Effects of hydrothermal treatment on the pyrolysis behavior of Chinese fan palm

Hydrothermal carbonization coupled with fast pyrolysis of almond shells: Valorization and production of valuable chemicals

In this study, it was found that hydrothermal carbonization (HTC) can be an effective method for almond shell (AS) valorization. The severity of HTC treatment had a significant effect on hydrochar yields, with higher severity promoting carbonization but reducing yields. Furthermore, the work found that HTC treatment effectively demineralized biomass samples by removing inorganic material that could catalyze carbonization. As residence time or temperature increased, the amount of carbon increased, while the amount of oxygen decreased. An acceleration in thermal degradation was detected for hydrochars after pretreating for 4 h. The hydrochars showed they had a higher volatile content than untreated biomass, making them potentially useful for producing quality bio-oil through fast pyrolysis. Finally, HTC treatment led to the production of valuable chemicals such as guaiacol and syringol. For syringol production, HTC residence time had more effect than HTC temperature. However, high HTC temperatures benefited levoglucosan production. Overall, the results demonstrated the potential for HTC treatment to be an effective method for valorizing agricultural waste, offering the possibility of producing valuable chemicals.

Effects of hydrophobic coating on properties of hydrochar produced at different temperatures: Specific surface area and oxygen-containing functional groups

Hydrochar's specific surface area (SSA) is important in environmental remediation; however, a hydrophobic coating formed on hydrochar creates a physical barrier that reduces that SSA. The formation and composition of the hydrophobic coating and its effects on hydrochar properties are unclear. In this study, hydrochar was produced from Chinese fan palm (Livistona chinensis) leaves at different temperatures. The resulting hydrophobic coatings were investigated by in situ characterization and then extracted with acetone for composition identification. Additionally, hydrochar properties were compared before and after hydrophobic coating removal. The results showed that the hydrophobic coating of the hydrochar produced at 180 °C was the insoluble cuticle layer of raw biomass, while the hydrophobic coatings formed above 180 °C were the depolymerization products of cutin. For the hydrochar above 180 °C, especially at 260 °C, the removal of the hydrophobic coating from hydrochar increased both its SSA and its oxygen-containing functional groups.

Effect of Biochar Prepared from Food Waste through Different Thermal Treatment Processes on Crop Growth

Biochar is generally accepted and increasingly valued in scientific circles as solid products in the thermochemical conversion of biomass, mainly because of its rich carbon content. The purpose of this research is to investigate the impact of biochar from different sources on wheat growth. In particular, this work focused on the effect of different preparation methods and raw material of biochar on the growth of wheat and aim to find a potential soil substitute that can be used for crop cultivation. Two synthetic methods were evaluated: hydrothermal conversion and pyrolysis. The characterization of biochar was determined to explore the impact of its microstructure on wheat growth. The results show that the yield of biochar produced from high-pressure reactor is significantly higher than that obtained by using microwave reactor. For example, the biochar yield obtained through the former is about six times that of the latter when using steamed bread cooked as biomass raw material. In addition, the growth trend of wheat indicates that biochar has different promoting effects on the growth of wheat in its weight and height. The pyrolyzed carbon is more suitable for wheat growth and is even more effective than soil, indicating that pyrolyzed biochar has more potential to be an alternative soil in the future. Moreover, this research tries to explore the reasons that affect crop growth by characterizing biochar (including scanning electron microscopy (SEM), biofilm electrostatic test (BET) and Fourier transform infrared (FT-IR)). The results indicate that the biochar containing more pits and less hydroxyl functional are more suitable for storing moisture, which is one of the significant factors in the growth of crops. This study provides evidence of the effects of biochar on crop growth, both in terms of microstructure and macroscopic growth trends, which provides significant benefits for biochar to grow crops or plants.

Synergy of Hydrothermal and Organic Acid Washing Treatments in Chinese Fir Wood Vinegar Preparation

Pretreatment is an effective method to change the pyrolysis behavior and improve the product properties of biomass. In this study, the effects of hydrothermal treatment (HTT) and hydrothermal treatment combined with organic acid washing (HTT-A) on Chinese fir waste (CF) pyrolysis and preparation of wood vinegar (WV) were investigated. The results indicated that HTT promoted the decomposition of hemicellulose and disrupted the chemical structure, while HTT-A partly removed the lignin as well as hemicellulose. HTT-A showed a more effective removal efficiency of alkali/alkaline earth metals (AAEMs) than HTT. Both HTT and HTT-A delayed the initial decomposition temperature but promoted the pyrolysis process. The yields of WVs increased after HTT and HTT-A, while the moisture contents reduced, obviously. HTT increased the relative contents of phenols from 47.04 to 59.85% but reduced the relative contents of acids from 24.31 to 18.38%, whereas HHT-A reduced the relative contents of phenols but increased those of aldehydes. In addition, HTT and HTT-A showed the different effects on chemical compositions of WVs, especially for phenolic and acid compounds. This study indicated that HTT and HTT-A were the efficient methods to produce WVs with target chemical components, which would be conducive to the efficient application of WVs.

Antifungal activity of water-soluble products obtained following the liquefaction of cornstalk with sub-critical water

Cornstalks are the leftover leaves and stems in a field after corn harvest. They are a potential biomass resource but are underutilized in agricultural production systems. To examine the chemical components in cornstalks and their corresponding functions, blocky cornstalks were treated in water at temperatures of 190, 210, 230, 250, and 270 °C in a high-pressure reactor. Water-soluble products (WSPs) were extracted from these treatments, and their chemical compositions were analyzed using gas chromatography-mass spectrometry (GC-MS), and their antifungal activities were determined using a bioassay. It was found that WSPs contained 28.7-40.1% phenols, 27.9-36.6% ketones, 0-2.6% alcohols, 4.9-10.1% esters, 5.4-7.8% organic acids, 1.3-12% aldehydes, and 5.5-18.4% of other organic compounds such as nitrogen- and sulfur-containing compounds, furan compounds, and benzene compounds. The inhibition the growth of the plant pathogen Fusarium oxysporum by WSPs was affected by temperature. WSP-270 (obtained at 270 °C) exhibited the best growth-inhibition efficacy. Under a biomicroscope, WSP-270-treated F. oxysporum showed a deformed and swollen hypha, and an increased number of bifurcations, as well as an expansion of growing apexes of new bifurcations. Therefore, the antifungal activity of WSPs could be used to manage soilborne plant pathogens.

Hydrothermal carbonization of Chinese fan palm

This study provided a detailed observation on hydrothermal carbonization (HTC) of Chinese fan palm. The heating value and chemical exergy was calculated. As the reaction severity increased, both heating value (18.84-27.61 MJ/kg) and chemical exergy (21.07-29.06 MJ/kg) had increase trend. The effect of temperature on HTC process was more significant than residence time. Due to the dehydration and decarboxylation, the O/C and H/C atomic ratios decreased gradually. However, the N/C ratio was not linear change. When the temperature was 240 °C, and reaction time was above 60 min, the fuel properties of hydrochar were close to lignite. The water uptake rate (7.22-3.59%) also had very decreased trend. The SEM and XRD analysis showed the surface morphology of hydrochar treated at 240 °C much differed from that of raw sample, the structure is partially destructed. Combustion characteristics of CFP and hydrochar was detected, the 180-60 had optimal combustion characteristics.

Fabrication of bean dreg-derived carbon with high adsorption for methylene blue: Effect of hydrothermal pretreatment and pyrolysis process

This study explored the cooperative effects of hydrothermal or activators pretreatment and pyrolysis process on the chemical composition of bean dreg (BD)-derived carbon materials and its adsorption characteristics for methylene blue (MB) further. The results showed that hydrothermal assisted pyrolysis carbon with or without activator (HBK and HB) possess higher BET surface area than no hydrothermal assisted carbon (BKs and B, respectively). But surface area alone was not a critical factor contributing to MB adsorption, it also depends on strong electrostatic interaction and the hydrogen bonding interaction between N⁺ in MB combines with OH and COO^- group of adsorbent surface by pH-dependent adsorption and pseudo-second-order model. Additionally, BK800 (pyrolysis at 800 °C) was identified as the most efficient adsorbent due to maximum adsorption capacity (434.78 mg g^-1), and BDP (BD-derived polymer composite hydrogel), possessing excellent adsorption property and high reusability, made BK800 easier to separate from the regenerated dye solution.

Degradation of PVC waste into a flexible polymer by chemical modification using DINP moieties

We propose a chemical modification method to produce flexible PVC with DINP moieties.

Effects of aqueous phase recirculation in hydrothermal carbonization of sweet potato waste

Aqueous phase recirculation was investigated in hydrothermal carbonization of sweet potato waste at 220 °C for 60 min. The result showed that the aqueous phase reuse significantly increased the hydrochar yield. The lower H/C and O/C ratios indicated that decarboxylation reaction was promoted. The CC vibration of the benzene backbone became intense, suggesting the occurrence of aromatization and polymerization reactions. Thus, the carbon content and HHV were improved. After recirculation, hydrochar showed a decrease in combustion ignition temperature whereas an increase in pyrolysis initial decomposition temperature. The burnout temperatures in combustion and terminated temperature in pyrolysis both showed an increase trend. The hydrochars obtained from the recirculation step possessed lower emissions of NO_X or SO₂ than that from reference step. The pyrolysis emission result showed that more high thermal stability components were formed during recirculation step. Overall, aqueous phase recirculation was a feasible way to improve hydrothermal carbonization process.

Towards a better understanding on mercury adsorption by magnetic bio-adsorbents with γ-Fe2O3 from pinewood sawdust derived hydrochar: Influence of atmosphere in heat treatment

Pyrolysis under protective atmosphere was regarded as an indispensable process for the preparation of biomass-based adsorbents to achieve higher surface areas. In this paper, magnetic carbon composites (MCC) that fabricated under air atmosphere showed an adsorption capacity of 167.22 mg/g in 200 ppm Hg(II), which was significantly higher than magnetic biochar (MBC, 31.80 mg/g) that fabricated under traditional nitrogen protection, and this remarkable performance of MCC was consistent in a wide range of pHs. Based on BET, XRD, FTIR, SEM and Boehm titration, MCC was demonstrated with limited surface area (43.29 m²/g) but large amount of surface functional groups comparing with MBC. Additionally, γ-Fe₂O₃ with a high degree of crystallization was generated in MCC, which led to a better magnetic property and recyclability. Moreover, characterizations, Langmuir isotherm and pseudo-second-order kinetics demonstrated the chemisorption was dominant for MCC in mercury capture, and surface complexation co-precipitate of Hg₄Fe₈O₁₆C₅₆H₄₀ were also formed.