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• The effect of dissolved organic matters (DOM) on organic degradation was explored. • Oxidation pathway of different DOM compounds was elucidated. • Evolution of DOM and inhibition mechanisms to pollutant degradation were revealed. • CHO-, CHON-, CHOS-, CHOP- and CHONP-based molecules showed moderate inhibition. Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular transformation behavior of DOM during peroxymonosulfate (PMS) activation by biochar for organic degradation in a secondary effluent were comprehensively analyzed. Evolution of DOM was identified and inhibition mechanisms to organic degradation were elucidated. DOM underwent oxidative decarbonization (e.g., –C 2 H 2 O, −C 2 H 6 , –CH 2 and –CO 2), dehydrogenation (–2H) and dehydration reactions by ·OH and SO 4 ·−. N and S containing compounds witnessed deheteroatomisation (e.g., –NH, –NO 2 + H , –SO 2 , –SO 3 , –SH 2), hydration (+H 2 O) and N/S oxidation reactions. Among DOM, CHO-, CHON-, CHOS-, CHOP- and CHONP-containing molecules showed moderate inhibition while condensed aromatic compounds and aminosugars exhibited strong and moderate inhibition effects on contaminant degradation. The fundamental information could provide references for the rational regulation of ROS composition and DOM conversion process in a PMS system. This in turn offered theoretical guidance to minimize the interference of DOM conversion intermediates on PMS activation and degradation of target pollutants. [ABSTRACT FROM AUTHOR]

Highlights • SVUV-PIMS was utilized to study the catalytic pyrolysis of xylan. • Main products were identified by PIE measurements. • The catalytic effect was enhanced with the Na 2 CO 3 -to-xylan ratio (<5%) increasing. • The formation of furfural and anhydro sugars were suppressed by Na+ and K+. • The activation energy of xylan degradation was decreased by Na+ and K+. Abstract Xylan is the primary hemicellulose polysaccharide found in biomass. In this study, catalytic pyrolysis of xylan with Na 2 CO 3 and K 2 CO 3 was conducted in a homemade tubular furnace at 300 °C. As a result of on-line sampling and the use of tunable synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), the evolution of unstable products, such as 4-hydroxy-5,6-dihydro-pyran-2-one (m/z 114), could be monitored in real time. The obtained photoionization mass spectra were interpreted by statistical analysis and the mechanisms of xylan pyrolysis with alkali metal salts were further discussed. The differences in thermogravimetry curves, photoionization mass spectra and time-evolved profiles revealed the important effects of alkali metal ions on both the decomposition temperature and reaction rates during xylan pyrolysis. Furthermore, we showed that alkali metal ions can promote the formation of char and lighter compounds. This work can provide guidance on the better utilization of hemicellulose resources with the help of alkali metal salts. [ABSTRACT FROM AUTHOR]

The catalytic cracking upgrading reactions over HZSM-5 of different model compounds of bio-oil have been studied with a self-designed fluid catalytic cracking (FCC) equipment. Typical bio-oil model compounds, such as acetic acid, guaiacol, n-heptane, acetol and ethyl acetate, were chosen to study the products distribution, reaction pathway and deactivation of catalysts. The results showed: C 6 –C 8 aromatic hydrocarbons, C 2 –C 4 olefins, C 1 –C 5 alkanes, CO and CO 2 were the main products, and the selectivity of olefins was: ethylene > propylene > butylene. Catalyst characterization methods, such as FI-IR, TG-TPO and Raman, were used to study the deactivation mechanism of catalysts. According to the catalyst characterization results, a catalyst deactivation mechanism was proposed as follows: Firstly, the precursor which consisted of a large number of long chain saturated aliphatic hydrocarbons and a small amount C C of aromatics formed on the catalyst surface. Then the active sites of catalysts had been covered, the coke type changed from thermal coke to catalytic coke and gradually blocked the channels of the molecular sieve, which accelerated the deactivation of catalyst. [ABSTRACT FROM AUTHOR]

Raw bio-oil was produced from fast pyrolysis of pine sawdust in a fluidized-bed boiler at 550 °C. Then the raw bio-oil is partially mixed with kitchen waste oil (100:0, 50:50, 0:100 by weight) and subsequently subjected to off line co-catalytic cracking process for upgrading over HZSM-5. The raw bio-oil mixed with kitchen waste oil test shows that the co-catalytic cracking improves the organic bio-oil yield and inhibits the coke formation. The oxygen content of organic bio-oil decreased significantly after upgrading. The reaction pathway of co-upgrading is proposed, which shows that kitchen waste oil, as a hydrogen supplier, transform hydrogen from high saturation degree to the unsaturation oxygenated compounds to form hydrocarbons. Co-catalytic cracking process of raw bio-oil and kitchen waste oil not only can be used in raw bio-oil upgrading but also can recycle kitchen waste oil with relatively low cost. Moreover, the deactivation catalysts are analyzed by TG-FTIR (Thermogravimetric-Fourier Transform Infrared spectroscopy) and SEM (Scanning Electron Microscope). [ABSTRACT FROM AUTHOR]

Due to the wide applications of polyurethane (PU), production is constantly increasing, accounting for 8% of produced plastics. PU has been regarded as the 6th most used polymer in the world. Improper disposal of waste PU will result in serious environmental consequences. The pyrolysis of polymers is one of the most commonly used disposal methods, but PU pyrolysis easily produces toxic and harmful nitrogen-containing substances due to its high nitrogen content. This paper reviews the decomposition pathways, kinetic characteristics, and migration of N-element by product distribution during PU pyrolysis. PU ester bonds break to produce isocyanates and alcohols or decarboxylate to produce primary amines, which are then further decomposed to MDI, MAI, and MDA. The nitrogenous products, including NH3, HCN, and benzene derivatives, are released by the breakage of C-C and C-N bonds. The N-element migration mechanism is concluded. Meanwhile, this paper reviews the removal of gaseous pollution from PU pyrolysis and discusses the removal mechanism in depth. Among the catalysts for pollutant removal, CaO has the most superior catalytic performance and can convert fuel-N to N2 by adsorption and dehydrogenation reactions. At the end of the review, new challenges for the utilization and high-quality recycling of PU are presented [Display omitted] • The factors influencing Ea of PU includes sample, model and experimental condition. • Nitrogen-containing products are produced by isocyanate cleavage and recombination. • The CaO with superior activity can convert NH 3 and HCN into N 2. • Changing raw materials and adding flame retardants will inhibit the formation of HCN. • The new challenges of PU utilization and high-quality recovery are put forward. [ABSTRACT FROM AUTHOR]

N-methyl pyrrole (NMP) is an important nitrogenous heterocyclic compound in bio-oils produced from biomass conversion. NMP can be used as surrogate model compound to clarify the combustion chemistry of nitrogenous fuels and NO X formation mechanism. The low- to moderate-temperature oxidation experiments of NMP are carried out in atmospheric pressure jet-stirred reactor for 0.5% NMP/oxygen/Argon mixtures at different equivalence ratios (0.5, 1.0, and 2.0) over the temperature range of 760 – 1030 K. More than twenty species, including reactants, nitrogen-containing species, and oxygenated products, are measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A detailed and comprehensive kinetic model for NMP oxidation is developed for the first time based on the pyrrole oxidation model developed by Pelucchi et al. and Chen et al.. Simulated results show that the present model can reasonably reproduce the experimental results. Rate of production analysis indicates that the H-abstraction reactions on the methyl group dominate in NMP oxidation at all equivalence ratios. NMP oxidation produces C4 and C5 nitrogen-containing compounds including pyridine and pyrrole. These species are found to be products of the primary reactions of NMP, and their formation pathways can be explained satisfactorily by the present model. The present work provides a basis to further understand the oxidation characteristics of nitrogen-containing heterocyclic fuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reutilizing ash to gasification process was feasible. • Ash played dual objective in improving gas product quality and adsorbing SO 2. • Metals in ash promoted the Dry or/and Steam reforming and Water-gas reaction. • The optimal condition of ash loading was 10 wt%. • The regenerated ash behaved a higher fertilizer potential. Due to the significant growth of the biomass gasification industry, management and disposal of ash has become one of the major environmental issues. This work proposed an innovative strategy that reutilizes ash into gasification process based on its potential catalysis to improve gas products. Reutilization of ash from corn straw (CS) air gasification in a downdraft fixed-bed gasifier was conducted for a feasibility analysis. The effect of ash loading rates (2 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%) on gasification performance were evaluated for an optimal condition analysis. Ash reutilization was proved to be feasible and able to achieve dual objective of improving gas product quality and reducing SO 2 release. Results revealed that loading ash exhibited catalysis promoting CO formation, which correlated with the metal active sites provided by the ash and led to an improvement in dry or/and steam reforming. H 2 production was also improved. These positive effects increased as ash loading rates increased, and maximum CO and H 2 content (19.97 vol% and 15.72 vol%) were achieved at the ash loading rate of 10 wt%. Accordingly, the maximum LHV of gas products (6.47 MJ/Nm3) and the minimum tar content (3.62 g/Nm3) were obtained. While excess ash (loading rate > 10 wt%) showed unsatisfactory performance, even being far behind CS gasification without ash addition. Due to containing CaO, gasification ash showed SO 2 capture capacity by forming CaSO 4. This reaction competed with the concurrent CaO carbonation, whereas the latter was the priority. The properties of by-products (regenerated ash) were evaluated for overall economic benefits, and the results indicated that it had a high fertilizer potential. These results seemed to be interesting and valuable for ash utilization and effective gasification. [ABSTRACT FROM AUTHOR]

The thermogravimetric (TG) experiments of cattle manure were carried out from room temperature to 900 °C at five different heating rates (10, 20, 30, 40 and 50 °C/min) and the kinetics of the main decomposition process were analyzed with different methods. TG curves indicate that the major decomposition process of cattle manure could be roughly divided into three stages. The average activation energy of each stage calculated by Coats-Redfern method are 68.95, 2.63 and 55.32 kJ/mol respectively. The kinetic parameters given by Distributed Activation Energy Model method, Flynn-Wall-Ozawa method and Vyazovkin method are all show that the activation energies keep stable (at around 122.4, 126 and 123.8 kJ/mol respectively) under 60% conversion degree and then changed dramatically (ranging from 129.9 to 454.9 kJ/mol). Power law (P3) was determined as an appropriate reaction mechanism using master-plots method. The kinetic parameters calculated by Vyazovkin method can give the best agreement with the experimental results. [ABSTRACT FROM AUTHOR]

• High precision schematic energetics calculation. • Site-specific reactivity. • Revealing the competing relationship between OH-addition and H-abstraction pathways. • Providing valuable kinetic data in a wide temperature and pressure condition. Oxidation of furan-based biofuels in the atmosphere and combustion are mainly initiated by reactions with small radicals (e.g. OH radical), the kinetics of which are crucial to obtain a comprehensive understanding of combustion processes, especially in engine operation. However, the structure- and site-dependent chemistry for OH-initiated reactions of furans with oxygenated substituents is unknown. In the present study, 2-furfuryl alcohol (2FFOH) was selected as a model fuel, and a full schematic energy diagram for 2FFOH with OH was calculated by a high-level quantum chemical method (CCSD(T)/CBS//M06-2X/def2-TZVP). The temperature- and pressure-dependent behavior of the rate coefficients k (T , P) for 2FFOH with OH was calculated at 298–2500 K and 0.01–10 atm by using the Rice–Ramsperger–Kassel–Marcus/Master equation method. Our calculations reveal that the rate coefficients of H-abstraction from the side chain are faster than those from the ring at T ≤ 2300 K. The observed temperature dependence behaviors of the total rate coefficients are consistent with prior experimental studies of other furans (e.g., furan, 25DMF and 2MF) with OH. The total rate coefficients of 2FFOH with OH exhibit a slightly positive pressure dependence only in the temperature range of 500–1000 K. We also found that the OH-addition pathways for 2FFOH with OH system dominate at T ≤ 1300 K. Moreover, the thermodynamic and kinetic data determined in the present work would be valuable for the future development of the fundamental chemical reaction mechanism of furan-based fuels in the atmosphere and combustion. [ABSTRACT FROM AUTHOR]

The rate constants for H-initiated reactions of 2-furfuryl alcohol (2FFOH) were calculated for the first time by a high-level quantum chemical method combined with the Rice–Ramsperger–Kassel–Marcus (RRKM) theory/Master equation method. A detailed potential energy surface was constructed by the CCSD(T)/CBS//M06–2X/def2-TZVP method, involving H-abstraction, initial H-addition, adduct-subsequent pathways and interconnected conversion pathways. The H-addition reaction on the β -carbon and δ -carbon sites to form bimolecular products 2-methylene-2,3-dihydrofuran plus OH and 2-methylene-2,5-dihydrofuran plus OH were found to be the major product channels at high temperatures. No significant pressure dependence is observed for the total rate constants of 2FFOH + H. However, the overall kinetics behavior does not reflect the site characteristics, i.e., the site-specific rate constants for each reaction channel show different temperature and pressure dependences. The total rate constants via the H-addition mechanism are higher by factors of 3.3–10 than those via H-abstraction channels under all studied conditions. The present updated kinetic model obtained by applying these new calculated rate constants can better predict 2FFOH decomposition, especially at 30 Torr, and it can also lead to good predictions of the speciation profiles (e.g., vinyl ketene) during 2FFOH pyrolysis. The data calculated in the present work can provide valuable information for the development of combustion models of furan-based biofuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • A zero-waste biorefinery concept was developed by pyrolyzing the residual microalgae biomass. • The pyrolysis process was effectively modeled using an integrated ANN and RSM technique. • The maximum H 2 production of 44.46 vol% was produced at optimal conditions. • At 500 °C, max. hydrocarbons and min. N- & O-containing compounds observed in bio-oil. • With the increasing temperature, the biochar exhibited more cracks and holes. The present work focused on the pyrolysis-based valorization of microalgae biomass residual for the generation of sustainable fuel and value-added chemicals. Key pyrolysis factors, including temperature, residence time, particle size, and heating rate, were modeled via an artificial neural network (ANN) and response surface methodology (RSM) models. The use of such an integrated technique was able to conquer the individual constraints of both modeling approaches. RSM model for H 2 -rich syngas demonstrated that the value; R2 = 0.99, minimum p = 0.00, and maximum F = 3877.16 has close relation among the statistical parameters. The ANN model for H 2 -rich syngas revealed that higher R2 = 0.9985 and lower RSME = 0.1038 were obtained for the training phase, while; the higher R2 and lower RSME values of 0.9862 and 0.2661 were estimated for the training phase hence showed a better agreement among the parameters. Optimum H 2 production of 44.46 vol% was produced at temperature = 516.76 °C, residence time = 17.7 min, particle size = 0.23 mm, and heating rate = 17.37 °C/min. All the pyrolytic products have been characterized in detail and are recommended for high end-use. The GC/MS technique revealed that bio-oil was constituted of various organic complexes, which could be used as a substitute for hydrocarbon fuels after undergoing certain upgradation procedures (e.g., hydrotreating, hydrodeoxygenation, hydrodenitrogenation, and hydrocracking) and extracted into different chemicals. In addition, the biochar was characterized using the SEM technique, which also demonstrated its potential as fuel and in a variety of other applications. The study showed that de-fatted Chlorella sorokiniana residue (De-CR) could be efficiently employed to produce bio-energy precursors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fast characterization method for biodiesel using ATR-FTIR and ML was proposed. • The optimal accuracy of the characterization method could reach as high as 100%. • Data downscaling improved the correlation of the biodiesel model to approx. 0.92. • PC4 and PC5 in the data downscaling had the highest weight in the biodiesel model. • This study is promising for the development of the biodiesel production industry. This study proposed a fast characterization method for biodiesel based on attenuated total reflection flourier-transform infrared spectroscopy and machine learning models. The concerning characteristics of biodiesel include unsaturated group content, O content, and contents of four representative esters. A total of 71 biodiesel samples were produced from a lab-scale reactor. Their spectral data and characteristics were collected and used as training data for machine learning models. The established model framework consisted of two data compression sections, a classification section, and a regression section, all of which use machine learning models, such as principal component analysis, support vector machine, artificial neural network, and random forest. The accuracy, correlation, and sensitivity of the proposed method were evaluated and optimized. Furthermore, the interpretation of the models was discussed. The results showed that the principal component analysis model was a satisfactory preprocessing procedure for the downstream classification and regression models. Under the optimal model parameters, the integrated framework could reach an average accuracy rate of 93.18% and a Pearson correlation coefficient of 0.92. Principal component number 4 and 5 showed the highest sensitivity towards the predicting results, implying that their highly weighted wavenumber ranges and the correlated functional groups played the most important role in the predicting process. The findings of this study could lead to a simple and efficient approach for characterizing the properties of biodiesel, which in turn could promote the development of similar biomass-derived liquid fuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Pt-decorated shrimp shell biochar was applied as cathode catalyst. • The Pt/SSB catalysts achieved efficient and selective conversion of phenol. • The C C and C O bonds in precursor were reduced by [H] to produce cyclohexanol. • The C O, Pt, and Pt-N x sites dominated in phenol conversion. The development of highly-active electrocatalysts and identification of active sites contribution are necessary for electrocatalytic hydrogenation (ECH) of bio-oil. Herein, the Pt-decorated shrimp shell biochar (SSB) catalysts with high nitrogen content was prepared successfully. The biochar-based catalysts were first used for the ECH of bio-oil model compounds. Results showed that the Pt/SSB catalysts exhibited excellent electrocatalytic activity and stability, realizing 100 % conversion of phenol and 98 % total selectivity of cyclohexanone and cyclohexanol within 5 h. By correlation analysis and density functional theory (DFT) calculations, the Pt, Pt-N x , and C O sites in Pt/SSB catalysts were found to play an important role in the stepwise hydrogenation of phenol. Furthermore, the Pt-N x sites were identified as the main contributor to the high selectivity of cyclohexanol generation. This study lays the foundation for the controllable preparation of electrocatalysts with high activity and stability, which is significant for large-scale upgrading of bio-oil in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • TAP can remove organic pollutants from wastewater effectively. • Direct, microwave and photo heating are major heating types for PS activation. • SO 4 •− and •OH are main ROS in TAP systems. • The synergistic activation of PS by catalysts and heat facilitates decontamination. • Most anions and DOM inhibit TAP oxidation, while catalysts usually promote it. Thermal activation of persulfates (TAP) is a facile and easy-to-operate advanced oxidation technology for on-site decontamination of organic pollutants. Sulfate (SO 4 •−) and hydroxyl radicals (•OH) are the typical reactive oxygen species (ROS) in the processes of TAP. To date, numerous TAP systems have been developed to degrade recalcitrant contaminants in water. However, a comprehensive analysis of different thermal activation modes, particularly mechanisms and controlled generation of ROS, has not yet been reported. In this work, we present an overall review on different TAP systems. Specifically, diverse heating approaches such as thermal heating, microwave-induced heating and photothermal heating have different features in TAP and generate varying performances. Microwave heating for persulfate activation usually performs better than thermal heating at the same temperature, due to the intensified generation of radicals and boosted oxidation kinetics. Photothermal heating is cost-effective and eco-friendly via using sustainable solar energy. Moreover, the most appealing aspect of TAP is the promise of leveraging industrial waste heat to establish upscale integrated systems. Solution pH and background factors (e.g. , anions and dissolved organic matters) have complicated impacts because of radical scavenging and the production of less reactive or reductive species. In addition, the presence of homogeneous and heterogeneous catalysts can enhance the activity of TAP systems at low temperature, while the synergistic contribution of catalytic oxidation will be less significant at high reaction temperature. Finally, conclusions and challenges of TAP systems in actual water remediation are presented. [ABSTRACT FROM AUTHOR]

Biochar (e.g. pyrochar and hydrochar) is considered a promising adsorbent for Cd removal from aqueous solution. Considering the vastly different physicochemical properties between pyrochar and hydrochar, the Cd2+ sorption capacity and mechanisms of pyrochars and hydrochars should be comparatively determined to guide the production and application of biochar. In this study, the hydrochars and pyrochars were prepared from Napier grass by hydrothermal carbonization (200 and 240 °C) and pyrolysis (300 and 500 °C), respectively, and the physicochemical properties and Cd2+ sorption performances of biochars were systematically determined. The pyrochars had higher pH and ash content as well as better stability, while the hydrochars showed more oxygen-containing functional groups (OFGs) and greater energy density. The pseudo second order kinetic model best fitted the Cd2+ sorption kinetics data of biochars, and the isotherm data of pyrochar and hydrochar were well described by Langmuir and Freundlich models, respectively. In comparison with hydrochar, the pyrochar exhibited better Cd2+ sorption capacity (up to 71.47 mg/g). With increasing production temperature, the Cd2+ sorption capacity of pyrochar elevated, while the reduction was found for hydrochar. The mineral interaction, complexation with surface OFGs, and coordination with π electron were considered the main mechanisms of Cd2+ removal by biochars. The minerals interaction and the complexation with OFGs was the dominant mechanism of Cd2+ removal by pyrochars and hydrochars, respectively. Therefore, the preparation technique and temperature have significant impacts on the sorption capacity and mechanisms of biochar, and pyrochar has better potential for Cd2+ removal than the congenetic hydrochar. [Display omitted] • Cd2+ sorption capacity of biochar was affected by production technique and temperature. • Pyrochar exhibited greater Cd2+ adsorption capacity than hydrochar. • The interaction with minerals dominated the Cd2+ adsorption on pyrochars. • Complexation with OFGs was the main mechanism of Cd2+ adsorption on hydrochars. [ABSTRACT FROM AUTHOR]

[Display omitted] • CLGOU of biogas residue was investigated on Mn-doped Ca 2 Fe 2 O 5 oxygen carrier. • Oxygen uncoupling capability was observed on Mn-doped Ca 2 Fe 2 O 5. • The doped Mn led to the conversion of lattice oxygen to active oxygen. • The cold gas efficiency and carbon conversion efficiency for MCF were 13.37% and 17.22% higher than CF. • The results proved the potential of CLGOU as an effective method to treat biogas residue. Anaerobic digestion is an important approach to treat and utilize kitchen waste, while kitchen waste derived biogas residue (BR) disposal remains a serious problem in this process. This study investigated the feasibility of chemical looping gasification (CLG) as an efficient way to treat and generate syngas from BR. Besides, Mn-doped Ca 2 Fe 2 O 5 (MCF) as a novel oxygen carrier with mild oxygen uncoupling capability was developed, and its performance against traditional Ca 2 Fe 2 O 5 (CF) oxygen carrier was compared. Results indicated that, significant oxygen release capability was observed on the prepared MCF oxygen carrier. In the gasification tests, CLG with MCF at 800 ℃ showed optimal total gas yield, carbon conversion, and cold gas efficiency, which increased 0.08 Nm3/kg, 17.22%, and 13.37% compared to CF, respectively. According to the XPS, H 2 -TPR and XRD characterization results, the optimal performance of MCF could be attributed to the oxygen uncoupling characteristic brought by Mn addition. The formation of the oxygen uncoupling capability of MCF could be explained by three reasons: (1) Mn in MCF mainly existed in form of Mn3+ and Mn4+, which resulted in the extremely strong oxidability at a temperature as low as 250 ℃. (2) The higher Fe3+/Fe2+ ratio of 1.55 in MCF than CF caused by Mn addition led to greater oxidability of Fe ions. (3) MCF had a higher lattice oxygen amount than CF at about 3.86%, and the lattice oxygen in its crystal structure had been transformed into active lattice oxygen species, which were between lattice oxygen (O2–) and atomic adsorbed oxygen (O−). As a result, this paper investigated the potential of CLG to treat and utilized BR, and the superiority of CLG with oxygen uncoupling (CLGOU) on MCF was highlighted. It's hoped that this study could provide a fundamental knowledge on CLG and CLGOU of BR, and benefit to better downstream process design of anaerobic digestion industry. [ABSTRACT FROM AUTHOR]

2-Furfuryl alcohol, derived from non-edible biomass, is the significant component of bio-oil in the pyrolysis of lignocellulose biomass and a potential alternative fuel or fuel additive. To better optimize the pyrolysis model of lignocellulose to improve the properties of pyrolysis bio-oil and further understand the combustion characteristics of 2-furfuryl alcohol, the pyrolysis experiments were performed in a flow reactor at 30 Torr for T = 1006 – 1339 K and 760 Torr for T = 850 – 1131 K, and in a jet-stirred reactor at 760 Torr for T = 750 – 1050 K. The pyrolysis products, including radicals (methyl, propargyl, allyl, and cyclopentadienyl), isomers (furfural/2-ethyl furan, furan/vinyl ketene, and allene/propyne), and aromatics (benzene, toluene, indene, etc.) were identified and measured using synchrotron vacuum ultraviolet photoionization mass spectrometry. A comprehensive kinetic model for 2-furfuryl alcohol pyrolysis was developed and was validated against the experimental data in the present and previous work. Rate of production analysis indicated that the C–O bond dissociation reaction, H-abstraction reactions on the hydroxymethyl group, and the H-addition reactions on the furan-ring controlled the consumption of 2-furfuryl alcohol and the formation of primary pyrolysis products like 2-methyl furan, 2-ethyl furan, furfural, and furan. In addition, the OH-addition reaction on the furan-ring had a certain contribution to the consumption of 2-furfuryl alcohol, while the contribution of H-shift reactions was negligible. The present work systematically compared the effects of methyl, ethyl, and hydroxymethyl groups on the decomposition of furanic fuels and the formation of major products. The results showed that the substituent groups can reduce the decomposition temperature of the fuels, especially the ethyl and hydroxymethyl groups. The alkyl substituent group can promote the formation of small hydrocarbons, of which the mole fraction increased with the length of the carbon chain increasing. The hydroxymethyl group facilitated the formation of oxygenated products. [ABSTRACT FROM AUTHOR]

• Effect of torrefaction temperature on the combustion characteristics of lignite was studied. • Torrefaction significantly improves combustion performance of lignite with a higher reactivity. • The optimum torrefaction temperature for lignite upgrading was determined as 200 °C. • Kinetic analysis indicates that torrefaction had no significant effects on activation energies. Torrefaction treatment is a promising method for lignite upgrading. However, its effect on the combustion characteristics has not been fully evaluated. In this study, the combustion characteristics of lignite and its upgrading samples by torrefaction were studied via non-isothermal thermogravimetric analysis. Results show that increasing the torrefication temperature decreases the volatile content while increasing the fixed-carbon in the fuels. The mole ratios of both H/C and O/C in the samples decreases as the torrefaction temperature increases. Torrefaction treatment significantly improves the combustion performance of lignite with a higher reactivity index S , and the optimum torrefaction temperature was determined to be 200 °C. The upgrading lignite by torrefaction at 200 °C has the lowest temperatures of T f and T p as well as the maximum corresponding DTG value. Furthermore, the results of three-parallel-DAEM model analysis results show that the activation energies corresponding to the three peaks are 176.1 kJ/mol, 186.5 kJ/mol and 221.7 kJ/mol, respectively, and that increasing torrefaction temperature had no significant effects on activation energies. With the torrefaction temperature increasing, the first standard deviation decreased while the third standard deviation increased. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is one of the most common 3D printing materials. However, once processed, the properties of its raw material are altered. 3D printed PLA waste (3DP-PLAW) has a relatively high calorific value with low impurities, which makes waste-to-energy utilization effective through thermal conversion. In this study, the pyrolysis characteristics of 3DP-PLAW were investigated using thermogravimetric–Fourier infrared spectroscopy/gas chromatography−mass spectrometry (TG-FTIR/GC-MS). Two main pyrolysis stages were observed at 260–390 ℃ and 390–500 ℃ during 3DP-PLAW pyrolysis, which contradicts with findings from previous research. Upon reaching 390 °C, residual ash and char triggered a secondary reaction. It is speculated that the occurrence of a second pyrolysis stage is attributed to changes in the physicochemical properties of the PLA during the 3D printing process. It was also found that 3DP-PLAW had a higher heating value (HHV) (20.949 MJ·kg−1) than that of the raw PLA. The pyrolysis kinetics of 3DP-PLAW was analyzed using the distributed activation energy model (DAEM) as well as Flynn-Wall and Ozawa (FWO), Starink, and Friedman methods; it was found that the activation energies obtained from these methods were similar (approximately 206 kJ·mol−1). Therefore, these methods are suitable for biomass plastics. The TG-FTIR/GC-MS results showed that CO, CO 2 , CH 4 , CH 3 CHO, esters, carbon-based compounds, and ethene were the main gaseous products of 3DP-PLAW pyrolysis. In contrast to a previous study on raw PLA, no ketone was detected in the gaseous products during 3DP-PLAW. These findings allow for the production of energy products, instead of the usage of natural gas for recycling, which underlines the potential value of 3DP-PLAW for energy recovery and subsequent improvements on the current 3DP-PLAW disposal methods. [Display omitted] • Pyrolysis of 3DP-PLAW as an emerging solid waste was studied via TG-FTIR/GC-MS. • 3DP-PLAW mainly decomposed in temperature stages of 260–390 ℃ and 390–500 ℃. • Activation energy of 206 kJ/mol was obtained via 4 pyrolysis kinetic methods. • Pyrolysis products distribution of 3DP-PLAW towards energy recovery was studied. • The results provide fundamentals for thermochemical utilization of 3DP-PLAW. [ABSTRACT FROM AUTHOR]

Defect type and interactions among active sites are critical in heterogeneous peroxymonosulfate (PMS) system. Herein, a continuous flow fixed bed PMS reactor with distilled spirits lees derived biochar (DSLBs)/quartz wool was designed to explore the synergistic roles of active sites. Satisfyingly, with high graphite N, C O content and defect degree, DSLB-800 exhibited superior catalytic activity, durability and applicability for sulfamethoxazole (SMX) removal. The dominant contribution of 1O 2 , and minor roles of SO 4 •− and •OH were confirmed. Single graphite N, C O and C-O, combined interactions between graphite N and pyridine N, graphite N and pyrrole N, pyridine N and pyrrole N, C O and O C-O, O C-O and C-O, as well as interactions among graphite N, pyridine N and pyrrole N contributed to 1O 2 generation. Notably, the double vacancy defect was also a preferential site for 1O 2 production. This study advances mechanistic understanding of collaborative contribution of active sites to PMS activation. [Display omitted] • Distilled spirits lees derived biochar (DSLB) was prepared with adjustable sites. • DSLBs showed high activity in a continuous flow fixed bed PMS reactor. • Synergistic contribution of different sites to PMS activation was revealed. • Double vacancy defect was identified as a preferential site for 1O2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Active site on sewage sludge-derived biochar was fine-tuned by regulated pyrolysis. • Single SO 4 •−, •OH with SO 4 •− or 1O 2 contributed to ciprofloxacin removal. • Each contribution site for reactive species generation was identified. • The synergy of Fe, N and O sites for oxidative species production was established. Active sites on the surface of heterogeneous catalysts accounted for the generation of reactive oxygen species (ROS) from peroxymonosulfate (PMS) toward organic degradation. In this study, the surface chemistry of sewage sludge-derived biochar (SSB) was regulated by controlled pyrolysis and SSB was used for PMS activation and oxidation of antibiotic ciprofloxacin (CIP). SSB-20–120 achieved high CIP removal efficiencies in both batch test (94.2%) and continuous column test (96.3%) with PMS. The species and contents of Fe, N and O as active sites on SSB and their relationships with generated ROS (SO 4 •−, •OH, and 1O 2) for CIP degradation were comprehensively identified. Fe(0), –OH, C = O and the pairwise interaction among Fe(0), Fe(II) and Fe(III) were responsible for SO 4 •− generation. Besides, pyrrolic N, graphitic N and the co-effect among pyridinic N, pyrrolic N and graphitic N exerted positive effects on •OH and SO 4 •− generation simultaneously. Meanwhile, Fe(II), Fe(III), pyrrolic N, graphitic N, lattice O with –OH, lattice O with C = O, the interactions among Fe(0), Fe(II) and Fe(III) as well as pyridinic N, pyrrolic N and graphitic N contributed to the production of •OH coupling with 1O 2. Moreover, SO 4 •− and 1O 2 , as well as the co-effects of •OH with SO 4 •− and •OH with 1O 2 were in favor of CIP degradation. This research provided new insights into the biochar synthesis, structure evolution, and the generation mechanism of reactive oxygen species from PMS activation. Outcomes are beneficial to sewage sludge utilization and developing low-cost catalysts for wastewater remediation. [ABSTRACT FROM AUTHOR]

Biomass fuel, as a kind of alternative fuel, offers the possibility of a higher sustainability of the energy system. Furanic fuels that are proposed as next-generation biomass-derived fuels have become one of the targets of recent researches. Here the studies on the low-temperature oxidation of 2-ethylfuran (EF2) in a jet-stirred reactor were performed at atmospheric pressure, at temperature range of 600–900 K and at three equivalence ratios of 0.5, 1.0 and 2.0, respectively. Over 20 oxidation products were detected and measured by using synchrotron vacuum ultraviolet photoionization mass spectrometry, including hydrocarbons, such as methane, ethylene, acetylene, et al., and oxygenated species, such as formaldehyde, ketene, acetaldehyde, 2-methylfuran and 2-vinylfuran, especially the isomers (furan/vinyl ketene) et al. A detailed low-temperature oxidation kinetic model with 723 species and 3300 reactions based on the reported models and theoretical calculations was developed to demonstrate the experimental results in this work. Rate of production analysis shows that, in the low-temperature oxidation of EF2, the consumption of EF2 is dominated by hydrogen atom-abstraction to produce 1-(2-furyl)ethyl radical and by hydroxyl radical-addition onto C(2) of EF2 to produce 2,3-dihydro-2-hyroxyl-2-ethyl-3-furanyl radical at 50% EF2 consumption. The subsequent dominant consumption pathway of 1-(2-furyl)ethyl radical reacting with hydroperoxyl radical will generate 1-(2-furyl)ethyloxyl radical or 2,5-dihydro-5-ethyliden-2-furanyloxyl radical, while 2,3-dihydro-2-hyroxyl-2-ethyl-3-furanyl radical will subsequently go through β -scission to produce carbon monoxide + acetylene + formyl radical eventually. Sensitivity analysis indicates that reactions related to these four radicals, i.e., hydroxyl, 1-(2-furyl)ethyl, 2,5-dihydro-5-ethyliden-2-furanyloxyl and 2,3-dihydro-2-hyroxyl-2-ethyl-3-furanyl, are critical in the consumption of EF2. Hydroxyl radical is mainly produced by the decomposition of hydroperoxide at the equivalence ratio of 0.5 and 1.0, while at the equivalence ratio of 2.0, reactions between 1-(2-furyl)ethyl radical and hydroperoxyl radical, as well as that between methyl radical and hydroperoxyl radical, become more important. [ABSTRACT FROM AUTHOR]

Duckweed easily growing in wastewater and absorbing a large amount of nitrogen and phosphorus from wastewater is now being considered as a promising solution to treat eutrophic water. However, if it is not salvaged in time, its rapid accumulation will cause secondary pollution to the water body. Duckweed is rich in protein and starch, but the content of lignin is rather low, making it an ideal biomass feedstock for energy production. This work reviews the detailed steps for producing bio-oil, bio-ethanol, biogas and other kinds of bioenergy from duckweed through hydrothermal liquefaction, pyrolysis, anaerobic digestion and fermentation processes. The reaction pathways of duckweed to produce bio-oil and bioethanol are introduced in detail. Opportunities and challenges of each conversion technology are thereafter discussed. The viability of producing biofuels and industrial precursors in a sustainable mode is also assessed. According to the characteristics of different kinds of duckweed, appropriate utilization methods should be applied to produce bioenergy to realize environmental, economic and energy benefits. [Display omitted] • Rapid growth and biochemical composition make duckweed a promising energy resource. • Bioenergy production from duckweed coping with energy shortage and water eutrophication simultaneously. • Biochemical composition of duckweed is a decisive factor of subsequent utilization and derived products. • The prospects of duckweed in high value-added industrial precursors production are encouraging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalytic ozonation of various Cl-VOCs exhibited different performances. • Synergistic/inhibited effects co-existed in catalytic ozonation of mixed Cl-VOCs. • Degradation difficulty and competitive adsorption jointly determined the priority. • H 2 O introduction exhibited negligible impact for Cl-VOCs catalytic co-ozonation. This paper investigated catalytic ozonation of different Cl-VOCs (chlorobenzene (CB), dichloroethane (DCE), dichloromethane (DCM) and trichloroethylene (TCE)) over series of supported MnO x catalysts. These Cl-VOCs with different molecule structures exhibited obviously difference in catalytic performances and byproducts formation. Interestingly, the correlation between catalytic behaviors and surface properties of catalysts was inconsistent for different Cl-VOCs. In comparison, Mn/HZSM-5(27) presented a better conversion and mineralization rate (MAR) for most of Cl-VOCs due to its abundant surface acidity and excellent pore structures. Catalytic co-ozonation of mixed Cl-VOCs over Mn/HZSM-5(27) showed co-existence of inhibitive and promotive effects. For instance, CB conversion occupied priority compared with DCE and TCE, and MAR was enhanced in the mixture. Thereafter, the temperature programmed desorption results of mixed Cl-VOCs proved competitive adsorption between molecules. Both competitive adsorption and difficulty of Cl-VOCs degradation were the determining factors in catalytic co-ozonation of Cl-VOCs. Besides, catalytic co-ozonation of Cl-VOCs with presence of H 2 O exhibited negligible impact. These observations provide valuable reference for industrial application with co-presence of multiple Cl-VOCs and water vapor. [ABSTRACT FROM AUTHOR]

The harmless treatment of heavy metal-enriched hyperaccumulator biomass is the main barrier to the industrialization of phytoremediation. Hydrothermal conversion of Sedum alfredii using different solvents (i.e ·H 2 O and HCl) at 210–300 ℃ was performed to investigate the behaviors of Cd and Zn, and the characteristics and potential application of the derived hydrochars were determined. Low temperature and HCl addition favored the removal of Cd/Zn from the solid phase. The highest removal efficiencies of Cd (95.0%) and Zn (89.3%) were achieved at 210 ℃ with the presence of HCl. The yield, pH, ash content, element concentration, functional groups, and crystalline minerals of the derived hydrochar were influenced by the reaction temperature and addition of HCl. The leaching risk of Cd and Zn was significantly reduced by hydrothermal conversion. The addition of HCl facilitated the immobilization of Zn, while it enhanced the mobility of Cd. Moreover, the hydrochar derived at 210 ℃ showed increased sorption capacity towards Cu, and the addition of HCl greatly improved the energy density of hydrochar. These results suggest that HCl-mediated hydrothermal conversion could be a promising technique to achieve the separation of Cd and Zn from hyperaccumulator biomass as well as the production of value-added hydrochar. [Display omitted] • Hydrothermal conversion of S. alfredii in water- and acid-medium was performed. • Low temperature and acid medium favored the removal of Cd/Zn from hydrochar. • The leachable contents of Zn and Cd in hydrochar decreased with addition of HCl. • Cu sorption capacity of hydrochar was reduced after modification with HCl. [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis of three butene isomers (C4H8) including 1-butene (1-C4H8), 2-butene (2-C4H8) and i-butene (iC4H8) were studied from 900 to 1900K at low pressure. Synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry with molecular-beam sampling technique was used for isomeric identification of products and intermediates and also for concentration measurement. Based on the experimental results, a kinetic model consisting of 76 species and 232 reactions was developed to simulate mole fractions of species. The mole fraction profiles of pyrolysis species predicted by the model are in good agreement with the experimental measurements. The decomposition pathways of C4H8 are illustrated according to the reaction flux analysis. Our analysis demonstrates that reaction sequences 1-C4H8 →aC3H5 →aC3H4 →pC3H4 →C2H2, 2-C4H8 →saxC4H7 →1,3-C4H6 →C2H3 →C2H2 and iC4H8 → iC4H7 →aC3H4 →pC3H4 →C2H2 are the major decomposition pathways of 1-butene, 2-butene and i-butene, respectively. [Copyright &y& Elsevier]

Renewable wood sponge with lamellar structure, compressibility and three-dimensional porous frameworks exhibits excellent functionalization application potential in various fields. Herein, cobalt and nitrogen (Co/N) co-doped carbonized wood sponge (CoNCWS800) was prepared successfully for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). The CoNCWS800 material exhibited admirable catalytic activity in PMS activation to oxidize SMX molecules (99.7% within 60 min). Electron paramagnetic resonance (EPR) analysis, quenching tests and electrochemical experiments confirmed the existence of both radical (SO 4 ·−,·OH and O 2 ·−) and non-radical (1O 2 and direct charge transfer) pathways during the SMX degradation process. Co species were verified as major contributors for the generation of multiple radicals via activating PMS. Surface defective structure and ketonic C O groups performed the positive linear correlation with reaction kinetic constants, revealing the critical role of the two active sites in PMS activation via non-radical process. This study provides a unique insight in PMS activation mechanism via both radical and non-radical pathways of wood sponge-based functional materials. [Display omitted] • 3D porous wood sponge was utilized to prepare CoNCWS catalyst for PMS activation. • Remarkable sulfamethoxazole degradation was achieved in the CoNCWS800/PMS system. • Defects and ketonic C O site contributed to non-radical pathway in PMS system. • Singlet oxygen and CoNCWS800/PMS complexes were critical active species. [ABSTRACT FROM AUTHOR]

2-Methylfuran (MF), a promising biofuel, produced from non-edible biomass, is desirable as an alternative fuel or fuel additive to internal combustion engines. For a better understanding of the ignition process in engines, the low-temperature oxidation experiments of MF at the temperature range of 600 – 925 K and atmospheric pressure with different equivalence ratios (0.5, 1.0, and 2.0), were performed in a jet-stirred reactor. Synchrotron vacuum ultraviolet photoionization mass spectrometry was used to identify and measure the intermediates and products in the oxidation process, especially for the isomers (furfural/2-ethylfuran and furan/vinyl ketene), species with identical mass-to-charge ratio (methanol/oxygen and aldehyde/carbon dioxide), and the other oxygenated and hydrocarbon products. The typical negative-temperature-coefficient behavior was not observed in the low-temperature oxidation of MF. The dominant consumption pathways of MF in low-temperature oxidation are the hydroxyl radical/hydrogen atom-addition reactions on the ring and hydrogen atom-abstraction reactions on the side methyl group by hydroxyl radical/hydroperoxyl radical/hydrogen atom, while the contribution of unimolecular decomposition reactions is almost negligible. 2-Furylmethyl radical is a key intermediate in the low-temperature oxidation of MF. Furfural and 2-ethylfuran, as the subsequent products from 2-furylmethyl low-temperature oxidation, were identified as the early-stage products. Besides, the important chemistry of other important species, especially acrolein and methyl vinyl ketone, were also discussed at different equivalence ratios. [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalytic co-pyrolysis of cellulose and PE over MgO was studied by TG/PI-TOF-MS. • The TG, mass spectra, and the temperature-evolved profiles were obtained. • The interaction of the feedstocks was observed during the catalytic co-pyrolysis. • TG/PI-TOF-MS is a powerful approach to study catalytic co-pyrolysis process. Due to rapid deactivation of catalysts, the effective conversion of biomass with oxygen-rich and hydrogen-deficient characteristics to transportation fuels and high-valued chemicals via catalytic pyrolysis remains a challenge for commercialization. Hydrogen-rich plastic is used as feedstock co-fed with biomass to improve the catalytic pyrolysis process. The present work aims to investigate the co-pyrolysis process of cellulose and polyethylene (PE) over MgO by TG combined with photoionization time-of-flight mass spectrometry (PI-TOF-MS), which features on-line detection of catalytic pyrolysis products in real time. The MgO catalyst could improve the pyrolysis of cellulose and enhance the C C bond breaking of PE, respectively. During catalytic co-pyrolysis, the yields from olefins and furan as well as its derivatives can be enhanced obviously. Further, the formation of additional aromatics can be observed due to the Diels-Alder reaction. This work shows TG coupled to PI-TOF-MS is a powerful setup to study and optimize catalytic co-pyrolysis process. [ABSTRACT FROM AUTHOR]

HCHO is the most concerned indoor air pollutant that photocatalytic degradation is a feasible approach. To achieve efficient and complete degradation of HCHO under visible light irradiation, heteroatoms are usually doped in TiO 2. But using natural materials as a dopant instead of expensive and toxic chemicals to fertilize TiO 2 remains challenging. This paper proposes a sustainable and green approach to synthesize an efficient N, Ca co-doped TiO 2 photocatalyst (TIMP) by using the insoluble matrix proteins (IMPs) extracted from abalone shell. TIMP-0.8 achieves near completely degradation HCHO within 45 min under visible light at ambient temperature and exhibits superior stability after 7 cycles. TIMP-0.8 has monodispersity with smaller diameter, high porosity, abundant defects and high adsorption affinity for surface hydroxyls compared with pure TiO 2. With the assistance of IMPs, the rate-determining step of HCHO degradation changes from −COOH oxidation to spontaneous decomposition of HCO 3 −, significantly facilitating the elimination and mineralization of HCHO. Overall, IMPs from abalone shell are natural surfactant, bio-templet, and dopant for TiO 2 modification, contributing to desirable visible-light photocatalytic performance for HCHO degradation. This paper provides new insight for high-value utilization of waste shell and photocatalytic indoor purification. [Display omitted] • The IMPs extracted from abalone shell acted as natural surfactant, bio-templet, and dopant. • TIMP-0.8 had abundant Ov and high adsorption affinity for surface hydroxyls. • Decomposition of HCO 3 − instead of −COOH oxidation became the rate-determining step. • Reaction pathway was proposed for TIMP-0.8 of HCHO. [ABSTRACT FROM AUTHOR]

• Furfural pyrolysis was studied using SVUV-PIMS in a flow reactor at 30 and 760 Torr. • A detailed kinetic model including 585 species and 3018 reactions was developed. • Nineteen pyrolysis products were identified and measured, especially free radicals. • Unimolecular non-radical decomposition channels dominated the furfural pyrolysis. • Pyrolysis characteristics of different typical furanic derivatives was compared. Furfural (2-furaldehyde) is a promising platform chemical for lignocellulosic biofuels, but its thermal decomposition channels are not well understood. To better understand furfural thermal decomposition kinetics, flow tube reactor pyrolysis combined with synchrotron vacuum ultraviolet photoionization mass spectrometry at low and atmospheric pressures and temperatures from 929 to 1365 K was investigated. Carbon monoxide, methane, acetylene, propyne, allene, furan, and vinylketene as the main products were detected and measured. A detailed kinetic model for furfural pyrolysis consisting of 585 species and 3018 reactions was built based on the potential energy surface, and validated against the experimental data from the current and previous studies. Rate of production analysis shows that furfural mainly underwent unimolecular non-radical decomposition channel to form vinylketene and carbon monoxide. Sequential decomposition of vinylketene led to the production of allene, propyne and carbon monoxide, etc. H-atom addition reactions on the furan ring was the main source of furan. HCO, CH 3 and COOCH 3 groups influence the decomposition pathways of furanic fuels, and accelerate their decomposition with decomposition temperatures in the sequence of methyl 2-furoate < furfural < 2,5-dimethylfuran < 2-methylfuran < furan. [ABSTRACT FROM AUTHOR]

• Pyrolysis pathways of microalgae were described based on different algae. • Pyrolysis of individual algae constituents and interactions between them were studied. • Lipids and carbohydrate have different effects on pyrolysis of protein. • Suggestions for industrial applications of algae pyrolysis were proposed. Pyrolysis of three algae, i.e. Nannochloropsis, Spirulina, and Sargassum was investigated by the combination of fixed bed pyrolysis with gas chromatography/mass spectrometry and pyrolysis photoionization mass spectrometry (py-PIMS) methods. Lipid, protein, and carbohydrate are the dominant components of the three algae, respectively. Mass spectrum profiles at different temperatures (400 °C, 500 °C, 600 °C, and 700 °C), temperature-programmed and time-evolved profiles of major products were measured. The decomposition reaction of fatty acids led to the formation of alkanes and alkenes. Aromatic compounds came from the nitrogen-containing compounds derived from protein and dehydrogenation of cyclic alkanes and alkenes through the Diels–Alder reaction from unsaturated fatty acids. Polycyclic nitrogenous compounds can be generated by the ring condensation reactions of monocyclic N-heterocyclic compounds. Lipids may interfere with the decomposition of protein. The presence of carbohydrates facilitates the formation of N-heterocyclic compounds. Two formation pathways of 1,4:3,6-dianhydro-α- d -glucopyranose and 2,4-dimethylfuran from hemicellulose and cellulose at different temperatures were observed. [ABSTRACT FROM AUTHOR]

With huge demand of herbal medicine worldwide, herb residue (HR) treatment is attracting growing attention. This work proposed an integrated energy conversion system to treat and utilize HR, which contained a crushing and drying section to pretreat HR, a gasification section to convert HR into syngas, and a boiling section to produce hot steam for HR drying and herb steaming. A pilot scale plant was established to validate its feasibility. The results showed that HR with particle size below 10 mm and moisture content about 20 wt% was qualified as gasification feedstock. The energy efficiency, syngas heat value, and syngas yield during gasification reached 76.1%, 5.7 MJ/Nm3, and 0.6 Nm3/kg HR , respectively. When treating each kg of HR, 1.0167 kg of wastewater was emitted, which primarily came from HR dehydration and herb steaming. Meanwhile, 0.3292 kg of hot steam with 0.89 MJ of enthalpy would be produced per kg of HR as net energy output. This integrated system fully considered the upstream and downstream adaption of HR gasification technique. Highly efficient disposal and utilization of HR were thus achieved. It is hoped that this work could promisingly enhance the overall efficiency of herbal medicine production industry. • A pilot scale herb residue (HR) disposal and utilization system was established. • Syngas derived from HR was used to produce hot steam for HR drying and herb steaming. • HR with <10 mm particle size and 20 wt% moisture was qualified for stable gasification. • 1 kg raw HR produced 0.89 MJ net energy output with 1.0167 kg wastewater emission. • The integrated system is a promising prototype for HR treatment and utilization. [ABSTRACT FROM AUTHOR]

• The duckweed for wastewater treatment was converted to bio-oil by HTL. • The highest bio-oil yield (35.6 wt%) and HHV (40.85 MJ/kg) were obtained at 370 °C. • The products of each phase had potential utilization value. Wastewater treatment by duckweed is a naturally sustainable technology. However, its development is limited due to the lack of a follow-up treatment of duckweed. The duckweed was proposed for the treatment of rural domestic wastewater and agricultural wastewater, and it was further processed to produce bio-oil via hydrothermal liquefaction at various temperatures (250 °C–370 °C) and residence times (15–60 min). The highest bio-oil yield of 35.6 wt% was obtained at 370 °C, 45 min. The higher heating value of bio-oil was 40.85 MJ/kg, and the H/C ratio (1.72–1.98) was similar to that of petroleum (1.84). The gas chromatography-mass spectrometry analysis results revealed that the bio-oil mainly consisted of N-heterocycles, cyclic ketones, esters, amides, long-chain hydrocarbons, phenols, and aromatic intermediates. Valuable compounds (3-pyridinol, 2-pyrrolidinone, and its analogues) of high concentration were identified in the water-soluble organic matter. Compared with other materials, this study produced higher-quality bio-oil and water-soluble organic matter. [ABSTRACT FROM AUTHOR]

• Temperature-programmed and time-evolved profiles of products were measured by PIMS. • The yields of alkenes and aromatics increased in the presence of HZSM-5. • The maximum deoxygenation occurred in palm shell/HZSM-5 ratio = 1:2 at 500 °C. • A predicted formation pathway of major products from palm shell pyrolysis was proposed. The catalytic pyrolysis characteristics of palm shell were investigated using pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) and pyrolysis photoionization mass spectrometry (py-PIMS) methods. Temperature-programmed results and time-evolved profiles of major products, such as alkenes, aromatics, furans, and phenols were measured. Temperature and catalysts can effectively influence the pyrolysis products distribution. Two peaks of temperature-programmed results of furfural indicated that hemicellulose and cellulose depolymerized at different temperatures. Two decomposition pathways of lignin were proposed: the ether linkages between monomer units of lignin and the methoxy groups on the aromatic rings would break at different temperatures. With the presence of HZSM-5, the yields of alkenes and aromatics increased and that of oxygenates reduced because primary oxygenates from pyrolysis underwent catalytic deoxygenation and cracking to form light alkenes, which subsequently react with furans or other large alkenes to produce aromatic hydrocarbons. The catalytic effect was intensified as the HZSM-5-to-palm shell mixing ratio was increased. Deoxygenation index shows the maximum deoxygenation occurred in palm shell/HZSM-5 ratio = 1:2 at 500 °C. [ABSTRACT FROM AUTHOR]

• The pyrolysis behavior of cattle manure was analyzed by PIMS and GCMS. • Products mainly contained ketones, phenols and N-heterocyclic compounds. • Maillard reaction had great effect on the pyrolysis process of cattle manure. • A predicted generation pathway of major products was proposed. Cattle manure is a kind of abundant agriculture waste but potential renewable resource to be converted into fuel by pyrolysis. The pyrolysis behavior of cattle manure was analyzed by three methods in this work: thermogravimetric analyzer (TG), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis photoionization time-of-flight mass spectrometry (Py–PI–TOFMS). The pyrolysis process of cattle manure included four stages, dehydration stage, lignocellulose decomposition stage, lignin and protein decomposition stage, char and mineral matter decomposition stage. The products were mainly classified into six groups: ketones, aldehydes, phenolic compounds, acids, hydrocarbons and N-containing compounds. Based on the time-evolved profiles and temperature-programmed profiles, the characteristics of these major products were analyzed and discussed. Maillard reaction has great effects on the pyrolysis process of cattle manure because cellulose can easily react with protein to produce abundant Amadori products and then generate cyclopentanes and furanmethanol. In addition, some Amadori products and amino acids can also be cyclized to generate N-heterocycle compounds like pyrroles and pyrazines. The decomposition of lignin basic units with more methoxy groups require higher reaction temperature, and the removal of hydroxy and methoxy group on phenols mainly occurred at around 350 °C. Furthermore, primary decomposition pathways of cattle manure were also proposed and discussed. [ABSTRACT FROM AUTHOR]

Mainstream biomass precombustion processes include anaerobic digestion (AD), gasification (GS), fast pyrolysis (FP), and hydrothermal liquefaction (HTL). Precombustion processes determine the forms of biomass-derived fuels, the energy production per mass of biomass and the creation of pollutants; consequently, it is important to determine the impacts of precombustion processes on these metrics. Current environmental evaluation methods have limitations when comparing various technologies. Accordingly, we proposed an index for the environmental impact of biomass preprocessing (EIBP), which includes carbon footprint reduction, pollutant impacts from byproducts and pollutant impacts from residuals. A higher EIBP value implies a worse environmental impact. We evaluated the EIBPs for a variety of processes and feedstocks. Technical levels of these processes were quantified by carbon conversion, which is equal to the sum of the carbon mass in the target products and byproducts divided by the total carbon mass in the feedstock. By adjusting the carbon conversion, we inferred the environmental potentials of these processes. We found that AD had the lowest EIBP and EIBP lower bound, the latter of which refers to the theoretically lowest EIBP under idealized conditions. This result implies that AD is likely to maintain its environmental impact advantage for a decade. Although the newly developed HTL technology had the highest EIBP for almost all feedstocks, it had an extremely high environmental impact improvement potential. The correlation analysis between the energy conversion efficiency and the EIBP showed that they do not necessarily have strong correlations, suggesting that environmental impact should be considered separately when optimizing biomass precombustion processes. • An environmental evaluation method of biomass precombustion processes is proposed. • The method solves drawbacks of life cycle assessment method for comparative study. • The method reveals environmental impact upper bound of these processes. • Anaerobic digestion shows better environmental impact and enhancement potential. • Energy and environment performances show weak correlation for these processes. [ABSTRACT FROM AUTHOR]

• A new method is proposed to characterize chemical features of biomass and waste. • The method is based on infrared spectroscopy and machine learning models. • The method is fast and the optimal accuracy could reach as high as 95.54%. • The robustness of this method is validated, and its properties are discussed. • The method can enhance sorting of biomass and waste for downstream utilization. Heterogeneity is a most serious obstacle for treatment and utilization of biomass and waste (BW). This paper proposed a fast characterization method based on infrared spectroscopy and machine learning models, thus to roughly predict the elemental composition and heating value of BW. The fast characterization results could be used to sort different BW components by their suitable downstream utilization techniques. The infrared spectra based hybrid model contained a feature compression section to extract core information from raw infrared spectra, a classification section to distinguish inorganic dilution, and a regression section to generate the elemental composition and heating value results. By parameters optimization, the accuracy of this hybrid model reached 95.54%, 85.53%, 92.40%, and 92.49% for C content, H content, O content, and low heating value prediction, respectively. The robustness analysis was conducted by completely rearranging the training and test sets, and it further validated the hypothesis that the infrared spectra contains enough qualifying and quantifying information to characterize these properties of BW. Compared with previous literature, the C–H, C–O, and O–H correlations in BW were also well kept in the predicted results. This work is hoped to enhance upstream sorting system design for treatment and utilization of BW. [ABSTRACT FROM AUTHOR]

Semipermeable membrane-covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semipermeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition, and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced bacterial richness and increased bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The directional regulation of oxidation capacity in the carbon-based peroxymonosulfate (PMS) activation system is a promising strategy for wastewater purification. In this work, a novel iron cobalt and nitrogen co-doped carbonized wood sponge (FeCoNCWS) was developed. A superb catalytic performance for sulfamethoxazole (SMX) degradation (∼100.0%) was obtained within 30 min in FeCoNCWS800/PMS system at 60 °C. Besides, the reactive oxygen species (ROS) contribution was verified at different reaction temperatures. Specifically, the primary roles of sulfate and hydroxyl radicals (SO 4 - and OH) in SMX removal weakened, while the secondary role of singlet oxygen ( 1 O 2 ) in SMX degradation was enhanced with the rise of reaction temperature in FeCoNCWS800/PMS system. Interestingly, defects, graphitic N and carbonyl (CO) groups were vital active sites for PMS activation to produce 1 O 2 , which was facilitated at higher reaction temperature. Besides, the metal sites were identified as PMS activators for SO 4 - and OH generation, which was promoted under lower reaction temperature. The findings revealed a novel internal temperature-dependent PMS activation mechanism, which can help to regulate the oxidation capacity of PMS activation system rationally for pollutant degradation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

This study investigated catalytic reforming, which is a thermochemical process, as a pioneering method to treat biogas slurry (wastewater from biogas plants) and generate hydrogen. Experimental validation for treating biogas slurries from digested cattle manure, fish intestine, and wheat straw was performed on Ni/α-Al 2 O 3 catalyst. The results showed that the total organic carbon, total nitrogen, and PO 4 3- ion contents in biogas slurry could be reduced by 98.69, 98.01, and 99.32%, respectively. The highest hydrogen yield was obtained in the treatment of biogas slurry from digested cattle manure at 750 °C, in which the hydrogen yield and hydrogen concentration were 13.85 L hydrogen / L BS and 79.77 vol %, respectively. Changes in the crystalline phase and structure of the catalyst were observed during catalytic reforming of biogas slurry. Active metal oxidization and carbon deposition were likely to be important factors affecting catalytic stability. The mass flow evaluation verified the hydrogen generation potential by the catalytic reforming of biogas slurry, which was close to the methane generation capability of the upstream biogas plant. However, additional effort is required to address the high energy consumption of this method. These findings provide fundamental knowledge about the potential of applying thermochemical techniques to treat and utilize high total organic carbon-containing wastewaters.

The thermal decomposition of furfural is investigated in a flow tube reactor at 30 Torr by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) at temperatures from 1023 to 1273 K. Over 20 kinds of pyrolysis products, including short-lived radicals, stable oxygen-containing compounds, and hydrocarbons, are identified from the scanning photoionization efficiency (PIE) spectra. Vinylketene (CH 2 ═CH-CH═C═O), which has been shown to be an important primary product, is also directly observed. The possible steps of hydrogen atom addition and hydrogen atom abstraction in the thermal decomposition of furfural are studied by theoretical calculations at the CBS-QB3 level. In addition to unimolecular decomposition, hydrogen atom addition followed by ring opening can lead to the production of vinylketene.