Char Surface Research Articles

Synthesis of PMM and Synergistic Flame Retardant Effect with Ammonium polyphosphate

A novel flame retardant poly {[(2-Methyl-acrylic acid 2-(dimethoxyphosphoryloxy)-ethyl ester]-co-[2-Methyl-acrylic acid 2-(trimethoxysiloxy)-ethyl ester]} (PMM) containing dimethoxyphosphoryloxy and trimethoxysiloxy groups in side chains was synthesized. The structure of PMM was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR), and the thermal performance of PMM was characterized by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of PMM on polypropylene’s flame retardancy and thermal behaviors was investigated by limited oxygen index (LOI), vertical burning test (UL-94), and TG tests. The experimental results indicate that the addition of PMM helps to improve the flame retardancy and thermal stability of PP. When the addition of PMM and APP in PC was 15% and 20%, the LOI value of PC reached 28.4%, and the UL-94 test rating reached V-0 level. The charred structure observed by scanning electron microscopy (SEM) indicated that the char surface for PP/APP/PMM system holds an intumescent char structure compared to neat PP, and the synergy exists in the composites. The PMM slightly decreased the tensile property in terms of strength but increased the elongation at break for PP composites.

Pyrolysis characteristics and product distribution of low-rank coal with heat-carrying particles adopting TG-FTIR and a novel self-mixing down tube reactor

A novel self-mixing down tube (SDT) pyrolyzer has been developed, which can separate the heat carrying particles preheated in the fluidized bed from the coal, and the two can be mixed through a specific structure to instantly heat the coal particles to a predetermined temperature. The present study investigated the pyrolysis behavior of low-rank coal with hot silica sand heat-carrying particles adopting TG-FTIR. Identifies optimal conditions for maximum tar production in a laboratory-scale SDT using a significantly larger range of coal feed rates (4 kg/h). An increase in the degree of coal metamorphism increased the initial temperature and the yield of char. The tar yield from Huolinhe lignite coal (6.56 %) and Daliuta bituminous coal (7.48 %) showing a trend of first increased and then decreased with elevating the operating temperature and optimal temperature at 520 °C, respectively. The effect of coal particle size on tar yield mainly comes from the different degrees of secondary cracking caused by contact with solid heat-carrying particles as well as the differences in the content of macerals. GC‒MS spectra of tar and deposited carbon on silica sand indicated that heavy tar can easily deposit on the surface of sand and form char through polymerization reactions.

The Effect of Different Diluents and Curing Agents on the Performance of Epoxy Resin-Based Intumescent Flame-Retardant Coatings.

The epoxy resin-based (ESB) intumescent flame-retardant coatings were modified with 1,4-butanediol diglycidyl ether (14BDDE) and butyl glycidyl ether (BGE) as diluents and T403 and 4,4'-diaminodiphenylmethane (DDM) as curing agents, respectively. The effects of different diluents and curing agents on the flame-retardant and mechanical properties, as well as the composition evolution of the coatings, were investigated by using large-plate combustion, the limiting oxygen index (LOI), vertical combustion, a cone calorimeter, X-ray diffraction, FTIR analysis, a N2 adsorption and desorption test, a scanning electron microscope (SEM), a tensile strength test, and a viscosity test. The results showed that the addition of 14BBDE and T403 promoted the oxidation of B4C and the formation of boron-containing glass or ceramics, increased the residual mass of char, densified the surface char layer, and increased the specific surface area of porous residual char. When their dosage was 30%, ESB-1T-3 coating exhibited the most excellent flame-retardant properties. During the 2 h large-plate combustion test, the backside temperature was only 138.72 °C, without any melting pits. In addition, the peak heat release rate (PHRR), total heat release rate (THR), total smoke production (TSP), and peak smoke production (PSPR) were reduced by 13.15%, 13.9%, 5.48%, and 17.45%, respectively, compared to the blank ESB coating. The LOI value reached 33.4%, and the vertical combustion grade was V-0. In addition, the tensile strength of the ESB-1T-3 sample was increased by 10.94% compared to ESB. In contrast, the addition of BGE and DDM promoted the combustion of the coating, affected the ceramic process of the coating, seriously affected the formation of borosilicate glass, and exhibited poor flame retardancy. The backside temperature reached 190.93 °C after 2 h combustion. A unified rule is that as the amount of diluent and curing agent increases, the flame retardancy improves while the mechanical properties decrease. This work provides data support for the preparation and process optimization of resin-based coatings.

Exploration of the NO-char reaction pathway by in-situ DRIFTS and isotope gas tracing techniques

For NO abatement by carbon-based material (for example, char), many studies have been performed on the reactions between carbon and NO. Oxygen is believed to play a key role during the denitrification process: not only positive, but also negative. Some specific intermediates are worth investigating, and reaction routes are needed to be clarified in order to reveal and explain the mechanism of the concerned reactions. To account for the reaction scheme, chemical evolution information of both solid surface side and gaseous side are collected and analyzed by means of in-situ DRIFTS analysis and isotopic gas tracing, respectively. In combination with experimental results of the NO-char reaction in a fixed bed, possible reaction pathway is proposed. The in-situ DRIFTS analysis shows that C(N) and thermodynamically active C = O complexes are produced during NO adsorption on coal char. The presence of O2 promotes the chemisorption of NO molecules. Oxygen combines with carbon to generate not only thermodynamically stable C-O complexes but active C = O complexes. Step response experiments using isotope gas tracing technique demonstrate that CO and CO2 are produced by C = O desorption and the combination between C-O and C = O complexes, respectively. N2 is generated by the reaction of C(N) complexes on the coal char surface with NO molecules in gas phase. The stable C-O complexes promote NO adsorption and dissociation by reaction with C = O complexes and subsequently producing new active sites.

Acid treatment for enhancing Hg0 removal efficiency of chlorine-loaded biochar: mechanism and kinetic analysis.

Adsorbents modified solely with chlorine have limited effectiveness in removing mercury at high temperatures. This study aims to investigate the influence of various acid (HNO3, H2SO4, and H2O2) loadings on the removal efficiency of mercury from NH4Cl-modified adsorbents. The objective is to develop rice straw carbon adsorbents that are both more efficient and cost-effective. The experiments were conducted on a fixed bed experimental platform, with SEM and BET to observe the physical property changes of the modified char samples. XPS analysis was employed to analyze the effects of oxygen, chlorine, and sulfur functional groups. Additionally, a kinetic model was used to investigate the interaction mechanism between the adsorbent and mercury. The findings demonstrate that co-modification surpasses the use of NH4Cl alone, with the combination of NH4Cl and HNO3 yielding the best results. Co-modification enhances the development of a more refined and compact pore structure on the char surface, promoting the physical adsorption of mercury. Moreover, an increased presence of chlorine and oxygen functional groups is observed on the char surface, particularly in the NH4Cl and HNO3 co-modified samples, further enhancing the chemical adsorption capacity of the char. The results from the kinetic analysis support this conclusion. Furthermore, the adsorption process of Hg0 relies on both external mass transfer and chemical adsorption, with the chemical adsorption process playing a more significant role as the controlling factor.

Investigation into application of biochar as a catalyst during pyrolysis-catalytic reforming of rice husk: The role of K specie and steam in upgrading syngas quality

This study investigated the role of K and steam in upgrading syngas quality over biochar in a two-stage fixed-bed reactor. The integration of K-char catalyst and steam greatly increased syngas (H2+CO) and H2 production. The syngas products yield (19.76 mmol/gbiomass) and a H2 yield (11.14 mmol/gbiomass) were achieved when K-char was used as catalyst in the presence of steam. In general, four ways could be concluded to promote volatiles reforming to improve syngas quality by K and steam: Firstly, K and steam interaction with biochar increased the surface area and developed the porous structure of biochar, providing the pyrolytic intermediates with full complete contact with the char surface, and improving the chance of contact with the active sites. Secondly, the condensation reactions of biochar were inhibited by K and steam, thus preventing the reduction of active groups on the aromatic ring of biochar. Thirdly, K and steam promoted the formation of O-containing groups with high reactive activity on the char surface, such as –COO and –CO. Moreover, volatile K migrated in biochar matrix during catalytic reforming, and steam inhibited the release of K in biochar, resulting in more K retaining on the char surface in the form of -COK and -COOK acting as the active sites, which ultimately improved the catalytic activity of biochar, and promoted tar destruction and hydrocarbon reforming.

Reverse combustion propagation in an oxygen-limited and -enriched N2/O2 flow for a bed packed with rice husk

Propagation characteristics of reverse combustion significantly impact the conversion of solid fuels in packed beds, especially under variable reaction atmosphere conditions. In this study, the propagation of reverse combustion was experimentally studied in an oxygen-limited and -enriched O2/N2 flow with an oxygen concentration range of 21–100 % for a bed packed with rice husk. The temperature profile measured by thermocouples along the bed height was processed to appreciate the driving mechanism of combustion front, as well as the reaction structure inside the bed. Besides, the contribution of volatiles gas-phase oxidation and char surface oxidation to reverse combustion was also evaluated. Results show that compared to the air case, an oxygen-enriched condition broadens the operating range of oxygen flow rate for the oxygen-limited reverse combustion. Under high oxygen concentration conditions, the low-temperature oxidation of rice husk inside the reaction front becomes enhanced. Such chemical reaction effect widens the whole reaction front thickness and thereby reduces the oxidation intensity in local regions, resulting in a faster ignition rate and a lower temperature for combustion front. It is found that this process is dominated by the gas-phase oxidation of volatiles, of which oxygen consumed is above 60 % of the supplied. As oxygen concentration increases, the gas-phase oxidation of volatiles becomes further enhanced. Correspondingly, the oxidation ratio of char is gradually approaching a limit, about 12 %, especially at the oxygen concentration above 50 %. These findings will facilitate a better fundamental understanding of driving mechanism of this special combustion process and thereby provide an important theoretical basis for efficient thermal conversion of solid fuels.

Micro-scale study of mineral transformation and coverability at single coal char particle surface during high-temperature gasification process

During the high-temperature coal gasification process, mineral transformation is essential to the formation of residual carbon and ash/slag discharge. The current work investigated the mineral transformation and coverability of the single coal char particle with various ash content during gasification, as well as established the correlation between the ash layer and carbon conversion. Three stages of the gasification process at 1350 °C were defined by the quadratic difference method based on the interaction between the char and the liquid slag, and the two critical points that distinguish the three stages were between 15%–20% and 71%–90% respectively. Further investigation showed that the melting behavior of coal char during gasification was affected by the inhomogeneous distribution of elements. Ca showed a tendency to migrate from the unmolten area to the molten area. The migration behavior was attributed to the eutectic formation between silica-aluminate in the molten area and calcium salts in the unmolten area, leading to a reduction in melting point and gradual melting of minerals in the unmolten area. Eventually, a homogeneous gehlenite phase was formed and covered on the residual char surface. Besides, the relationship between liquid slag coverage and carbon conversion was established, and for SF, YL, and XLT chars, the maximum coverage of liquid product occurs at the conversion of 0.86, 0.78, and 0.66, respectively. This paper provides an in-depth understanding of the slag melting behavior and residual carbon formation in the entrained gasifiers.

Investigations of NO reduction by coal-based activated carbon with KOH activation: Performance and mechanism

Selective catalytic reduction of ammonia is the most widely used technology for NOx removal, but there have been serious ammonia leaks and a narrow reaction temperature window. To overcome these limitations, a coal-based activated carbon (CAC) approach using KOH activation for the ammonia-free reduction of NO was investigated in this work. A preparation process was investigated by evaluating the De-NOx performance at different mass ratios (KOH:coal = 0–3:1), and activation temperatures (700–900 °C). The optimum conditions were an activation temperature of 700 °C and a 1:1 ratio of KOH/coal, named CAC-1:1-700. Between 330 and 500 °C, the NO conversion efficiency is maintained at 100% within 90 min. The CAC-1:1-700 showed excellent denitrification performance and SO2 resistance. Based on BET, SEM, XRD, Raman, FT-IR, and XPS characterization analysis, it was found showed that KOH activation could increase the amorphous carbon, pore structure, and C(O) functional groups in CAC, which had positive effects on the denitrification performance. Furthermore, the evolution of char structures and surface species before and after the Char-NO-O2 reaction was evaluated by Raman and XPS, and the possible reaction mechanisms was proposed. Aliphatic structures and small aromatic rings can play the same role in De-NOx, O2 is adsorbed on the carbon to form an oxygen-containing functional group, generating more C–O groups and creating reactive sites C*. NO then interacts with these reactive sites and is reduced to N2. This research prepared CAC as a promising potential alternative to ammonia reductants due to its excellent denitration performance over a medium temperature range and complex flue gas environments, while providing the high-value utilization of coal resources.

Experimental and density functional theory study on role of calcium in NO reduction by NH3 on char surface during ammonia co-firing with pulverized coal

As a carbon-free energy, NH3 has attracted increasing attention from scholars. Ammonia-coal co-firing, as a technology for ammonia energy utilization, has great application potential. However, the NOx generated during ammonia combustion cannot be ignored due to the N element in NH3. At present, the reaction mechanism of NH3 and NO on char, together with the influence mechanism of mineral Ca, in the combustion reduction zone during ammonia-coal co-firing is still unclear. In this study, the effects of Ca on the NO reduction with NH3 on the char surface have been investigated in the high-temperature reaction system. The NO reduction efficiency and the evolutions of char structural characteristics during the reaction processes were analyzed for both demineralized coal char and CaCl2-loaded coal char. The reaction mechanism was also investigated at the molecular level using density functional theory (DFT) to clarify NO reduction and CO release pathways with and without Ca. The DFT results showed that during NO reduction on char surface, NNH group formation and CO desorption are crucial steps in the presence of NH3. Ca plays a catalytic role in NO reduction reaction, which affects NO reduction by NH3 on char surface in two ways. On the one hand, Ca facilitates the reduction of NO to N2 by lowering the energy barrier for NNH group formation (20.98 kJ/mol) and N2 release (93.70 kJ/mol). On the other hand, the formation of Ca–O–C structure increases the energy barrier for CO release from char surface (377.25 kJ/mol), which is unfavorable for NO reduction. The experimental results showed that between 1300 °C and 1500 °C, Ca increases the NO reduction efficiency by 5 %, promoting NO reduction, because Ca lowers the energy barrier of the rate-determining step, thus accelerating the reaction. At this temperature, the inhibition effect of Ca on CO release is not obvious. However, between 1000 °C and 1300 °C, Ca exhibits an inhibition effect on NO reduction. This is because Ca significantly inhibits CO release. At this temperature, the formation rate of NNH species is relatively slow, and NO reduction is influenced by homogeneous reduction. This study aims to provide fundamental information for exploring the application potential of ammonia coal co-firing in industrial furnaces.

Volatile-char interactions during biomass pyrolysis: Effects of AAEMs removal and KOH addition in char

The effects of Alkali/alkaline earth metals (AAEMs) removal and KOH addition in char on formation and distribution of wheat straw pyrolysis products during volatile-char interactions were studied in a fixed-bed reactor. The results showed that after AAEMs removal from char, significant interactions between volatiles and char still existed, as its non-condensable gas yield greatly increased with less detectable organics observed in bio-oil compared to pure wheat straw pyrolysis. XPS results indicated that more aromatic carbon structures (C-Cprimary) were exposed on char surface after AAEMs removal, which might act as active sites during the interactions. KOH addition in char exhibited much bigger cracking performance than its interior K in char, resulting in a significant reduction in bio-oil yield and a great increase in non-condensable gas yield. KOH addition in char might promote decarboxylation, decarbonylation and sugar-ring opening reactions, leading to the decrease of linear acids and carbonyls and anhydrosugars and the increase of phenols and other aromatics in bio-oil. The cracking/decomposition of furans, cyclopentenones, and phenols and other aromatics would also be largely enhanced with the increasing amount of KOH addition. In addition, KOH in char could act as a catalyst for the char self-reforming by volatiles during the interactions.

The effect of ash fusion characteristic on the structure characteristics of carbon and the migration of potassium during rice straw high-temperature gasification process

The effect of ash fusion characteristic on the structure characteristics and gasification activity of residual carbon, and the migration of K during biomass (rice straw, BRS) gasification at 1100 °C were investigated. Results showed that the carbon and AAEMs were wrapped by molten ash, and the residual carbons in BRS gasification char were composed of pyrolytic carbon and partial-gasified carbon. The molten ash formed spherical particles adhering to the surface of gasification char, and the particle size gradually enlarged. With the progress of BRS gasification, the BET surface area and microporous surface area decreased monotonously, and the ID1/IG values increased firstly and then decreased, and the total active sites were poorer at the gasification time of 15 and 20 minutes. The gasification activity of residual carbon had no linear relationship with gasification time, and followed the order of DBRS-25> DBRS-10> DBRS-20≈DBRS-15≈DBRS-5. Furthermore, the total content of K increased obviously, and the water-soluble K, ion-exchanged K, and acid-soluble K were changed to insoluble K with the increase of gasification time.

Effect of a layered combination of APP and TBC on the mechanics and flame retardancy of poplar strandboards

How to balance the flame-retarding and physico-mechanical properties of wood composites treated with chemicals remains a big challenge. Herein, a layered pattern of bi-component flame-retarding agent in strandboards was established by applying tris (2,3-dibromo-propyl) isocyanate (TBC) in the core and ammonium polyphosphate (APP) in the surface layers. The mechanical and flame retardant properties of treated strandboards were controlled by adjusting the addition ratio of APP to TBC. X-Ray computed tomography was applied to disclose the on-site distribution of APP and TBC chemicals in the strandboard matrices. Both oxygen index meter and cone calorimeter were used to characterize the burning behavior of the strandboards. Addition of TBC resulted in a higher-density core of strandboards. Compared to the untreated and evenly-distributed strandboards, internal bond (IB) strength and modulus of elasticity (MOE) were enhanced by up to 6% and 62.9%, respectively. Meanwhile, the peak heat release rate (pk-HRR) of strandboards after APP/TBC/APP treatment decreased by 33.6%, and the limited oxygen index (LOI) reached a maximum value of 38.2%. When exposed to combustion, the core layer of strandboard treated with TBC generates non-combustible gas and expands the surface char barrier established by APP, thereby enhancing flame retardancy. Compared to traditional methods, a lamination pattern of flame retardants in strandboards exhibits improved bonding performznd satisfied fire resistance. This innovative approach holds great potential for application in the fire safety wood composites industry.

A pilot-scale test facility of 500 kWth for industrial CFB boilers on low nitrogen combustion-discussion of design, experiment, and economic analysis

The design and construction of a pilot-scale test facility of 500 kWth for a novel CFB boiler with three separate sub-furnaces and two steps for material circulation are introduced in detail. A thorough test was conducted with the facility to verify the applicability of fuel staging on NOx abatement in the novel CFB. The varied trends of temperature distribution and NOx emissions during fuel staging are presented in the study. It was observed that fuel staging can effectively and immediately reduce the initial emission concentration of NOx in the flue gas. Under the tested conditions, the NOx removal efficiency can reach up to 40% at a fuel-staged proportion of 5%. The initial NOx emission concentration can be controlled to below 80 mg/m3, even. The main reason for the NOx reduction is the heterogeneous reduction of NO on the surface of coal char formed after the devolatilization of staged fuel. In addition, economic analysis was made by comparing fuel staging and SNCR. The estimated operating costs showed that fuel staging can be applied as an alternative technology for SNCR when the initial concentration of NOx in the flue gas ranges from 300 to 360 mg/m3.

Comparative investigation of chemical and structural properties of charred fir wood samples by Raman and FTIR spectroscopy as well as X-ray-micro-CT technology

Abstract Wood surface charring is a treatment method commonly employed to enhance weather protection and aesthetic appearance of building exteriors. This study aims to investigate the differences between two wood surface charring processes: the traditional Japanese method known as Yakisugi and an alternative charring technique industrially manufactured with a gas burner. The objective of the study was to assess whether a thicker layer after Yakisugi treatment has any advantages over a thinner layer after the alternative process. Vibrational spectroscopy techniques including UV resonance Raman (UVRR) and Fourier transform infrared (FTIR) spectroscopy, were utilized in conjunction with X-ray-micro-CT analysis. The findings revealed that ATR-FTIR spectroscopy detected the degradation of carbohydrates and changes in lignin within the charred surface, although both processes exhibited similar vibrational contributions. In contrast, UVRR spectroscopy provided insights into the carbonized layers, revealing spectral differences indicating variations in temperature during the charring processes. X-ray micro-CT analysis visually highlighted significant differences in the coal layers, suggesting distinct combustion profiles. Remarkably, the macrostructure of wood treated with Yakisugi remained intact despite a thicker charred layer compared to the alternative charring techniques. However, further investigations are required to assess the weather stability of the alternative charring method for a comprehensive understanding.

Extensive sorption of Amoxicillin by highly efficient carbon-based adsorbent from palm kernel: Artificial neural network modeling

In the present study, a new sorbent was fabricated from Palm kernel (PK) by dry thermochemical activation with NaOH and characterized by FTIR, X-ray diffraction, FE-SEM and BET, which was used for the Amoxicillin (AMX) sorption from aqueous solution. The influence of effective parameters such as pH, reaction time, adsorbent dosage, AMX concentration and ionic strength on the sorption efficacy of AMX removal were evaluated. The main functional groups on the surface of the magnetic activated carbon of Palm Kernel (MA-PK) were C–C, C–O, CO and hydroxyl groups. The specific surface of char, activated carbon Palm Kernel (AC-PK) and MA-PK were 4.3, 1648.8 and 1852.4 m2/g, respectively. The highest sorption of AMX (400 mg/L) was obtained by using 1 g/L of sorbent at solution pH of 5 after 60 min contact time, which corresponding to 98.77%. Non-linear and linear models of isotherms and kinetics models were studied. The data fitted well with Hill isotherm (R2 = 0.987) and calculated maximum sorption capacity were 719.07 and 512.27 mg/g from Hill and Langmuir, respectively. A study of kinetics shows that the adsorption of AMX follows the Elovich model with R2 = 0.9998. Based on the artificial neural network (ANN) modeling, the MA-PK dosage and contact time showed the most important parameters in the removal of AMX with relative importance of 36.5 and 25.7%, respectively. Lastly, the fabricated MA-PK was successfully used to remove the AMX from hospital wastewater.

Impacts of fresh bed materials on alkali release and fuel conversion rate during wood pyrolysis and char gasification

Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed.

Lightweight Flame-retardant Material Reinforced with Hevea Brasiliensis Ash Intumescent Agent

Flame retardant materials play an important role in many building construction components. The ability of building components to resist fire is crucial to the safety and well-being of the occupants. This research examines a lightweight flame-retardant material-Vermiculite (V) reinforced with a renewable Hevea Brasiliensis Biomass Ash Intumescent Agent (HBAIA) in different compositions. Four specimens of vermiculite reinforced with HBAIA (V/HBAIA) with standard size 200 mm x 200 mm x 10 mm (W x Lx H) were fabricated for investigations. All V/HBAIA specimens were assessed in terms of their density, fire-resistant, fire endurance and smoke, char surface morphology, and flexural toughness. Data disclosed V/HBAIA-2 with the composition of 90% vermiculite reinforced with 10% HBAIA obtained the most prominent outcomes in overall. V/HBAIA-2 attained the lightest density of 37.5 kg/m3 and weight of 0.20 kg, with lowest end temperature of 122 °C after exposure to one-hour of 1000 °C fire. This indicated the best fire-resistant performance in V/HBAIA-2. No structural deformation and only mild smoke and odor were observed in V/HBAIA-2 during the fire endurance examination. V/HBAIA-2 was able to resist the maximum loading force of 67.4 N before and 52.5 N after the fire resistant, with the higher flexural toughness value of 1.47 MPa. Scanning electron microscopy revealed a more uniform, denser, closely connected air cavities char cell quality in V/HBAIA-2 explained its superior outcomes in fire-resistant and flexural toughness as compared to the rest of specimens.

Performance and mechanism of simultaneous Sb(III) and Cd(II) removal from water by Fe-Mn binary oxide/bone char.

A novel Fe-Mn binary oxide (FMBO)/bone char composite (FMBC) was synthesized and utilized to simultaneously adsorb Sb(III) and Cd(II) from aqueous phase in this study. The successful loading of Fe-Mn binary oxide on the bone char surface was revealed by the results of scanning electron microscope, X-ray diffraction patterns, and energy dispersive spectroscopy of FMBC. The FMBC exhibited remarkable ability of simultaneous removing Sb(III) and Cd(II) from aqueous, and the presence of Cd(II) enhanced Langmuir theoretical maximum adsorption capacity for Sb(III) significantly from 67.8 to 209.0mg/g. Besides, FMBC could efficiently remove Sb(III) and Cd(II) in the wide initial pH range of 2-7. The influences of ionic strength, co-existing anions, humic acid, and temperature on the adsorption of Sb(III) and Cd(II), and the application potential of FMBC in actual groundwater were investigated. The main mechanisms of Sb(III) and Cd(II) adsorption onto FMBC involved redox, electrostatic interaction, surface complexation, ion exchange, and precipitation. The result of X-ray photoelectron spectroscopy and mapping spectrum analysis revealed that Mn(III) on FMBC played the key role in the Sb(III) oxidation, while FeOOH worked as the adsorption sites of FMBC. Meanwhile, the hydroxyapatite on FMBC also contributed to the removal of Cd(II). The presence of Cd(II) not only increased the positive charge on the surface of FMBC but also formed the Fe-Sb-Cd ternary complex, promoting the removal of Sb. This work provides valuable information for the application of FMBO/bone char as a cost-effective adsorbent to remediate co-pollution of Sb(III) and Cd(II) in aqueous environment.

Interaction of the lignin-/cellulose-derived char with volatiles of varied origin: Part of the process for evolution of products in pyrolysis

The interaction between volatiles and homologous and/or heterologous char is almost inevitable during the transfer or diffusion of volatiles from inner core to outer surface of a biomass particle in pyrolysis. This shapes both composition of volatiles (bio-oil) and property of char. In this study, the potential interaction of lignin- and cellulose-derived volatiles with char of varied origin was investigated at 500 °C. The results indicated that both the lignin- and cellulose-char promoted polymerization of the lignin-derived phenolics, enhancing production of bio-oil by ca. 20%–30%, generating more heavy tar but suppressing gases formation, especially over cellulose-char. Conversely, the char catalysts, especially the heterologous lignin-char, promoted cracking of the cellulose-derivatives, producing more gases while less bio-oil and heavy organics. Additionally, the volatiles-char interaction also led to gasification of some organics and also aromatization of some organics on surface of char, resulting in enhanced crystallinity and thermostability of the used char catalyst, especially for the lignin-char. Moreover, the substance exchange and formation of carbon deposit also blocked pores and formed fragmented surface dotted with particulate matters in the used char catalysts.