-C3N4 have been explored to simultaneously tune the crystallographic, textural and electronic structures for improving photocatalytic activity by enhancing the light absorption, facilitating the charge separation and transportation and prolonging the charge carrier lifetime. Finally, the current challenges and the crucial issues of element doped g-C3N4 photocatalysts that need to be addressed in future research are presented. This review presented herein can pave a novel avenue and add invaluable knowledge to the family of element doped g-C3N4 for the develop of more effective visible-light-driven photocatalysts.Download high-res image (221KB)Download full-size image

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.

Sewage sludge liquefaction bio-oil is capturing extensive attention for its sustainability and easy availability. However, some limitations of bio-oil such as high viscosity and poor cold flow properties hamper its direct application in engines. Two microemulsions including ethanol-in-diesel (M1) and diesel microemulsion (M2) were produced to upgrade bio-oil. Adding ethanol in M1 facilitated bio-oil solubilization and improved fuel properties of bio-oil. Because of low viscosity and low pour point of ethanol, M1 with ethanol as polar phase produced a more promising biofuel with acceptable viscosity and better cold flow properties compared with M2. Through microemulsification in diesel, hydrophilic and hydrophobic bio-oil components may penetrate into the polar core and the continuous phase, respectively, while amphiphilic components mainly located at the interface. The hydrogen bonding between ethanol and hydrophilic bio-oil components could enhance solubility and improve stability. Besides, polar phase ethanol could also act as a solvent to dissolve more less-hydrophilic bio-oil components into the polar core.

•Novel full-spectrum-response Co2.67S4 was fabricated by facile solvothermal route.•Co2+/Co3+ redox couple was the predominant mechanism in photocatalytic process.•O2− and OH formed in the photocatalytic process led to the MB degradation.Sparked by growing pollution issues, research aiming at a better harvesting of solar energy in photocatalysts for environmental remediation has been thriving. In this study, a novel mixed valence state of Co2.67S4 nanoparticles with full-spectrum-responsive photocatalytic activity had been fabricated via a facile solvothermal route. The as-synthesized samples were systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis-NIR diffuse reflection spectroscopy (UV–vis-NIR DRS). The photocatalytic performance of as-obtained samples had been investigated by the degradation of methylene blue (MB) in aqueous solution. The Co2.67S4 nanoparticles with the particle size of 5–20 nm could degrade MB with the efficiency of 64%, 84% and 68% under the UV light, visible light and near-infrared light exposure, respectively. Furthermore, a possible photocatalytic mechanism toward the near-infrared region had been proposed to be that the Co2+/Co3+ redox couple played vital parts in the photocatalytic activity of Co2.67S4. This study provides a novel full solar spectrum-responsive photocatalyst for solar-light utility and environmental remediation.Download high-res image (148KB)Download full-size image

•The reduced graphene oxide decorated NH2-MIL-68(Al) is synthesized by one-pot solvothermal.•The reduced graphene oxide decorated NH2-MIL-068(Al) has a maximum congo red adsorption capacity of 473.93 mg/g.•The Langmuir isotherm model and Pseudo-second-order kinetic fit well to the congo red adsorption process.•The co-removal of congo red and cationic dyes is highly feasible.•The photoreduction rate of Cr(VI) by congo red loaded adsorbent under visible light is 93.6%.The reduced graphene oxide decorated NH2-MIL-68(Al) (RGO/NMA) is synthesized via one-pot solvothermal process and systematically characterized for the congo red (CR) removal from single and binary water with cationic dyes. The characterization results show that the surface area of negatively charged RGO/NMA is significantly enhanced by the introduction of reduced graphene oxide (RGO). The CR adsorption is investigated as a function of contact time, initial CR concentration, temperature, pH and ionic strength. It shows that the maximum CR adsorption capacity of RGO/NMA (473.93 mg/g) is 121% and 1337% higher than NH2-MIL-68(Al) (NMA) and RGO, respectively. The adsorption dynamic analysis shows that the Pseudo-second-order model presents the best fitting to CR adsorption compared with Pseudo-first-order and Elovich model. The adsorption rate-limited step is successively controlled by film-diffusion and intra-particle diffusion according to the applicability measurement of intra-particle diffusion, boyd's film-diffusion models and external mass transfer plots. Based on the suitability of isotherm models, the CR adsorption process can be described in order of Langmuir > Temkin > Freundlich > Hill. The adsorption mechanism involved the electrostatic attraction, π–π dispersion interaction and hydrogen bonds for the spontaneously exothermic adsorption process are indentified using the three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectrum The synergistic effect occurs in the simultaneous removal CR and cationic from water. The RGO/NMA has the excellent reusability and the resource utilization of CR loaded RGO/NMA as photocatalyst for Cr(VI) reduction under visible light irradiation is highly feasible.Download high-res image (300KB)Download full-size image

•ZSH-Bi microparticle was fabricated by precipitation, hydrolysis and UV-photoreduction process.•The photodegradation rate of ZSH-3-Bi was 81 times higher than that of pure ZSH.•High photocatalytic activity was due to the SPR of metallic Bi, exposed {111} facet and interfacial interaction.Perovskite-type structure materials have attracted considerable attention in the field of solar cell and photocatalysis. In this study, novel plasmonic Bi nanoparticles and BiOCl sheets co-decorated ZnSn(OH)6 (ZSH) with various morphologies (hence exposure facets) was successfully synthesized via one-pot precipitation, hydrolysis and UV-photoreduction process. The as-obtained materials were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflection spectroscopy and photocurrent-time measurement. Results indicated that the cubic, 14-facets polyhedral and octahedral ZSH were decorated by plasmonic Bi particles and BiOCl sheets, which improved visible-light absorption, charge carrier separation and migration performance. Compared with pure ZSH, the composites showed enhanced photocatalytic activity, with the highest photocatalytic performance achieved by the octahedral ZSH decorated by Bi and BiOCl (i.e., ZSH-3-Bi). The photo-degradation rate of ZSH-3-Bi was about 81 times higher than that of pure octahedral ZSH. This phenomenon was mainly ascribed to the surface plasmon resonance effect for visible light absorption, the exposed {111} facets relative to other facets of octahedral ZSH, and the improved charge carrier separation efficiency due to the strong interfacial interaction of three components. The radical and hole trapping, and electron spin resonance spin-trap experiments verified that the OH, O2− and h+ were the main reactive species in this system, which were responsible for the decoloration and part mineralization of the RhB molecules. Therefore, this work provides new insights into the in situ fabrication of plasmonic Bi-based photocatalyst with facet-oriented polyhedron for full utilization of solar energy and wastewater treatment.Download high-res image (147KB)Download full-size image

•The format of pseudo first-order kinetics equation is corrected.•The original papers of BET isotherm and pseudo-second-order kinetic are introduced.•The explanation of suitability for BET plots is proposed.

•Co-pelletization of biomass with sludge could reduce the mean activation energy.•The reactivity of sludge–biomass pellets was improved with increasing biomass.•The slagging hazard of sludge–straw pellet was more serious than sludge–fir pellet.•Fir would be preferable rather than straw for sludge–biomass pellet.In this study, the combustion behaviors of sludge–biomass mixed pellets with different sludge ratios in air atmosphere were investigated by thermogravimetric analysis. The pellets consisted of sludge and Chinese fir or rice straw with sludge ratios of 0%, 25%, 50%, 75% and 100%, respectively. The thermogravimetric data were applied for kinetic analysis using the Coats and Redfern (CR) equation. Results showed that there were four main stages such as dehydration, volatile oxidation, char burning and burnout during thermal decomposition of pellets. The reactivities of sludge–biomass pellets were improved by the increment of the mixing ratio of biomass. In addition, the potential slagging behaviors of the resultant ashes were evaluated by X-ray fluorescence (XRF). The suitable sludge to biomass ratio should consider the combustion properties and ash slagging deposition of pellets. It is inappropriate for the production of sludge–straw pellet in the present state due to the high ash slagging potential.

•Co-pelletization of biomass with sludge could reduce the mean activation energy.•The reactivity of sludge-biomass pellets was improved with increasing biomass.•The slagging hazard of sludge-straw pellet was more serious than sludge-fir pellet.•Fir would be preferable rather than straw for sludge-biomass pellet.

Solubilization of n-decane, dodecane, tetradecane and hexadecane by monorhamnolipid biosurfactant (monoRL) at concentrations near the critical micelle concentration (CMC) was investigated. The apparent solubility of all four alkanes increases linearly with increasing monoRL concentration either below or above the CMC. The capacity of solubilization presented by the molar solubilization ratio (MSR), however, is stronger at monoRL concentrations below the CMC. The MSR decreases following the order dodecane > decane > tetradecane > hexadecane at monoRL concentrations below the CMC. Formation of aggregates at sub-CMC monoRL concentrations was demonstrated by dynamic light scattering (DLS) and cryo-transmission electron microscopy. DLS-based size (d) and zeta potential of the aggregates decrease with increasing monoRL concentration. The surface excess (Γ) of monoRL calculated based on alkane solubility and aggregate size data increases rapidly with increasing bulk monoRL concentration and then asymptotically approaches the maximum surface excess (Γmax). The relationship between Γ and d indicates that the excess of monoRL molecules at the aggregate surface greatly impacts the surface curvature. The results demonstrate formation of aggregates for alkane solubilization at monoRL concentrations below the CMC, indicating the potential of employing low concentrations of rhamnolipid for enhanced solubilization of hydrophobic organic compounds.

•The pellets’ physical properties and moisture content were reduced during storage.•Ethanal and hexanal were the main compounds emitted from the pellets during storage.•The emission of aldehyde/ketone during pellets’ storage was evaluated systematically.•A correlation between aldehyde/ketone emission and influence factors was established.Considering self-heating and hazardous gaseous emission, the safety of wood pellets storage has become one of the important aspects for woody biomass utilization. In this study, the emissions of aldehydes/ketones were analyzed by high performance liquid chromatogram (HPLC). The properties of pellets stored in semi-closed tanks with different temperatures and relative humidity (RH) were also investigated. The emissions of aldehydes and ketones from pellets were increased with raising temperature and RH during storage, while the pellets’ physical properties (dimension, density, Meyer hardness and moisture content) were reduced, except for 70% and 90% RH runs. The fatty acids compositions were extracted from both the surface and the inner part of pellets, which were analyzed by gas chromatography–mass spectrometry (GC–MS). The interaction between pellets’ physical properties variation and unsaturated fatty acid oxidation was revealed by the investigation of differences of extracted unsaturated fatty acids concentration between the surface and the inner part of pellets, which affected the aldehydes and ketones emissions.

•RL and glycerol contribute to increased Tburnout and Tmax and decreased DTGmax.•Higher glycerol content/formation of emulsion leads to higher activation energies.•Emulsion fuel probably results in incomplete combustion and heavy pollutant.•Microemulsification is more preferable for glycerol upgrading than emulsification.Thermal and oxidative behavior of glycerol-in-diesel hybrid (GDH) fuel systems with different contents of glycerol and their corresponding pyrolysis and combustion kinetics were studied. The thermogravimetric (TG) analysis indicates that different fuel systems had similar TG curves, which means their thermal and oxidative degradation similarities. The different compositions of the fuel systems or the addition of surfactant rhamnolipid and glycerol by forming microemulsion fuel with proper amount of glycerol and forming emulsion with excess glycerol, led diesel to an increasing degradation temperature and decomposition rate without exception. However, the kinetic performance of these fuel systems was different. Although GDH fuel with different contents of glycerol had comparable average activation energies, GDH fuel with high glycerol content (the emulsion fuel) had significantly higher activation energies at high conversion rate in air atmosphere than that of microemulsion fuel (with low glycerol content). Emulsion GDH fuel may have long ignition delay and can possibly result in incomplete combustion and further lead to heavier pollutant emissions when it is used in engines. GDH fuel should be produced with proper amount of glycerol addition in order to achieve better engine performances and emission characteristics.

•Liquefaction bio-chars have good performances on MB adsorption (capacity 160.5 mg/g).•MB adsorption capacity of liquefaction bio-chars exceed pyrolytic bio-chars reported.•MB adsorption mechanism may be described to be monolayer chemisorption.Three bio-chars from liquefaction of spirulina (SP), rice straw (RS), and sewage sludge (SS) were characterized with an elemental analyzer, Fourier transformation infrared spectrometer, thermogravimetric analyzer, scanning electron microscope, and surface area analyzer and used as adsorbents for methylene blue (MB) removal. The analyzed characteristics of enriched oxygen-functional groups, thermally stable and porous structure on the surface may qualify the mesopores bio-chars to be potential adsorbents. In the MB removal experiments, the effects of pH and initial MB concentration on MB adsorption capacity were investigated. The equilibrium adsorption data were well fitted to Langmuir isotherm. MB adsorption may be described to be a monolayer “chemisorption” process. The maximum MB adsorption capacities were found to be 144.2, 128.6, and 160.5 mg/g for SS char, SP char, and RS char, respectively, which exceeded pyrolytic bio-chars reported by other researchers (12–130 mg/g), quantifying the liquefaction bio-chars to be suitable adsorbents for MB removal.

A series of metal sulfides have been used to sensitize titanium metal–organic frameworks to form heterostructures through a facile photodeposition strategy. Graphene-like MoS2 sheets, Ag2S, CdS and CuS quantum dots were uniformly deposited onto MIL-125(Ti) under ultraviolet light conditions. The as-obtained heterostructure hybrids exhibited interesting photocatalytic activity for Cr(VI) reduction under visible light irradiation.

BiOCl and AgVO3 have aroused great interest as photocatalysts in environmental remediation. They could be combined to improve their photocatalytic activity. A novel Ag/AgVO3/BiOCl composite photocatalyst was produced via a facile ultrasound assisted hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) emission spectroscopy and Brunauer Emmett Teller (BET) specific surface area analysis. It is revealed that the Ag/AgVO3/BiOCl composite was successfully synthesized with a large specific surface area, mesoporous structure, enhanced light absorption performance and good recyclability. The photocatalytic activity for methylene blue (MB) degradation was investigated under visible light irradiation. The Ag/AgVO3/BiOCl composite photocatalyst exhibited superior photocatalytic activity, and about 93.16% of MB was removed within 60 minutes of irradiation, which was better than that of pure BiOCl (29.24%) and Ag/AgVO3 (37.52%). The enhanced photocatalytic activity could be attributed to the effective visible light absorption and separation of electrons and holes. Therefore, it is reasonable to believe that the Ag/AgVO3/BiOCl composite photocatalyst has great potential in environmental remediation.

Solubilizaiton of hexadecane by two surfactants, SDBS and Triton X-100, at concentrations near the critical micelle concentration (CMC) and the related aggregation behavior was investigated in this study. Solubilization was observed at surfactant concentrations lower than CMC, and the apparent solubility of hexadecane increased linearly with surfactant concentration for both surfactants. The capacity of SDBS to solubilize hexadecane is stronger at concentrations below CMC than above CMC. In contrast, Triton X-100 shows no difference. The results of dynamic light scattering (DLS) and cryogenic TEM analysis show aggregate formation at surfactant concentrations lower than CMC. DLS-based size of the aggregates (d) decreases with increasing surfactant concentration. The zeta potential of the SDBS aggregates decreases with increasing SDBS concentration, whereas it increases for Triton X-100. The surface excess (Γ) of SDBS calculated based on hexadecane solubility and aggregate size data increases rapidly with increasing bulk concentration, and then asymptotically approaches the maximum surface excess (Γmax). Conversely, there is only a minor increase in Γ for Triton X-100. Comparison of Γ and d indicates that an excess of surfactant molecules at the aggregate surface has a great impact on surface curvature. The results of this study demonstrate the formation of aggregates at surfactant concentrations below CMC for hexadecane solubilization, and indicate the potential of employing a low-concentration strategy for surfactant applications such as remediation of HOC contaminated sites.

Dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM) tests demonstrated aggregate formation for dirhamnolipid biosurfactant (diRL) at concentrations lower than surface-tension-based critical micelle concentration (CMCst). An increase of diRL concentration and solution pH results in a decrease of the aggregate size at diRL concentrations below CMCst, whereas it has no influence at diRL concentrations above CMCst. The cryo-TEM micrographs show spherical morphology of the aggregates, and the logarithm of aggregate size follows Gaussian distribution. The aggregates are negatively charged. The zeta potential of the aggregates decreases with an increase of diRL concentration to CMCst, and stabilizes at diRL concentrations higher than CMCst. An increase of the solution pH causes a decrease of the zeta potential. A transitional state assumption is raised for the interpretation of the diRL aggregation behavior. The results demonstrate formation of aggregates at significantly low diRL concentrations, which is of importance for the cost-effective application of rhamnolipid biosurfactants.

Three-dimensional spherical Sb2S3/Sb4O5Cl2 microcrystallines were synthesized for the first time via a facile hydrothermal process without any oxychlorides at 100 °C. The powder X-ray diffraction pattern showed that the product corresponded to the Sb2S3/Sb4O5Cl2 composites. The combination of the product was further confirmed by X-ray Photoelectron Spectroscopy (XPS), energy dispersive X-ray (EDX) and high-resolution transmission electron microscopy (HRTEM). Scanning electron microscopy (SEM) studies revealed that the irregular shaped nanoblocks self-organized into spherical assemblies. The suitable temperature, the possible mechanistic pathway in the formation of the structures and the mechanisms are discussed. Moreover, the as-prepared materials also had an excellent visible light photoactivity for methyl orange (MO) degradation, and could remove 82.9% MO in 60 min.

•Rhamnolipid and tween 80 were used to form mixed reverse micelles system.•The effect of pH and ionic concentration on pseudo-ternary phase diagrams for the system were studied.•The properties of conductivity and dynamic viscosity, were discussed.•The catalytic activity of Lignin peroxidase and some important factors were investigated.Reverse micelles have drawn attention of many research workers. However, most of the early efforts were focused on the single-phase reverse micelles. In this study, rhamnolipid, a kind of biosurfactant, was firstly tested to form a mixed reversed micellar systems with tween 80. The pseudo-ternary phase diagrams and the properties of this formed reverse micellar systems were investigated, and the catalytic activity of lignin peroxidase was explored. The results show that the phase diagram was sensitive to some critical factors, such as pH and ionic concentration. The properties electrical conductivity of mixed reverse micelles indicated that electrical conductivity increased with the increase of water concentration, and viscosity varied as function of water content in a non-monotonic way giving two peaked plot. The highest activity of lignin peroxidase was up to 350% in the appropriate conditions. The findings further provide theoretical knowledge that the pseudo-ternary systems can increase the potential of lignin peroxidase as catalysts for various oxidations.

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.

A heterostructure photocatalyst consisting of one-dimensional (1D) CdS nanorods (NRs) and cerium dioxide (CeO2) nanoparticles (NPs) was successfully synthesized via a solvothermal method. Different characterization techniques confirmed that CeO2 NPs were intimately attached on CdS NRs. The visible-light-driven photocatalytic activity was evaluated by the discoloration of rhodamine B (RhB). It was indicated that, under visible light illumination, the photocatalytic rate constant of CdS/CeO2 was nearly 3.4 times and 28 times higher than that of pure CdS and pure CeO2, respectively, owing to the high oxygen storage capacity of the CdS/CeO2 heterostructure, and the inhibition of electron–hole pair recombination benefitting from efficient electron transfer from CdS NRs to CeO2 NPs. In addition, the degradation mechanism of RhB on CdS/CeO2 was also discussed. This durable nanocomposite catalyst, with its excellent combination of CdS NRs and CeO2 NPs, is able to be a promising catalyst for RhB degradation under visible-light irradiation.

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.

Rhamnolipid was applied to degrade anthracene and pyrene in reversed micelles. The parameters in degradation were optimized for the purpose of improving degradation rates. The proper amount of rhamnolipid (RL) used for degrading anthracene was 0.065 mM, while 0.075 mM for pyrene. However, reaction time for degrading both anthracene and pyrene was 48 h. The optimum water content, pH, laccase concentration, polycyclic aromatic hydrocarbon (PAH) initial concentration, and volume ratio of n-hexanol to isooctane for both were found out. The highest degradation rates of anthracene and pyrene were 37.52 and 25.58 %, respectively. Although the degradation rates were not higher than the results previous literatures reported, this method was of novelty and provided guidance in application in degrading PAHs by reversed micellar system, especially for biosurfactant-based reversed micelles.

•RL based diesel microemulsion system was effective on glycerol upgrading.•Properties of the glycerol-in-diesel microemulsion fuel were comparable to diesel.•CP and PP of microemulsion fuel were improved by the addition of glycerol.•Glycerol dispersed in microemulsion fuel acted like an anti-freezing additive.Microemulsion technology was found to be a promising fuel-upgrading process for glycerol. Biosurfactant rhamnolipid (RL) was successfully tested to obtain nano-scaled glycerol-in-diesel microemulsion (GDM) and glycerol/water-in-diesel microemulsion (G/WDM). These microemulsion fuels were stored at 4 °C without phase separation for over six months. Fuel properties like high heating value (HHV), dynamic viscosity, corrosivity, and thermal decomposition characteristics of GDM and G/WDM were comparable to those of diesel. Thus, the microemulsion fuel may be qualified as commodity fuel like diesel. In addition, the cold flow properties cloud point and pour point of GDM and G/WDM were improved by the addition of glycerol or glycerol/water mixtures. Glycerol—the commonly used raw material for fuel additive production—could be directly introduced into fuel as cold flow property improver by microemulsion technology.

•Rice husk bio-char was effective on Malachite green removal from aqueous.•Malachite green adsorption capacity depended strongly on carboxylic groups.•Electrostatic attraction was believed to be the major adsorption mechanism.•Bio-char produced with ethanol at low temperature favored Malachite green adsorption.The byproduct (bio-char) from liquefaction of rice husk with water, water/ethanol (V/V, 5:5), or ethanol as the solvent at 260–340 °C was characterized in terms of its elemental composition, thermogravimetric characteristics, surface area and pore size distribution, morphology, and oxygen-containing functional group composition. The liquefaction bio-char produced with water (WBC) or water/ethanol (WEBC) as the solvent was rich in phenolic groups and bio-char with ethanol as the solvent (EBC) was rich in carboxylic and lactonic groups. Dye adsorption results indicate that the liquefaction bio-char was effective on cationic Malachite green (MG) removal from aqueous solution, but was not on anionic Methyl orange. It was also shown that the MG adsorption behaviors depended strongly on the oxygen-containing functional groups especially carboxylic groups. EBC (adsorption capacities, 32.5–67.6 mg g−1) was more effective on MG adsorption than WBC and WEBC. The adsorption equilibrium, kinetic, thermodynamic, and mechanism analysis indicate that electrostatic attraction was the major force for MG adsorption onto the bio-char. The MG adsorption kinetic fitted Pseudo-second-order model well and the isotherm can be well described by Langmuir, Freundlich, and Temkin models. The RH bio-char (byproduct) produced from liquefaction could be served as potential low-cost adsorbent for cationic dye removal from aqueous solution.

•Bio-oil/diesel microemulsion fuel was produced with Span80 as surfactant.•The optimum volume ratio of bio-oil to diesel was 5:5.•The ideal cosurfactant was n-octanol and the rational dosage of Span80 was 0.36 M.•A cosurfactant/surfactant ratio of 0.40 was suggested.•The fuel properties of bio-oil/diesel microemulsion were close to those of diesel.Bio-oils obtained from liquefaction/pyrolysis of biomass have undesired properties such as high water content (15–25 wt.%), high oxygen content (low heating value), high corrosiveness (acidity) and instability. Therefore, they cannot be directly adopted for fuel applications. Solubilizing bio-oil in diesel by microemulsion technology is one of the most convenient approaches for further upgrading bio-oil. In this work, a synthetic bio-oil was prepared to overcome the limitation posed by complex nature and instability of crude bio-oil. Effects of several microemulsion parameters on the solubilization capacity of bio-oil in diesel were evaluated, including initial bio-oil/diesel volume ratio (B/D ratio), surfactant concentration (Span80), cosurfactant type (n-butanol, n-pentanol, n-hexanol, n-heptanol and n-octanol) and the mass ratio of cosurfactant/surfactant (C/S ratio). The optimum bio-oil/diesel volume ratio was 5:5. The proper concentration of Span80 was 0.36 M. N-octanol was certified as an ideal cosurfactant. A proper C/S ratio of 0.40 was suggested. Meanwhile, fuel properties of bio-oil/diesel microemulsion were examined, including heating value, density, kinematic viscosity, cloud point, pour point, water content, corrosivity and stability. Elemental analysis and thermogravimetric analysis of bio-oil/diesel microemulsion were conducted. Compared with the original synthetic bio-oil, the bio-oil/diesel microemulsion had more desirable fuel properties close to diesel.

The utilization of vegetable oils as a source of renewable fuels has attracted much attention. However, the high viscosity of vegetable oils limits their long-term application. The microemulsion technique of vegetable oils has the advantages of viscosity reduction and environment-friendly properties. In this study, the phase behavior of the microemulsion and the solubilization mechanism of water and castor oil in diesel were researched to evaluate the solubilization capacity of water and castor oil in diesel under given conditions. The proper concentration of rhamnolipid (RL) was 50 g/L. N-octanol was certified as an ideal co-surfactant with the optimal co-surfactant/surfactant (C/S) mass ratio (w/w) of 0.60. The optimum castor oil/diesel (V/D) volume ratio (v/v) was 0.18. Moreover, fuel properties of water-containing castor oil/diesel (WCD) microemulsion were identified, including density, dynamic viscosity, cloud point, pour point, water content, corrosivity, heating value, and elemental composition. The thermal and storage stability of WCD microemulsion were also conducted. Compared with castor oil, WCD microemulsion has lower viscosity, which presents similar fuel characteristics as diesel.

•The biosurfactant rhamnolipid was employed in reversed micellar extraction.•Synchronous extraction of lignin and manganese peroxidase was carried out.•Parameters in both forward and backward extraction process were optimized.•Activity recoveries of LiP and MnP were up to 93.56% and 88.79%, respectively.Two extracellular peroxidases from Phanerochaete chrysosporium, named lignin peroxidase (LiP) and manganese peroxidase (MnP), were extracted simultaneously by biosurfactant-based reversed micellar extraction method. Rhamnolipid (RL) was applied during the experiment. N-hexanol was chosen for the extraction from five different co-solvents including n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol. Parameters (RL concentration, salt concentration, pH, temperature, extraction time, and ethanol dosage) in forward and backward extraction process were investigated. Under the optimum conditions, the highest activity recoveries of LiP and MnP were up to 93.56% and 88.79%, respectively. This observation may be helpful in developing a more effective method to monitor the process of synchronous extraction of different enzymes by reversed micellar extraction.

•The liquefaction characteristics of rice husk in ethanol were systematically studied.•Too high temperature and solvent filling ratio resulted in lower bio-oil yields.•The bio-oil yields declined continuously with the increment of solid–liquid ratio.•NaOH was certified to be an ideal catalyst for rice husk liquefaction.•The bio-oils mainly consisted of phenolic compounds, long-chain alkanes and esters.Rice husk was converted into bio-oil via thermochemical liquefaction with ethanol as solvent in an autoclave (500 mL). The influences of reaction parameters on the yields of liquefaction products were investigated. Liquefaction experiments were performed at various reaction temperatures (T, 513–633 K), solid–liquid ratios (R1, 5–15%), and solvent filling ratios (R2, 10–30%) with or without catalyst. Two types of catalysts were involved, including iron-based catalysts (FeSO4 and FeS) and alkali metal compounds (NaCO3 and NaOH). The dosage of catalyst (R3) was also optimized. Without catalyst, the bio-oil yields ranged from 11.8% to 24.2%, depending on T, R1 and R2. And the bio-oil yields increased firstly and then decreased with increasing T and R2, while the bio-oil yields continuously declined with increasing R1. NaOH was certified to be an ideal catalyst for rice husk liquefaction and the optimal dosage was approximately 10%. The obtained bio-oils had much higher caloric values of 20.9–24.8 MJ/kg compared to 14.9 MJ/kg for the crude rice husk sample. Without catalyst, the main components of bio-oil were phenolic compounds. In the case of NaOH as catalyst, long-chain alkanes were the major compositions of bio-oil.

•NH2 functionalized MIL-125(Ti) was fabricated by a facile solvothermal method.•The photocatalyst could reduce Cr(VI)–Cr(III) under visible light irradiation.•The Ti3+–Ti4+ intervalence electron transfer is important for Cr(VI) reduction.•Used NH2-MIL-125(Ti) can be recycled for the photocatalytic 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 Ti3+–Ti4+ 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.Download full-size image

•g-C3N4–Sb2S3/Sb4O5Cl2 microspheres were synthesized via a facile hydrothermal method.•MO could be almost decomposed by the component SCL-C2 photocatalyst in 60 min.•O2− and H+ played the main roles in the degradation of the dye.A series of g-C3N4–Sb2S3/Sb4O5Cl2 (SCL-CX) composite photocatalysts were successfully prepared via a hydrothermal method. The as-prepared materials were characterized by TM3000, powder X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and UV–vis diffuse reflectance spectra (UV–vis DRS). The obtained photocatalyst showed higher photocatalytic activity than pure g-C3N4, Sb4O5Cl2 and Sb2S3/Sb4O5Cl2 (SCL). The optimum photocatalytic of the composite with the mass of 170 mg g-C3N4 and a degradation efficiency up to 95% for methyl orange (MO) under visible light was achieved within 60 min. The enhanced photocatalytic performance could be attributed to the stronger absorption in the visible region and the more efficient electron–hole separation.Download high-res image (197KB)Download full-size image