Hydrochar derived from hydrothermal carbonization (HTC) has been recognized as a promising carbonaceous material for environmental remediation. Organic solvents are widely used to extract bio-oil from hydrochar after HTC, but the effects of solvent extraction on hydrochar characteristics have not been investigated. This study comprehensively analyzed the effects of different washing times and solvent types on the hydrochar properties. The results indicate that the mass loss of hydrochar by tetrahydrofuran washing occurred mainly in the first 90 min, and the loss ratios of elements followed a descending order of H > C > O, resulting in a decrease in the H/C atomic ratio and an increase in the O/C atomic ratio. The use of various solvents for washing brought about hydrochar loss ratios in a descending order of petroleum ether < dichloromethane < acetone < tetrahydrofuran. The results from the Van Krevelen diagram and Fourier transform infrared, 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopies further confirmed that demethanation controlled this washing process. Most importantly, the surface area of hydrochar increased after bio-oil removal via washing, which promoted the surface area development for hydrochar-derived magnetic carbon composites, but to some extent decreased the microporosity. Additionally, hydrochar washing by organic solvent has important implications for the global carbon cycle and its remediation application.

•Monosaccharides, organic acids and phenolic compounds in HTL hydrolysates were recovered.•Hydrolysates derived from different conditions were separated by different ion exchange resins.•Separation processes of typical compounds: glucose, acetic acid and phenol, were inspected.This paper describes two effective ion exchange chromatography processes to separate and recover monosaccharides, organic acids and phenolic compounds from two kinds of hydrothermal liquefaction (HTL) hydrolysates derived under different temperatures. Anion exchange resin Amberlyst A21 (OH−) and cation exchange resin Amberlite IR-120 (Na+) were selected to separate synthetic solution and real hydrolystes by column chromatography. The results showed that glucose and acetic acid could be successfully separated by anion resin with purities of 87% and 98%, respectively. Acetic acid and phenol could be recovered by cation resin with purities up to 97% and 81%. In separation processes of real HTL hydrolysates, monosaccharides and organic acids in hydrolysate derived from low-temperature HTL were separated by anion exchange resin with recoveries of about 80% and 90%, respectively. Phenolic compounds in high-temperature HTL hydrolysate were recovered by cation exchange resin with recovery of about 70%.

•Combining HTL with subsequent technologies should be an important research direction.•Formic acid and formaldehyde are promising reagent for lignin depolymerization.•A breakthrough is needed in the development of new materials for advanced reactor.•Finding multifunctional catalysts is important for cutting down energy consumption.•Novel technologies for bio-oil refining and upgrading should be developed.Hydrothermal liquefaction has been widely applied to obtain bioenergy and high-value chemicals from biomass in the presence of a solvent at moderate to high temperature (200–550 °C) and pressure (5–25 MPa). This article summarizes and discusses the conversion of agricultural and forestry wastes by hydrothermal liquefaction. The history and development of hydrothermal liquefaction technology for lignocellulosic biomass are briefly introduced. The research status in hydrothermal liquefaction of agricultural and forestry wastes is critically reviewed, particularly for the effects of liquefaction conditions on bio-oil yield and the decomposition mechanisms of main components in biomass. The limitations of hydrothermal liquefaction of agricultural and forestry wastes are discussed, and future research priorities are proposed.

•Hydrothermal liquefaction of rice straw is conducted with NiO nanocatalyst.•Catalyzed reaction at 300 °C yielded 30.4% bio oil.•HHV of light oil and heavy oil is 24.9 MJ/kg and 31.9 MJ/kg respectively.•Phenols, alcohols and ketones are dominant chemical species in light oil.•Heavy oil mainly contained cyclic alkanes and organic acids.In this study, rice straw as an abundant agricultural waste was subjected to hydrothermal liquefaction for production of bio oil. The series of batch experiments were conducted at different temperatures (200 °C, 230 °C, 260 °C, 280 °C and 300 °C) for reaction time of 120 min with and without NiO nanocatalyst. The resulting bio-oil was categorized into light and heavy oils (LO and HO). In presence of nanocatalyst, the yields of LO and HO were maximized up to 13.2% and 17.2% at 300 °C, respectively. The carbon recovery of bio oil was significantly improved to 52.8% with 46.6% energy recovery in catalyzed reaction. Typical H/C and O/C atomic ratio of catalyzed HO are 1.2 and 0.3 respectively. The highest calorific values of LO and HO are 24.9 MJkg−1 and 31.9 MJkg−1 respectively. The tested nanocatalyst increased the yield of bio oil, but could not incite the elemental compositions and heating values of bio oil. The valuable chemical compounds in bio-oil had been analyzed by GC-MS. The LO samples mainly contained phenols, alcohols and ketones while HO consisted alkanes and organic acids. Additionally, aldehydes and other organic compounds were also found in products.Download high-res image (117KB)Download full-size image

Hydrothermal liquefaction (HTL) has been well studied for the bio-oil production from biomass. However, a large amount of wastewater with high organic content is also produced during the HTL process. Therefore, the present study investigated the methane potentials of hydrothermal liquefaction wastewater (HTLWW) obtained from HTL of rice straw at different temperatures (170–320 °C) and residence times (0.5–4 h). The characteristics (e.g., total organic content, organic species, molecular size distribution, etc.) of the HTLWW were studied, and at the same time, microbial community compositions involved in AD of HTLWW were analyzed.The highest methane yield of 314 mL CH4/g COD was obtained from the sample 200 °C–0.5 h (HTL temperature at 200 °C for 0.5 h), while the lowest methane yield 217 mL CH4/g COD was obtained from the sample 320 °C–0.5 h. These results were consistent with the higher amounts of hard biodegradable organics (furans, phenols, etc.) and lower amounts of easily biodegradable organics (sugars and volatile fatty acids) present in sample 320 °C–0.5 h compared to sample 200 °C–0.5 h. Size distribution analysis showed that sample 320 °C–0.5 h contained more organics with molecular size less than 1 kDa (79.5%) compared to sample 200 °C–0.5 h (66.2%). Further studies showed that hard biodegradable organics were present in the organics with molecular size higher than 1 kDa for sample 200 °C–0.5 h. In contrast, those organics were present in both the organics with molecular size higher and less than 1 kDa for sample 320 °C–0.5 h. Microbial community analysis showed that different microbial community compositions were established during the AD with different HTLWW samples due to the different organic compositions. For instance, Petrimonas, which could degrade sugars, had higher abundance in the AD of sample 200 °C–0.5 h (20%) compared to sample 320 °C–0.5 h (7%). The higher abundance of Petrimonas was consistent with the higher content of sugars in sample 200 °C–0.5 h. The higher Petrimonas abundance was consistent with the higher content of sugars in sample 200 °C–0.5 h. The genus Syntrophorhabdus could degrade phenols and its enrichment in the AD of sample 320 °C–0.5 h might be related with the highest content of phenols in the HTLWW.HTL parameters like temperature and residence time affected the biodegradability of HTLWW obtained from HTL of rice straw. More hard biodegradable organics were produced with the increase of HTL temperature. The microbial community compositions during the AD were also affected by the different organic compositions in HTLWW samples.

Facile fabrication of magnetic carbon composites (MCs) via pyrolysis of hydrochar in the presence of ZnCl2 and an iron salt has been attracting enormous interest to simultaneously realize high-surface area and magnetization. During this synthesis, the interactions between the carbon matrix and iron salts have remained unknown. In this work, a closer look was taken on iron salt interactions and their respective effect on MC characteristics. These newly fabricated MCs can provide guidance for further design of efficient MCs. It was discovered that ferric chloride (FeCl3) promoted the enhancement of MC porosity, largely due to the strong reduction reaction between amorphous carbon and iron oxide (γ-Fe2O3 and Fe3O4). Various other iron salts (including ferrous oxalate (FeC2O4), ferric citrate (FeC6H5O7), and ferric sulfate (Fe2(SO4)3) were also evaluated. These compounds inhibited pore structure development, resulting from decreased carbonization seen in the composite. This phenomenon was observed from complexation reactions between Zn2+ and the corresponding anions of these salts. Also, high Fe content and low γ-Fe2O3:Fe3O4 ratios led to decreased acid resistance of the MC. Finally, higher porosity in resultant MCs resulted in larger adsorption capacity for organic pollutants (roxarsone). This study will aid in further optimization of MCs to ultimately maximum performance.

•Reductive CuZnAl catalyst was used to improve the yields of monomeric phenols.•Rice straw was reacted in sub-/supercritical water and ethanol mixtures.•The CuZnAl catalyst was observed with strong stability.This work investigated the yields of monomeric phenols in bio-oil derived from hydrothermal liquefaction of rice straw (RS) in water and ethanol mixtures using a reductive CuZnAl catalyst. Based on the results of an initial analysis, five monomeric phenolic compounds were selected for research due to their higher concentrations, namely phenol, 4-ethyl-phenol, 2-methoxy-phenol, 2-methoxy-4-ethyl-phenol and 2,6-dimethoxy-phenol. The optimized conditions for the production of monomeric phenols can be determined as: 2 g of CuZnAl catalyst, a ratio of 50% ethanol/50% water (v/v), a temperature of 300 °C and a reaction time of 30 min. Results suggested that the maximum yield of total monomeric phenols could reach as high as ~ 26.8% (based on the mass of RS lignin), and that the aqueous phase yielded 95.5% of the monomeric phenols due to the solubilization of the ethanol. The CuZnAl catalyst was recycled five times, and a slight loss in activity was observed and examined using a number of technologies, including inductively coupled plasma, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray detection. The low-cost nature of the CuZnAl catalyst makes it an ideal catalyst for the enhancement of monomeric phenols yields in water and ethanol mixtures.

This study investigated the potential of eight types of green landscaping waste as feedstock to produce bio-oil through hydrothermal liquefaction (HTL). The eight selected plants differed in terms of botanical classification, morphology, leaf state, and growth habit. Leaves and branches as waste from these plants were separately subjected to HTL in a high-pressure batch reactor at 300 °C for 0.5 h. Results indicated the bio-oils and biochars of leaves obviously differed from those of branches in terms of yields and higher heating values (HHVs). However, less difference in yields and HHVs was found for HTL products within the eight leaves even though they were different in composition components such as cellulose, hemicelluloses, and lignin. The same was observed for branches. The average bio-oil yields of the leaves and branches were 33.74 and 43.22 wt%, respectively. The optimal bio-oil yield was 50.44 wt%, which was obtained when Cinnamomum camphora branches were used as feedstock. The average HHVs of light and heavy oils in the leaves were 25.13 and 31.27 MJ kg−1, respectively. These HHVs were higher than those of light and heavy oils in the branches (21.51 and 28.71 MJ kg−1, respectively). Among the oil products, the heavy oil derived from Salix alba leaves yielded the optimum HHV (35.63 MJ kg−1). The mean HHV of biochar was 24.17 MJ kg−1, which was considerably higher than that of feedstock (17.21 MJ kg−1). Gas chromatography-mass spectrometry and Fourier-transform infrared spectrometry revealed the presence of value-added chemicals, such as phenolics, ketones, esters, acids, and alcohols, in bio-oils. The amounts of alkanes, alkenes, and alkynes in the bio-oils derived from the leaves were higher than those in the bio-oils derived from the branches. These results indicated the feasibility of using different types of green landscaping waste as feedstock to produce bio-oils with high HHV and yield through HTL.

In recent years, chemical activation of hydrochar (a solid material from hydrothermal carbonization (HTC) of lignocellulosic biomass) has been shown to be effective in producing advanced porous materials. However, the linkage between the properties of hydrochar and the porosity of hydrochar-based porous carbon (a material from the chemical activation of hydrochar) has not yet been clearly explored. In the present study, the results indicated that the properties of hydrochar (including stability, thermal recalcitrance, aromaticity and polarity) were greatly affected by the HTC process (peak temperature and retention time). Accordingly, the porosities of hydrochar-based porous carbon (including surface area and pore volume) were determined by the properties of hydrochar. For instance, positive correlations were founded between porosities of porous carbon materials and element compositions (H/C, O/C, and (O+N)/C) of hydrochar materials. Moreover, negative correlations were observed between the porosities of porous carbon materials and thermal recalcitrance of hydrochar materials. In general, a porous carbon with high porosity was produced from a hydrochar with HTC process of low peak temperature and retention time. Undoubtedly, hydrochar-based porous carbons retain features characteristic of its parent material.Keywords: Correlation; Hydrochar; Porosity; Porous carbon; Properties;

Hydrothermal carbonization (HTC) is an aqueous-phase procedure to prepare charred material using biomass. To obtain a charred material with high porosity, ash content, and thermal recalcitrance, it is necessary to investigate the influence of HTC conditions (peak temperature, retention time, and feedstock type) on the properties of hydrochar and its derived pyrolysis char (HDPC). Additionally, the relative importance of these conditions for the selected properties was also investigated by heterogeneity index. The results indicated that the properties of both hydrochar and HDPC samples were greatly influenced by the HTC process. The ash content and major metal elements (Na, Mg, K, and Ca) of hydrochar and HDPC samples were strongly influenced by the feedstock type; other properties, such as surface area, carbon sequestration potential, total carbon, total nitrogen, and dissolved organic carbon were moderately influenced by the feedstock type. Overall, this study provided new insights into the relative importance of different HTC conditions in the properties of hydrochar and HDPC samples, which was an important process toward obtaining a “required” charred material for environmental remediation.

The effects of hydrochar properties on the environmental performances of its derived magnetic carbon composites have been overlooked. In the present work, various hydrochars (produced at different hydrothermal carbonization temperatures, 160–300 °C) were selected as the carbonaceous precursors. Then, magnetic carbon composites were fabricated by simultaneously carbonizing hydrochar, ZnCl2 and FeCl3 (namely simultaneous activation and magnetization). It was observed that a magnetic carbon composite with high porosity, acid resistance and adsorption capacity for roxarsone, and low graphitization degree was prepared from a hydrochar with low hydrothermal carbonization temperature. More importantly, strong linear correlations were obtained between hydrochar properties (recalcitrance index, H/C and O/C atomic ratios) and the environmental performances of its derived magnetic carbon composites (porosity, acid resistance, degree of graphitization, and adsorption capacity for roxarsone). The adsorption of ROX molecules onto the as-prepared magnetic carbon composites were mainly regulated by the pores of materials under certain pH of the solution. This work provides novel insights into the role of hydrochar properties in determining the environmental performances of its derived magnetic carbon composites.

•Recovery of sugar, aromatics and acetic acid from hydrolysates of lignocellulose.•Separation performances of ultrafiltration and nanofiltration were compared.•Two-stage NF process fractioned hydrolysates in to three usable fractions.Two-stage nanofiltration (TSNF) process was proposed for recovering high-value chemicals, including monophenols, cyclopentenones, glucose and acetic acid, from hydrolysates of lignocellulosic biomass (rice straw) through hydrothermal liquefaction (HTL). The separation performances of three single nanofiltration (NF) processes and three TSNF processes were studied. Results showed that at the first stage of (DL + DK) TSNF process, DL membrane had high glucose rejection of 97.12%, and lower acetic acid rejection as well as lower aromatics rejections than DK membrane. At the second stage, DK membrane had rather low acetic acid rejection of 5.04% to ensure acid separation from aromatics. Unlike glucose or acetic acid, aromatics were unable to be recovered into one fraction due to scattered rejections of different aromatic compounds on NF membrane. The (DL + DK) TSNF process was proved to be a feasible way to fractionate hydrolysates into three parts: glucose concentrate, monophenols and cyclopentenones concentrate, and acetic acid permeate.

Increasing attention is being paid to hydrothermal carbonization (HTC) of waste biomass, due to energy shortages, environmental crises and developing customer demands. However, most research has been dedicated to the production of bio-oil, with few studies focusing on the application of hydrothermal carbon (hydrochar), a solid residue from HTC of biomass. In this study, a novel porous carbon (PC) was prepared from hydrochar, via pyrolysis at different temperatures (300–700 °C), the characteristics of PC as well as tetracycline (TC) adsorption behavior were investigated. The hydrochar and PC samples showed a remarkable range of surface properties, as characterized by Boehm titration, the Fourier transform infrared spectra and nuclear magnetic resonance spectra. The changes in characteristics suggested that the PC samples produced at high activation temperature (500–700 °C) were well carbonized and exhibited a high surface area (>270 m2/g). Linear relationships were obtained between Freundlich adsorptive capacity (KF) and elemental atomic ratios, surface area and pore volume. The high adsorption capacity of PC samples can be attributed to its low polarity and high aromaticity, surface area and pore volume. The molecular variations among the hydrochar and PC samples translated into differences in their ability to adsorb TC.

Advanced magnetic carbon composites with high specific surface area and high microporosity are required for both environmentally and agriculturally related applications. However, more research is needed for the development of a facile and highly efficient synthesis process. In the present work, a novel approach of simultaneous activation and magnetization is proposed for the fabrication of magnetic carbon composites via the thermal pyrolysis of hydrochar (i.e., a solid residue from a hydrothermal carbonization process) that has been pretreated with mixtures of ferric chloride (FeCl3) and zinc chloride (ZnCl2). The main objective of this study is the investigation of the variation of characteristics of magnetic carbon composites produced at various conditions, as well as triclosan (TCS) adsorption behavior on such composites. This presented simple one-step synthesis method has the following advantages: (a) the hydrochar is activated with high surface area and pore volume (up to 1351 m2/g and 0.549 cm3/g, respectively), (b) activation and magnetization are simultaneously achieved without further modification, (c) the magnetic particles (γ-Fe2O3) are stable under an acidic medium (pH of 3.0 and 4.0), and (d) the products have the potential to remove TCS from aqueous solutions with a maximum adsorption capacity of 892.9 mg/g. The results indicate the effectiveness of this facile synthesis strategy in converting low-value biowaste into a functional material with high performance for pollutant removal from aqueous solutions.

In recent years, more and more attention has been paid to the hydrothermal liquefaction (HTL) of waste biomass for the production of bio-oil and hydrochar (a solid residue from HTL process). However, hydrochar possesses limited porosity and surface area, hindering its environmental application. In the present work, to promote the development of a sustainable application of waste biomass, waste hydrochar was activated and modified to a novel magnetic carbon composite, which exhibited high performance for dye removal from aqueous solutions. The composite possessed a saturation magnetization of 38.5 emu g–1 at room temperature and could be facilely attracted from an aqueous solution by an external magnet. The as-prepared composite exhibited a superior malachite green (MG) adsorption capacity (476 mg g–1), which was much higher than the known magnetic adsorbents. Our results suggested that the waste hydrochar could be efficiently transformed to a high-performance sustainable material for dye removal.Keywords: Adsorption; Hydrochar; Magnetic carbon composite; Malachite green

Recently, considerable attention has been given to the hydrothermal liquefaction (HTL) of waste rice straw for the production of bio-oil and hydrochar. However, hydrochar material could not be directly applied in the environmental field, due to its limited porosity and surface area. In order to improve the porosity and adsorption capacity of rice straw-derived hydrochar, it was activated and magnetized to a magnetic activated carbon. The activation condition for hydrochar was firstly considered, due to the negative effect of the magnetic medium. Results suggested that the as-prepared magnetic activated carbon possessed a large surface area (around 674 m2 g−1), and exhibited both a high adsorption capacity and a fast adsorption rate for triclosan (TCS) removal. In addition, magnetic activated carbon can be easily recovered from aqueous solutions by an external magnetic field. Overall, the waste rice straw-derived hydrochar can be transformed to a highly efficient magnetic adsorbent for TCS removal.

The liquefaction of “green tide” macroalgae Enteromorpha prolifera in sub-/supercritical alcohols in a batch reactor had been investigated. Effects of the temperature and algae/solvent ratio on the liquefaction yields in methanol and ethanol were studied. The results showed that, under the conditions of the reaction time of 15 min and algae/solvent ratio set at 1:10, the macroalgae in methanol at 280 °C produced a bio-oil yield at 31.1 wt % of dry weight and the ethanol at 300 °C yielded bio-oil at 35.3 wt %. Different from bio-oils obtained by hydrothermal liquefaction of microalgae as well as macroalgae in our previous work, the bio-oils obtained by liquefaction of macroalgae in alcohols are mainly composed of ester compounds. A variety of fatty acid (C3–C22) esters (methyl or ethyl) in the bio-oils obtained in methanol and ethanol, respectively, were qualified by gas chromatography–mass spectrometry, and their relative contents are above 60% of the total area for each bio-oil. In addition, some N-containing compounds, sugars, fatty alcohols/ketones, and very few hydrocarbons were also qualified. Overall, bio-oils obtained in two alcohols are much similar to biodiesel on the composition. The elemental analysis of bio-oils indicated that bio-oils still have high oxygen contents. Moreover, the bio-oils are found to contain a considerable fraction of light components using thermogravimetric analysis (TGA), and the contents of low-boiling-point (bp < 350 °C) compounds are up to 70% of the weight for both bio-oils; therefore, it might help for the further separation and refining of bio-oils to produce fuels and chemicals.

This study investigated the feasibility, kinetics, and reaction pathways of the photocatalytic degradation of dimethyl sulfide (DMS) in a light-emitting-diode- (LED-) based continuous reactor. Four types of LEDs, with peak wavelengths at 365, 375, 385, and 402 nm, were used for comparison. The data were fitted with the Langmuir–Hinshelwood kinetic model, in which the rate constants for 365- and 375-nm LEDs were significantly larger than those for the 385- and 402-nm LEDs. The effect of wavelength on the reaction rate followed the TiO2 absorption spectrum. The effect of radiation intensity agreed with a nonlinear power law and was attributed to the TiO2 absorption of photon energy. For the 365- and 375-nm LEDs, the transition of the exponent values from first-order to one-half-order was estimated to occur at 0.5–1.0 mW·cm–2, whereas the 385- and 402-nm LEDs did not show a transition at this intensity. Dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO2), dimethyl disulfide (DMDS), methanethiol (MT), methanesulfonic acid (MSA), and sulfate were identified as the reaction products by gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and ion chromatography (IC). A plausible reaction mechanism is proposed for DMS photocatalytic degradation based on the reaction products detected and possible intermediates formed.

Marine macroalgae Enteromorpha prolifera, one of the main algae genera for green tide, was converted to bio-oil by hydrothermal liquefaction in a batch reactor at temperatures of 220−320 °C. The liquefaction products were separated into a dichloromethane-soluble fraction (bio-oil), water-soluble fraction, solid residue, and gaseous fraction. Effects of the temperature, reaction time, and Na2CO3 catalyst on the yields of liquefaction products were investigated. A moderate temperature of 300 °C with 5 wt % Na2CO3 and reaction time of 30 min led to the highest bio-oil yield of 23.0 wt %. The raw algae and liquefaction products were analyzed using elemental analysis, Fourier transform infrared (FTIR) spectroscopy, gas chromatography−mass spectrometry (GC−MS), and 1H nuclear magnetic resonance (NMR). The higher heating values (HHVs) of bio-oils obtained at 300 °C were around 28−30 MJ/kg. The bio-oil was a complex mixture of ketones, aldehydes, phenols, alkenes, fatty acids, esters, aromatics, and nitrogen-containing heterocyclic compounds. Acetic acid was the main component of the water-soluble products. The results might be helpful to find a possible strategy for use of byproducts of green tide as feedstock for bio-oil production, which should be beneficial for environmental protection and renewable energy development.

Characterization and quantification of livestock odorants is one of the most challenging analytical tasks because odor-causing chemicals are very reactive, polar, and often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this research was to develop a novel analytical method for characterization of the livestock odorants including their odor character, odor intensity, and hedonic tone and to apply this method for quantitative analysis of the key odorants responsible for livestock odor. Field samples were collected with sorbent tubes packed with Tenax TA. The automated one-step thermal desorption module coupled with multidimensional gas chromatography–mass spectrometry/olfactometry system was used for simultaneous chemical and odor analysis. Fifteen odorous VOCs identified from livestock operations were quantified. Method detection limits ranged from 30 pg for indole to 3590 pg for acetic acid per sample. In addition, odor character, odor intensity, and hedonic tone associated with each of the target odorants were also analyzed simultaneously. The mass of each VOC in the sample correlated well with the log stimulus intensity of odor. All of the coefficients of determination (R2) were greater than 0.74, and the top 10 R2s were greater than 0.90. Field air samples from swine and dairy operations confirmed that target compounds quantified represented typical odor-causing compounds emitted from livestock.

Bi2WO6 multilayer films have been fabricated successfully by a layer-by-layer (LbL) technique from Bi2WO6 nanoplates, which show higher visible-light photoactivity (λ>420 nm) than that of Bi2WO6 nanoplate powders and P25 TiO2 films. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV–visible absorption spectroscopy. Photocatalytic activities of the films were evaluated by the rhodamine B (RhB) decomposition under UV and visible-light irradiation. Thickness and photoactivity of the film can be modified easily by changing the deposition cycles. Bi2WO6 films have the spectral selectivity of the photocatalytic degradation of RhB. Under the wavelength greater than 300 nm, the RhB molecules tend to be transformed to rhodamine over Bi2WO6 films selectively. However, in the case of shorter wavelength (λ=254 nm) light irradiation, the RhB molecules can be photodegraded completely.Bi2WO6 multilayer film fabricated by layer-by-layer technique.

•Recovery of sugar, aromatics and acetic acid from hydrolysates of lignocellulose.•Separation performances of ultrafiltration and nanofiltration were compared.•Two-stage NF process fractioned hydrolysates in to three usable fractions.Two-stage nanofiltration (TSNF) process was proposed for recovering high-value chemicals, including monophenols, cyclopentenones, glucose and acetic acid, from hydrolysates of lignocellulosic biomass (rice straw) through hydrothermal liquefaction (HTL). The separation performances of three single nanofiltration (NF) processes and three TSNF processes were studied. Results showed that at the first stage of (DL + DK) TSNF process, DL membrane had high glucose rejection of 97.12%, and lower acetic acid rejection as well as lower aromatics rejections than DK membrane. At the second stage, DK membrane had rather low acetic acid rejection of 5.04% to ensure acid separation from aromatics. Unlike glucose or acetic acid, aromatics were unable to be recovered into one fraction due to scattered rejections of different aromatic compounds on NF membrane. The (DL + DK) TSNF process was proved to be a feasible way to fractionate hydrolysates into three parts: glucose concentrate, monophenols and cyclopentenones concentrate, and acetic acid permeate.