Soluble Organic Fraction Research Articles

Experimental investigation into the pore structure and oxidation activity of biodiesel soot

To investigate the effect of diesel fuel and different fatty acid methyl esters (FAMEs) biodiesels on the pore structure and oxidation activity of exhaust soot, an experiment was performed on a 4-cylinder high-pressure common-rail diesel engine fueled with commercial diesel fuel and three types of biodiesels (used soybean oil methyl eater (SME), palm oil methyl eater (PME), and waste cooking oil methyl eater (WME) as the main resources, respectively). Results showed that four kinds of exhaust soot had similar porous morphology, while the C/O ratio of biodiesel soot was lower than diesel soot. The N2 adsorption of four kinds of soot belonged to the multi-layer adsorption of mesopore or macropore media, and the N2 adsorption capacity of biodiesel soot was more substantial than that of diesel soot. The specific surface area, the pore volume, and the fractal dimension of three biodiesel soot were larger than that of diesel soot, and the mean pore size was smaller, which meant that the porosity of biodiesel soot was higher than that of diesel soot, and it had a rougher surface. Biodiesel particles contained more aliphatic C–H surface functional groups (SFGs), which may be related to the adsorption of more soluble organic fractions (SOF) by soot surface. A larger surface area and a higher porosity of biodiesel soot also improved the reactivity of soot. The iodine number and oxygen content of biodiesel had a significant effect on the pore structure and oxidation activity of soot. The low iodine number and high oxygen content of biodiesel (mainly consist of WME) helps to reduce PM emissions and improve the porosity and oxidation activity of biodiesel soot.

Sulfur transformations during two-stage anaerobic digestion and intermediate thermal hydrolysis

The formation of hydrogen sulfide (H2S) during anaerobic digestion (AD) imposes constraints on the valorisation of biogas. So far, inorganic sulfur compounds -mainly sulfate - have been considered as the main contributors to H2S formation, while the contribution of organic sulfur compounds is mostly neglected. This study investigates the fate of organic and inorganic sulfur compounds during two-stage anaerobic digestion with intermediate thermal hydrolysis for treatment of primary and secondary sludge in a WWTP treating domestic wastewater. The results of a seven-week monitoring campaign showed an overall decrease of organic sulfur compounds in both stages of anaerobic digestion. Further fractionation of organic sulfur revealed a high conversion of the particulate organic fraction during the first digestion stage and of the soluble organic fraction during the second digestion stage. The decrease of soluble organic sulfur during the second digestion stage was attributed to the solubilisation and hydrolysis of sulfur-containing organic compounds during thermal hydrolysis. In both digestion stages, more organic sulfur was taken up than particulate inorganic sulfur (metal sulfide) was produced, indicating the formation of other reduced sulfur forms (e.g. H2S). Further batch experiments confirmed the role of organic sulfur uptake in the formation of H2S during anaerobic digestion as sulfate reduction only partly explained the total sulfide formed (H2S in biogas and precipitated FeS). Overall, the conversion of organic sulfur was demonstrated to play a major role in H2S formation (and thus the biogas quality), especially in case of thermal hydrolysis pretreatment.

Effects of diesel from direct and indirect coal liquefaction on combustion and emissions in a six-cylinder turbocharged diesel engine

The aim of this study is to evaluate the effects of diesel from direct coal liquefaction (DDCL) and diesel from indirect coal liquefaction (DICL) on combustion and emissions. A six-cylinder turbocharged diesel engine fueled with DDCL, DICL, petroleum diesel (PD), 58% DDCL, and 42% DICL blended by volume (BD58) is used. The experiments are carried out at 1400 and 2300rpm engine speeds and various engine loads (10%, 25%, 50%, 75%, and 90% of the full-load). The results show that the brake thermal efficiency (BTE) of PD was higher than that of CTL (the maximum difference was 2%) at medium and high loads. At 10% load of 1400 rpm, the CO, HC and formaldehyde emissions of DDCL are 88.9%, 44.3% and 26.5% higher than those of PD respectively, and the CO, HC, and formaldehyde emissions of DICL are 30.1%, 15.3%, and 15.2% lower than those of PD. The differences among four fuels decrease rapidly with the increase of load. The NOX emissions of PD are the highest due to high nitrogen content (102.3 μg/g) and low hydrogen-carbon (H/C) ratio. The fuel with higher cetane number has less formaldehyde emission at low loads, while the fuel with lower H/C has less formaldehyde emission at high loads. The particle size distribution shows a bimodal shape at different loads and the peak particle size of accumulation mode and nucleation mode all increases with the increase of load. The particulate emission of different fuels from high to low is the order of PD > DDCL > BD58 > DICL. In addition, the emissions of polycyclic aromatic hydrocarbons (PAHs) and toxicity equivalent (TE) of PD are highest at all loads. The proportion of soluble organic fractions (SOF) from DDCL, DICL, and BD58 is higher than that of PD.

Investigation on the adsorption characteristics and influencing factors of diesel engine exhaust particulate matter.

In the exhaust pipe, the adsorption process of diesel exhaust particulate matter (PM) is affected by the combination of its adsorption capacity and the environment. A diesel exhaust particle collection system was established to collect samples with different environmental conditions. The adsorption capacity of the samples was characterized by an isothermal adsorption test. Changes in sample characteristics were investigated by scanning electron microscope and thermogravimetric analyzer. The correlation analysis of the factors influencing the adsorption process was performed. The results showed that the diesel exhaust particulate matter has adsorption capacity, the pore diameter is distributed continuously in the range of 8 to 80 nm, and the specific surface area and pore structure parameters are similar to carbon black and belong to the category of mesopores and macropores. As the engine speed increased from 1500 to 3600 r·min-1, the specific surface area of samples increased from 65.408 to 101.885 m2·g-1, and the pore volume expanded from 0.093 to 0.152 mL·g-1, with a more complex pore structure and enhanced adsorption capacity. The samples at the outlet of the exhaust pipe had increased box dimension (DB), moisture, and soluble organic fraction (SOF) content compared to the samples at the inlet of the exhaust pipe. The activation energies (E) of the three samples were reduced by 34.77 kJ∙mol-1, 38.88 kJ∙mol-1, and 47.43 kJ∙mol-1, respectively. Among the influencing factors, the increase of hydrocarbon concentration contributes to the increase of adsorption volume and the reduction of E. The increase of the average temperature inhibits the increase of the DB, and the increase of the temperature difference between the inlet and outlet facilitates the adsorption of water and SOF by samples. The reduction of adsorption time is one of the main reasons for delaying the increase of DB. Average pore diameter has the largest positive correlation with the variation amount of DB, and the growth of the specific surface area and pore volume is the dominant reason for the improvement of adsorption capacity and oxidation activity.

Analytical pyrolysis and thermal analysis to chemically characterise bitumen from Italian geological deposits and Neolithic stone tools

The chemical study of bitumen from stone tools from Italian Neolithic sites was carried out using analytical pyrolysis-based techniques, EGA-MS (evolved gas analysis mass spectrometry) and DSPy-GC/MS (double shot pyrolysis-gas chromatography/mass spectrometry). The study was mainly aimed at demonstrating the suitability of analytical pyrolysis for studying archaeological bitumen and for obtaining information regarding its origin. EGA-MS was employed to obtain information on the thermal complexity, that is the set of thermal properties and behaviours, of the samples and on their thermal degradation areas and DSPy-GC/MS along with Principal Component Analysis (PCA) were tested for biomarker analysis to assess bitumen source in archaeological objects. Geological bituminous rocks from Central-Southern Italy were selected and used as reference materials to both optimize experimental parameters and to support data interpretation for archaeological samples. Geological samples were also preliminary characterised by thermogravimetric analysis coupled with FTIR spectroscopy (TG-FTIR) under nitrogen and by TG analysis under oxygen to quantify their relative content of organic and inorganic species.The combination of thermal analysis and analytical pyrolysis-based techniques allowed us to quantify the organic content of the bitumen samples and to obtain information on both soluble and insoluble organic fractions. In addition, the proposed approach highlighted the main degradative patterns and the main differences among samples coming from different geographical areas as well as differences between geological and archaeological bitumen. Finally, DSPy-GC/MS associated with PCA proved to be successful in assessing the bitumen source in archaeological objects by the detection of terpanes, distinctive biomarkers.

Cloud condensation nuclei characteristics at the Southern Great Plains site: role of particle size distribution and aerosol hygroscopicity

The activation ability of aerosols as cloud condensation nuclei (CCN) is crucial in climate and hydrological cycle studies, but their properties are not well known. We investigated the long-term measurements of atmospheric aerosol properties, CCN concentrations (NCCN) at supersaturation (SS = 0.1%–1.0%), and hygroscopicity at the Department of Energy’s Southern Great Plains (SGP) site to illustrate the dependence of NCCN on aerosol properties and transport pathways. Cluster analysis was applied to the back trajectories of air masses to investigate their respective source regions. The results showed that aged biomass burning aerosols from Central America were characterized by higher accumulation mode particles (Naccu; median value 805 cm−3) and relatively high aerosol hygroscopicity (κ; median value ∼0.25) values that result in the higher CCN activation and relatively high NCCN (median value 258–1578 cm−3 at a SS of 0.1%–1.0%). Aerosols from the Gulf of Mexico were characterized by higher Naccu (∼35%), and NCCN (230–1721 cm−3 at a SS of 0.1%–1.0%) with the lowest κ (∼0.17). In contrast, relatively high nucleation mode particles (Nnucl; ∼20%) and low NCCN (128–1553 cm−3 at a SS of 0.1%–1.0%) with higher κ (∼0.30) values were observed on the aerosols associated with a westerly wind. The results indicate particle size as the most critical factor influencing the ability of aerosols to activate, whereas the effect of chemical composition was secondary. Our CCN closure analysis suggests that chemical composition and mixing state information are more crucial at lower SS, whereas at higher SS, most particles become activated regardless of their chemical composition and size. This study affirms that soluble organic fraction information is required at higher SS for better NCCN prediction, but both the soluble organics fraction and mixing state are vital to reduce the NCCN prediction uncertainty at lower SS.

Effect of Operating Parameters on Oxidation Characteristics of Soot under the Synergistic Action of Soluble Organic Fractions and Ash.

Diesel particulate filter is used to reduce particulate matter (PM) emission due to the stringent emission standards. The accumulated PM has been oxidized by the periodical regeneration method to avoid pressure buildup. The innovation of this study is to explore the oxidation performance of Printex-U (PU), which is mixed with ash and soluble organic fractions, under different operating conditions. Different aspects of operating parameters, such as the oxygen ratio in an O2/N2 atmosphere, total flow rate, initial PU mass, and heating rate, on PU oxidation properties have been critically discussed using a thermogravimetric analyzer. The oxygen ratio in the O2/N2 atmosphere is positively correlated with the oxidation characteristics of PU. The comprehensive oxidation index (S ) of PU under the 20% O2/80% N2 atmosphere increases by 184% compared with the 10% O2/90% N2 atmosphere. When the initial PU mass is 3 mg, the combustion stability coefficient (Rw) and S reach the best values, which are 55.53 × 105 and 2.03 × 107 %2min–2 ° C–3, respectively. With the increase in the heating rate, the oxidation properties of PU become sensible and deflagration occurs easily, so that 10 °C/min heating rate is the best option. This study provides a theoretical basis for the optimization design of diesel particulates during the regeneration process.

Toxicity of Water- and Organic-Soluble Wood Tar Fractions from Biomass Burning in Lung Epithelial Cells.

Widespread smoke from wildfires and biomass burning contributes to air pollution and the deterioration of air quality and human health. A common and major emission of biomass burning, often found in collected smoke particles, is spherical wood tar particles, also known as “tar balls”. However, the toxicity of wood tar particles and the mechanisms that govern their health impacts and the impact of their complicated chemical matrix are not fully elucidated. To address these questions, we generated wood tar material from wood pyrolysis and isolated two main subfractions: water-soluble and organic-soluble fractions. The chemical characteristics as well as the cytotoxicity, oxidative damage, and DNA damage mechanisms were investigated after exposure of A549 and BEAS-2B lung epithelial cells to wood tar. Our results suggest that both wood tar subfractions reduce cell viability in exposed lung cells; however, these fractions have different modes of action that are related to their physicochemical properties. Exposure to the water-soluble wood tar fraction increased total reactive oxygen species production in the cells, decreased mitochondrial membrane potential (MMP), and induced oxidative damage and cell death, probably through apoptosis. Exposure to the organic-soluble fraction increased superoxide anion production, with a sharp decrease in MMP. DNA damage is a significant process that may explain the course of toxicity of the organic-soluble fraction. For both subfractions, exposure caused cell cycle alterations in the G2/M phase that were induced by upregulation of p21 and p16. Collectively, both subfractions of wood tar are toxic. The water-soluble fraction contains chemicals (such as phenolic compounds) that induce a strong oxidative stress response and penetrate living cells more easily. The organic-soluble fraction contained more polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs and induced genotoxic processes, such as DNA damage.

PM Reduction for Marine Diesel Engines with Electrostatic Cyclone Precipitator - Effect of Engine Types on Reducing PM and Onboard Test of 2-Stroke Main Propulsion Engines

In this study, the authors investigated particulate matter (PM) collection efficiency of an electrostatic-cyclone precipitator (ESP-cyclone) by conducting bench tests and onboard measurements of PM emissions with three diesel engines. A small sized high-speed 4-Stroke diesel was used for a bench test and two types of low-speed 2-Stroke marine diesels were utilized for another bench test and onboard PM measurements aboard a ship of 2,703 gross-tonnage. In order to study PM collection efficiency of the ESP-cyclone, PM concentrations in exhaust gas were measured upstream and downstream of the ESP-cyclone with a partial flow dilution tunnel system. Experimental results showed that the PM collection efficiency was as high as 60-80% with the ESP-cyclone collecting not only insoluble organic fraction (ISF), but also soluble organic fraction (SOF). The ESP-cyclone realizes stable PM reduction from the diesel engine on the actual ship.

Study on Particulate Structure Characteristics of Diesel Engines Fueled with a Methanol/Biodiesel Blend

Methanol and biodiesel are both alternative fuels of diesel engines. In order to study the effects of methanol on the microstructure of particulates produced from the diesel engine fueled with a methanol/biodiesel blend, the methanol/biodiesel blend fuels with 0, 10, and 20% methanol were prepared (named B100, BM10, and BM20, respectively). SEM and TG experiments have been carried out, and the structural and oxidative characteristics of particulates for the methanol/biodiesel blend were investigated. The results showed that the average diameters of B100, BM10, and BM20 particulates were 35, 32.6, and 31.2 nm, respectively. With the increase of methanol blending ratio, the H2O and SOF (soluble organic fraction) contents were increased and the soot content in particulates was reduced slightly. In addition, the activation energy of the particulate pyrolysis reaction was reduced with the increase of methanol mixing ratio, and the oxidative reaction of particulates was easier to carry out.

H2SO4 and Organosulfur Compounds in Laboratory Analogue Aerosols of Warm High-metallicity Exoplanet Atmospheres

Abstract Recent transit spectra suggest organic aerosol formation in the atmosphere of sub-Neptunes. Sulfur gases are expected to be present in warm exoplanet atmospheres with high metallicity. Many aspects of the sulfur fixation process by photochemistry in planetary atmospheres are not fully understood. In this work, tholins produced in a CO2-rich atmosphere simulation experiment with H2S were analyzed with very high-resolution mass spectrometry (HRMS) that allows for searching specific molecules in addition to providing some insight on the mixture complexity. To our knowledge, this is the first experimental investigation of sulfur-bearing organic aerosol formation from irradiation of H2S at temperatures relevant to warm exoplanets. The analysis of the mass spectra shows that the soluble organic fraction of the solid particles contains over 2500 organosulfur (CHS/CHOS/CHNS/CHNOS) molecular formulas (73% of all assigned signals) within a broad mass range (from 50 to 400 u, atomic mass unit). In particular, 14 sulfuric acid derivatives were detected and 13 unique molecular formulae that could correspond to amino acid derivatives were identified. This high molecular diversity indicates a rich and active sulfur chemistry triggered by irradiation of H2S. The average elemental composition (wt%) of the soluble fraction of the particles is 40%C, 30%O, 21%S, 6%H, and 3%N, making the sulfur abundance a factor of ∼14 larger than in the initial gas composition. Our analysis of experimental simulations shows that organosulfur species are likely an important component of the haze in exoplanet atmospheres.

Effects of iron-based fuel borne catalyst addition on combustion, in-cylinder soot distribution and exhaust emission characteristics in a common-rail diesel engine

In order to reduce soot emission and assist diesel particulate filter regeneration, iron-based fuel borne catalyst (Fe-FBC) was added into diesel fuel with Fe element mass fractions of 0, 200 and 400 mg/kg in the preparation of FBC fuels (marked as Diesel, Fe200 and Fe400). The in-cylinder soot distribution, pollutant emissions and particle physicochemical properties of FBC fuels were investigated on a visualization modified common-rail engine. The results show that the combustion starting point is advanced with Fe-FBC addition, while the maximum combustion pressure and heat release rate increase. The addition of Fe-FBC in diesel fuel will shorten ignition delay period, accelerate combustion process and lead to the increase of in-cylinder flame temperature, while the in-cylinder soot concentration and soot area occupation ratio are reduced significantly. HC, CO and soot emissions along with the unconventional emissions such as HCHO, CH3CHO and polycyclic aromatic hydrocarbons (PAHs) decrease at each load as the increase of Fe-FBC addition ratio. Compared with Diesel, the peak soot area occupation ratio and soot emissions of Fe400 decrease by 41.6% and 20.4% respectively at full load. It is also found that Fe-FBC addition decreases particle box-counting dimension, which indicates that the polymerization degree between the particles becomes weaker and their arrangement becomes more sparse and loose, so the oxidation characteristic temperature and the activation energy of soot particles decrease significantly. Fe-FBC addition can effectively reduce the type and content of PAHs and the high carbon atom number compounds in soluble organic fraction from exhaust particles.

Limited effects of the soluble organic phosphorus fraction on the root phosphorus uptake efficiency of upland rice genotypes grown in acid soil

ABSTRACT The root phosphorus (P) uptake efficiency (RE), defined as plant P uptake per unit root mass or root area, may contribute to the P efficiency of upland rice grown in acid, P-deficient soils. The identification of root traits conferring RE of rice has been compromised by the lack of attention given to P speciation when evaluating P-mining mechanisms. Here we disentangled the effect of soluble organic P (PO) from that of total soluble P (PT) on the RE in rice seedlings in acid soil. Six rice genotypes were grown for 21 days in P-deficient substrates, i.e. a sample of an acid mineral soil, an acid peat and a mixture thereof. Each of the three substrates were amended with different P doses, partially limed and incubated, yielding substrates with significant differences in total soluble P (0.005–0.41 mg P/L) and in the percentage of organic P in that pool (PO/PT, 0–55%). Plants showed a large growth response to the P addition. There was a significant genotypic variation in P uptake (0.9–1.5mg P/plant) and RE (4.4–8.3 mg P/g root mass) under moderate P deficiency but these traits were unaffected by the PO/PT in the soluble fraction of the substrates. Along the same lines, phosphatase activity in the rhizosphere soil was unaffected by genotypes and did not explain the RE among all data (R2 = 0.17, ns). A multiple regression model showed that the RE of rice seedlings was mainly affected by the inherent genotypic effects, the PO/PT and the total soluble P concentration in soil (R2 = 0.73), while the genotype-PO/PT interaction only marginally improved the RE model (R2 = 0.78). This suggests limited genotypic effects due to the better use of organic P. A root elongation test in the acid mineral soil that was either or not limed suggests that the differences in acid soil tolerance may play a larger role in the genotypic performance of RE than organic P utilization potential.

Pretreatment of spent coffee grounds with alkaline soju bottle-washing wastewater for enhanced biomethanation

The production of spent coffee grounds (SCG) is steadily increasing, and its proper treatment has become an increasingly challenging task. This study explored the potential use of alkaline bottle-washing wastewater (BWW) from a soju (a Korean hard liquor) manufacturer as an alternative pretreatment agent to enhance the biodegradability and thus the biomethanation of SCG through anaerobic digestion. Thermo-alkaline pretreatment with BWW was effective in increasing the soluble organic fraction of SCG (i.e., improved bioavailability) at all temperatures tested (23–70 °C). The disintegration degree of the particulate organic matter in SCG ranged from 8.6 to 13.1% and increased with increasing pretreatment temperature. The 30-day methane yield (per g chemical oxygen demand (COD) of SCG fed) was significantly higher for the BWW-pretreated SCG (342.4–361.2 mL/g COD) than for the raw SCG (284.7 mL/g COD) and even for the NaOH-pretreated SCG (at the same pH as BWW, pH 12.3) tested for comparison (299.7–320.9 mL/g COD). This significant increase in methane production can be attributed to the presence of readily biodegradable ethanol derived from waste soju in BWW and the alkaline solubilization of SCG. Our results suggest a straightforward way to manage SCG and BWW together in a sustainable and economical manner.

Effects of PODE/diesel blends on particulate matter emission and particle oxidation characteristics of a common-rail diesel engine

The current study focused on the particulate matter emissions of polyoxymethylene dimethyl ethers (PODE)/diesel blends with PODE blending ratios of 0, 10%, 20% and 30% have been experimentally investigated in a common-rail engine. The influences of PODE blending ratio on the smoke emission, particle size distribution and particle oxidation characteristic are discussed. Results show that the addition of PODE in diesel fuel can effectively reduce smoke emission and its decreasing range becomes larger with increasing PODE blending ratio. With the increment in PODE blending ratio, the particle concentration distribution moves towards the direction of small particle size, and the total particle number concentrations decrease. Besides, the peak values of particle number concentration, surface area concentration, and volume concentration are all decreased. Adding PODE in diesel fuel increases the soluble organic fraction (SOF) content of particles, rises maximum weight loss rate of particles, and lower the peak temperature of particles. Also, the activation energy of pyrolysis reaction of particles decreases, which indicates that the oxidation of particles becomes easier as PODE blending ratio increases. The apparent morphology of particles was measured by scanning electron microscope, and the results show that the morphology of particles sample are mostly chain like or flocculent.

Physicochemical and mutagenic analysis of particulate matter emissions from an automotive diesel engine fuelled with fossil and biofuel blends

In this paper, a complete characterization of diesel Particulate Matter (PM) in terms of mass, chemical composition, particles number, size distribution and mutagenic potential was carried out. As a test case, a Euro 5 1.3L passenger car diesel engine fueled with Ultra Low Sulphur Diesel (ULSD) and high-percentage blends (B30 − 30% vol.) of ULSD and biofuels (Rapeseed Methyl Ester, RME, and Hydrotreated Vegetables Oil, HVO) was considered. In addition, PM gravimetric analysis was compared with soot measurements carried out by means of standard laboratory equipment (e.g. smokemeters), showing a good correlation at medium and high load operating points. On the contrary, at low loads, as confirmed by thermo-gravimetric analysis, smokemeter measurements underestimated the Soluble Organic Fraction (SOF) fraction of PM, especially when for RME (B30). Then, a detailed investigation on Particles Number (PN) and size distribution was carried out, running the engine with the same fuel matrix. The results showed that adopting biofuel blends, both RME (B30) and HVO (B30), produces negligible differences in particles number distributions with respect to standard diesel. Finally, the analysis of the mutagenic potential of PM samples highlighted an increased genotoxicity for HVO (B30) and a decreased genotoxicity for RME (B30) with respect to ULSD.

Ultrafiltration pretreatment enhances membrane distillation flux, resilience and permeate quality during water recovery from concentrated blackwater (urine/faeces)

In this study, the pretreatment of concentrated blackwater using ultrafiltration (UF) was shown to improve the permeability, selectivity and robustness of membrane distillation (MD) for application to wastewater treatment. Concentrated blackwater comprises urine and faeces, with minimal flushwater added. The faecal contribution increased the soluble organic fraction and introduced coarse and colloidal particles into the urine, which increased resistance to filtration during dead-end UF. Ultrafiltration removed the particulate and colloidal fractions (MW > 500 kDa) from the blackwater, which permitted similar permeability and robustness for MD to that observed with urine (29.9 vs 25.9 kg m−2h−1), which comprises a lower colloidal organic concentration. Without UF pretreatment, a higher density organic layer formed on the MD surface (197 vs 70 gCODm−2) which reduced mass transfer, and transformed the contact angle from hydrophobic to hydrophilic (144.9°to49.8°), leading to pore wetting and a dissipation in product water quality due to breakthrough. In comparison, with UF pretreatment, MD delivered permeate water quality to standards satisfactory for discharge or reuse. This is particularly timely as the ISO standard for non-sewered sanitation has been adopted by several countries at a national level, and to date there are relatively few technologies to achieve the treatment standard. Membrane distillation provides a robust means for concentrated blackwater treatment, and since the energy required for separation is primarily heat, this advanced treatment can be delivered into areas with more fragile power networks.

Specific Adsorption of Heavy Metals in Soils: Individual and Competitive Experiments

The partitioning between the soil solid phase and the soil solution determines the mobility of pollutants like heavy metals. If nonspecific sorption takes place, the reactions are easily reversible and heavy metals are released to soil solution increasing the probability of leaching through soil profile. Mobility and leaching are also favoured if other metals are in the system and competition for specific adsorption sites takes place. In this study, desorption equilibrium experiments were conducted after adsorption ones. The specific adsorption was evaluated through the amounts of the still adsorbed Cu, Pb, Cr, Ni and Zn after desorption experiments in ten different soils. In addition, competition adsorption and desorption binary experiments were conducted for evaluating the metal competition in three of the soils. Pb and Cu are the metals adsorbed and retained in higher amounts in all the studied soils. In slightly neutral soils, Cr is retained in lesser amounts while in acidic soils Zn is the metal less retained. Results showed that despite the high and variable amounts of organic matter in the soils, soil pH is the most important variable in neutral soils. In acidic soils, soil properties different than pH play important roles and specific sorption of Pb is related to the cationic exchange capacity of the soils while that of Zn to the clay content. Instead, the release of Cu during desorption experiments is probably due to the more soluble organic fraction of the soils. The individual retention of Cu, Zn, Ni and Pb is higher than when they are in competition, except if Cr is present. In this case, the amount of those four metals and that of Cr increased. Therefore, the presence of Cr together with cationic heavy metals favoured the adsorption of those metals in multi-metal polluted areas. Specific adsorption is also important during competition as soil affinities increase during competition experiments.

Study on physicochemical properties of biodiesel and Fischer–Tropsch diesel exhaust particle

ABSTRACT In this study, the physicochemical properties of exhaust particulate matter (PM) from the combustion of biodiesel, Fischer–Tropsch (F-T) diesel, and diesel are studied. The experiment was carried out on the four-stroke air-cooled single-cylinder diesel engine under the same engine operating conditions. The microstructure, particle size, box-counting dimension, element, and oxidation characteristics of the particles were studied. The results show that, compared with diesel particles, the average particle size of biodiesel particles is reduced by 10.8%, and the average particle size of F-T diesel particles is reduced by 27%. Biodiesel particles are closely arranged, followed by diesel particles, and F-T diesel particles are loose. Compared with diesel particles, the relative content of O element in biodiesel particles is high, and the relative content of O element in F-T diesel particles is low. The content of soluble organic fraction (SOF) in biodiesel, diesel, and F-T diesel particles was 23.4%, 17.6%, and 12.7%, respectively. In addition, compared with diesel particles, the activation energy of biodiesel particles is the lowest, while the activation energy of F-T diesel particles is the highest, it means that oxidation of biodiesel particles is more actively.

Application of Boehm Titration for the Quantitative Measurement of Soot Oxygen Functional Groups

The oxygen functional groups on diesel soot have potential effects on its oxidation reactivity, which is of great importance for diesel particulate filter (DPF) operation. For the quantitative measurement of oxygen functional groups on diesel soot, Boehm titration was adopted and procedures considering CO2 removal and sample characteristics involving sample mass as well as the interferences of soluble organic fractions (SOFs) were evaluated to ensure the titration precision possible. Titration was also conducted on samples of nitric acid (HNO3)-modified soot as well as real soot samples and the results were combined with X-ray photoelectron spectroscopy (XPS) analysis to verify the reliability of titration procedures. Results showed that heating at 105 °C for 90 min can eliminate CO2 interference to an acceptable extent. Integrated with mixing and titration error, a sample mass of 70 mg showed the best repeatability. Very little oxygen functional groups were detected for pure diesel oil. Titration with samples varied in SOF content showed a comparable amount of oxygen functional groups, indicating that SOF wrapped around soot surface had little physical and chemical effect on titration. Titration tests with HNO3-modified samples correctly reflect the changing trend of oxygen functional groups after acid treatment, which was further verified by XPS analysis. However, due to the relatively large standard deviation and error propagation, the concentration value of oxygen functional groups calculated by subtraction often showed a large error range, especially for low-concentration samples. Titration error was much lower for high-concentration samples. For real diesel soot, much higher concentrations of 941 ± 119, 376 ± 151, and 903 ± 106 μmol/g were measured for phenolic hydroxyl, lactones, and carboxyl groups, respectively. In all, the Boehm titration process conducted in this article showed the capability and reliability of the quantitative measurement of oxygen functional groups on soot surface. Coupled with XPS analysis, more information about the current state and possible transformation process of carbonyl groups and the possible distribution of functional groups between internal and external surfaces can be inferred.