N2 Surface Area Research Articles

CO2 adsorption in biochars obtained from soursop (Anonna muricata) seeds by chemical activation with metallic salts

Environment remediation is one of the primary goals of sustainable development and anthropogenic activities, and the use of fuels in various industrial processes through combustion has led to an increase in CO2 as well as big damage to the atmosphere by the greenhouse effect. Biochar has been used for the capture of carbon dioxide due to its high surface area. In this study, we obtained biochar from soursop seeds. The materials were synthesized by pyrolysis of precursor materials and chemical activation with chlorides of Ca and Mg at a concentration of 5% w/v. The effect of the defatting process of the soursop seeds on the obtained carbon was also researched. The absorbed solids were characterized through thermogravimetric analysis, X-ray diffraction, and CO2 adsorption, followed by infrared spectroscopy, N2-physisorption, CO2-physisorption, CO2, XPS, DRIFTS and TPD of NH3. The type of activating agent and pretreatment conditions used were more favorable than the defatted process at obtaining carbons with N2 surface areas between 26 and 220 m2g−1. The biochars were analyzed by CO2 surface area to describe the microporous framework, and the solid with the best CO2 surface area was the one with the highest CO2 adsorption. According to the statistical analyses conducted, the evaluated models Langmuir, Freundlich, and Redlich-Peterson presented good fits to the experimental data. However, the Redlich-Peterson model showed the lowest values for the residual variance, which were of the order of 0.001 or less in all cases based on the CO2 adsorption isotherms on the studied activated carbons. However, the carbons obtained by defatting showed favorable hydrophilic behavior along with adsorption capacities in the bioremediation process and affinity towards of this GHG.

Surface area and porosity analysis in nanoporous carbons by atomistic pore domain model

We present a new atomistic model for evaluating the surface area and porosity of micro-mesoporous carbons. This method, referred to as the atomistic pore domain model (APDM), advances the adsorption porosity methodology by calculating textural properties of micro-mesoporous carbons without relying on assumptions about pore geometry. A thorough analysis of porosity across eleven porous carbons demonstrates a robust correlation between the surface area accessible to N2 molecules, as computed using APDM and the Brunauer-Emmett-Teller method with Rouquerol criterium. This correlation is observed across a spectrum of nanoporous carbons, ranging from ultramicroporous activated carbon fibers and nanoporous carbon beads to supermicro-mesoporous activated carbons and activated carbon fibers. APDM facilitates the extraction of the information regarding the N2 surface area accessibility and the intrinsic geometric surface area of micro-mesoporous carbons. The N2-to-He surface area accessibility ratio of the investigated porous carbons varies from approximately 57 %–94 %, indicating varying degrees of pore sieving among studied carbon samples. Except for ACF-25 micro-mesoporous activated carbon fiber, the intrinsic geometric surface areas of the studied micro-mesoporous carbons are smaller than the geometrical surface area of a single graphene sheet (2640 m2/g).

High-Concentration Self-Assembly of Zirconium- and Hafnium-Based Metal-Organic Materials.

Metal-organic frameworks (MOFs) are crystalline, porous solids constructed from organic linkers and inorganic nodes that are promising for applications in chemical separations, gas storage, and catalysis, among many others. However, a major roadblock to the widespread implementation of MOFs, including highly tunable and hydrolytically stable Zr- and Hf-based frameworks, is their benchtop-scalable synthesis, as MOFs are typically prepared under highly dilute (≤0.01 M) solvothermal conditions. This necessitates the use of liters of organic solvent to prepare only a few grams of MOF. Herein, we demonstrate that Zr- and Hf-based frameworks (eight examples) can self-assemble at much higher reaction concentrations than are typically utilized, up to 1.00 M in many cases. Combining stoichiometric amounts of Zr or Hf precursors with organic linkers at high concentrations yields highly crystalline and porous MOFs, as confirmed by powder X-ray diffraction (PXRD) and 77 K N2 surface area measurements. Furthermore, the use of well-defined pivalate-capped cluster precursors avoids the formation of ordered defects and impurities that arise from standard metal chloride salts. These clusters also introduce pivalate defects that increase the exterior hydrophobicity of several MOFs, as confirmed by water contact angle measurements. Overall, our findings challenge the standard assumption that MOFs must be prepared under highly dilute solvothermal conditions for optimal results, paving the way for their scalable and user-friendly synthesis in the laboratory.

Preparation of activated carbon from pine (Pinus radiata) sawdust by chemical activation with zinc chloride for wood dye adsorption

Wastewater containing dyes are released into water bodies generating serious problems in human health and marine life. To contribute to the solution of this problem, a novel activated carbon was prepared from untreated pine (Pinus radiata) sawdust by dry chemical activation with ZnCl2 and was used for wood dye adsorption. The carbon was characterized by point of zero charge, N2 and CO2 adsorption isotherms, SEM-EDX, and FTIR. N2 and CO2 surface areas were 471.4 and 319.5 m2 g−1, respectively, with 91% of micropores. Wood dye adsorption was studied in function of pH (2–12), adsorbent dose (0.1–4 g L−1), time (up to 48 h for blue and red and 12 h for black), and initial concentration (5–500 mg L−1). The equilibrium data for the blue and black dyes were satisfactorily fitted to the Freundlich model while those for the red dye to the Langmuir model. Kinetic data were explained by the pseudo-second order (chemisorption process) and intraparticle diffusion models. At 5 mg L−1, a 100% removal efficiency was achieved at all pH for the blue dye, whereas for the red and black, natural pH (5.1) and pH = 2, respectively, led to the best removal efficiencies, 96 and 56%. Increasing concentration above 25 mg L−1 significantly reduced adsorption efficiency for blue and red dyes. For the black dye increasing the dose to 1 g L−1, the adsorption efficiency reached 82% at 25 mg L−1. High removal efficiencies were achieved for all dyes at 25 mg L−1 and 4 g L−1.

Effect of Structural Fe Reduction on Water Sorption by Swelling and Non-Swelling Clay Minerals

Ferruginous clay minerals in saturated soils and within hydrocarbon deposits often exist in a reduced state. Upon introduction of dissolved oxygen, or other oxidants, the clay minerals oxidise and changes in mineral surface charge and sorption capacity occur, resulting in changes in hydration as well as flux of intercalated species. Here we examine the sorption of water to the Fe-containing clay minerals nontronite NAu-2 (23 wt% Fe) and illite IMt-2 (7 wt% Fe) as a function of Fe oxidation state and exchangeable cations by means of water vapour volumetry and N2 surface area analysis. The clay minerals were chemically reduced using sodium dithionite. Sorption isotherms of water vapour and nitrogen, controlled relative humidity diffractograms, and chemical analyses were recorded. The results show that, after reduction using sodium dithionite, increased amounts of water vapour and nitrogen were adsorbed to the high Fe content nontronite, despite decreased interlayer separation. Little change was observed for the non-swelling and low Fe content illite. Sodium from the reducing agent was found to exchange with calcium present in the starting clay minerals, and sodium balanced the additional mineral charge generated during reduction. The findings presented in this study deliver improved understanding of sorption at the surface of the reduced clay minerals, which aid constrain the role of clay mineral interfaces in subsurface environments.

Fabrication of S-scheme TiO2/g-C3N4 nanocomposites for generation of hydrogen gas and removal of fluorescein dye

Herein, an effective S-scheme heterojunctions were fabricated with ultrasonic aspects for effective decomposition of fluorescein dye and evolution of green hydrogen gas. Mesoporous pristine titania nanoparticles with anatase phase structure and 156 m2/g surface area were synthesized by sol-gel mechanism using pluronic solution as templating agent, however, g-C3N4 sheets generated by thermal treatment of urea at 515 °C. The a-synthesized nanocomposites embedded various compositions of g-C3N4 (1−10) wt% were synthesized by ultrasonic pathway. The properties of the specimens were recorded by HRTEM, XRD, DRS, N2-surface area measurement, PL and XPS. The experimental results reveal the noticeably reduction in sample crystallinity and intensity of PL peak with introduction of 8 wt% g-C3N4 supporting the efficient charge carriers separation. The sonicated heterojunction with 8 wt% g-C3N4 is account for decomposition of 94% of fluorescein anionic dye and production of hydrogen gas with rate 4.9 mmolg−1 h−1 which is eleven fold greater than that of pristine TiO2. The strong redox power of this heterojunction is ascribed to step S-scheme mechanism which promote the charge transportation and enhance the separation efficiency of the charge carriers. This charge migration route is established by trapping scavengers and PL experiments. The photocatalytic property of the optimum sample is still with exceptional reactivity for decomposition of anionic dye pollutant and evolution of hydrogen gas after six consecutive cycles.

Metallo-stannosilicates as inorganic supports to immobilization of lipase from Thermomyces lanuginosus for biodiesel production

This study reports the application of metallo-stannosilicates as potential inorganic solid matrixes for enzymes immobilization and their use as a heterogenous catalysts in enzymatic transesterification reactions for the conversion of triacylglycerides into fatty acid ethyl esters (FAEEs). Several stannosilicates were synthesized and physicochemical characterized by X-ray powder diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), Brunauer-Emmett-Teller (BET)-N2 surface area analysis and solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR 29Si and 119Sn nuclei) techniques. The experimental results for enzymes immobilization were promising, especially for a nickel ion-exchanged metallo-stannosilicate, which were able to immobilize 82 +- 6% of Thermomyces lanuginosus lipase and also kept a high enzymatic activity (42 +- 3 U mg�1). Systematic catalytic reactions for conversion of refined palm oil (Elaeis guineensis) using some of these stannosilicates enzymes complexes yielded 63.3 +- 0.7% of FAEEs. It is worth noticing that, when the transesterification reaction was performed with (a) the as-made stannosilicate without enzymes and (b) the equivalent amount of immobilized Thermomyces lanuginosus lipase in its free form, the FAEEs yield sharply decreased to less than 5.0% and 6.3 +- 0.3%, respectively. This result is a clear evidence of a synergistic effect among the metallo-stannosilicates and the immobilized enzymes.

Pore characterization of Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation shale gas reservoirs, Sichuan Basin, China

In order to investigate pore structure characteristics of Wufeng and Longmaxi Formations shales in the Sichuan Basin, the organic geochemical parameter and petrologic experiments, N2 and CO2 adsorptions, field emission scanning electron microscopy analysis and helium porosity measurement are carried out. Results showed that the thermal maturity of shales belong to over-maturity stage with TOC content and porosity of 1.84%–6.82% and 2.6%–5.1%, respectively. The TOC content has a good correlation with quartz, weak correlation with clay and no correlation with carbonate, indicating that the organic matter is mainly controlled by quartz content. The N2 and CO2 specific surface areas of organic-rich shale is generally 16.86–29.71 m2/g and 13.76–26.47 m2/g, respectively and the average N2 and CO2 specific surface area of organic-poor shale are 8.91 m2/g and 9.11 m2/g respectively, which indicating that the organic-rich shale has higher specific surface area, pore volume and smaller average pore diameter than that of organic-poor shale. The specific surface area in organic-rich shale is mainly contributed by micropores, while the pore volume is mainly contributed by mesopores, followed by micropores. There is a very strong correlation between TOC and CO2 and N2 specific surface area, indicating that pores were controlled by organic matter. Both porosity and specific surface have a positive relation when clay content is less than 28% for organic-rich shale, and its correlation is not obvious when clay content is more than 28% for organic-poor shale, indicating that the clay has a certain effect on reservoir.

Activated carbon from sawdust for naphthalene removal from contaminated water

Naphthalene, simplest polycyclic aromatic hydrocarbon (PAH), is extensively liberated in aqueous systems through wastewaters of various industries. The present study proposes the removal of naphthalene from aqueous solutions inexpensively and efficiently using high quality activated carbon synthesized from waste material, sawdust. The Brunauer–Emmett–Teller(BET) N2 surface area for sawdust activated carbon (SDAC) was over 1400 m2/g. The influence of contact time, dosage of prepared activated carbon, temperature, and pH for naphthalene adsorption has been investigated. Results were evaluated using Langmuir and Freundlich equations. Based on obtained isotherm parameters, Freundlich isotherm was found to be more favourable for naphthalene adsorption. Results revealed efficient adsorption of naphthalene with sawdust activated carbon under given conditions. Equilibrium time for the adsorption on SDAC was found to be 90 min. Samples were analysed using UV–Visible spectrophotometry. The study furnishes high quality, easily acquirable, and cheap adsorbent which is highly effective for the treatment of polycyclic aromatic hydrocarbons.

Influence of linear and branched amine functionalization in mesoporous silica on the thermal, mechanical and barrier properties of sustainable poly(lactic acid) biocomposite films

Recently, biopolymer based materials are regarded as potential alternative for conventional plastics. Poly (lactic acid) (PLA) is one among the biopolymers, which is rapidly commercialized for food packaging application. However, PLA has its own limitations, which confines its commercial application in food packaging sector. With the aim to overcome these limitations, an effort has been undertaken in the current work to use organically modified pore expanded MCM-41 mesoporous silica (MS) as filler for fabrication of PLA based composites via solution casting method. The current work investigates the influence of incorporation of linear (tetraethylene pentamine & pentaethylene hexamine) and branched (polyethylenimine) amine impregnated MS on the morphological, structural, thermal, mechanical and barrier properties of PLA. The N2 adsorption-desorption isotherms, surface area and pore volume analyses clearly indicated that the mesopores present in MS are filled with amine moieties after modification using impregnation agents. Thermo-gravimetric analysis revealed that the branched amine impregnated MS showed enhanced Tonset and Tmax values in comparison with neat PLA and PLA composites impregnated with linear (L1 and L2) amine. DSC results confirmed that the incorporated branched amine modified MS acted as nucleating agent by enhancing the crystallization rate for PLA. Mechanical studies revealed that the presence of branched amine in MS helped in enhancing the ductility property for PLA-MS composite films. Oxygen transmission rate analysis indicated that the presence of branched amine modified MS in the PLA matrix enhanced tortuosity path for passage of O2 molecules through the films. All these results indicated that the branched amine impregnated MS incorporated PLA composite film shows promising features for sustainable food packaging.

Re-designing a viable ELTs depolymerization in circular economy: Pyrolysis prototype demonstration at TRL 7, with energy optimization and carbonaceous materials production

The present study aims to demonstrate challenge-based innovations of ELTs depolymerization, show evidence of promising developments and improve pyrolysis performance towards its economic viability. A pyrolysis prototype, with a ELTs mass flow rate of 20 kg h−1 was designed, constructed, and demonstrated. Up to 100 kg h−1 of steel-free tyre granulates were pyrolyzed for up to 100 h continuous operation. The tests were carried out at 550 °C, under atmospheric pressure and residence time ∼12 min with good reliability and reproducibility. All three pyrolysis products showed good fuel characteristics. The LHV of the obtained producer gas estimated to 23.5 MJ Nm−3 and 26% of the prototype energy requirements were provided by using the producer gas as fuel. Pyro-oil showed high carbon content (86.04 wt%), GCV of 44.2 MJ kg−1 and H/C ratio (1.74). Despite its higher sulphur content, pyro-oil is comparable to diesel fuel in all other characteristics. Chars exhibited high percentage of fixed carbon (>80 wt %) and a high GCV = 30.3 MJ kg−1. S, Zn and Si were detected in chars, at low concentration. Based on surface and structural characteristics, chars were considered comparable to carbon blacks of N400-N500 series. Upgrading of char to activated carbon by physical and chemical activation, increased N2 surface area to 589 m2 g−1 and 402 m2 g−1, respectively. The study contributes significantly to increase knowledge on the viability of pyrolysis, providing to the recycling sector an opportunity for the deployment of take-off systems, within a Circular Economy. End of Life Tyres (ELTs) pyrolysis can be viable, if all produced streams are valorized.

Adsorption Mechanisms of Dodecylbenzene Sulfonic Acid by Corn Straw and Poplar Leaf Biochars.

Biochar is an eco-friendly, renewable, and cost-effective material that can be used as an adsorbent for the remediation of contaminated environments. In this paper, two types of biochar were prepared through corn straw and poplar leaf pyrolysis at 300 °C and 700 °C (C300, C700, P300, P700). Brunaer–Emmett–Teller N2 surface area, scanning electron microscope, elemental analysis, and infrared spectra were used to characterize their structures. These biochars were then used as adsorbents for the adsorption of dodecylbenzene sulfonic acid (DBSA). The microscopic adsorption mechanisms were studied by using infrared spectra, 13C-nuclear magnetic resonance spectra, and electron spin resonance spectra. The surface area and pore volume of C700 (375.89 m2/g and 0.2302 cm3/g) were the highest among all samples. Elemental analysis results showed that corn straw biochars had a higher aromaticity and carbon to nitrogen (C/N) ratio than the poplar leaf biochars. High temperature caused the increase of carbon content and the decrease of oxygen content, which also gave the biochars a higher adsorption rate. Pseudo-second order kinetic provided a better fit with the experimental data. Adsorption isotherm experiments showed that the adsorption isotherm of C300 fit the linear model. For other biochars, the adsorption isotherms fitted Langmuir model. Biochars with high temperatures exhibited enhanced adsorption capacity compared with ones at low temperatures. The qmax values of biochars to DBSA followed the order of P700 > C700 > P300. The adsorption mechanisms were complex, including partition, anion exchange, the formation of H bonds, covalent bonds, and charge transfer. The adsorption by covalent bonding might be the key mechanism determining the adsorption capacity of P700.

Effect of particle size on high-pressure methane adsorption of coal

AbstractAdsorbed gas cannot be neglected in the evaluation of coalbed methane and shale gas since a significant proportion of gas is stored in the form of adsorbed gas. Adsorbed methane of coal and shale has been widely studied by high-pressure methane adsorption experiment. In sample treatment of the experiment, the sample is crushed and sieved to a particular particle size range. However, how particle size influence high-pressure methane adsorption is still unclear. In this study, low-pressure nitrogen (N2) and high-pressure methane adsorption have been measured on coal samples with different particle size. According to N2 sorption analysis, pore volume and surface area increase with particle size reduction. Pore size distribution of small pores (<10nm) changes among varying particle size. Pore volume proportion of small pores (<10nm) increases and pore volume proportion of big pores (>10nm) decreases with decreasing particle size. Decreasing particle size by crushing sample introduces new connectivity for closed pores to the particle surface. The responses of isotherms of high-pressure methane adsorption are different with different particle size. Methane adsorption at initial pressure (145psi) increases with decreasing particle size. Adsorption increase rate at high pressure (435-870psi) decreases with particle size reduction. This can be explained that fine sample has more pore volume and higher pore volume proportion of small pores (<10nm). Sample with particle size of 150-250μm has the highest Langmuir volume.

The effect of sample particle size on the determination of pore structure parameters in shales

The combination of low-pressure N2 and CO2 adsorption could provide an effective approach for characterizing the pore structure of shales. Although gas adsorption methods generally do not destroy the pore structure during experimental process, sample particle sizes could significantly affect experimental results that can approach or deviate from the real value. Therefore, the determination of pore structure is closely related to the sample particle size. In the current study, 4 fresh core samples of different compositions and total organic carbon (TOC) ranges collected from the Sichuan Basin were analyzed to elucidate the effect of sample particle size on the determination of pore structure parameters. Samples were ground and then sieved into seven groups based on particle size ranges, i.e., <60, 60–80, 80–100, 100–120, 120–140, 140–200 and >200 mesh, for measurements of low-pressure N2 and CO2 adsorption, TOC contents, and X-ray diffraction (XRD) mineralogy.TOC results show a slight enrichment whereas XRD minerals vary irregularly, with sample particle size decreases. Meanwhile, the TOC and mineral contents show insignificant statistical relation with pore structure parameters in all sample particle size ranges. Therefore, variations in organic matter content and mineral composition that result from sieving are unlikely to have a significant influence on the pore structure of shale. Rather, sample particle size may be the most important control on pore structure characteristics in the samples analyzed in this study.The relative standard deviations (RSDs) for Brunauer–Emmett–Teller (BET) N2 surface areas, Dubinin–Radushkevich (D–R) CO2 micropore surface areas and non-local density functional theory (NLDFT) N2 and CO2 nanopore surface areas measurements are <5%, within analytical error. Therefore, in the studied grain size range (60–200 mesh), the sample particle size shows insignificant effects on surface area results. However, samples with smaller particle size have a greater effect on pore volume and pore size, especially for pore size distribution (PSD) of N2 low-pressure adsorption. The RSDs of the Barrett–Joyner–Halenda (BJH) pore volumes and BET pore sizes of all samples in the 140–200 mesh range are obviously greater than the values of other mesh ranges. Moreover, in the dV/dlogw plots of PSD analysis, high N2 peaks and new N2 peaks appeared in the 10–100nm pore-width range, particularly for samples in the >140 mesh range. The 60–140 mesh particle-size range is therefore recommended for N2 low-pressure adsorption. Finally, the sample particle size has insignificant effect on the pore system parameters for grains in the 60–200 mesh range for CO2 low-pressure adsorption. Overall, the results confirm that the 60–140 mesh particle-size range can be used for both N2 and CO2 low-pressure adsorption measurements.

Properties of biochar-amended soils and their sorption of imidacloprid, isoproturon, and atrazine

Biochars produced from rice straw, wheat straw and swine manure at 300, 450 and 600°C were added to soil at 1, 5, 10, or 20% levels to determine whether they would predictably reduce the pore water concentration of imidacloprid, isoproturon, and atrazine. The sorption capacity of the mixtures increased with increasing biochar amounts. The enhanced sorption capacity could be attributed to the increased organic carbon (OC) content and surface area (SA) as well as the decreased hydrophobicity. Biochar dominated the overall sorption when its content was above 5%. The OC contents of the mixtures with 10% and 20% biochar were generally lower than the predicted values. This implies possible interaction between soil components and biochar and/or the effect of biochar oxidation. For soils amended with biochars produced at 300°C, the N2 SA (N2-SA) values were underestimated. The predicted CO2 SA (CO2-SA) values of the mixtures at the biochar content of 10% and 20% were generally higher than the experimental values. Sorption of imidacloprid to the soils amended with biochar at 10% and 20% levels, excluding the soils amended with rice (SR300) and wheat (SW300) straw-derived biochar produced at 300°C, was lower than the predicted value. For SR300 and SW300, the intrinsic sorption capacity of biochar was enhanced by 1.3–5.6 times, depending on the biochar, solute concentration, and biochar dose. This study indicates that biochars would be helpful to stabilize the soil contaminated with imidacloprid, isoproturon, and atrazine, but the sorption capacity of the mixtures could exceed or fall short of predicted values without assuming a cross-effect between soil and biochar.

カーボンブラックの１次・２次凝集構造のキャラクタリゼーション

New characterization method of Carbon Blacks（CB） for rubber industries were proposed. The proposed method is based on the measurements using alternative technologies of a N2 gas adsorption, a He gas replacement and a laser diffraction and scattering without using several solvents such as CTAB and DBP. These measurements are easy and safe to investigate the basic structures for of CB. The new characterization method provide a multipoint N2 surface area （NSA）, a statistical thickness surface area （STSA） and skelton densities of CB as well as a domain particle size and primary and secondary aggregate size, the structures by utilizing porosity, true density, STSA and external surface areas.

Adsorption of polycyclic aromatic hydrocarbons on banana peel activated carbon

Polycyclic aromatic hydrocarbons (PAHs) are potential pollutants, released in aqueous systems through various sources such as industrial wastewaters, agricultural run-off, and deposition from the polluted air. The present study proposes an efficient and inexpensive approach to remove PAHs from aqueous system using activated carbon synthesized from waste banana peel. The Brunauer–Emmett–Teller N2 surface area of the developed banana peel-activated carbon (BPAC) is more than 900 m2/g. Effects of contact time, adsorbent dose, pH, and temperature on adsorption of PAHs have been examined. Results were fitted to Langmuir and Freundlich models, and characteristic parameters for both the adsorption isotherms were calculated. Data is better fitted to Freundlich model. The equilibrium time for the adsorption on BPAC is found to be 80 min. Equilibrium constants obtained from Langmuir adsorption isotherms have been used to calculate the thermodynamic parameters, such as ΔG°, ΔH°, and ΔS°. The result revealed that adsorption of PAHs onto BPAC is spontaneous and endothermic. Quantitative desorption of PAHs from BPAC has been achieved using sodium hydroxide and ethanol mixture, indicating the reuse of prepared activated carbon. The study thus provides cheap and easily acquirable adsorbent which effectively removes PAHs from aqueous system.

Structural features and gasification reactivity of coal chars formed in Ar and CO2 atmospheres at elevated pressures

The structural features and gasification reactivity of chars derived from pyrolysis of a bituminous coal under Ar (Ar char) and CO2 atmosphere (CO2 char) have been investigated, respectively. The pyrolysis was performed in a fixed bed reactor at a final temperature of 700 °C and pressures ranging from 0.1 to 1.5 MPa. It was found that CO2 affect the char yield, pore structure and surface area. The N2 surface area of the CO2 char at ambient pressure increased by nearly 42 times compared to the Ar char. The chemical structure features were characterized by using Raman spectroscopy. The recorded spectra between 800 and 1800 cm−1 were curve-fitted with 10 Gaussian bands representing typical structural features of chars to quantitatively compare the char structure difference. The ratio I(Gr+Vl+Vr)/ID between the band intensities of amorphous char structures with small aromatic ring (3–5 rings) systems and condensed aromatic ring systems (>6 rings) is seen to decrease with increasing pyrolysis pressure. The I(Gr+Vl+Vr)/ID of CO2 char is always lower than that of Ar char in the whole pressure range. The non-isothermal CO2 gasification from 700 to 1000 °C in a TGA (thermogravimetric analyzer) indicates that the char prepared under Ar atmosphere was more reactive.

Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars.

Chars from wildfires and soil amendments (biochars) are strong adsorbents that can impact the fate of organic compounds in soil, yet the effects of solute and adsorbent properties on sorption are poorly understood. We studied sorption of benzene, naphthalene, and 1,4-dinitrobenzene from water to a series of wood chars made anaerobically at different heat treatment temperatures (HTT) from 300 to 700 °C, and to graphite as a nonporous, unfunctionalized reference adsorbent. Peak suppression in the NMR spectrum by sorption of the paramagnetic relaxation probe TEMPO indicated that only a small fraction of char C atoms lie near sorption sites. Sorption intensity for all solutes maximized with the 500 °C char, but failed to trend regularly with N2 or CO2 surface area, micropore volume, mesopore volume, H/C ratio, O/C ratio, aromatic fused ring size, or HTT. A model relating sorption intensity to a weighted sum of microporosity and mesoporosity was more successful. Sorption isotherm linearity declined progressively with carbonization of the char. Application of a thermodynamic model incorporating solvent-water and char-graphite partition coefficients permitted for the first time quantification of steric (size exclusion in pores) and π-π electron donor-acceptor (EDA) free energy contributions, relative to benzene. Steric hindrance for naphthalene increases exponentially from 9 to 16 kJ/mol (∼ 1.6-2.9 log units of sorption coefficient) with the fraction of porosity in small micropores. π-π EDA interactions of dinitrobenzene contribute -17 to -19 kJ/mol (3-3.4 log units of sorption coefficient) to sorption on graphite, but less on chars. π-π EDA interaction of naphthalene on graphite is small (-2 to 2 kJ/mol). The results show that sorption is a complex function of char properties and solute molecular structure, and not very predictable on the basis of readily determined char properties.

Palygorskite–TiO2 nanocomposites: Part 1. Synthesis and characterization

In this paper we describe the synthesis and characterization of small-sized TiO2 particles supported on palygorskite (Pal) with Pal to TiO2 mass ratios of 10:90, 20:80, 30:70, 40:60 and 50:50. The above Pal–TiO2 nanocomposites were prepared by deposition of anatase form of TiO2 on the Pal surfaces using a sol-gel method with titanium isopropoxide as a precursor under hydrothermal treatment at 180°C. Phase composition, particle morphology and physical properties of these samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflection using Fourier transform infrared spectroscopy (ATR-FTIR) and N2 surface area analysis by BET. In order to investigate the absorption properties of the catalysts, UV–vis reflection spectra were measured. Preparation of Pal–TiO2 nanocomposites led to good dispersion of TiO2 on Pal surfaces. By increasing the amount of TiO2, the deposited 3–10nm TiO2 particles were found to be aggregated on the surfaces of the Pal particles. However, by decreasing the amount of TiO2, the Pal particles were found to be aggregated. After treating with TiO2, Pal samples largely showed interparticle mesopores of about 5.8nm. It was observed that the commercial titania P25 showed no absorption in visible light region. In contrast, the prepared Pal–TiO2 samples showed gray color and absorption in visible light region.