Ultrafine Particle Size Research Articles

Effect of rice flour ultrafine particle size on β-glucanase inactivation by microwave treatments and pasting properties in treated flours

The main problem in developing gluten-free products enriched with β-glucans (BG) is the hydrolysis they suffer due to the endogenous β-glucanase content of raw materials. The depolymerization causes a decrease in the molecular weight and viscosity, which is the most important parameter related to the health claims of BG. Hence, it is necessary to inactivate the β-glucanase. Therefore, this study aimed to inactivate the β-glucanase activity present in rice flour (Indica variety) with fine particle size using the microwave (MW) hydrothermal treatment method. The rice flour was conditioned at three different humidities 13, 16, 19 and 25%. Samples of 50 g were subjected to different microwave treatments 1, 2, 4 and 8 min, at 900 W power at 20 seconds intervals of treatment and 1-minute rest. The effect of particle size on inactivating the β-glucanase activity and the effect of MW treatment on the flour pasting property were also studied. The inactivation process followed a first-order kinetic response, and the apparent rate constant of thermal inactivation increased exponentially with the moisture content (M) of the flour, according to the equation -0.02t·exp (0.19·M) (R2 = 0.987). Among the treatments employed 4 min treatment at 25% initial M was found effective for complete β-glucanase inactivation. The effect of flour particle size did not show a significant (p> 0.05) difference on the efficiency of β-glucanase inactivation. Keywords: particle size, β-glucans, rice flour, microwave treatment, β-glucanase activity.

Synthesis of High-Loading Pt/C Electrocatalysts Using a Surfactant-Assisted Microwave Discharge Method for Oxygen Reduction Reactions.

High-loading Pt/C catalysts play an important role in the practical application of metal-air batteries and fuel cells because of their superior activity, high conductivity, and commercial availability. It is well known that high loadings always lead to the agglomeration of Pt nanoparticles, resulting in a loss of catalytic activity and stability; thus, it still remains a challenge to prepare high-loading Pt/C catalysts with high dispersion and small particle sizes. Here, we introduce a surfactant-assisted microwave discharge method to prepare high-loading (>40 wt %) Pt/C electrocatalysts with ultrafine particle sizes (∼3.19 nm) and good dispersion. Benefitting from the high-temperature property and reducibility of carbon-induced-arc, the surfactant and Pt precursors undergo rapid decomposition, reduction, and carbonization, generating the structure of Pt@C on carbon black. The carbon derived from the surfactant can not only inhibit the agglomeration of Pt nanoparticles but also prevent the Pt core from toxication, ensuring high activity and stability of the high-loading Pt/C catalyst. When evaluated in the oxygen reduction reaction, the as-prepared Pt/C catalyst demonstrates a comparable activity and better methanol resistance to commercial Pt/C.

An Experimental Study on Behaviour of Concrete by Partial Replacement of Aggregate with Bamboo Pieces and Cement with Alccofine

Abstract: In this paper, we are going to partially replace a coarse aggregate with bamboo pieces and a cement with Alccofine respectively. Alccofine is advanced micro fine material of new generation which is important in terms of workability as well as strength. The main aim of this work is to highlight the importance of bamboo and Alccofine 1203 as a coarse aggregate and cement replacement respectively in construction or concrete industries. ALCCOFINE 1203 of ultrafine particle size is added as a replacement of cement which wills not only help to improve the strength of the concrete but also provide resistance against chloride attack on concrete, sea water attack, and accelerated corrosion attack on concrete. An experimental investigation has been conducted to replace the natural coarse aggregate with different percentages of bamboo aggregate (by weight). The percentage of bamboo added by 0%, 4%, 8%, 12% , 16% , 20% and 24% as partial replacement of coarse aggregate used in concrete. Similarly, the percentage of alccofine added by 0%, 3% , 6%, 9%, 12%, 15% and 18% as partial replacement of cement (by weight) used in concrete.

Ultrafine particle exposure and biomarkers of effect on small airways in children

The small size and large surface area of ultrafine particles (UFP) enhance their ability to deposit in the lung periphery and their reactivity. The Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH) cross-sectional study was conducted in 8–11-year-old schoolchildren attending 25 primary (elementary) schools, randomly selected from the Brisbane Metropolitan Area, Queensland, Australia. Main study findings outlined indirect evidence of distal airway deposition (raised C reactive protein) but as yet, there is no direct evidence in the literature of effects of UFP exposure on peripheral airway function. We present further UPTECH study data from two sensitive peripheral airway function tests, Oscillometry and Multiple Breath Nitrogen Washout (MBNW), performed in 577 and 627 children (88% and 96% of UPTECH study cohort) respectively: mean(SD) age 10.1(0.9) years, 46% male, with 50% atopy and 14% current asthma. Bayesian generalised linear mixed effects regression models were used to estimate the effect of UFP particle number count (PNC) exposure on key oscillometry (airway resistance, (Rrs), and reactance, (Xrs)) and MBNW (lung clearance index, (LCI) and functional residual capacity, (FRC)) indices. We adjusted for age, sex, and height, and potential confounders including socio-economic disadvantage, PM2.5 and NO2 exposure. All models contained an interaction term between UFP PNC exposure and atopy, allowing estimation of the effect of exposure on non-atopic and atopic students. Increasing UFP PNC was associated with greater lung stiffness as evidenced by a decrease in Xrs [mean (95% credible interval) −1.63 (−3.36 to −0.05)%] per 1000#.cm−3]. It was also associated with greater lung stiffness (decrease in Xrs) in atopic subjects across all models [mean change ranging from −2.06 to −2.40% per 1000#.cm−3]. A paradoxical positive effect was observed for Rrs across all models [mean change ranging from −1.55 to −1.70% per 1000#.cm−3] (decreases in Rrs indicating an increase in airway calibre), which was present for both atopic and non-atopic subjects. No effects on MBNW indices were observed. In conclusion, a modest detrimental effect of UFP on peripheral airway function among atopic subjects, as assessed by respiratory system reactance, was observed extending the main UPTECH study findings which reported a positive association with a biomarker for systemic inflammation, C-reactive protein (CRP). Further studies are warranted to explore the pathophysiological mechanisms underlying increased respiratory stiffness, and whether it persists through to adolescence and adulthood.

Efficient Separation of Ultrafine Coal Assisted by Selective Adsorption of Polyvinylpyrrolidone

The efficient separation of ultrafine coal is a challenging process due to the ultrafine particle size and gangue entrainment. In this study, a polymer, polyvinylpyrrolidone (PVP), was introduced as a regulator for ultrafine coal beneficiation. The addition of PVP improved the combustible recovery of clean coal and decreased the ash content. This effect was also presented by the selectivity index. The regulation mechanism of PVP was investigated using diverse methods. The adsorption tests performed demonstrated the adsorption amount of PVP on coal, kaolinite, and quartz, which were related to the increase in the separation efficiency. A zeta potential analyzer was employed to elucidate the effect of PVP on the electrical properties of ultrafine particles. The results revealed that the electrokinetic potential of mineral was sensitive to the varying PVP concentration. The particle size distribution was observed to value the influence of PVP on the particle behavior, which was tested by a laser particle size analyzer. X-ray photoelectron spectroscopy was used to investigate the surface elemental compositions of coal, kaolinite, and quartz, which were regulated by the adsorption of PVP. This research is beneficial to understanding the role of PVP as regulators and provides a basis for the efficient separation of ultrafine coal.

Exfoliation of graphitic carbon nitride and homogeneous loading of Cu2O catalyst

In order to get desired Cu2O catalyst on two-dimensional (2D) g-C3N4, bulk melamine-derived g-C3N4 with a very small specific surface area was exfoliated first and then Cu2O catalyst was loaded using solvothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Electrochemical impedance spectroscopy (EIS), N2 adsorption/desorption and Fourier transform infrared (FT-IR) techniques as well as catalytic evaluation were performed to investigate the structure-properties relationship of the composite catalyst. The results show that the as-prepared Cu2O catalyst with the exfoliated g-C3N4 as support not only exhibits a uniform dispersion of Cu2O nanoparticles with ultrafine particle size, but also inherits a large specific surface area up to 165.3 m2/g that hasn't been reported before for transition metal oxide being supported on 2D g-C3N4 with high loading, in the meantime improved catalytic performance towards the removal of some organic pollutants is obtained.

Simulation of the effects of low-volatility organic compounds on aerosol number concentrations in Europe

Abstract. PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of reactions of chemical aging of semivolatile anthropogenic organic vapors, the emissions and chemical aging of intermediate-volatility organic compounds (IVOCs), and the production of extremely low-volatility organic compounds (ELVOCs) by monoterpenes. The model is applied in Europe to quantify the effect of these processes on particle number concentrations. The model predictions are evaluated against both ground measurements collected during the PEGASOS 2012 summer campaign across many stations in Europe and airborne observations by a zeppelin measuring above Po Valley, Italy. PMCAMx-UF reproduces the ground level daily average concentrations of particles with a diameter larger than 100 nm (N100) with normalized mean error (NME) of 45 % and normalized mean bias (NMB) close to 10 %. For the same simulation, PMCAMx-UF tends to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily NMB of 23 % and a daily NME of 63 %. The model was able to reproduce more than 75 % of the N10 and N100 airborne observations (zeppelin) within a factor of 2. According to the PMCAMx-UF predictions, the ELVOC production by monoterpenes leads to surprisingly small changes of the average number concentrations over Europe. The total number concentration decreased due to the ELVOC formation by 0.2 %, N10 decreased by 1.1 %, N50 (particles with a diameter larger than 50 nm) increased by 3 %, and N100 increased by 4 % due to this new secondary organic aerosol (SOA) source. This small change is due to the nonlinearity of the system, with increases predicted in some areas and decreases in others, but also the cancelation of the effects of the various processes like accelerated growth and accelerated coagulation. Locally, the effects can be significant. For example, an increase in N100 by 20 %–50 % is predicted over Scandinavia and significant increases (10 %–20 %) are predicted over some parts of central Europe. The ELVOCs contributed on average around 0.5 µg m−3 and accounted for 10 %–15 % of the PM2.5 OA. The addition of IVOC emissions and their aging reactions led to a surprising reduction of the total number of particles (Ntot) and N10 by 10 %–15 % and 5 %–10 %, respectively, and to an increase in the concentration of N100 by 5 %–10 %. These were due to the accelerated coagulation and reduced nucleation rates.

Investigation on Variables Contributing to the Synthesis of C-S-H/PCE Nanocomposites by Co-Precipitation Method.

The usage of nanoscale calcium silicate hydrate (nano C-S-H) proved to have an excellent promotion effect on the early performance of concrete as nano C-S-H with ultra-fine particle size can act as seeding for cement hydration. Therefore, it is of importance to tune the particle size during the synthesis process of nano C-S-H. In this paper, the influence of several variables of the particle size distribution (PSD) of nano C-S-H synthesized by chemical co-precipitation method with the aid of polycarboxylate (PCE) was studied by orthogonal experimental design. In addition, the composition, microstructure, and morphology of the C-S-H/PCE nanocomposites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectrum. The results showed that the concentration of reactants had a significant impact on the PSD of C-S-H/PCE nanocomposites, followed by the dosage of dispersant. Ultrasonic treatment was effective in breaking the C-S-H/PCE aggregates with unstable agglomeration structures. The change in synthetic variables had a negligible effect on the composition of the C-S-H/PCE nanocomposites but had a significant influence on the crystallinity and morphology of the composites.

Size and charge distribution characteristics of fine and ultrafine particles in simulated lunar dust: Relevance to lunar missions and exploration

Astronaut anecdotal data, biologic studies, and multi-perspective reports indicate that lunar dust will be a significant hindrance to exploring the Moon, both robotically and by humans. Hence, important characteristics of the lunar dust must be established. Critically needed are detailed particulate matter size, dust cloud concentration, and charge distribution analyses to determine the viability of methods for real-time measurement on the lunar surface. In this study, we applied various state-of-the-art aerosol measurement techniques to characterize fine (0.1–2.5 ​μm) and ultrafine (<0.1 ​μm) JSC-1A lunar simulant particles. The different techniques were assessed at 1 ​atm and evaluated for viability on the lunar surface (i.e., hard vacuum). To represent suspended dust, the simulant was dispersed as an aerosol and size distributions were measured in real-time using multiple aerosol instruments. Results show a unimodal distribution centered at approximately 0.2 ​μm, in fair agreement with previously reported measurements. To demonstrate portability and networkability, two low-cost particulate matter sensors were evaluated for measurement of suspended dust concentration. Strong correlations with an industry standard instrument support the potential candidacy of these sensors for future in-situ measurements on the Moon. Evaluating the capability of compact, low-cost instruments and larger, more robust instruments to precisely and accurately measure particle size distributions is a critical step to determine the prospect of measuring particulate matter with lightweight sensors in multiple lunar environments. In addition, assessing the compact instrument mass, power, portability, complexity, and measurement speed will provide key guidance into mitigating dust-related challenges to future lunar missions.

Metal Organic Framework Derived Cu–Doped Ni2P Nanoparticles Incorporated with Porous Carbon as High Performance Electrocatalyst for Hydrogen Evolution Reaction in a Wide pH Range

AbstractThe development of highly efficient and low cost electrocatalysts for hydrogen evolution reaction (HER) is crucial for electrochemical water splitting, which is considered as the most promising strategy to resolve the problems caused by the overexploit and consume of fossil fuel. Herein, we report the fabrication of copper nickel bimetallic phosphide nanoparticles encapsulated within hierarchical porous carbon (CuxNi1‐xP@PC) based on a bimetallic organic frameworks (BMOFs) assisted phosphorization route. The size‐controlled effect of BMOFs led to the ultrafine particle sizes (average about 10 nm), which possess large active surface area and high dispersity in the final catalyst materials. Remarkably, when investigated as electrocatalysts for HER, the fabricated CuxNi1‐xP@PC composites exhibited outstanding electrocatalytic activity and excellent long‐term stability toward HER at all pH values. It required overpotentials of 102 and 118 mV to reach a current density of 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH solution respectively, as well as Tafel slopes of 85.8 mV dec−1 and 73.1 mV dec−1. This work offers a promising route to explore BMOFs as precursor for the fabrication of hybrid electrocatalysts with high performance toward water splitting.

Sustainable use of normal and ultra-fine fly ash in mortar as partial replacement to ordinary Portland cement in ternary combinations

In fiscal year 2020 about 4.1 billion tonnes of ordinary Portland cement (OPC) is produced across the globe. The demand of cement in pace with construction of buildings and infrastructure is expected to increase year by year. Harmful gases such as carbon dioxide is emitted in to the environment in the process of cement production. Researchers and scientists are trying to reduce the consumption of cement significantly by blending cement with any industrial by-products such as Fly Ash (FA), Slag, Metakaolin, ultra-fine slag (UFS), ultra-fine fly ash (UFFA) etc. The present research aims to investigate the effect of OPC, FA and UFFA in 9 ternary combination. OPC is replaced with FA in proportion of 10, 20 and 30% with 10, 15 and 20% of UFFA, there by examining 9 different ternary combinations. The cost, strength and workability properties of 9 ternary mortar mixes are compared with reference mortar (100% OPC). Due to ultra-fine particle size of UFFA, it was observed that, the ternary mix are capable of providing better early strength, which was not possible with only normal fly ash. The study will help to determine the optimum proportions which can satisfy strength requirements and reduce cement consumption with effective utilization of industrial wastes.

Reduce and concentrate graphene quantum dot size via scissors: vacancy, pentagon-heptagon and interstitial defects in graphite by gamma rays

Graphene quantum dots (GQDs) with ultrafine particle size and centralized distribution have advantages of small size, narrow size distribution and large specific surface area, which make it be better applied in bioimaging, drug delivery and so on. In our research, we used graphite irradiated by γ-rays to successfully prepare GQDs with ultrafine particle size, narrow size distribution and high quantum yields through solvothermal method. Vacancy defects, pentagon–heptagon defects and interstitial defects were introduced to graphite structure after irradiation, which caused the abundance and concentrated distribution of defects. The defects generated by irradiation could damage the lattice structure of graphite to make it easy for introduction of C–O–C inside graphite sheets. The oxygen-containing functional groups in graphene oxide (GO) increased and centrally distributed after irradiation in graphite, especially for C–O–C group, which were beneficial for cutting of GO and grafting of functional groups in GQDs. Therefore, average size of GQDs was successfully reduced to 1.43 nm and concentrated to 0.6–2.4 nm. After irradiation in graphite, the content of carbonyl and C–N in GQDs had a promotion, which suppressed non-radiative recombination and upgraded the quantum yields to 13.9%.

Impact of vehicular pollution on carboxyhemoglobin levels and respiratory response in urban cyclists

BACKGROUND AND AIM: The present case-crossover study evaluated changes in carboxyhemoglobin (COHb) levels and spirometry values of 37 volunteers caused by vehicular pollution on a bike path parallel to a road with a high vehicular flow in two exposure scenarios (high exposure on weekdays and low exposure on Sundays) in the city of Bogotá, Colombia METHODS: For each scenario, ultrafine particles (UFP), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon black concentrations were measured, as well as vehicular flow and speed at two points on the road of interest, to explore the possible associations among these variables and exposure to each pollutant. RESULTS:Significant differences were obtained for UFP, CO, NO2, and SO2 concentrations between the high- and low-exposure scenarios, and between the estimated exposure doses (EED) of UFP, CO, and SO2. A strong correlation was found between the EED of CO and the percentage change in COHb before and after each bike ride (r=0.7571). Concerning UFP, a greater weight of background pollution was found in the high exposure scenario, followed by the impact of meteorological variables, and emission sources along the road under study. CONCLUSIONS:To explain the variability of respiratory parameters, the only statistically significant model was obtained for peak expiratory flow (25-75%) of the forced expiratory maneuver (MMEF25-75%), having EED of CO and average UFP size as explanatory variables. Cyclists arrived at the endpoint of the ride with high COHb levels due to exposure to air pollutants along the route they used to arrive at the study site. KEYWORDS: Air pollution, Mixtures, Biomarkers of exposure, Respiratory outcomes, Short-term exposure

Contributions of traffic emissions and new particle formation to the ultrafine particle size distribution in the megacity of Beijing

The important role of traffic emissions in air pollution has been widely recognized. However, the corresponding contributions to the ultrafine particle distribution and new particle formation (NPF) are poorly understood due to the mixed influences of various sources. Measurements of particle evolution and NPF were made at a heavy traffic site near the 5th Ring Road of Beijing from August 2017 to October 2019. A positive matrix factorization receptor model (version 5.0) consisting of the log-normal fit method and the k-means clustering method was used to identify and quantify the major sources of particle number concentrations. Based on the characteristics of NPF, additional analyses were performed to identify formation sources, including back-trajectory clustering and correlations between auxiliary variables and the relative contributions of all resolved factors. Traffic emissions mainly influenced Aitken mode (25–100 nm) particles (>60%), and NPF significantly contributed to the ultrafine particle distribution (47.2%). Additionally, regional transport notably affected the occurrence of NPF at the observation site, with northwest airmass transport influencing the nucleation mode the most and southeast airmass transport influencing the Aitken mode the most.

Synthesis and characterization of bacterial cellulose/graphene oxide nano‐biocomposites

AbstractBacterial cellulose/graphene oxide (BC/GO) nano‐biocomposites constructed using two methods of in situ and immersion. Scanning electron microscopy showed that a lower amount of GO formed a stronger composite with smaller pores. The in situ method formed a nanostructured composite with an ultrafine particle size distribution. X‐ray diffraction peaks indicated that GO embedded in BC network uniformly. The Young's modulus of the fabricated composites for both methods increased compared to pure BC. DSC analysis showed that the prepared samples were endothermic and in the 350–370°C, the BC/GO sample experienced a 46.9% weight loss. The immersion method formed a composite with higher thermal stability.

Study on the effect of fineness and dosage of fly ash on mechanical properties of concrete

Ultrafine fly ash concrete is one of the main directions for the development of concrete materials in the future. In order to study the mechanical properties of ultra-fine fly ash concrete, the compressive strength, splitting tensile strength and flexural strength of concrete under different ages and different ultra-fine fly ash particle sizes and dosages were tested. (1) The slump of concrete mix under different fly ash particle size increases with the increase of ultrafine fly ash content, but the rate of increase decreases gradually. Under the same fly ash content, the smaller the particle size of ultrafine fly ash particles, the greater the slump of the corresponding fly ash concrete, and it has the exponential relationship between the particle size and the particle size of fly ash. (2) The smaller the particle size of ultra-fine fly ash, the larger the optimum dosage in concrete. When the particle size of ultrafine fly ash is less than 5μm, the optimal dosage of ultrafine fly ash in concrete is 30% to ensure 60d compressive strength. (3) When the concrete curing age is 60d, the splitting tensile strength and flexural strength of ultra-fine fly ash concrete under different particle sizes increase first and then decrease with the increase of ultrafine fly ash content. The law of variation is that the split tensile strength and flexural strength of fly ash concrete are the highest when the content of ultrafine fly ash is 20%-30%.

Improving the physicochemical properties of NaCl-assisted solution combustion synthesized iron oxide nanoparticles by controlling the thermodynamics of the process

Salt-assisted solution combustion synthesis (SSCS) method is a promising technique for synthesizing various nanopowders with ultra-fine particle size and high surface area. It is known that the introduced soluble salt into the synthesis process plays a role as a particle separator which leads to the particle size reduction. However, the potential effects of soluble salts on the thermodynamic aspects of SSCS procedure and the other physical and chemical properties of the obtained nanopowders have not been investigated in detail. In this study, various amounts of sodium chloride (1–15mol for obtaining 0.3mol iron oxide) were introduced to the iron nitrate-glycine system to investigate effect of alkali metal salt on the thermodynamics aspects of the synthesis process and the final properties of the prepared nanoparticles. Obtained results indicated that the phase composition of the synthesized nanopowders was varied from a mixture of Fe3O4+α-Fe2O3 to γ-Fe2O3+α-Fe2O3, and eventually to single-phase α-Fe2O3 by increasing the amount of sodium chloride. Such phase transformation suggested that the phase composition of multi-phase compounds prepared via SSCS method can be controlled by sodium chloride. Ultra-fine powders with 9 nm particle size and surface area of 148 m2/g were obtained when 11mol sodium chloride was used in the synthesis process. Magnetization of the synthesized nanoparticles were decreased from 34emu/g to 2.7emu/g due to the decrement of particle size. The combusted single-phase hematite nanopowders were submitted to the 100 mL nickel ion (Ni2+) solution with the ion concentration of 50 mg/L to explore the effect of salt on the adsorption activity of the nanoparticles. 0.4g of the synthesized powders adsorbed ~90% of the nickel ions within 120 min. Note that the removal percentage of the nickel ion using the synthesized hematite nanoparticle (90%) was higher than that of prepared hematite powders in the previous studies (35%).

Ultradispersed Ir x Ni clusters as bifunctional electrocatalysts for high-efficiency water splitting in acid electrolytes.

Design and synthesis of electrocatalysts with high activity and low cost is an important challenge for water splitting. We report a rapid and facile synthetic route to obtain IrxNi clusters via polyol reduction. The IrxNi clusters show excellent activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic electrolytes. The optimized Ir2Ni/C clusters exhibit an electrochemical active area of 18.27 mF cm−2, with the overpotential of OER being 292 mV and HER being 30 mV at 10 mA cm−2, respectively. In addition, the Ir2Ni/C used as the cathode and anode for the H-type hydrolysis tank only needs 1.597 V cell voltages. The excellent electrocatalytic performance is mainly attributed to the synergistic effect between the metals and the ultra-fine particle size. This study provides a novel strategy that has a broad application for water splitting.

Shipping Remains a Globally Significant Source of Anthropogenic PN Emissions Even after 2020 Sulfur Regulation.

Shipping is the main source of anthropogenic particle emissions in large areas of the globe, influencing climate, air quality, and human health in open seas and coast lines. Here, we determined, by laboratory and on-board measurements of ship engine exhaust, fuel-specific particle number (PN) emissions for different fuels and desulfurization applied in shipping. The emission factors were compared to ship exhaust plume observations and, furthermore, exploited in the assessment of global PN emissions from shipping, utilizing the STEAM ship emission model. The results indicate that most particles in the fresh ship engine exhaust are in ultrafine particle size range. Shipping PN emissions are localized, especially close to coastal lines, but significant emissions also exist on open seas and oceans. The global annual PN produced by marine shipping was 1.2 × 1028 (±0.34 × 1028) particles in 2016, thus being of the same magnitude with total anthropogenic PN emissions in continental areas. The reduction potential of PN from shipping strongly depends on the adopted technology mix, and except wide adoption of natural gas or scrubbers, no significant decrease in global PN is expected if heavy fuel oil is mainly replaced by low sulfur residual fuels. The results imply that shipping remains as a significant source of anthropogenic PN emissions that should be considered in future climate and health impact models.

Recovery of K2SO4 and Separation of SiO2/Al2O3 from Brown Corundum Fly Ash

Brown corundum fly ash (BCFA), which is the collected ash in brown corundum production, has received lots of environmental concerns due to its ultra-fine particle size and complex composition. Aiming to recycle the major elements including K, Al and Si from BCFA environmentally, this work proposed a simple and non-pollution process to utilize BCFA by water leaching, size screening and solution evaporation. The influences of water leaching conditions including leaching temperature, time and liquid-to-solid ratio was considered to optimize the K2SO4 recovery efficiency. Results show that the potassium sulfate content of the product is 75.7% after water leaching at 60 °C for 15 min with the liquid–solid ratio of 20:1. The wet screening and size separation with a 1 μm sieve can separate and enrich aluminum and silicon significantly. The aluminum-rich product is composed of 54.65% of alumina and 11.04% silica, with the alumina and silica ratio (A/S) of 4.95. The silicon-rich product with a particle size of less than 1 μm has a silica content of 57.57% can be used as high-value micro-sphere silica. The research results revealed in this work offers a potential and environmentally industrial treatment technique for the BCFA.