Lignite Surface Research Articles

Microscopic adsorption properties of methyl acrylate on lignite surface: Experiment and molecular simulation study

Quality improvement of low-rank lignite is highly desirable for sustaining the increasing demand for primary fossil fuel. In order to characterize the microscopic adsorption behavior of nonionic methyl acrylate (MA) on the low-rank lignite, the Fourier transform infrared (FTIR) experiments, contact angle instruments, Grand Canonical Monte Carlo (GCMC), and molecular dynamics (MD) simulations were adopted in this study. The FTIR results suggested that the MA can be adsorbed in the oxygen-containing functional group region of lignite during the adsorption process. The adsorption performance of the hydrophilic organic matter of lignite to methyl acrylate was better than that of ash minerals. Contact angle results showed that the adsorption of methyl acrylate can improve the hydrophobicity of lignite. The adsorption of MA on lignite can be divided into monolayer adsorption stage (0–0.8 g/L), towards the critical micelle concentration (CMC) adsorption stage (0.8 g/L-CMC), micellar adsorption stage (CMC-1.6 g/L). From the perspective of saving the dosage of surfactant and improving the hydrophobicity of lignite, 0.8 g/L is the most suitable MA concentration. Finally, molecular simulations demonstrated that the adsorption isotherm of methyl acrylate on lignite surface conformed to the type-Ⅰ Langmuir model, and the adsorption of methyl acrylate on lignite belongs to physical adsorption. Polar water molecules have advantages in the competitive adsorption process between water molecules and MA, while water molecules are greatly affected by temperature.

How does coal interact with organic groups in an aqueous solution?

Interactions between coal matrix and organics are vital for adsorption [1], surfactant adsorption on lignite [2-5], and solid–liquid separation of coal slurry [6-10]. Herein, for studying the interaction between hydrophobic surface (coal surface) and small molecules (organics), we measured interactions between organics [nitro and phenyl, pyridine, phenyl, alkyl chain (hexyl) or cycloalkyl (hexyl)] and the coal matrix (liptinite or inertinite) using atomic force microscopy. The strength of interaction followed the order: nitro and phenyl > pyridine > phenyl > alkyl chain (hexyl) > cycloalkyl (hexyl), and liptinite > inertinite. The liptinite has a greater hydrophobicity than inertinite, the greater the attraction force. The lignite surface and coal slurry were modified in an aqueous solution using five surfactants (dodecyl trimethyl ammonium chloride, DTAC; hexadecyl trimethyl ammonium chloride, CTAC; octadecyl trimethyl ammonium chloride, STAC; hexadecyl dimethyl benzyl ammonium chloride, HDBAC; and cetyl pyridine chloride, CPC). Subsequently, the moisture adsorption on treated lignite coal surface and the sedimentation of the treated tails was compared to characterize hydrophobic modifications which showed the order of CTAC > HDBAC > DTAC > CPC > STAC. Thus, the interaction between coal surface and organics needs to consider two rules: 1) The desolvation or the hydrophobic property of the coal surface; 2) The VDW force of the organics. The nature of the difference between rules No. 1 and 2 is that with the size of hydrophobic molecules increased to a surface, the H-bond structure between water molecules in the around would change a lot, which formats great hydrophobic property or desolvation. SynopsisInteraction between organic reagents and coal reveals the mechanism of restraining moisture reabsorption of lignite and solid–liquid separation of coal slurry by organics.

Adsorption behaviors and mechanisms of Cu2+, Zn2+ and Pb2+ by magnetically modified lignite

The study aims to solve the problems of limited capacity and difficult recovery of lignite to adsort Cu2+, Zn2+ and Pb2+ in acid mine wastewater (AMD). Magnetically modified lignite (MML) was prepared by the chemical co-precipitation method. Static beaker experiments and dynamic continuous column experiments were set up to explore the adsorption properties of Cu2+, Zn2+ and Pb2+ by lignite and MML. Lignite and MML before and after the adsorption of heavy metal ions were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectrometer (FTIR). Meanwhile, the adsorption mechanisms of Cu2+, Zn2+ and Pb2+ by lignite and MML were revealed by combining the adsorption isotherm model and the adsorption kinetics model. The results showed that the pH, adsorbent dosage, temperature, initial concentration of heavy metal ions, and contact time had an influence on the adsorption of Cu2+, Zn2+ and Pb2+ by lignite and MML, and the adsorption processes were more in line with the Langmuir model. The adsorption kinetics experiments showed that the adsorption processes were jointly controlled by multiple adsorption stages. The adsorption of heavy metal ions by lignite obeyed the Quasi first-order kinetic model, while the adsorption of MML was chemisorption that obeyed the Quasi second-order kinetic model. The negative ΔG and positive ΔH of Cu2+ and Zn2+ indicated the spontaneous and endothermic nature reaction, while the negative ΔH of Pb2+ indicated the exothermic nature reaction. The dynamic continuous column experiments showed that the average removal rates of Cu2+, Zn2+ and Pb2+ by lignite were 78.00, 76.97 and 78.65%, respectively, and those of heavy metal ions by MML were 82.83, 81.57 and 83.50%, respectively. Compared with lignite, the adsorption effect of MML was better. As shown by SEM, XRD and FTIR tests, Fe3O4 was successfully loaded on the surface of lignite during the magnetic modification, which made the surface morphology of lignite coarser. Lignite and MML removed Cu2+, Zn2+ and Pb2+ from AMD in different forms. In addition, the adsorption process of MML is related to the O–H stretching vibration of carboxylic acid ions and the Fe–O stretching vibration of Fe3O4 particles.

Microscopic adsorption behaviors of ionic surfactants on lignite surface and its effect on the wettability of lignite

Microscopic adsorption behaviors of ionic surfactants on lignite surface and its effect on the wettability of lignite

Study on the microscopic aggregation behavior of lignite molecules in water

Molecular simulation is a reliable tool for studying the self-aggregation behavior of lignite molecules in a solution. To explore how the molecular structure of lignite influences its aggregation behavior, 13C NMR analysis was first performed to construct its molecular structure. Molecular simulation results show that the extreme regions of the electrostatic potential on the lignite surface mainly appear near the polar functional groups. In a solution, the hydrogen bonding and van der Waals interactions between lignite and water molecules will hinder the self-aggregation of the former ones. The self-aggregation process of lignite molecules can be divided into three stages: Brownian (random) motion, agglomeration, and structural adjustment. Driven by the Lennard-Jones and electrostatic potentials, the lignite molecules gradually aggregate to form a cluster. This process will destroy the hydration film on the lignite surface, ultimately decreasing the number of hydrogen bonds and changing the orientation of the water molecules. Increasing the number of lignite molecules will help their spontaneous aggregation. This work reveals the self-aggregation process of lignite molecules and helps to understand their aggregation behavior in solution. This work provides theoretical guidance for solving the flocculation settlement of slime water.

Study on Adsorption Characteristics of Sulfonate Gemini Surfactant on Lignite Surface

In order to explore the adsorption characteristics of sulfonate gemini surfactants on the surface of lignite, the molecular dynamics simulation method was used, and A kind of sulfonic acid bis sodium salt (S2) and the sodium dodecyl sulfate (SDS) were selected. A binary model of surfactant/lignite adsorption system and a ternary model of water/surfactant/lignite system were constructed, and a series of properties such as adsorption configuration, interaction energy, order parameters, relative concentration distribution, number of hydrogen bonds, etc., were analyzed. The results showed that the adsorption strength of S2 on the surface of lignite was higher than that of SDS. The results indicated that the large-angle molecular chain in S2 tended to become smaller, the small-angle molecular chain tended to become larger, and the angle between the molecular chains and the Z axis tended to be concentrated, making the formed network structure denser during the adsorption process. The number of hydrogen bonds in the water-coal system was 42, and the number of hydrogen bonds in the system after S2 adsorption was 15, which was much lower than the 23 hydrogen bonds in the system after SDS adsorption, and S2 could better adsorb and wrap the oxygen-containing groups on the surface of the lignite. The comparative study of the adsorption characteristics of the two surfactants on the surface of lignite can help us better understand the influence of the surfactant structure on the adsorption strength. The research results have important theoretical and practical significance for developing new surfactants, and enriching and developing the basic theory of coal wettability.

Microscopic adsorption behaviors of ionic surfactants on lignite surface and its effect on the wettability of lignite: A simulation and experimental study

In this study, the microscopic adsorption behaviors of two ionic surfactants, sodium dodecyl sulfonate (SDS) and dodecyltrimethylammonium bromide (DTAB), on the lignite surface were investigated at the molecular level through molecular dynamics simulations. A series of properties of surfactant–lignite adsorption systems, including relative concentration profiles, radial distribution functions, surface areas (surface roughness), mean square displacements, and interaction energies were calculated to illustrate the microscopic adsorption behaviors in detail. Analysis of the equilibrated interfacial properties indicated that the adsorption of SDS on the lignite surface is dominated by van der Waals force and can decrease the surface area (roughness) of lignite. In addition, there is no preferential orientation for SDS adsorption on lignite surface. However, driven by electrostatic attraction, the head group of DTAB can be strongly adsorbed on the lignite surface. Furthermore, it was also found that the effect of surfactant adsorption on the surface wettability of lignite showed the same trends as the adsorption strength. The change in the wettability of lignite resulting from surfactant adsorption was discussed in depth, and the explanations were given based on the charge characteristics of head group of surfactant and adsorption orientation. The simulation evaluations of the adsorption behaviors and wettability alteration of lignite surface caused by these two ionic surfactants agreed well with the existing experimental data. This investigation present here visualized the microscopic characteristics of surfactant adsorption and facilitated a better understanding about the involved mechanism.

Drying kinetics and upgrading characteristics analysis of Zhaotong lignite with microwave deep drying

ABSTRACT Dewatering is considered as extremely significant and primary step to enhance the quality of lignite. A great number of research focus on conventional fluidized-bed drying technology or dynamics. In this paper, the microwave deep drying kinetics of Zhaotong lignite under different power levels and with different sample thicknesses were investigated. The drying kinetics of microwave deep drying was fitted by 13 different drying models given in the literature. Experimental results indicated that the microwave deep drying process exists three segments: increasing-rate, falling-rate and brief constant-rate segment. The drying time decreased and drying rate increased with microwave output power level increase, while the microwave penetration depth in lignite was affected by sample thickness, hence there is an irregular relationship between lignite sample thickness and microwave drying time or drying rate. Based on non-linear regression analysis, the Page model was considered adequate to describe the microwave deep drying behavior of Zhaotong lignite under various conditions, and the model could be used for residual moisture water content prediction at any time during the microwave deep drying process. Effective diffusion coefficient increased along with microwave output power level increase. The activation energy of the moisture emission from the lignite under different power levels was estimated at 10.2202 W/g using modified Arrhenius equation. The pore structure damage was observed in the lignite samples after microwave deep drying by SEM analysis. The surface of upgraded lignite had visible cracks, defects and small fragments compared with the samples by conventional drying.

Generating of Electric Energy by a Declined Overburden Conveyor in a Continuous Surface Mine

Exploitation of lignite in continuous surface mines requires removing masses of overburden, which are hauled to a dumpsite. There are some technological arrangements where the overburden is transported several dozen meters down to a spreader operating on a lower located dumping level. Depending on an angle of a declined transportation route, there is a possibility to convert the potential gravitational energy of conveyed down overburden masses into electric energy. To recover the maximum percentage of stored energy, an energy-effective and fully loaded belt conveyor should work in a generator mode. Due to the implementation of such a solution, a lignite continuous surface mine, which is a great electric energy consumer, can obtain the status of an electricity prosumer and reduce its environmental impact, in particular demonstrating significant savings in primary energy consumption. Though lignite surface mining is phasing out in Europe, the recuperative, overburden conveyors for downhill transport match up the targets of sustainable mining, understood as getting the maximum benefits from the exploited natural resources. According to the analyzed case study, an investment into the installation of regenerative inverters for the electric power supply of the declined overburden conveyor would pay off within 3–4 years.

Effect of Hydrothermal Dehydration on the Slurry Ability of Lignite.

The high moisture content limits the large-scale utilization of lignite. Hydrothermal dehydration (HTD) has been confirmed as an effective method to improve the quality of lignite for further utilization. In this study, the effects of the changes in the lignite interface properties caused by the HTD modified final temperature on the slurry ability were investigated in the range of 160–200 °C. The results indicated that with the gradual rise of the HTD modified final temperature, the content of the carboxyl groups and phenolic hydroxyl groups on the surface of lignite decreased by 21.95 and 36.34%, respectively. In the meantime, the atomic ratio of oxygen/carbon, the content of equilibrium moisture, and the thickness of the hydrated film were reduced from 0.293, 14.63%, and 34.26 nm to 0.252, 9.43%, and 13.33 nm, respectively. Therefore, these changes of interfacial properties improved the slurry ability of lignite, with higher fixed-viscosity solid concentration, lower yield stress, increased pseudo-plasticity, and gradually decreased static stability of the prepared lignite coal water slurry. hydrothermal dehydration; slurry ability; oxygen-containing functional groups; hydrated film

Adsorption of ammonia nitrogen and phenol onto the lignite surface: An experimental and molecular dynamics simulation study

Ammonia nitrogen and phenol are typical inorganic and organic pollutants in the coal chemical wastewater, respectively. In this study, the adsorption characteristics of ammonia nitrogen and phenol on lignite were investigated through experimental and molecular dynamics simulations. The results show that the adsorption of ammonia nitrogen was carried out via ion exchange, which was significantly faster than the adsorption of phenol driven by the π–π interaction. In the binary adsorption, the surface electronegativity of lignite decreased with the adsorption of ammonia nitrogen thereby promoting the adsorption of phenol. However, the extent of ammonia nitrogen adsorption was slightly reduced in the presence of phenol. Molecular dynamics simulation results indicated that the adsorption of phenol molecules on the lignite surface was closer than that of ammonium ion. The addition of ammonium ions could enhance the adsorption of phenol molecules on the lignite surface. The simulation results were well consistent with the experimental findings. This study indicates lignite has a promising potential in coal chemical wastewater adsorption pretreatment.

Enhanced lignite flotation using interfacial nanobubbles based on temperature difference method

Froth flotation is the primary method for the separation and upgrading of fine coal particles. However, this method is ineffective for lignite which is more hydrophilic than other types of coal due to the abundant oxygenated functional groups, cracks, and micropores on its surface. This study develops a new method that introduces interfacial nanobubbles (INBs) based on the temperature difference method for enhancing lignite flotation. The mechanism of lignite flotation enhanced by INBs is systematically explained through the induction time and bubble-particle collision-attachment behavior. The experimental results show that the lignite flotation efficiency is evidently improved using the temperature difference method. AFM imaging of the changes on a highly oriented pyrolytic graphite surface due to temperature difference demonstrate the production of INBs. In the presence of INBs, the induction time of lignite can be reduced from 400 ms to 27.21 ms, the number of bubble-particle collisions from 4 to 3, and the attachment time from 208 ms to 128 ms. When a macroscopic air bubble approaches to a lignite surface with INBs, the air bubble first merges with the INBs, not only decreasing the induction time but also increasing the apparent contact angle and length of three-phase contact line.

The Effect of Hydrothermal Treatment on Structure and Flotation Characteristics of Lignite and a Mechanistic Analysis.

Lignite is difficult to obtain highly efficient indexes by conventional flotation due to its poor surface hydrophobicity. Although the modification of flotation reagents has made some progress in improving the flotation performance, they all remain at the stage in the laboratory. Here, we proposed to improve the flotation performance by hydrothermal treatment dewatering (HTD) for lignite. Combined with the 13C NMR and FT-IR analysis, the impact of the HTD process on lignite’s chemical structural evolution and flotation performance was investigated. The results showed that the HTD process is an effective means for dehydration and deoxygenation to increase lignite quality and the metamorphic degree of coal. The content of oxygen-containing functional groups generally decreases during the HTD process, especially carboxyl acid and ether groups. Therefore, surface properties and wettability of HTD coal samples were changed, and the contact angle gradually increases with the HTD temperature increased, which enhance the hydrophobicity and decrease hydrophilia of the lignite surface. The HTD process effectively improves the flotation performance of lignite during the conventional flotation operation condition, even if the coal pulp after HTD was directly used as a flotation feedstock. Specifically, the coal oil and capryl alcohol were used as collector and forming agents, respectively, and the pulp concentration was adjusted to 60 g/L. The yield of the cleaned coal increased from 12.14% of the raw coal to 55.58% of HTD310, and combustible matter recovery increased from 13.83% of the raw coal to 65.17% of HTD310 by raw coal basis.

A numerical solution to the effects of surface roughness on water\u2013coal contact angle

Coal dust is a great threat to coal mine workers' health and safety in coal mine production. Wet dust removal is one of the effective dust removal methods. As a solid, coal has different rough surfaces, which have a certain effect on the wetting effect of coal. In this paper, three coal samples with different surface wettability are used as the research objects. Phase-field interface tracking method is used to simulate the wetting of droplets on rough surfaces. From the simulation results, it can be concluded that the influence of the rough interface on the contact angle of the droplets is in accordance with the change rule described in the Wenzel model. As the roughness increases, the contact angle of the hydrophilic lignite surface gradually decreases. As the roughness increases, the contact angle of hydrophobic coking coal gradually increases. The change trend of the contact on the surface of weakly hydrophilic anthracite coal is the same as that of lignite. Due to the local and global differences, the contact angles obtained from the numerical model are slightly different from the values calculated from the Wenzel model.

Evaluation of surface mining areas through geospatial analysis. The case of Ptolemais lignite mines

The lignite surface mines often occupy large areas to develop the mining activities: pits, dumping areas, bunkers, buildings, workshops, and other auxiliary facilities. The land reclamation methods and the corresponding land use alternatives after the mine closure constitute an important part of an integrated mining planning. In the present contribution, the main parameters of geospatial planning are investigated in order to assess the changes in land uses in a mining area and to correlate them with the spatiotemporal development of the extraction works. As a case study, geospatial analysis of the current situation in Ptolemais mines is presented. In particular, seven dumping areas are assessed regarding their suitability for specific land uses. The assessment is based on the following criteria: a) slope gradient, b) reclamation works already completed, c) slope aspect, d) proximity to the road network, and e) proximity to residential areas. Furthermore, the ArcGis software is used to compile the layer maps of the corresponding parameters.

Method for the adsorption of surfactants by lignite in a dry condition using mechanical mixing

Previous studies verified that the moisture adsorption on the lignite can be reduced by adsorption of surfactant on the surface. However, these surfactant adsorption processes were realized in aqueous solutions, result in a great deal of water bring into the system. It seems that the surfactant is affinity to the surface of lignite and the adsorption can be realized in dry condition with a well-designed method. In this study, we propose a method to reduce the adsorption of moisture by lignite in dry condition, by mechanically mixing it with a surfactant in a ball mill. The surfactant is adsorbed by the lignite surface toward due to the electrostatic interactions during the mixing process, which makes the lignite surface hydrophobic. Untreated and treated samples of lignite were exposed in an environment of 100% relative humidity, maintained at 20 °C, for 36 h. Compared to the untreated sample, the moisture content in the treated sample decreased from 25.9% to 11.6%. This reduction in the adsorbed moisture content is due to the modification of the hydrophobicity of the original sample. The particle size of the lignite decreases significantly after ball milling. As the particle size required for the commercial utilisation of lignite is usually low, the proposed method can be applied after the dry beneficiation process.

Determining the effect of the non-ionic surfactant AEO9 on lignite adsorption and wetting via molecular dynamics (MD) simulation and experiment comparisons

By combining a molecular dynamics (MD) simulation approach with experimental measurements, this study elucidated the molecular interactions between the fatty alcohol polyoxyethylene ether-9 (AEO9; i.e., a surfactant) and lignite. Moreover, the micro-dynamic process of wetting and adsorption of surfactant molecules onto coal dust molecules were also studied. In the wettability test, the evaporation rate of coal decreased significantly after AEO9 addition. The measured contact angle first decreased and then increased with increased AEO9 concentration. A lower contact angle was indicative of better wetting performance. Using the Materials Studio software, the motion process of the water/AEO9/lignite system was simulated. The resulting structural chart indicated that AEO9 can be adequately adsorbed onto the coal surface. By analyzing the changes in the relative concentration curves along the Z-axis and water mobility before and after AEO9 addition, it was found that AEO9 can enhance the hydrophilicity of lignite. The simulated adsorption isotherms and the calculated interaction energy between molecules suggested simultaneous adsorption onto the lignite surface. X-ray photoelectron spectroscopy (XPS) analysis also revealed that the elemental C content of the surface decreased while the O content increased after coating the lignite surface with AEO9. Given that a great number of oxyethylene groups are present in AEO9, we concluded that AEO9 efficiently adsorbed onto the lignite surface. The present study is of great significance to the enhancement of dust suppressant performance and reducing coal dust hazards.

Molecular dynamics simulation and experimental characterization of anionic surfactant: Influence on wettability of low-rank coal

The influence of the anionic surfactant sodium fatty alcohol polyoxyethylene ether carboxylate (AEC) on the wettability of coal surfaces was studied by combining molecular dynamics simulations and experimental research. First, a molecular dynamics simulation of the AEC adsorption process on a low-rank coal surface was carried out. The simulation results show that AEC promotes the adsorption of water molecules on the coal surface, moves more water molecules to the coal surface, and improves the mobility of water molecules; AEC molecules were detected at the coal-water interface. After adsorption, the AEC molecules were connected to each other through alkyl chains to form a spherical-like structure, which covered the coal surface laterally. The calculated interaction energy between coal and water is negative, which shows that the adsorption process is spontaneous, and AEC enhances the interaction between coal and water. Second, the abovementioned simulation results are verified by experiments. The adsorption experiments show that AEC adsorbs on the lignite surface by monolayer adsorption, which can be described by the Langmuir isothermal adsorption equation; the contact angle first increases and then decreases, reaching a maximum near the critical micelle concentration (CMC). The XPS analysis shows that the change in the content of the oxygen-containing functional groups is the main reason for the wettability of the lignite surface. Among these oxygen-containing functional groups, the C-O group has the most significant effect on the wettability.

From wasted sludge to valuable biochar by low temperature hydrothermal carbonization treatment: Insight into the surface characteristics

In this study, the hydrothermal carbonization (HTC) technology at low temperature was applied to convert the wasted sludge into biochar, by establishing the correlation between the operation conditions and biochar characteristics. The contents of C, H, O, N and S, and the values of (O + N)/C and O/C in biochar were negatively correlated to the temperature, retention time and initial pH conditions. This implies that increasing temperature and retention time are beneficial for sludge dewatering and reduction. The maximum high heating value of biochar at 15.21 MJ/kg was achieved, which is similar to the cellulosic biochar and lignite surface known as the primary renewable fuel. The typical macromolecules such as proteins and lipids still existed on the biochar surface after low temperature HTC treatment. Decreasing the initial pH enforced the protonation effect and structural stability of the organic macromolecules in sludge, resulting in a diverse morphology with more compact microspheres on the biochar surface. Particularly, the catalytic ability to generate the carbon-centered persistent radicals was enhanced with g-factor at 2.01138–1.98428. In terms of environmental safety, the detected concentrations of heavy metals (Zn, Pb, Cu and Al) during the secondary dissolution of biochar were below 0.25 mg/L, indicating the low leaching risk for the land application. In addition, some humic acid and fulvic acid analogues were also detected in the secondary dissolution liquid, which can facilitate the redox reaction in soil microenvironment. In sum, this study confirmed that the low temperature HTC is a feasible method for sludge treatment and resource recovery.

Preparation and evaluation of lignite flotation collector derived from waste hot-pot oil

Due to poor hydrophobicity, large amounts of petroleum-based collectors are required for upgrading lignite. In this paper, Waste Hot-pot Oil (WHPO) collectors from the catering industry were prepared via filtration, heating, and catalysis. The catalytic experiment was optimized using the Design-Expert software. The optimum catalytic conditions were found to be a pyrolysis temperature of 85 °C, alcohol-oil ratio of 35:1, catalyst dosage of 2%, and reaction time of 1 h. The Separation Efficiency (SE) of WHPO was 3.04 percentage higher than that of the conventional collector (kerosene), while the ash content of Lignite Surface Treated with WHPO (LWHPO) was 1.14 percentage lower than that of kerosene. Response surface methodology was used to analyse the factors influencing the SE; the effect of the studied factors followed the order catalyst amount > alcohol-to-oil ratio > reaction temperature. GC–MS showed that WHPO contained both long-chain alkyl groups and other ester and hydroxyl groups. XPS tests confirmed that the hydrophobic group (CC, CH) content of LWHPO increased, while its hydrophilic group content (except CO) decreased, demonstrating the improved hydrophobicity of lignite after WHPO treatment. FT-IR analysis indicated that WHPO more effectively decreased the content of hydrophilic groups and increased the content of hydrophobic groups than kerosene. Contact angle (CA) analysis showed WHPO was more conducive to lignite surface hydrophobicity improvement than kerosene. WHPO possessed strong collecting ability and better selectivity, and could be used as an alternative collector for lignite flotation.