Hydrothermal pretreatment of bamboo sawdust using microwave irradiation

Methylene Blue Dye Adsorption on Iron Oxide-Hydrochar Composite Synthesized via a Facile Microwave-Assisted Hydrothermal Carbonization of Pomegranate Peels' Waste

The toxicity of dyes has a long-lasting negative impact on aquatic life. Adsorption is an inexpensive, simple, and straightforward technique for eliminating pollutants. One of the challenges facing adsorption is that it is hard to collect the adsorbents after the adsorption. Adding a magnetic property to the adsorbents makes it easier to collect the adsorbents. The current work reports the synthesis of an iron oxide-hydrochar composite (FHC) and an iron oxide-activated hydrochar composite (FAC) through the microwave-assisted hydrothermal carbonization (MHC) technique, which is known as a timesaving and energy-efficient method. The synthesized composites were characterized using various techniques, such as FT-IR, XRD, SEM, TEM, and N2 isotherm. The prepared composites were applied in the adsorption of cationic methylene blue dye (MB). The composites were formed of crystalline iron oxide and amorphous hydrochar, with a porous structure for the hydrochar and a rod-like structure for the iron oxide. The pH of the point of zero charge (pHpzc) of the iron oxide-hydrochar composite and the iron oxide-activated hydrochar composite were 5.3 and 5.6, respectively. Approximately 556 mg and 50 mg of MB dye was adsorbed on the surface of 1 g of the FHC and FAC, respectively, according to the maximum adsorption capacity calculated using the Langmuir model.

Microbial Biogas Production from Pork Gelatine

This research describes the results of the anaerobic digestion of gelatine as a potential hydrogen source with heat-shocked inoculum. The concentrations of applied gelatine were of VSS (volatile suspended solids) ranging from 10 g VSS/L to 30 g VSS/L. The initial process pH was 5.5, and, depending on the concentration, reached pH values from 7.5 to 7.8 after 55 days. Although the inoculum was heat-shocked in 30 g VSS/L of collagen, the process that occurred was hydrogenotrophic anaerobic digestion. In gelatine concentrations below 30 g VSS/L, hydrogen production was dominant only during the first 5 days of the experiments. Then, there was a change from dark fermentation to hydrogenotrophic methane production. The optimal hydrogen and methane yields resulted from the concentrations of 10 g VSS/L (7.65 mL ± 0.01 mL H2/g VSS and 3.49 ± 0.01 L CH4/g VSS). Additionally, 10 g VSS/L had the lowest accumulated emission of hydrogen sulphide (10.3 ± 0.01 mL of H2S), while 30 g VSS/L (0.440 ± 0.01mL H2S/g VSS) produced the lowest yield. After a lag time, the hydrogen production and hydrogen sulphide grew with a specific ratio, depending on the concentration. The hydrogen sulphide emission and sulphur added analysis proved that hydrogen sulphide originating from biogas created by bacteria remains longer than that from a substrate.

Evaluation of sulfuric acid-pretreated biomass-derived biochar characteristics and its diazinon adsorption mechanism

In this study, hemicellulose was mostly removed from biomass (larch and oak) using a sulfuric acid pretreatment. Biochar was then prepared from raw and pretreated biomass using a carbonization process. Biochar derived from pretreated biomass had an aromatic and graphitized structure, and functional groups were observed on the surface. The specific surface area was higher for biochar obtained from pretreated biomass than biochar derived from raw biomass. The biochar obtained from pretreated biomass contained a greater number of micropores than biochar derived from raw biomass. The diazinon removal rate was the highest for biochar that was obtained from pretreated biomass when 10% of the biochar was added to the soil. As a result of the adsorption of diazinon onto the biochar obtained from pretreated biomass, the R² value of the Langmuir isotherm was higher than that of the Freundlich's R².

Effect and Optimization of Process Conditions during Solvolysis and Torrefaction of Pine Sawdust Using the Desirability Function and Genetic Algorithm

Understanding optimal process conditions is an essential step in providing high-quality fuel for energy production, efficient energy generation, and plant development. Thus, the effect of process conditions such as the temperature, time, nitrogen-to-solid ratio (NSR), and liquid-to-solid ratio (LSR) on pretreated waste pine sawdust (PSD) via torrefaction and solvolysis is presented. The desirability function approach and genetic algorithm (GA) were used to optimize the processes. The response surface methodology (RSM) based on Box-Behnken design (BBD) was used to determine the effect of the process conditions mentioned above on the higher heating value (HHV), mass yield (MY), and energy enhancement factor (EEF) of biochar/hydrochar obtained from waste PSD. Seventeen experiments were designed each for torrefaction and solvolysis processes. The benchmarked process conditions were as follows: temperature, 200-300 °C; time, 30-120 min; NSR/LSR, 4-5. In this study, the operating temperature was the most influential variable that affected the pretreated fuel's properties, with the NSR and LSR having the least effect. The oxygen-to-carbon content ratio and the HHV of the pretreated fuel sample were compared between the two pretreatment methods investigated. Solvolysis pretreatment showed a higher reduction in the oxygen-to-carbon content ratio of 47%, while 44% reduction was accounted for the torrefaction process. A higher mass loss and energy content were also obtained from solvolysis than the torrefaction process. From the optimization process results, the accuracy of the optimal process conditions was higher for GA (299 °C, 30.07 min, and 4.12 NSR for torrefaction and 295.10 °C, 50.85 min, and 4.55 LSR for solvolysis) than that of the desirability function based on RSM. The models developed were reliable for evaluating the operating process conditions of the methods studied.

Upgrading of Light Bio-oil from Solvothermolysis Liquefaction of an Oil Palm Empty Fruit Bunch in Glycerol by Catalytic Hydrodeoxygenation Using NiMo/Al2O3 or CoMo/Al2O3 Catalysts

Hydrodeoxygenation (HDO) of bio-oil derived from liquefaction of a palm empty fruit bunch (EFB) in glycerol was investigated. To enhance the heating value and reduce the oxygen content of upgraded bio-oil, hydrodeoxygenation of light bio-oil over Ni- and Co-based catalysts on an Al2O3 support was performed in a rotating-bed reactor. Two consecutive steps were conducted to produce bio-oil from EFB including (1) microwave-assisted wet torrefaction of EFB and (2) solvothermolysis liquefaction of treated EFB in a Na2CO3/glycerol system. The HDO of as-prepared bio-oil was subsequently performed in a unique design reactor possessing a rotating catalyst bed for efficient interaction of a catalyst with bio-oil and facile separation of the catalyst from upgraded bio-oil after the reaction. The reaction was carried out in the presence of each mono- or bimetallic catalyst, namely, Co/Al2O3, Ni/Al2O3, NiMo/Al2O3, and CoMo/Al2O3, packed in the rotating-mesh host with a rotation speed of 250 rpm and kept at 300 and 350 °C, 2 MPa hydrogen for 1 h. From the results, the qualities of upgraded bio-oil were substantially improved for all catalysts tested in terms of oxygen reduction and increased high heating value (HHV). Particularly, the NiMo/Al2O3 catalyst exhibited the most promising catalyst, providing favorable bio-oil yield and HHV. Remarkably greater energy ratios and carbon recovery together with high H/O, C/O, and H/C ratios were additionally achieved from the NiMo/Al2O3 catalyst compared with other catalysts. Cyclopentanone and cyclopentene were the main olefins found in hydrodeoxygenated bio-oil derived from liquefied EFB. It was observed that cyclopentene was first generated and subsequently converted to cyclopentanone under the hydrogenation reaction. These compounds can be further used as a building block in the synthesis of jet-fuel range cycloalkanes.

Removal of aqueous Cr(VI) by Zn- and Al-modified hydrochar

Pristine hydrochar is a carbonaceous material that can sorb hexavalent chromium (Cr(VI)), a kind of toxic pollutants and difficult to removal, from aqueous solution but its capacity is limited. With the goal of improving this ability, two modified hydrochars were produced by co-hydrothermal carbonization (200 °C, 7h) of bamboo sawdust with zinc chloride (ZnCl₂) or aluminum chloride (AlCl₃). Compared to the pristine hydrochar, the ZnCl₂-and AlCl₃-modified hydrochars were more fully carbonized (higher C content and lower H/C) and had higher surface area (increased by 26 and 4.3 times, respectively) and larger pore volume (increased by 43 and 5.5 times, respectively). Due to these improved properties, the Cr(VI) maximum adsorption capacity (modeled via Langmuir isotherms) of ZnCl₂-and AlCl₃-modified hydrochar increased by 3.4 and 2.8 times, respectively. In addition, Cr(VI) adsorption kinetic of modified hydrochar was well fitted by the pseudo-second-order model. Cr sorption capacity increased at low pH and ion strengths, suggesting the potential roles of electrostatic interaction and ion exchange mechanisms. These results indicate that hydrochars modified by ZnCl₂ and AlCl₃ treatment are promising in environmental applications that require Cr(VI) removal.

Zirconium based metal-organic framework in-situ assisted hydrothermal pretreatment and enzymatic hydrolysis of Platanus X acerifolia exfoliating bark for bioethanol production

Metal-organic framework (MOF) assisted hydrothermal pretreatment and co-catalysis strategy based on UiO-66 MOF is developed for the first time. The Planetree exfoliating bark was pretreated with or without UiO-66 assisted hydrothermal method at a temperature ranging from 160 to 240 °C for 1-3 h residence. With the rise of pretreatment severity, the total reducing sugar (TRS) was increased till reached maximum, 180 mg g^-1, in the presence of UiO-66. The fitting models validate the optimal hydrothermal condition was at 180 °C and 1 h, which was characterized with high TRS and very low yield of furfural and HMF. The TRS from enzymatic hydrolysis reaches maximum, 391 mg g^-1, in the presence of MOF co-catalysis and the maximum ethanol yield achieved was 73%. Altered morphology, higher surface area and porosity are noticed after MOF assisted hydrothermal pretreatment. This study insights the MOFs' application in lignocellulose biomass processing.

Physicochemical characteristics and pyrolysis performance of corn stalk torrefied in aqueous ammonia by microwave heating

The physicochemical characteristics and pyrolysis performance of corn stalk (CS) torrefied in water and aqueous ammonia by microwave heating were investigated. Physicochemical characterization revealed that both microwave water torrefied CS (MCS) and microwave ammonia torrefied CS (MACS) showed low hemicellulose content, disrupted macrostructure, improved porous properties, and low ash content. MACS exhibited a significantly lower crystallinity degree of 44.34% than CS (79.55%) and MCS (89.50%). MACS also showed increased methyl/methylene groups intensity, and complete acetyl groups disrupture. Pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) revealed that compared with CS and MCS, MACS exhibited higher peak areas for ketones, aldehydes, furans and esters, and significantly lower peak areas for acids and phenols. A possible mechanism was proposed for the effects of wet torrefaction with aqueous ammonia on changes in physicochemical structure and pyrolysis behavior of corn stalk.

Exploration and optimization of mixed acid synergistic catalysis pretreatment for maximum C5 sugars

The liquid hot water (LHW) pretreatment could be strengthened by acetic and lactic acids produced from the process. The synergistic effect of the mixed acid catalyst of lactic acid and acetic acid was investigated for the purpose of maximization of the overall C5 sugars yield. Individual acids (acetic and lactic acid) and mixed acid were used to strengthen the LHW pretreatment at different conditions. The results showed that the suitable conditions of mixed acid synergistic catalysis was at 180 °C for 60 min and 3 wt% mixed acid where the ratio of 40% (i.e. 0.40 in mass fraction of lactic acid in mixed acid). Response surface methodology (RSM) was applied to further optimize this process. The highest yield of C5 sugars of 93.83% according to theoretical predicted model, was close to the experiment value of 92.53% at 177 °C for 67 min and with the ratio of mixed acid of 40%.

The effects of temperature and color value on hydrochars' properties in hydrothermal carbonization

In order to investigate the influence of hydrothermal carbonization (HTC) on the properties of the hydrochars, sawdust with a particle size below 0.45mm was treated in an autoclave at 200-260°C. The physical and chemical characteristics of products were studied, including proximate analysis, elemental composition, fiber content, surface area, bulk density, energy yield, color value, combustion activities and pyrolysis kinetics, etc. It showed that the color of hydrochars turned blacker, greener, and bluer after HTC. The ash, carbon, hydrogen and lignin contents showed a good correlation (R²>0.96) with color coordinates. The decrement in stage 1 and increment in stage 2 of temperature intervals were attributed to the volatile matters removal and fixed carbon accumulation, improving the stability and safety of hydrochars combustion. As shown by the Kissenger-Akahira-Sunose (KAS) and Coats-Redfern calculations, the HTC process can also make the pyrolysis more stable.