Tracking the conversion of nitrogen during pyrolysis of antibiotic mycelial fermentation residues using XPS and TG-FTIR-MS technology

Impact of several sludge dewatering conditioners on municipal sludge pyrolysis properties, kinetics, by-products, and environmental risk assessment

The pyrolysis characteristics of four different types of conditioned sludge were ascertained, and PAM, CaO, K2FeO4, and K2FeO4-CaO-PAM (KCP) conditioners were employed as sludge dewatering conditioners. The sludge pyrolysis reaction's activation energy (E) dropped with the addition of four conditioners. CaO, PAM, KCP, and K2FeO4 were the sequences of E needed for the pyrolysis of four different types of conditioned sludge. The addition of K2FeO4, CaO, and KCP resulted in an increase in the yields of H2 and CO. Except for the K2FeO4 conditioning sludge carbon, the pyrolytic carbon of the other three groups of samples showed an increase in S contents, while the pyrolytic carbon of the four groups of samples treated with conditioners clearly showed lower C and N contents compared to the raw sludge carbon. Protein-N made up the majority of N in sludge pyrolytic carbon. After adding conditioner, the level of organic sulfur decreased. Organic sulfur could then be broken down by K2FeO4 and CaO. The four conditioners efficiently mitigated the ecological and environmental risks posed by heavy metals. Alkynes were the most abundant result in pyrolytic volatiles of sludge pyrolysis; the other products included acids, alcohols, lipids, furans, ketones, phenols, hydrocarbons, N-components, and so on. All samples' acids, alcohols, and ketones from pyrolysis were decreased once the conditioner was added. The acid reduction rate reached 66.7 %, and the alkynes clearly increased during the KCP conditioned sludge's pyrolysis. The sulfur level of the bio-oil was decreased by all four conditioners. Everything mentioned above indicated that the KCP aided in the subsequent pyrolysis of the sludge, leading to the production of an advantageous pyrolysis bio-oil.

Study on the effect of conditioner on NOx precursor control behavior from sewage sludge pyrolysis: Focusing on conditioner assessments and in-situ fixation mechanism

The nitrogen transformation during sludge pyrolysis is affected by the dewater conditioner. However, the comparative analysis of the conditioner under identical pyrolysis conditions has been previously absent. In this study, Ca-, Fe- and Al-based conditioners were selected as the representatives. A comprehensive evaluation considering the cost of the conditioners and the product characteristics was conducted. Additionally, the in-situ fixation mechanism of the conditioner on nitrogen-containing gas was concurrently revealed. Among the six conditioners, CaO and AlCl3 were identified as the top performers, ranking first and second, respectively. Furthermore, Fe/Ca-based conditioners reduced NH3 and HCN release by 1.5 ∼ 5.53 % and 0 ∼ 1.55 %, respectively, by facilitating the conversion of amine-N to a more stable form in condensable fraction. Fe promoted volatile amine-N cyclization, while Ca encouraged its dehydrogenation. Both Fe/Ca-based conditioners increased 7.5 ∼ 14.8 % nitrogen retention in char, by inhibiting the decomposition of protein-N. Al-based conditioners had little effect on NH3 and HCN, but contributed to 2.3 ∼ 2.8 % production of stabilized nitrogen in char. The introduction of Cl in Fe/Ca/Al chloride conditioners would promote the decomposition of inorganic ammonium salts to produce NH3 at 30 ∼ 185 °C. And Cl also reacted with volatiles through electrophilic substitution reaction, leading to the formation of halogenated hydrocarbons in condensable fraction and the release of more NH3, HCN, and HNCO at 30 ∼ 465 °C. The findings of this study provide a detailed comparative analysis of various conditioners under uniform conditions and reveal the in-situ fixation mechanism of nitrogen-containing gas. This will provide guidance for the sludge conditioning-dewatering-drying integrated treatment and disposal.

Detoxification of vancomycin fermentation residue by hydrothermal treatment and pyrolysis: Chemical analysis and toxicity tests

Vancomycin fermentation residue (VFR) is a by-product of the pharmaceutical industry with high ecotoxicity caused by the residual antibiotics, antibiotic resistance genes (ARGs), and heavy metals (HMs). In this study, the detoxification effect of hydrothermal treatment (HT) and pyrolysis for VFR was assessed using chemical analysis and toxicity tests. When VFR was subjected to HT and pyrolysis at ≥400 °C, more than 99.70 % of the residual vancomycin and all ARGs were removed. The HMs contents in VFR followed the order of manganese (676.2 mg/kg) > zinc (148.6 mg/kg) > chromium (25.40 mg/kg) > copper (17.20 mg/kg), and they were highly bioavailable and easily leached. However, HT and pyrolysis (≥400 °C) substantially reduced the bioavailable fractions and leaching properties of the HMs. After HT and pyrolysis at ≥ 400 °C, the potential ecological risk of HMs in VFR was reduced from considerable to moderate/low levels. The elutriate acute toxicity test suggested that HT and pyrolysis at ≥ 400 °C effectively reduced the toxicity of VFR to an acceptable level (p < 0.05). This study demonstrates that HT and pyrolysis (≥400 °C) are promising methods for treating VFR and detoxifying it, and the treated products are safe for further reutilization.

Biomass directional pyrolysis based on element economy to produce high-quality fuels, chemicals, carbon materials - A review

Biomass is regarded as the only carbon-containing renewable energy source and has performed an increasingly important role in the gradual substitution of conventional fossil energy, which also contributes to the goals of carbon neutrality. In the past decade, the academic field has paid much greater attention to the development of biomass pyrolysis technologies. However, most biomass conversion technologies mainly derive from the fossil fuel industry, and it must be noticed that the large element component difference between biomass and traditional fossil fuels. Thus, it's necessary to develop biomass directional pyrolysis technology based on the unique element distribution of biomass for realizing enrichment target element (i.e., element economy). This article provides a broad review of biomass directional pyrolysis to produce high-quality fuels, chemicals, and carbon materials based on element economy. The C (carbon) element economy of biomass pyrolysis is realized by the production of high-performance carbon materials from different carbon sources. For efficient H (hydrogen) element utilization, high-value hydrocarbons could be obtained by the co-pyrolysis or catalytic pyrolysis of biomass and cheap hydrogen source. For improving the O (oxygen) element economy, different from the traditional hydrodeoxygenation (HDO) process, the high content of O in biomass would also become an advantage because biomass is an appropriate raw material for producing oxygenated liquid additives. Based on the N (nitrogen) element economy, the recent studies on preparing N-containing chemicals (or N-rich carbon materials) are reviewed. Moreover, the feasibility of the biomass poly-generation industrialization and the suitable process for different types of target products are also mentioned. Moreover, the enviro-economic assessment of representative biomass pyrolysis technologies is analyzed. Finally, the brief challenges and perspectives of biomass pyrolysis are provided.

Unexpected variations in the effects of ultrasound-assisted myofibrillar protein processing under varying viscosity conditions

The efficient synthesis of myofibrillar protein(MRN)-gallic acid (GAD) complex in ultrasound (UID)-assisted processing is a challenging problem in food manufacturing. In this investigation, the effect of viscosity characteristics on the efficiency of UID processing in MRN-based beverages was analyzed. Both viscosity and surface tension can increase sono-physico-chemical effects on the degradation of terephthalic acid and crystal violet, with surface tension having a more significant effect (negative correlation, R2 = 0.99) than viscosity (positive correlation, R2 = 0.79). The structural indicators and microstructure demonstrated that the reaggregation and refolding of the MRN structure during the modification procedure occurred with relatively small three-dimensional dimensions. Compared to the MRN/GAD4 group, the water contact angle of the MRN/GAD7 system enhanced by 129.44%, leading to greater system stability. The ABTS-scavenging capacity of the system increased by approximately 19.45% due to the increase in viscosity of these two categories.

New insights into nitrogen control strategies in sewage sludge pyrolysis toward environmental and economic sustainability

Sewage sludge (SS) contains a certain amount of nitrogen (N), resulting in various content of N in the pyrolysis products. Investigates on how to control the generation of NH₃ and HCN (deleterious gas-N species) or convert it to N₂ and maximize transforming N in sewage sludge (SS-N) into potentially valuable N-containing products (such as char-N and/or liquid-N) are of great significance for SS management. Understanding the nitrogen migration and transformation (NMT) mechanisms in SS during the pyrolysis process is essential for investigating the aforementioned issues. Therefore, in this review, the N content and species in SS are summarized, and the influencing factors during the SS pyrolysis process (such as temperature, minerals, atmosphere, and heating rate) that affect NMT in char, gas, and liquid products are analyzed. Furthermore, N control strategies in SS pyrolysis products are proposed toward environmental and economic sustainability. Finally, the state-of-the-art of current research and future prospects are summarized, with a focus on the generation of value-added liquid-N and char-N products, while concurrently reducing NO_x emission.

Fenton oxidation treatment of oxytetracycline fermentation residues: Harmless performance and bioresource properties

The pharmaceutical factories of oxytetracycline (OTC) massively produce OTC fermentation residues (OFRs). The high content of residual OTC and antibiotic resistance genes in OFRs must to be considered and controlled at an acceptable level. This study therefore investigated the applicability of Fenton oxidation in OTC degradation and resistant gene inactivation of OFRs. The results revealed that Fe²⁺ as catalyzer could very rapidly activate H₂O₂ to produce HO^•, leading to instantaneous degradation of OTC. The optimum conditions for OTC removal were 60 mM H₂O₂ and 140 mg/L Fe²⁺ under pH 7. After Fenton oxidation treatment, the release of water-soluble polysaccharides, NO₃-N, and PO₄-P was enhanced, whereas for proteins and NH₃-N were reduced. Three soluble fluorescence components (humic, tryptophan-like, and humic acid-like substances) were identified through fluorescence spectra with parallel factor analysis, and their reduction exceeded 50% after Fenton oxidation. There were twelve intermediates and three degradation pathways of OTC in OFRs during Fenton process. According to toxicity prediction, the comprehensive toxicity of OTC in OFRs was alleviated via Fenton oxidation treatment. In addition, Fenton oxidation showed the ability to reduce antibiotic resistance genes and mobile genetic elements, and even tetO, tetG, intI1, and intI2 were eliminated completely. These results suggested that Fenton oxidation treatment could be an efficient strategy for removing OTC and resistance genes in OFRs.

Characteristic analysis of bio-oil from penicillin fermentation residue by catalytic pyrolysis

The hazardous waste penicillin fermentation residue (PR) is a huge hazard to the environment. The bio-oil produced by the pyrolysis of the penicillin fermentation residue has the potential to become a biofuel in the future. This paper studied the pyrolysis characteristics of PR at 400°C ∼700°C. According to the weight loss and weight loss rate of PR, the whole process of pyrolysis can be divided into three stages for analysis: dehydration and volatilization, initial pyrolysis, and pyrolytic char formation. The experimental results showed that the yield of the liquid phase is the highest (33.11%) at 600°C. GC-MS analysis results showed that high temperature is beneficial to reduce the generation of oxygenated hydrocarbons (73%∼31%) and the yield of nitrogenous compounds gradually increased (19%∼43%); the yield of hydrocarbons was low in 400°C∼600°C pyrolysis (2%∼5%) but significantly increased around 700°C (22%). In the temperature range of 400°C to 700°C, the proportion of C5-C13 in bio-oil gradually increased (26%-64%), and the proportion of C14-C22 gradually decreased (47%-16%). The catalyst can increase the proportion of hydrocarbons in the bio-oil component. And the Fe₂O₃/HZSM-5 mixed catalyst has a significant reduction effect on oxygen-containing hydrocarbons and nitrogen-containing compounds.

Pyrolysis of antibiotic mycelial residue for biochar: Kinetic deconvolution, biochar properties, and heavy metal immobilization

The safe disposal of antibiotic mycelial residue (AMR), a hazardous waste, is a pressing problem owing to the spread of antibiotic and heavy metal pollution. In this study, AMR pyrolysis at different temperatures and heating rates was investigated to prepare valuable biochar for heavy metal immobilization. The results showed that AMR decomposition mainly involved three pseudo-reactions, with average activation energies of 252.4, 149.8, and 219.7 kJ/mol, that fitted a three-dimensional diffusion model. Increasing the pyrolysis temperature and heating rate decreased the yield and volatile matter content of biochar, but the ash content, fixed carbon content, and aromaticity increased. The AMR-derived biochar had a favorable fuel property (18.1-19.8 MJ/kg) and stability against degradation in soil. Calcium oxalate hydrate, a major mineral in AMR, degraded during biochar formation. Furthermore, high pyrolysis temperature promoted the residual fractions of Cr, Cu, Zn, Cd, and Pb in biochar, more so than did the heating rate, inducing a low potential ecological risk. In particular, the leaching rate of Zn decreased from 46.9% in AMR to 0.3% in biochar obtained at 700 °C with a heating rate of 10 °C/min. This study elucidates the formation process and physicochemical properties of AMR biochar, which helps in the harmless utilization of AMR as a carbon resource.

Pyrolysis temperature-switchable Fe-N sites in pharmaceutical sludge biochar toward peroxymonosulfate activation for efficient pollutants degradation

Pyrolysis of pharmaceutical sludge (PS) is a promising way of safe disposal and to recover energy and resources from waste. The resulting PS biochar (PSBC) is often used as adsorbent, but has seldom been explored as catalyst. Herein we demonstrate that PSBC (0.4 g/L) could efficiently activate peroxymonosulfate (PMS) to 100% degrade 4-chlorophenol (4-CP) with rate constants of 0.42-1.70 min^-1, outperforming other reported catalysts. Interestingly, the PMS activation pathway highly depended on PSBC pyrolysis temperature, which produced dominantly high-valent iron species (e.g., Fe^IVO²⁺) at low temperature but more sulfate radical (SO₄^·-) and hydroxyl radical (·OH) at higher temperature, e.g., 0.17, 0.23, 0.12 mmol/L of Fe^IVO²⁺ and 0.009, 0.038, 0.102 mmol/L of SO₄^·-/·OH were produced within 10 min by PSBC-600/PMS, PSBC-800/PMS, and PSBC-1000/PMS, respectively. Characterization, density functional theory (DFT) simulation and Pearson correlation analysis revealed that along with the increase of pyrolysis temperatures, the active sites of PSBC gradually shifted from atomically dispersed N-coordinated Fe moieties (FeN_x) to iron nitrides (Fe_xN), which activated PMS to produce Fe^IVO²⁺ and SO₄^·-/·OH, respectively. This study clarifies the structure-activity relationships of PSBC for PMS activation, and opens a new avenue for the treatment and utilization of PS as high value-added resources.

Pyrolysis of hydrazine hydrate waste salt: Thermal behaviors and transformation characteristics of organics under aerobic/anaerobic conditions

The production of large quantities of industrial waste salts is becoming an issue of increasing concern with the adoption of the "zero liquid discharge" process for wastewater treatment. Recovery of waste salts as a useful resource after purification provides the best means of solving this problem. In this study, pyrolysis was studied as a purification technique to treat waste salt generated during hydrazine hydrate production (N₂H₄ WS) within the temperature range of 25-600 °C under aerobic and anaerobic conditions. Aerobic pyrolysis achieved 99.3% organic removal at a temperature that was 50 °C lower than was that achieved by anaerobic pyrolysis (600 °C). The formation of strong fluorescent species at 400 °C during anaerobic pyrolysis was detected using fluorescence excitation emission matrix (FEEM). These species were confirmed to be heterocyclic-N compounds, including pyridinic N and pyrrolic N, that were formed through cyclization reactions, as revealed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric-Fourier transform infrared spectroscopy-mass spectrometry (TG-FTIR-MS). Harmful gases such as HCN and NH₃ were released during anaerobic pyrolysis, and this may have been partially associated with the decomposition of heterocyclic-N compounds. Moreover, aerobic pyrolysis effectively reduced CO₂ emissions by 8.7% based on energy consumption calculations. Therefore, aerobic pyrolysis is preferable for the purification of N₂H₄ WS owing to its low decomposition temperature, minimal release of harmful gaseous compounds, and low carbon emissions.

Mechanistic insights into the generation and control of Cl-DBPs during wastewater sludge chlorination disinfection process

Chlorination disinfection has been widely used to kill the pathogenic microorganisms in wastewater sludge during the special Covid-19 period, but sludge chlorination might cause the generation of harmful disinfection byproducts (DBPs). In this work, the transformation of extracellular polymeric substance (EPS) and mechanisms of Cl-DBPs generation during sludge disinfection by sodium hypochlorite (NaClO) were investigated using multispectral analysis in combination with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The microorganism Escherichia coli (E. coli) was effectively inactivated by active chlorine generated from NaClO. However, a high diversity of Cl-DBPs were produced with the addition of NaClO into sludge, causing the increase of acute toxicity on Q67 luminous bacteria of chlorinated EPS. A variety of N-containing molecular formulas were produced after chlorination, but N-containing DBPs were not detected, which might be the indicative of the dissociation of -NH₂ groups after Cl-DBPs generated. Additionally, the release of N-containing compounds was increased in alkaline environment caused by NaClO addition, resulted in more Cl-DBPs generation via nucleophilic substitutions. Whereas, less N-compounds and Cl-DBPs were detected after EPS chlorination under acidic environment, leading to lower cell cytotoxicity. Therefore, N-containing compounds of lignin derivatives in sludge were the major Cl-DBPs precursors, and acidic environment could control the release of N-compounds by eliminating the dissociation of functional groups in lignin derivatives, consequently reducing the generation and cytotoxicity of Cl-DBPs. This study highlights the importance to control the alkalinity of sludge to reduce Cl-DBPs generation prior to chlorination disinfection process, and ensure the safety of subsequential disposal for wastewater sludge.

Analysis of Pyrolysis Characteristics of Oily Sludge in Different Regions and Environmental Risk Assessment of Heavy Metals in Pyrolysis Residue

As a resource treatment method, pyrolysis realizes the recovery of oil and immobilization of heavy metals in oily sludge (OS). The results showed that the composition of OS had little effect on the trend of the whole pyrolysis process, but it had different effects on the mass loss and maximum weight loss rate at each pyrolysis stage. SEM-EDS results showed that the pyrolysis residue had a porous internal structure, which was similar to that of activated carbon. The elements S, Ca, O, Fe, Al, and Si were embedded in the carbon skeleton. After OS pyrolysis, the oil content of the solid residue was far less than 2%, which met the pollution control requirements for comprehensive utilization specified in China's oil and gas industry standard. At the same time, the ratio of exchangeable fraction decreased and the ratio of residual fraction increased after OS pyrolysis. The potential ecological hazard coefficient (E _r) of Cd in OS2, OS2-500, and OS2-600 was greater than 40, which were strong and medium hazards. The E _r values of OS2-700 and other metals were far lower than 40, which were low hazards. With the increase of pyrolysis temperature, the comprehensive ecological hazard index (RI) of heavy metals in the residue gradually decreased and the RI value of OS2-700 decreased to 28.01. Therefore, the pyrolysis residue had an internal porous structure and controllable environmental risk. It could be used as an adsorption material for heavy metals to realize the comprehensive utilization of OS.

Pretreatment of straw using filamentous fungi improves the remediation effect of straw biochar on bivalent cadmium contaminated soil

Carbonized products of waste agricultural straws used for soil remediation can reduce impact of heavy metals on soil ecology and crop growth. Here, we demonstrated straw fermentation residues to be suitable for preparation of soil remediation agents by pyrolysis. Lignocellulose degradability of filamentous fungi during fermentation was found to significantly enhance properties of biochar for cadmium (Cd (II))-contaminated paddy soil remediation. Obtained biochars were indicated to have rich oxygen-containing groups, thus showing enhanced removal ability of Cd (II). Adsorption capacity of biochar (BaWS) prepared from wheat straw, which has been fermented by Trichoderma asperellum T-1, reached 105.9 mg g^-1, 372.8% higher than that from natural wheat straw (BWS). Fermentation of straws by Trichoderma reesei QM6a can also improve the adsorption performance of biochar, but the effect is much weaker. The content of bioavailable Cd (II) in paddy soil reduced 83.7% within 15 days after addition of 1% BaWS. Significantly, adding 1% BaWS had better effect on increasing soil pH and removing available Cd (II) , than adding 3% BWS. These results suggest that the used dosage of microbial pretreated straw biochar for the remediation of Cd (II)-contaminated paddy soil was only 1/3 of that of conventional biochar. The enhanced property of biochar was attributed to deconstruction of straws by filamentous fungi before being pyrolyzed. Thus, fermented straws were indicated more suitable for the preparation of biochar used as effective soil remediation agents.

Removal and Mechanism of Cadmium, Lead and Copper in Water by Functional Modification of Silkworm Excrement Biochar

A new type of biochar, called GBC, was prepared from silkworm excrement, and then modified by chitosan combined with pyromellitic dianhydride. The removal of mono-metal and polymetals (Pb, Cd and Cu) from an aqueous solution by GBC was investigated in this research. Compared to unmodified biochar, the removal rate of Pb and Cd by GBC was about 12% higher, while that of Cu was about 94.6% higher. It also shows the types of functional groups in biochar have a great impact on their adsorption. The removal of Pb is mainly involved in the N-C=O functional group, the removal of Cd is mainly involved in N-containing functional group and C=C bond, and that of Cu is mainly involved in N-containing functional group, carboxyl group, hydroxyl group, and a carbonyl group. Five adsorption–desorption cycles of GBC were carried out, and it was found that the adsorption capacities of GBC for Pb, Cd and Cu decreased by 7.28%, 10.78% and 6.07%, respectively, indicating that GBC had a good renewable performance. The adsorption capacity of GBC for Cu in different water samples is between 89.62 and 93.47 mg·g⁻¹, indicating that GBC has great application potential for the removal of Cu in wastewater.

Pyrolysis of food waste and food waste solid digestate: A comparative investigation

The effects of anaerobic digestion (AD) on pyrolysis were elaborated by comparing the pyrolysis performance of food waste (FW) and food waste solid digestate (FWSD). The pyrolysis mechanisms of FW and FWSD were revealed by experimental and kinetic analysis. The properties and potential applications of pyrolytic products from FW and FWSD were discussed. The results showed that part of organic matters of FW were consumed during AD, which altered the pyrolysis performance of FWSD. The pyrolytic gas from FW had better quality due to its higher lower heating value (LHV) (20.52 kJ/Nm³). The pyrolytic oil and biochar derived from FWSD showed better qualities as oil fuel and carbon-based absorbent. Pyrolysis of FWSD produced less nitrogen-containing pollutants (NCPs) indicated that AD coupled with pyrolysis is more environmental-friendly to treat FW. This study provides potential approach and theoretical guidance for the treatment and resource utilization of FW and FWSD.

Effects of demineralization and devolatilization on fast pyrolysis behaviors and product characteristics of penicillin mycelial residues

In this study, the effects of demineralization and devolatilization methods including of water washing (WW), torrefaction (TF), washing-torrefaction (WT) and hydrothermal treatment (HT) on the fast pyrolysis characteristics of penicillin mycelial residues were studied. The materials and pyrolysis products were characterized by analysis methods including of thermogravimetric (TG), gas chromatograph (GC), gas chromatography-mass spectrometry (GC-MS), x-ray diffractometer (XRD), fourier transform-infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS), etc. The results showed WW increased the yields of tar and decreased the yields of pyrolysis biochar due to the removal of alkali and alkaline earth metals (AAEMs), while TF and HT showed opposite results due the devolatilization. XPS and FT-IR results proved that the conversion from aliphatic C-(C, H) to aromatic groups C-O-C and CO was the key point for improving the aromatization of biochar. Pretreatments increased the relative proportions of N-containing heterocyclic compounds and phenolic compounds, reduced the proportions of O-containing heterocyclic compounds in pyrolysis tar. And TF and HT could eliminate the residual antibiotic and satisfy the principle of AMR harmless disposal.

Flue gas torrefaction of municipal solid waste: Fuel properties, combustion characterizations, and nitrogen /sulfur emissions

Flue gas torrefaction (FGT) was proposed as the pretreatment of the municipal solid waste (MSW) combustion process to improve the fuel properties of MSW and achieve better combustion performance. The optimal FGT parameters were obtained at 300 ℃ and 30 min, with the energy-mass co-benefit index (EMCI) reaching the maximum of 23.38. FGT could significantly increase the heating value and energy density of MSW while reducing the H/C and O/C ratio. Then, the pyrolysis and combustion experiments were performed by tube furnace and TG-MS. The results proved the chemical compositions of MSW were altered, and the heat transfer was enhanced. With FGT, NO_x and SO₂ emissions could be reduced by 25.7 % and 52.4 %, respectively. This study provides an in-depth understanding of the mechanism of FGT and paves the way for the clean treatment and energy utilization of MSW.

Analysis of Pyrolysis Performance and Molecular Structure of Five Kinds of Low-Rank Coals in Xinjiang Based on the TG-DTG Method

Taking five coal samples (FCSs) in Xinjiang as the research object, characterizations such as proximate analysis, ultimate analysis, Fourier transform infrared (FTIR), and thermogravimetry-differential thermal analysis (TG-DTG) were carried out. The Coats-Redfern model was used to simulate pyrolysis kinetics of FCSs under different reaction orders (ROs). The results showed that except for HSBC, the R ² of the other four coal samples are all higher than 0.9, which showed a good correlation effect. FCSs present similar reaction activation energy in the same RO and temperature range. Results of FTIR showed that the hydroxyl groups of FCSs, in the range of 3100-3600 cm^-1, were mainly self-associated hydroxyl hydrogen bonds and hydroxyl π bonds, and they occupied over 63%. Among them, the pyrolysis characteristic index (D) of XBC was 4.139 × 10^-6, higher than those of other samples, and it showed good pyrolysis performance. Moreover, by reducing the temperature range appropriately, the fitting results showed a better correlation effect.

Insight into the evolution of antibiotic resistance genes and microbial community during spiramycin fermentation residue composting process after thermally activated peroxydisulfate pretreatment

Previous research has been demonstrated that the residual unextracted antibiotics in spiramycin fermentation residue (SFR) could be efficiently removed by thermally activated peroxodisulfate (TAP) pretreatment, indicating the improvement of biodegradability. This study aimed to investigate the effect of TAP pretreatment on the succession of bacterial community and fate of antibiotic resistance genes (ARGs) during SFR composting. Results indicated that TAP pretreatment increased the composting temperature and promoted the decomposition of organic matters. Furthermore, TAP pretreatment could increase bacterial alpha diversity and significantly reduce the relative abundance of ARGs (1.13-1.75 times) and mobile genetic elements (MGEs) (1.13-1.32 times) after composting. The compost of pretreated SFR by TAP could reduce the enrichment of ARGs and MGEs in the bacterial community, especially the rRNA methylase genes of ermB (4-142-folds). Redundancy analysis showed that Actinobacteria, Bacteroidetes, Proteobacteria and horizontal gene transfer mediated by MGEs (intI1) was positively related to the changes in ARGs (accounted for 97.4%). Network analysis showed that Firmicutes was the main bacterial hosts of ARGs and MGEs. These findings demonstrated that TAP pretreatment combined composting was a promising strategy for SFR safe treatment and disposal that could reduce the proliferation and transfer of ARGs.

N,N-Dimethylformamide solvent assisted hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots

Microalgae are considered as a promising alternative to fossil fuels due to their ease of cultivation, short growth cycle and no occupation of cultivated land. In this study, N,N-Dimethylformamide (DMF) solvent was employed to assist hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots (CDs). The effect of pretreatment conditions on the composition and pyrolysis bio-oil distribution of hydrothermal solid residues as well as CDs characteristic were investigated by varying the temperature (180-220 ℃) and reaction time (1-9 h). The results showed that pretreated residues had higher cellulose. And the yield of sugar and N-contained compounds reached 41.59% and 63.57% in the pyrolysis bio-oil of pretreated algae residues, respectively. Moreover, CDs obtained from hydrothermal solution fluoresced red under 365 nm excitation. The paper provides a new method for the complete utilization of microalgae.

Characteristics of bio-oil and biochar from cotton stalk pyrolysis: Effects of torrefaction temperature and duration in an ammonia environment

In this study, nitrogen-containing chemicals and nitrogen-rich biochar were prepared using ammonia (NH₃) torrefaction pretreatment technology. The effects of temperature and duration of torrefaction on the characteristics of torrefaction and pyrolysis products were evaluated. The results indicated that when the torrefaction temperature was increased to 290 °C, the nitrogen content increased significantly from 0.98% to 6.85%. XPS analysis showed that the raw biomass mainly contained amide-N and pyrrole-N. As the torrefaction temperature and duration increased, quaternary-N formation was promoted, while amide-N, pyrrole-N, and pyridine-N were consumed. Potential nitrogen doping and transformation pathways during the ammonia torrefaction process were proposed. GC-MS analysis showed that ammonia torrefaction promoted the formation of pyridines, while reducing the content of oxygen-containing species. In addition, torrefaction duration had positive effects on the yield of nitrogen-containing chemicals.

Formation mechanism of NOx precursors during the pyrolysis of 2,5-diketopiperazine based on experimental and theoretical study

Incineration of food waste leads to the release of NO_x pollutants, whereas the formation mechanism of the NO_x precursors (HCN, NH₃, and HNCO) during the initial pyrolysis process is far from well-studied, limiting the source control on NO_x release. In this work, 2,5-diketopiperazine (DKP) was selected as the N-containing model compound to study the formation mechanism of NO_x precursors in food waste pyrolysis, by combining experiments and density functional theory (DFT) calculations. The C1-N2 bond broken via the N2-to-N5 H-transfer possesses the lowest energy barrier, together with the largest reaction rate constants in the range of 400-800 °C. NH₃ can be easily generated with low energy barriers and high rate constants at low temperatures (below 630 °C). Whereas, the rate constants of the pathways for HCN formation will exceed those for NH₃ generation in the range of 630-740 °C. In addition, the DKP pyrolysis can also lead to the formation of HNCO with a very low energy barrier, and it can convert into HCN and NH₃ through further hydrogenation and decomposition. These calculation results are exactly consistent with the experimental results that NH₃ was the main precursor in the range of 400-600 °C, and the yield of HCN exceeded that of NH₃ when the temperature was over 600 °C. Our current work on the formation mechanism of NO_x precursors during the pyrolysis of DKP can provide theoretical guidance for the development of NO_x control technology in the pyrolysis/combustion process of organic waste.

Flue gas torrefaction of distilled spirit lees and the effects on the combustion and nitrogen oxide emission

Flue gas torrefaction (FGT) integrated with combustion was introduced for the clean treatment of distilled spirit lees (DSL). The effects of temperature, residence time, and volumetric flow rate of FGTs were investigated. The improvement in the physicochemical and combustion characteristics of the torrefied DSL and the reaction mechanisms were clarified by a tube furnace and the TG-MS device. The results showed that FGT could effectively improve the properties of DSL. With increasing temperature, residence time, and volumetric flow rate, the mass and energy yields decreased. FGT showed positive effects on the removal of free and bonding water, as well as the enrichment of lignin. FGT effectively inhibited the release of NO_x. The overall emission of NO_x was reduced by 57.3%. Additionally, the cost of DSL drying and denitrification could be greatly reduced by FGT. This study provided a practical treatment for DSL and new insight into FGT.

Petroleum oil and products recovery from oily sludge: Characterization and analysis of pyrolysis products

Oily sludge (OS) has attracted special interest because of its hazardous nature and high potential as an energy resource. This study investigated the oil recovery from OS by thermal cracking and catalytic pyrolysis. The oil yield increased when the temperature exceeded 450 °C and reached a maximum (76.84 wt%) at 750 °C. Catalysts significantly improved the quality of oil produced during catalytic pyrolysis. Aromatic hydrocarbons were dominant (10.01-52.69%) in pyrolysis oil (PO) from OS catalytic pyrolysis, and the catalysts significantly reduced the presence of oxygen heterocycles. In addition, KOH and CaO reduced the I_D (D-band peak intensity)/I_G (G-band peak intensity) of OS char (OC) and increased the degree of graphitization. Owing to its higher iodine adsorption value and methylene blue (MB) adsorption value, OC exhibits potential as an adsorbent. The environmental assessment and potential applications of OC, along with possible reaction mechanisms and kinetic characteristics, are also discussed.

Functional Group Characteristics and Pyrolysis/Combustion Performance of Karamay OS Based on FT-IR and TG-DTG Analyses

Proximate analysis, ultimate analysis, Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetry-differential thermal analysis characterization were carried out on oily sludge (OS) samples OS1-OS5, from Karamay, Xinjiang, China. The Coast-Redfern model (CRm) was used to simulate the pyrolysis and combustion kinetics of oily samples. The results showed that the peak area percentage of benzene ring trisubstitution of OS5, in the range of 700-900 cm-1, is close to 75%, corresponding to its high volatile content. Based on the kinetic analysis by the CRm, it is found that the fitting degree of the five samples is better when the reaction order is selected as n = 2, with R 2 close to 1.00 and 2RT/E to 0. Among them, the S N and D W of OS5 are 17.8 × 10-10%2 min-2 °C-3 and 0.10899 × 10-5% min-1 °C-2, respectively, higher than those of other samples, indicating a good combustion performance.

Catalytic upgrading of penicillin fermentation residue bio-oil by metal-supported HZSM-5

Antibiotic fermentation residue (AR) is composed of hazardous organic waste produced by the pharmaceutical industry. AR can be effectively converted into bio-oil by fast pyrolysis, but its high nitrogen content limits the prospect of bio-oil as a fuel resource. In order to further reduce the nitrogen content of AR bio-oil, we have examined the catalytic removal of N and O from penicillin fermentation residue (PR) bio-oil under fast pyrolysis conditions. We have used M/HZSM-5 (M = Fe, Co, Ni, Cu, Zn, Zr, Mo, Ag and Ce) metal catalysts, with a metal oxide content of 10%. Additionally, the effect of mixed and separated catalytic forms on catalytic upgrading were analyzed, and changes in the catalyst itself before and after pyrolysis under separated catalytic conditions were specifically investigated. Our results show that the metal elements in the fresh catalyst will exist in the form of oxides, ions and simple metals. In-situ reduction caused by pyrolysis gas in the catalytic pyrolysis process makes some ionic metals (e.g., Co²⁺, Cu²⁺ and Ag⁺) in the catalyst transform into oxides, and some metal oxides are reduced to simple metals or suboxides (including Fe, Ni, Cu and Mo). The N content in the mixed catalytic bio-oil decreased from 10.09 wt% to Zn/HZSM-5 (6.98 wt%), Co/HZSM-5 (7.1 wt%), Cu/HZSM-5 (7.18 wt%) and Ce/HZSM-5 (7.18 wt%). We also observed significant reduction in the O content (9.77 wt%) with Ag/HZSM-5 (3.75 wt%), Mo/HZSM-5 (6.86 wt%), Ce/HZSM-5 (8.39 wt%) and Fe/HZSM-5 (8.54 wt%) in the separated catalytic bio-oil. The Ni/HZSM-5 catalystcan reduce the organic acid content in bio-oil from 22.9% to 10.8%. The separated catalysis methodology also promoted an increase of hydrocarbons in the bio-oil: Zn/HZSM-5, Ag/HZSM-5, Mo/HZSM-5, Zr/HZSM-5 and Ce/HZSM-5 reached 11.6%, 11.5%, 11.1%, 10.1%, and 8.8%, respectively. Carbon deposition formed by aromatic carbon/graphite carbon, pyrrole and pyridine compounds leads to deactivation of the catalyst.

Influence of process parameters on hydrothermal modification of soybean residue: Insight into the nutrient, solid biofuel, and thermal properties of hydrochars

Soybean (SB) solid residue after oil extraction was investigated in a hydrothermal modification process to provide an eco-friendly solution to SB solid waste disposal for an actual environmental management effort. SB hydrochars (HCs) were derived either by conventional heating hydrothermal treatment (HTT) under intense conditions (200, 250, and 300 °C for 2 h) or by microwave-assisted hydrothermal treatment (MHTT) under mild conditions (160, 190, and 220 °C for 1 h). Physicochemical properties of SB HCs and the transformation of nitrogen (N) and phosphorus (P) functionalities during HTT and MHTT were characterized using several tools. Ultimate and XPS analyses elucidated N transformation, e.g., 5.51 wt % N of raw SB residue decreased to 3.48 and 3.51 wt % after HTT and MHTT, respectively. The P bioavailability of raw SB (3.46 mg/g) was improved after HTT (26.7 mg/g) and MHTT (10.9 mg/g), depicting the practical application of HCs for soil amendment. Atomic H/C and O/C ratios of SB HCs decreased as treatment temperature increased. HCs showed credible higher heating value (HHV; 22.3-25.5 MJ/kg for HTT and 20.5-22.1 MJ/kg for MHTT), higher than various low-rank coals. Besides, energy densification and fuel ratio improved in intense conditions. The thermogravimetric analysis showed HCs possessed better thermal stability. The improved performance of SB HCs indicated that HTT and MHTT provided a green environmental route of SB waste management, valorization, and utilization.

Pyrolysis of antibiotic mycelial dreg and characterization of obtained gas, liquid and biochar

The disposal and utilization of antibiotic mycelial dreg (AMD), which has been identified as a hazardous waste in China, are a serious concern because of the residual antibiotic and huge annual output. Pyrolysis is a promising technology to treat AMD. However, the pyrolysis of AMD is not studied in an adequate degree, particularly no attention has been paid to the release and distribution of the phosphorus in AMD during pyrolysis. Therefore, the present work studied the pyrolysis of AMD more comprehensively. The influence of pyrolysis temperature on product yields and characteristics, together with the release and distribution of nitrogen and phosphorus, and the antibiotic residue in products, were investigated. The results suggested that residual antibiotic was eliminated after pyrolysis. Nitrogen was mainly contained in the biochar and liquid products, while phosphorus was mainly retained in the biochar. Liquid products were characterized by abundant oxygen and nitrogen-containing compounds, while biochar was featured of both abundant nitrogen and inorganic phosphate groups. Pyrolysis temperature showed a significant effect on product yields and characteristics, and a low pyrolysis temperature is recommended considering the recycling of nitrogen and phosphorus. The disposal of AMD through pyrolysis conforms to the principles of AMD disposal.

Evolution of chemical functional groups during torrefaction of rice straw

The evolution of CHON functional groups during torrefaction of rice straw at 200-300 °C were investigated. The results showed that 300 °C was more suitable for rice straw torrefaction due to the ideal fuel ratio, energy densification, energy-mass co-benefit index and the significantly improved HHV of the torrefied products. The functional groups such as O-H, N-H, C-H, C = O in the solids decreased with rising temperature accompanied by the releases of H₂O, CH₄, CO₂, CO and NH₃, et al. At 300 °C, 40.04% of fuel-N was released in the form of NH₃, HCN, HNCO et al. due to the decomposition of N-A which was the overall N-functionality in the raw rice straw. It is worth noting that the absorbance of NH₃ and HCN has the same order of magnitude as CO. Therefore, the releases of N-containing gases should be highly concerned for the application of torrefaction technology from the environmental perspective.

Study on the nitrogen migration mechanism during penicillin fermentation residue fast pyrolysis based on the substance transformation and canonical variational theory

Antibiotic fermentation residue (AR) is not only a kind of hazardous waste, but also a biomass resource that rich in organic matter. The fast pyrolysis of penicillin fermentation residue (PR) and the model compounds was performed in this study. In PR bio-char, protein nitrogen was mainly converted into pyrrole nitrogen and pyridine nitrogen. When the temperature exceeded 500 °C, pyridine nitrogen further converted into quaternary nitrogen. NH₃, HCN and HNCO were the main nitrogen-containing compounds in the PR fast pyrolysis gas, among which HNCO was mainly the decomposition product of 2,5-piperazinedione (DKP). The yield of PR bio-oil reached 33.1 wt%, and the content of nitrogen was 8.9 wt% at 600 °C. It was found that the decomposition of glutamic acid and aspartic acid resulted in the formation of several cycloamides in PR bio-oil. The decomposition of histidine led to the formation of imidazole and aromatic imidazole. The reaction rate constants in the pathways of DKP decomposition were evaluated by the canonical variational theory (CVT). It was indicated that the pathway of HNCO formation has the highest reaction rate in the PR fast pyrolysis ranging from 400 °C to 700 °C. The DKPs that existed in PR bio-oil were mainly the molecules produced by the condensation between proline and another amino acid, which due to the inhibition of HCNO formation by the proline R-group. With the increase of temperature, the rapid increase in the rate constant of dehydrogenation promoted the formation of indole from aromatic amino acids.

N-rich hydrochar derived from organic solvent as reaction medium generates toxic N-containing mineral in its pyrochar

Low-grade hydrochar is often thermally activated to produce pyrochar. However, the interaction between inherent metals and N element during hydrochar activation process has never been considered. Present study revealed that a highly toxic N-containing mineral (MCN, M: metal) can be formed in N-rich hydrochar-based pyrochar via N rearrangement and subsequent carbothermal reactions. This atypical hydrochar is mainly produced from organic wastes with K₂CO₃ or Na₂CO₃ (such as food waste) in an organic solvent medium. The CN^- concentration of studied pyrochar can reach to 9807 mg/kg, which is mainly determined by content and type of metal in hydrochar. The low N conversion rate (<4.2%) indicates that formation of MCN is independent of N content in hydrochar. Essentially, formation of MCN can be significantly inhibited by FeCl₃ via the anionic interactions between Fe and K salt. This discovery can likely offer a new guide for the application of N-rich hydrochar-based pyrochar.

Phosphorus and nitrogen transformation in antibiotic mycelial residue derived hydrochar and activated pyrolyzed samples: Effect on Pb (II) immobilization

In this study, lincomycin residue (LR, a type of antibiotic mycelial residue) derived hydrochar samples (LR-HCs) were obtained from hydrothermal carbonization (HTC), and pyrolysis applied to these LR-HCs to produce activated pyrolyzed samples (LR-APs). Transformation of phosphorus (P) and nitrogen (N) species during HTC and pyrolysis was of primary interest and characterized by several techniques. Nitrogen content of dry LR was calculated by elemental analysis, being 7.91 wt. %, decreasing to 2.51 after HTC and 1.12 wt. % after concesutive HTC and pyrolysis. FT-IR analysis provided evidence for amine groups in LR samples. XPS analysis described N species (Pyridinic-N, Amine-N, Protein-N, Pyrrolic-N, and Quaternary-N) and P species (ortho-P/pyro-P and Ar-P) in LR samples, effectively. Sequential extraction showed that the HTC and pyrolysis changed the proportion of the P species from labile (P-NaHCO₃ and P-NaOH) to stable ones (P-residue). Utilization and suitability of as-prepared LR-HCs and LR-APs for heavy metal Pb (II) immobilization show promising results. To help understand immobilization process, kinetic (pseudo-1st-order and pseudo-2nd-order) and isotherm (Freundlich) models were tested and verified. Results confirmed that P and N species were transformed during HTC and pyrolysis and that these processes lead to an advantageous effect on Pb (II) removal from solution.

Conversion of phosphorus and nitrogen in lincomycin residue during microwave-assisted hydrothermal liquefaction and its application for Pb2+ removal

Treatment of antibiotic fermentative residue (AFR) produced from pharmaceutical industries and their application in the environment has been gaining researchers' interest. In this study, lincomycin residue (LMR, the type of AFR) was treated with microwave-assisted hydrothermal liquefaction (MW-HTL) in a temperature range 120-210 °C, transforming effect of phosphorus (P) and nitrogen (N) functional groups in LMR samples was characterized with elemental analysis, XRD, XPS, FT-IR, and P-extraction, and utilized LMR samples for Pb²⁺ removal from aqueous solutions. The temperature had a significant impact on P and N functional groups conversion justified by characterization techniques and also responsible for Pb²⁺ adsorption. LMR hydrochar produced at 210 °C was accounted highest Pb²⁺ adsorption capacity (57.4 mg g^-1), higher four folds than raw LMR (13.8 mg g^-1). To understand the mechanism and rate defining phase of adsorption equilibrium isotherm and kinetic models were applied systematically. Adsorption results of LMR and its derived hydrochar samples found connectivity with Langmuir and pseudo-first-order isotherm models. Adsorption mainly occurred as ion-exchange dependent on the substitution of metal ions (Pb²⁺) to Ca²⁺ ions present in P-materials, and surface adsorption dependent on surface functional groups of LMR samples. Better operation feasibility of MW-HTL treated LMR, elaboration of P and N conversion behavior and high sorption of Pb²⁺ ions could make LMR a frontrunner for heavy metals immobilization.

Degradation of antibiotics and antibiotic resistance genes in erythromycin fermentation residues using radiation coupled with peroxymonosulfate oxidation

Ionizing radiation coupled with peroxymonosulfate (PMS) oxidation was developed to degrade antibiotics and antibiotic resistance genes (ARGs) from the erythromycin fermentation (EryF) residual wastes. The experimental results showed that the ERY content and ARGs abundance decreased with increase of the absorbed dose and PMS dosage and gamma irradiation was more effective to abate ARGs from the EryF wastes. The removal efficiency of ERY reached 49-55% and more than 96-99% of ARGs (1.32-2.55 log) was eliminated with the absorbed dose of 25-50 kGy and PMS dosage of 50-100 mM. Illumina pyrosequencing revealed that 3 bacterial phyla, Proteobacteria, Firmicutes and Fusobacteria were highly enriched and the ARGs-linked hosts were affiliated to the genera Aeromonas, Enterobacteriaceae and Enterobacter in the phylum Proteobacteria. The abundance of the ARGs-linked bacteria decreased by gamma/PMS treatment. Ionizing radiation/PMS treatment with the doses of 25 kGy and 50 mM PMS is proposed for potential practical application.

Thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue

This work studied thermal characteristics and product formation mechanism during pyrolysis of penicillin fermentation residue (PR). Results showed that PR pyrolysis proceeded in four stages. The kinetic triplet of each stage was calculated using Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and integral master-plot methods. The kinetic model for stage 1 was the three-dimensional diffusion model, the simple reaction order model for stage 2 and stage 4, and the nucleation-growth model for stage 3. FTIR analysis suggested that the intensities of absorption peaks of NH, CO, CH, CN, and CO in chars weakened gradually with increasing temperature, corresponding to the production of CH₄, CO, NH₃, and HCN. GC-MS results indicated that the high protein content in PR resulted in a high fraction of nitrogenated compounds (amides and amines, nitriles, and N-heterocyclic species) in bio-oil. The formation mechanism of these compounds was discussed. Besides, bio-oil also contained large quantities of oxygenated compounds and a few hydrocarbons.

Biochar produced from mineral salt-impregnated chicken manure: Fertility properties and potential for carbon sequestration

In this study, nutrient properties and carbon sequestration potential of biochars derived from chicken manure (CM) impregnated with mineral salts (calcium chloride, magnesium chloride, ferric chloride) were evaluated. Pretreatment with mineral salts reduced phosphorus (P) availability via the formation of insoluble metal phosphate minerals. Less carbon was lost during the pyrolysis of pretreated CM, and the produced biochars (BC_Ca, BC_Mg, and BC_Fe) were more stable (i.e., reduced C loss during chemical oxidation and less CO₂ release during incubation) than pristine biochars. Spectroscopic evidence indicated that enhanced biochar stability via metal salt pretreatment before pyrolysis was related to increased aromatization and enhanced physical protection due to the metal-oxygen interaction, together with the formation of metal mineral phases on biochar surfaces. Moreover, ferric chloride was the optimal additive, as it significantly decreased biochar P leachability and increased carbon sequestration potential.

Denitrification and desulphurization of industrial biowastes via hydrothermal modification

In attempt to decrease NO_X and SO₂ emission from thermochemical utilization, three industrial biowastes (penicillin mycelia waste, sewage sludge and peat waste) contained high nitrogen (N) and sulfur (S) were chosen to investigate the denitrification and desulphurization of hydrothermal modification. The results demonstrated that hydrothermal modification destroyed the structure of N- and S-containing components, thereby altering their existed conformations. Inorganic-N (N-IN) and most of amino-N/polyamide-N (N-A) were enriched by liquid phase in the forms of NH₄⁺-N and soluble organic-N (Org-N), respectively; subsequently, Org-N could further decompose to NH₄⁺-N at higher temperature. Residual N in hydrochars was converted from N-A to heterocyclic-N (pyrrolic-N, pyridinic-N and quaternary-N) via hydrolysis and cyclization. Similarly, over 60% of S was remove form biowastes at 240 °C. In solid phase, part of organic-S was altered to thiophenes-S after modified, while the remainder was transformed to inorganic-S; but the variation of inorganic-S in hydrochars strongly affected by its specific species.

Co-pyrolysis characteristics and kinetic analysis of organic food waste and plastic

In this work, typical organic food waste (soybean protein (SP)) and typical chlorine enriched plastic waste (polyvinyl chloride (PVC)) were chosen as principal MSW components and their interaction during co-pyrolysis was investigated. Results indicate that the interaction accelerated the reaction during co-pyrolysis. The activation energies needed were 2-13% lower for the decomposition of mixture compared with linear calculation while the maximum reaction rates were 12-16% higher than calculation. In the fixed-bed experiments, interaction was observed to reduce the yield of tar by 2-69% and promote the yield of char by 13-39% compared with linear calculation. In addition, 2-6 times more heavy components and 61-93% less nitrogen-containing components were formed for tar derived from mixtures.

Co-pyrolysis behavior of fermentation residues with woody sawdust by thermogravimetric analysis and a vacuum reactor

This study aimed at cost-effective utilization of fermentation residues (FR) from biogas project for bio-energy via co-pyrolysis of FR and woody sawdust (WS). In this study, a vacuum reactor was used to study the pyrolysis behaviors of individual and blend samples of FR and WS. Obvious synergistic effects were observed, resulting in a lower char yield but a higher gas yield. The presence of woody sawdust promoted the devolatilization of FR, and improved the syngas (H₂ and CO) content in the gaseous products. Compared to those of the char from pyrolysis of individual feedstock, co-pyrolysis of FR and WS in the vacuum reactor promoted the cracking reactions of large aromatic rings, enlarged the surface area and reduced the oxygenated groups of the resulted char.

Removal behaviors and mechanisms of hexavalent chromium from aqueous solution by cephalosporin residue and derived chars

Cephalosporin residue (CR) was used to produce biochar (BC) and activated carbon (AC) at 600°C (BC600 and AC600). To compare the removal behaviors and mechanisms of Cr(VI) by CR and derived chars, batch adsorption tests were performed in Cr(VI) microenvironment like pH, Cr(VI) concentration, adsorbent dosage, combing with the characterization of adsorbents before and after adsorption. Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) techniques were used. Results showed that the Cr(VI) removals by CR and CR-chars fitted Freundlich and Langmuir models. Based on the Langmuir model, the maximum adsorption capacities of CR, BC600 and AC600 towards Cr(VI) were 107.41, 88.19 and 74.07mgg^-1, respectively. The CR rich in dissolved carbon (DOC), -NH₂ and -COOH, chiefly acted as chelating and reducing agents, while the AC600 with high surface area mainly supported Cr(VI) adsorption during Cr(VI) removal process.

Transformation of Nitrogen and Evolution of N-Containing Species during Algae Pyrolysis

Transformation and evolution mechanisms of nitrogen during algae pyrolysis were investigated in depth with exploration of N-containing products under variant temperature. Results indicated nitrogen in algae is mainly in the form of protein-N (∼90%) with some inorganic-N. At 400-600 °C, protein-N in algae cracked first with algae pyrolysis and formed pyridinic-N, pyrrolic-N, and quaternary-N in char. The content of protein-N decreased significantly, while that of pyrrolic-N and quaternary-N increased gradually with temperature increasing. Pyridinic-N and pyrrolic-N formation was due to deamination or dehydrogenation of amino acids; subsequently, some pyridinic-N converted to quaternary-N. Increasing temperature decreased amides content greatly while increased that of nitriles and N-heterocyclic compounds (pyridines, pyrroles, and indoles) in bio-oil. Amides were formed through NH₃ reacting with fatty acids, that underwent dehydration to form nitriles. Besides, NH₃ and HCN yields increased gradually. NH₃ resulted from ammonia-N, labile amino acids and amides decomposition, while HCN came from nitrile decomposition. At 700-800 °C, evolution trend of N-containing products was similar to that at 400-600 °C. While N-heterocyclic compounds in bio-oil mainly came from pyrifinic-N, pyrrolic-N, and quaternary-N decomposition. Moreover, cracking of pyridinic-N and pyrrolic-N produced HCN and NH₃. A mechanism of nitrogen transformation during algae pyrolysis is proposed based on amino acids decomposition.

Investigation of free radicals and carbon structures in chars generated from pyrolysis of antibiotic fermentation residue

The aromatization level of AFR was enhanced sharply with the increase of pyrolysis temperature, and the free radicals in raw AFR samples gradually transformed into carbon free radicals on the aromatic structures in chars.

In situ synthesis of flame retardant organic–inorganic hybrids by a molten blending method based on thermoplastic polyurethane elastomer and polybutyl titanate

A novel type of organic–inorganic hybrid prepared using an in situ synthesis method by molten blending polybutyl titanate (BTP) and thermoplastic polyurethane elastomer (TPU) is reported.