With the deterioration of underground coal quality, hundreds of millions of tons of coal slime in China need to be treated using flotation methods every year. However, the design and selection of coal slurry flotation collectors lack theoretical guidance. In this paper, the quantitative structure–activity relationship (QSAR) model between the molecular structure descriptors of collectors and the flotation recovery and selectivity index is established by using pure kaolinite/clean coal flotation experiments and molecular simulation techniques. Flotation results showed that the flotation recovery rate of kaolinite by collectors with larger head group size, such as DDMAC, DDP, and DTAC, is higher than that of the other collectors with smaller head group size. DDA, DDP, and DD have similar flotation capabilities for clean coal, and their selectivity was slightly better than others. The QSAR model between the molecular structure descriptor and the selectivity index was successfully constructed by combining flotation experiments and molecular simulation results. The reliability of this model has been proven through theoretical analysis and flotation experiments. The molecular simulation results indicate that all eight collectors can advertise on 001 (−) surface of kaolinite, but the final advertisement configuration is different. DDA has less coverage on the surface of kaolinite. When the collector is DDA, the concentration of water molecules near the 001 (−) surface of kaolinite is the highest, indicating that the collector DDA has the weakest effect on improving the hydrophobicity of the 001 (−) surface of kaolinite. DDMAC and DDBAC have the best facilitation to the surface hydrophobicity of kaolinite 001 (−). The research results have theoretical guidance significance for the selection and design of mineral flotation collectors.

As a general coal flotation collector, diesel is often used in the industrial production process, and diesel is not renewable and belongs to the hazardous reagents, so there is an urgent need to find a new type of flotation collector to replace diesel. In this paper, three intermediate products produced by Fischer-Tropsch synthesis technology were used as collector. And five emulsifiers, Span80, Tween80, sodium dodecyl sulfate, betaine, and hexadecyl trimethyl ammonium bromide were used to emulsify 3# synthetic oils to produce emulsion with good stability. The flotation performance of three synthetic oil products as well as emulsified collectors were investigated, and the adsorption capacity of 2# and 3# synthetic oils on the coal surface was studied by molecular dynamics simulation. The results showed that the flotation results of synthetic oil were better than those of diesel, with collector 1# having the best flotation results. The oil in water (O/W) emulsion formulated with Tween80 had the best properties, and remained unstratified in half a month, and there were a large number of 0.1-1 mu m oil droplet in the emulsion. Moreover, the emulsified collector of Tween80 with oil -water ratio of 4:6 showed excellent flotation performance, which was nearly 1.5 % higher than that of diesel. The molecular dynamics results are consistent with the synthetic oil flotation results at high concentration dosages, where 3# oil showed better adsorption behavior on the coal surface than 2# oil, but was slightly inferior to diesel adsorption. Therefore, the synthetic oil can be completely used as a substitute for diesel, and the emulsion with oil -water ratio of 4:6 formulated with Tween80 has excellent flotation performance and greatly saves the actual consumption of synthetic oil, which has very high economic and environmental value.

低阶煤泥浮选过程中,由于其表面疏水性差,烃类油捕收剂能否顺利吸附在其表面,对最终的浮选效果具有重要影响.为强化烃类油捕收剂在低阶煤表面的吸附,采用理论计算、分子模拟和试验分析方法研究了高剪切调浆对低阶煤泥浮选的影响规律和强化机理.通过吸附量测试和理论计算研究了正十二烷油滴在煤颗粒表面的吸附规律;借助分子动力学模拟方法构建了正十二烷-水-低阶煤模拟体系,探索了正十二烷与煤表面的初始距离对最终吸附结果的影响;通过开展高剪切调浆浮选试验研究了叶轮转速对浮选精煤产率和灰分的影响规律.结果表明,高剪切调浆可显著提高捕收剂正十二烷在低阶煤表面的吸附量,当叶轮转速超2 000 r/min时,吸附量增幅逐渐降低,最终吸附量趋于稳定;正十二烷油滴与煤颗粒之间存在一个能垒,越过能垒后,总势能迅速降低;初始状态下正十二烷油滴与低阶煤表面的距离对最终模拟平衡结果有重要影响,初始距离较近时,油滴可在煤表面吸附并铺展,而初始距离较远时,则无法吸附;高剪切调浆可显著改善低阶煤的浮选效果,调浆叶轮转速为2 000r时,浮选精煤产率增加了近13%,而灰分基本保持不变.

Soil is the main aggregation site of polycyclic aromatic hydrocarbons and an important pathway of migration to other media. In this paper, the adsorption behavior of pyrene and seven different types of surfactants on kaolinite surfaces was studied by molecular dynamics simulation and desorption testing. The molecular dynamics simulation results showed that pyrene was more easily adsorbed on the 001 (-) side of kaolinite. SDBS, SDS, TW80, and TX-100 had strong interactions with pyrene, encapsulating pyrene molecules in aggregates. However, when the concentration of surfactant was too high, the desorption of pyrene molecules on a kaolinite surface will be inhibited. The desorption of pyrene molecules will be inhibited in the presence of BS-12, TW80, and TX-100, while the desorption process can be promoted by using CTAC, DDBAC, SDBS, and SDS as soil remediation agents. The removal rate of pyrene gradually increased with the increase of SDS dosage, while for SDBS, the removal rate showed a trend of first increasing and then decreasing. When the concentration of SDS was 0.014 mol/L, the elution rate of pyrene reached 72.86%. The molecular dynamics simulation results were similar to the desorption test results, verifying the reliability of molecular dynamics simulation. The research results provide theoretical support for the selection of surfactants in the remediation process of pyrene-contaminated soil.

The molecular structure of cationic surfactants is closely related to their flotation performance. In this paper, three cationic surfactants with different head group structures were selected as collectors of kaolinite, and the substituent effects were studied by the DFT method. The DFT calculation results showed that increasing the number of substituents in the dodecylamine head group can significantly increase its surface and head group charge. Dodecylamine has the lowest LUMO orbital energy, so dodecylamine has the strongest electron attraction ability and the strongest interaction with kaolinite. Electron density differential showed that there was an area of electron aggregation between the collector and the surface of the kaolinite. The interaction energy of DDA on kaolinite surfaces was greater than that of the other two collectors, indicating that the adsorption of DDA on the surface of kaolinite was more stable. Flotation results showed that higher a kaolinite yield was obtained in the presence of dodecyl dihydroxyethyl methyl ammonium chloride. The calculated results of the solvent-accessible surfaces, the head group charge, and the number of bonds between the collector and the kaolinite show good consistency with the actual flotation results of the three collectors, which can be used as a screening index for kaolinite flotation collectors.

Coal slime is not only a solid waste, but also a source of energy. With the improvement of environmental protection requirements, the comprehensive utilization of slime has become an urgent problem for coal preparation plants. In this paper, we put forward a promising way of coal slime resource utilization. X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF) and laser particle sizer was used to analyze the properties of coal slime. Obtained results showed that the slime was mainly composed of the coal, kaolinite and quartz with a particle size of -100 mu m. Most kaolinite minerals can be enriched in overflow when the feed pressure is 0.2 MPa by using hydrocyclone. 21.3% clean coal with ash content of 12.3% and 33.46% kaolinite with particle size of -5 mu m can be recovered by forward flotation and reverse flotation respectively. Coal water slurry with 61% concentration can be prepared from reject of forward flotation and concentrate of reverse flotation at shear rate of 100 s-1. This study has an important practical application value in clean and efficient utilization of coal.

Reverse flotation was proposed as a potential method for the upgradation of low rank thermal coal. Higher combustible matter recovery in the float could be obtained using reverse flotation method compared to conventional flotation method. In order to reduce the entrainment of fine particles, oleic acid (OA) was used as froth regulator in coal reverse flotation process. Experimental data showed that the total volume of froth product in the absence of OA was almost 3 times more than that in the presence of 0.45 kg/Mg OA dosage. Reverse flotation results showed that the ash content of froth product increased with the increase of OA dosage which indicated that the entrained coal particles could be decreased by the addition of froth regulator OA.

Coal gangue is not just solid waste, but also has the potential to yield useful energy. In China, a mining group and a local power plant power plant joined forces with a local university to look at ways to recycle coal gangue to improve the revenue, cut down on resource utilization, and reduce environment pollution.