•Contact angle of bubble on coal surface decreased with the increasing roughness.•Induction time of bubble on coal surface increased with the increasing roughness.•To explain the experiment result, ...the famous Wenzel theory was used.•Water pocket phenomenal was introduced to descript the bubble trapping test.•Rough surface entrapped water preventing spreading of three-phrase contact line.
The wettability of coal is an important parameter for representing the surface hydrophobicity and floatability of coal particle, and hence determines coal flotation behavior. The wettability of coal is primarily governed by the surface functional groups. However, the role of surface topography in the wettability of coal has not attracted enough attentions. This paper was to investigate the effect of roughness on the wettability of coal by measuring the contact angle between air bubble and flat coal surface. Besides, a new method to measure the contact angle is introduced. The shape of the bubble is fitted by both the circle and the ellipse. The lump coal particles were used as coal sample and polished by sand papers of different meshes to gain the specific flat coal surfaces of different roughness. The attachment time measurements and Wenzel theory were used to further explain why the surface roughness has significant effects on the contact angle of air bubble on coal surface. Throughout this paper, it was found that the wettability of coal was decreased with the increase of surface roughness. The water may be entrapped in the pores/cracks of rough coal surface which prevents the attachment between coal surface and bubble as well as the spreading of three-phrase contact line. Therefore, both the attachment time and contact angle were decreased with the increase of roughness.
•XPS and SEM were used to indicate surface properties of bituminous coal.•Natural weathering processes of bituminous coal were conducted on the roof.•Weathering processes changed surface chemical ...composition of bituminous coal.•Weathering processes changed surface topography of bituminous coal.•Natural weathering processes made bituminous coal surface more hydrophilic.
In this investigation, XPS and SEM were used to indicate the changes in surface properties of bituminous coal during natural weathering processes. Natural weathering processes of bituminous coal were conducted on the roof. XPS results showed that the content of CC and CH groups on bituminous coal surface decreased but the content of CO, CO, and OCO groups increased after natural weathering processes. Meanwhile, the contents of Al and Si elements on bituminous coal surface were also increased. SEM results showed that the surface roughness of bituminous coal was increased after natural weathering processes. Natural weathering processes not only changed surface chemical composition of bituminous coal but also changed surface topography of bituminous coal. In addition, natural weathering processes made bituminous coal surface more hydrophilic.
α-Synuclein (α-Syn) can form different fibril strains with distinct polymorphs and neuropathologies, which is associated with the clinicopathological variability in synucleinopathies. How different ...α-syn fibril strains are produced and selected under disease conditions remains poorly understood. In this study, we show that the hereditary mutation G51D induces α-syn to form a distinct fibril strain in vitro. The cryogenic electron microscopy (cryo-EM) structure of the G51D fibril strain was determined at 2.96 Å resolution. The G51D fibril displays a relatively small and extended serpentine fold distinct from other α-syn fibril structures. Moreover, we show by cryo-EM that wild-type (WT) α-syn can assembly into the G51D fibril strain via cross-seeding with G51D fibrils. Our study reveals a distinct structure of G51D fibril strain triggered by G51D mutation but feasibly adopted by both WT and G51D α-syn, which suggests the cross-seeding and strain selection of WT and mutant α-syn in familial Parkinson's disease (fPD).
Low rank/oxidized coals are difficult to float with oily collectors. The presence of polar hydroxyl, carbonyl, phenol groups and some peroxide type oxygenated moieties on the surface of low ...rank/oxidized coals is the main factor which decreases the coal hydrophobicity. Pretreatments may be used to enhance the flotation of low rank/oxidized coals due to improved hydrophobicity. The primary methods of pretreatments are grinding, premixing/preconditioning, ultrasound, thermal, microwave and direct contact mixing of the reagents with dry coal before wetting. Among these pretreatment methods, grinding, premixing/preconditioning may be considered to remove the oxide layer on the oxidized coal surface, which is also reflected by ultrasound treatment. Thermal and microwave treatments are attributed to the removal of pore water, hydration water and some hydroxy functional groups in low rank/oxidized coals. Direct contact procedure makes the oxidized coal avoid the prevention for the collectors absorbing on the coal surface. The prevention usually comes from hydration shell on wet coal surface while the coal is wetted by water. This review is to highlight the effect of different pretreatment methods on the flotation of low rank/oxidized coals.
This review is to highlight the effect of different pretreatment methods on the flotation of low rank/oxidized coals. Display omitted
► Pretreatments may be used to enhance the flotation of low rank/oxidized coals. ► This review is to highlight different pretreatment methods. ► Low rank/oxidized coals are difficult to float with oily collectors.
Human heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) serves as a key regulating protein in RNA metabolism. Malfunction of hnRNPA1 in nucleo-cytoplasmic transport or dynamic phase separation ...leads to abnormal amyloid aggregation and neurodegeneration. The low complexity (LC) domain of hnRNPA1 drives both dynamic phase separation and amyloid aggregation. Here, we use cryo-electron microscopy to determine the amyloid fibril structure formed by hnRNPA1 LC domain. Remarkably, the structure reveals that the nuclear localization sequence of hnRNPA1 (termed PY-NLS), which is initially known to mediate the nucleo-cytoplamic transport of hnRNPA1 through binding with karyopherin-β2 (Kapβ2), represents the major component of the fibril core. The residues that contribute to the binding of PY-NLS with Kapβ2 also exert key molecular interactions to stabilize the fibril structure. Notably, hnRNPA1 mutations found in familial amyotrophic lateral sclerosis (ALS) and multisystem proteinopathoy (MSP) are all involved in the fibril core and contribute to fibril stability. Our work illuminates structural understandings of the pathological amyloid aggregation of hnRNPA1 and the amyloid disaggregase activity of Kapβ2, and highlights the multiple roles of PY-NLS in hnRNPA1 homeostasis.
In this investigation, we discussed the flotation behavior of oxidized coal treated by different pre-wetting times. The pre-wetting time is 1min, 2min, 3min, 4min and 5min, respectively. X-ray ...photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle measurements were used to indicate the surface properties of oxidized coal. XPS results show that the hydrophobicity of oxidized coal is very low and the oxidized coal should be pre-wetted quickly as there are many hydrophilic functional groups and few hydrophobic functional groups on the oxidized coal surface. In addition, there are also many cracks and holes on the oxidized coal surface from SEM pictures. The cracks and holes should be covered or filled up with water during pre-wetting process. Contact angle measurement results show that the contact angle between the water drop and oxidized coal surface decreases rapidly with the increase of measurement time. Both of the combustible matter recovery and concentrate ash content decrease with the increase of pre-wetting time.
XPS, SEM and contact angle measurements indicate why oxidized coal is difficult to float. Oxidized coal has many hydrophilic functional groups, such as C═O, C―O and COOH. There are few hydrophobic functional groups, such as C―H and C―C. There are also lots of cracks and holes on oxidized coal surface which can be filled with the water. Display omitted
•The pre-wetting time is 1min, 2min, 3min, 4min and 5min, respectively.•The pre-wetting time has a significant effect on oxidized coal flotation.•XPS and SEM were used to indicate surface properties of oxidized coal.
Coal spontaneous combustion can make coal suffer a high temperature heating process. This heating process can change physical and chemical properties of coal, but the changes in the hydrophobicity of ...coals before and after high temperature heating process have not been investigated adequately since the natural hydrophobicity of coal usually determines the flotation behavior of fine coals. Therefore, this paper is to investigate the changes in the hydrophobicity of coals before and after the high temperature heating process. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate these changes. The heating temperature was 600°С. The heating times were 0 (original coal), 10, 20, 60, and 120min, respectively. An ultra-low-ash anthracite coal with ash content of 1.55% was used to conduct the high temperature heating process in the laboratory. Throughout this study, the hydrophobicity of anthracite coal can be reduced quickly after high temperature heating process since the content of hydrophilic functional groups on anthracite coal surface is increased while the content of hydrophobic functional groups is reduced by the high temperature heating process.
High temperature heating process reduces the content of hydrophobic functional groups (CH and CC) but increases the content of hydrophilic functional groups (CO, CO and COOH) The contact angles of heated anthracite coals are much lower than that of fresh (original) anthracite coal. After the high temperature heating process, anthracite coal surface becomes more hydrophilic. Display omitted
•XPS and contact angle were used to indicate surface properties of anthracite coal.•High temperature heating process makes anthracite coal surface more hydrophilic.•Coal surface can be wetted quickly after high temperature heating process.
The oxidized coal should be well recovered as the demand for energy is increasing. But the hydrophobicity of oxidized coal is much lower than that of fresh coal, the improvement in floatability of ...oxidized coal is a key issue. Microwave pretreatment is used to improve the floatability of oxidized coal in this investigation. FTIR was used to show the changes in the main functional chemical groups of microwave treated oxidized coal at different times. The moisture content of microwave treated oxidized coal at different times was also measured. The results of FTIR and moisture content measurements show that microwave pretreatment seems to have weak effect on the chemical properties of oxidized coal surface but can reduce the moisture content. The results of flotation tests show that the combustible recovery increases with microwave pretreatment time. The mechanism of microwave pretreatment improving the floatability of oxidized coal is discussed in this investigation.
The combustible matter recovery of oxidized coal increases with the increase of microwave pretreatment time and/or the decrease of moisture content. The main purpose of microwave pretreatment, enhancing the oxidized coal flotation may be, to reduce the moisture content of oxidized coal and weaken the peak at 3450cm−1 as observed from FTIR spectrums. Display omitted
► Microwave pretreatment is used to improve the flotation of oxidized coal. ► Microwave pretreatment can reduce the moisture content. ► Combustible matter recovery increases with microwave pretreatment time.
•XPS, SEM and contact angle were used to indicate surface properties of coal.•Storing coal inside can avoid the heavy weathering processes.•Outside weathering processes are more intense than inside ...weathering processes.
XPS, SEM and contact angle measurements were used to indicate the changes in surface properties of anthracite coal before and after inside/outside weathering processes. Weathering processes of anthracite coal were conducted on the roof and in the room respectively. XPS results showed that the content of CC and CH groups on the surface of anthracite coal was decreased after weathering processes while the content of CO, CO and OCO groups was increased. SEM results showed that the surface roughness of anthracite coal was increased after the weathering processes. Contact angle measurements showed that the contact angle of weathered coal was lower than that of fresh coal. Throughout this paper, it was found that inside weathering processes were less intense than outside weathering processes. The hydrophobicity of anthracite coal was less changed by inside weathering processes than outside weathering processes. Hydrophobic coal surface should be more useful for the flotation processes of fine coals than hydrophilic coal surface. It was recommended that storing coal inside, such as in the room or in the raw coal barns could avoid the heavy weathering processes.
The filtration and dewatering of fine clean coal not only ensure industrial water recycle in coal washing plant, but also reduce the moisture of coal product in order to meet the requirements of ...combustion or coking industry. Fine clean coal is mainly composed by organic matter, and the property difference of different organic matter determines the filtration and dewatering behavior. In this investigation, vitrinite and inertinite were separated from a clean bituminous coal, and the comparative filtration and dewatering behavior of vitrinite and inertinite were conducted. The results showed that inertinite has lower dewatering rate and higher filter cake moisture than vitrinite. The analysis of filter cake structure showed that inertinite particle is easier to be broken into small particles due to the difference of mechanical properties, thus forming more compact filter cake than vitrinite. The analysis of particle surface properties showed that vitrinite is more hydrophobic than inertinite, which makes water easier drained from filter cake. The simulation study showed that the structure of inertinite is more porous than that of vitrinite, and the interaction between inertinite and water is stronger than that between vitrinite and water. This study provides a theoretical basis for improving coal dewatering by selectively improving coal maceral hydrophobicity.
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