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Liberation and reduction of cathode material are the necessary procedures for improving the recycling efficiency of cathode material derived from spent lithium-ion batteries. In this research work, a pyrolysis technology was utilized to remove the organic binder and enhance liberation of electrode materials. At the same time, pyrolysis treatment can facilitate the thermal-reduction of Co3+ in LiCoO2 to Co2+ with surface organics, which lays a foundation for the subsequent reductant-free acid leaching. Results indicate that the crystal structure of pure LiCoO2 is not changed at a pyrolysis temperature of 600 °C, but LiCoO2 transforms to CoO, Li2CO3, LiF, and Li2O under the reduction action of HF, pyrolytic carbon, and additive carbon black. Water-impact crushing is synchronized with water-leaching to separate electrode materials from aluminum foil and recover Li element. Afterwards, reductant-free acid leaching technology can be utilized to recycle Li and Co from spent LiCoO2 batteries. Recovery efficiency of Li element in water-leaching process was up to 92.17% while the remaining 7.83% of Li and all Co elements were recovered during reductant-free acid leaching process. Based on the foundation analysis, the green chemical process for recovering valuable metals from spent lithium-ion batteries was proposed.

Organics retained in electrode materials decrease the liberation and flotation efficiency of electrode materials. The pyrolysis-assisted sustainable process was used to remove the organic binder an...

Electrostatic effects are commonly found in gas-solid fluidized beds. With an electrical field applied in a gas-solid fluidized bed, the charged particles there would be separated according to the opposite charge polarity. A charge-to-mass ratio test showed that quartz can easily be given a negative charge when tribo-charging with coal. A binary particle mixture was employed to explore the enrichment effect in an electrical-field fluidized bed unit. The results showed that the mass fraction of quartz in the products decrease gradually from negative plate to positive plate. The increase of fluidization time, plate voltage and gas velocity, along with low bed height, were beneficial to the improvement of the enrichment effect. The mass fraction of quartz close to the positive plate was >40%, while that of negative was around 10%. This work demonstrates the possibility of separating fine coal using a fluidized bed with applied electrical field.

In this study, a novel process of mechanical crushing combined with a pyrolysis-enhanced flotation was developed to recover LiCoO2 and graphite from spent lithium-ion batteries, which lays the foundation for the subsequent metallurgical process. Pyrolysis technology was used to solve the problem of low flotation efficiency of electrode materials. The pyrolysis characteristics of the electrode materials were carefully analyzed, and based on the results, the effects of pyrolysis treatment on the surface micro-characteristics, surface element chemical states, and mineral phases of electrode materials were fully investigated to explore the pyrolysis flotation enhancement mechanism. Afterwards, flotation methods were utilized to separate LiCoO2 from graphite. Surface micro-characterization analysis showed that the residual organic binders and electrolytes were the main reason that resulted in a low flotation efficiency of electrode materials. The thermogravimetric analysis and pyrolysis products indicated that the organic binders and electrolyte can be removed at a pyrolysis temperature of 500 °C. X-ray powder diffractometer analysis demonstrated that the electrode particle mineral phases were not altered at a pyrolysis temperature of less than 550 °C. The optimum flotation behavior was presented at a pyrolysis temperature of 550 °C with heating rate of 10 °C/min and pyrolysis time of 15 min LiCoO2 grade is 94.72% with the recovery of 83.75% in this condition. Two stage pyrolysis-enhanced flotation processes can further upgrade the LiCoO2 grade to 98.00%. This research proposes a novel method to improve the flotation efficiency of electrode materials, and the relevant mechanism is explored, which provides an alternative recycling flowchart of spent lithium-ion batteries.

The nonmetallic fractions (NMFs) from waste printed circuit boards mainly comprise organic materials (OMs) and inorganic materials, taking up a large proportion of E-waste. The NMFs can be used as fillers for composite materials by decreasing the content of inorganic materials. In this study, a novel conical surface triboelectric separator based on the tribocharge difference of organics and inorganics was used to concentrate OM and remove inorganics to improve the usability of NMFs. The X-ray fluorescence (XRF) analysis showed that the content of OM in the raw samples was up to 73.03%, and Si, Al, Br, and Ca were the main inorganic elements in the NMFs. The experimental results demonstrated that the organic particles were negatively charged while the inorganic particles were positively charged in the process of particle friction and collision. The effects of feed rate, rotation speed, and voltage on the triboelectric separation of NMFs were investigated, and the optimum separation was achieved at 12.96 kg/h feed rate, 500 r/min rotation speed and 50 kV voltage. The OM content in the positive plate product increased to 85.12% with a yield of 28.81%, while that in the negative plate product decreased to 59.22% with a yield of 36.45%. The test results demonstrated that the novel conical surface triboelectric separator can effectively recycle OM from the NMFs and facilitate the subsequent reutilization of NMFs.

Recycling of valuable metals from spent lithium ion batteries (LIBs) is of great significance considering the conservation of metal resources and the alleviation of potential hazardous effects on environment. Thus, the present work focuses on enhancing the efficiency of leaching process for the recovery of cobalt and lithium from the cathode active materials of spent LIBs. In this study, benzenesulfonic acid (C6H5SO3H) with a reducing agent hydrogen peroxide (H2O2) was innovatively used as leaching reagents, and the operating variables were optimized to obtain higher leaching efficiencies. Results show the optimized leaching recovery of 99.58% Li and 96.53% Co was obtained under the conditions of 0.75 M benzenesulfonic acid, 3 vol% H2O2, a solid to liquid (S/L) ratio of 15 g/L, 500 rpm stirring speed, and 80 min leaching time at 90 °C. Moreover, a new kinetic model was introduced to describe the leaching kinetics of LiCoO2 from the cathode material. The apparent activation energies Ea for leaching of lithium and cobalt are 41.06 and 35.21 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. Further, the proposed recovery mechanism for spent cathode material was raised by analyzing the experimental results and characterizing the morphological and chemical state (i.e. SEM-EDS, XPS and XRD) of raw material and leaching residues. In comparison with the previous leaching process, this research was found to be efficient, low energy consumption, and environmental friendly.

Scrapers are important inner components in continuous fluidized beds in the state where they are most commonly used industry. Dynamic scrapers have significant effects on fluidization characteristics. A lab-scale continuous air dense medium fluidized bed (CADMFB) was designed, and the influences of operational parameters were studied. Moving scrapers lead to velocity gradients in the horizontal direction among magnetite particles in different bed heights, which assisted in loosening of the dense medium bed. Hence, bed pressure drop and minimum fluidization airflow rate were lower than those in beds with static scrapers. If the scraper velocity is kept constant, minimum fluidization airflow rate increases with increasing scraper distance. But the ratio of standard deviation to average bed pressure drop increases with the increase in the scraper distance, which indicates a decrease in bed stability. Minimum fluidization airflow rates also increased with increasing scraper velocities, but a fast scraper speed may also cause bed pressure fluctuations. Dynamic scrapers can inhibit the generation of big gas bubbles. Optimum scraper velocities for various scraper distances can be calculated by v > L g 0.6 π 0.2 1.43 Q 0.2 . Results indicate that 50 mm was the ideal scraper distance, and the optimum scraper velocity was about 0.35 m/s. Results also show that fluidization in boundary zones between dynamic scrapers and static sidewalls was worse than that of middle zones of CADMFB.

Nonmetallic fractions are essential byproducts of the physical-mechanical recycling process of waste printed circuit boards. Large amounts of metals remain in fine nonmetallic fractions because it is very hard for recycling metals from fine size fraction by traditional technologies. In this study, a vibrated gas-solid fluidized bed was utilized to recover residual metals from fine particles (−0.25 mm size) of nonmetallic fractions obtained from the corona electrostatic separation process. The basic mineralogical characteristics and properties of nonmetallic fractions with a size of −0.25 mm indicated that a considerable amount of clavate glass fibers existed in these nonmetallic fractions. The content of residual metals in the −0.25 mm nonmetallic fractions was up to 19.84 wt%. The major metallic elements found in the nonmetallic fractions were Fe, Cu, Pb, and Sn. The results indicated that removing glass fibers from nonmetallic fractions by triboelectric separation can strengthen the gravity-segregation process between heavy and light particles in fine nonmetallic fractions, resulting in improved metal recovery from 76.39% to 81.41%. Based on this research, an industrial flowsheet for the recovery of metals from fine WPCBs is proposed.

The efficient recycling of spent anode material (SAM) from spent lithium-ion batteries (LIBs) is generally critical in terms of electronic waste recyclingas well as increasing resource shortage and environmental problems. This research reported a novel and green method to recycle lithium, copper foil, and graphite from SAM by water leaching treatment. The results indicated that 100% of graphite was exfoliated from the anode material and 92.82% leaching efficiency of lithium was obtained under the optimal conditions of 80 °C, 60 g/L, 300 rpm, and 60 min, respectively. This finding revealed that the SAM got a full liberation characteristic due to the removal of binder, which produced an ideal leaching lithium efficiency rivaling the acids’ performance. The mechanism of the liberation of SAM and lithium leaching is presented based on the analysis of results. The graphite was purified and recovered after water leaching treatment. Besides, lithium was recovered in the form of lithium carbonate (Li2CO3), and the copper foil was recovered in a sheet. This study endeavors to develop an economical and environmentally feasible plan to recycle graphite, copper, and lithium from SAM.

Proper disposal of spent lithium-ion batteries is beneficial for the resource recycling and pollution elimination. Full liberation of electrode materials, including the liberation between electrode material and current collector (copper/aluminum foils) and the liberation among electrode material particles, is the pivotal precondition for improving the recovery efficiency of electrode materials. In this article, authors attempt to carry out a summary of current technologies used in the liberation of electrode materials derived from spent lithium-ion batteries. However, specialized studies about the liberation of electrode materials are insufficient at present. This research clearly shows that: (1) Organic binder must be removed so as to improve the liberation and metallurgy efficiency of electrode materials; (2) A collaboration of varied technologies is the necessary process to achieve high liberation efficiency between electrode materials and copper/aluminum foils; (3) Pyrolysis may be a recommended technology for removal of organic binder because part of pyrolysis products can be recovered. Finally, an alternative recycling flowchart of spent LIBs is proposed.

Spent lithium-ion batteries contain metals, LiCoO2, graphite and other substances that can cause environmental pollution in the case of random disposal. Thus recycling of spent lithium-ion batteries is important. In this study, components in spent lithium-ion batteries are fully dissociated by crushing and screening in the first step. LiCoO2 and graphite particles are enriched in −0.25 mm products. Density and particle size of LiCoO2 particles are larger than those of graphite based on the analysis of physical property. Subsequently, the separation effect is obtained by adjusting the rotating speed and water counter pressure of Falcon centrifuge as well as particle size. Composition of sorted products and optimal sorting conditions are determined by calculation of roasting test and scanning electron microscope. Optimum conditions are as follows: water counter pressure at 0.025 MPa, rotation frequency at 50.00 Hz. Best grade and recovery efficiency of LiCoO2 are 84.87% and 83.14%, respectively. The result also indicates when the particle size ranges between 0.045 mm and 0.09 mm, the sorting performance reaches the best effect.

In this study, pyrolysis was utilized to enhance the liberation of electrode particles in the recycling process of spent lithium-ion batteries. Pyrolysis characteristics of cathode and anode materials and the effects of pyrolysis on the liberation of electrode materials were fully investigated. Afterwards, scanning electron microscope coupled with an energy dispersive spectrometer and X-ray photoelectron spectroscopy were used to reveal the changes of mineralogical characteristics of electrode materials before and after pyrolysis. The results indicate that organic binder wrapped on electrode particles is the main reason that electrode materials are hard to liberate from foils and difficult to liberate each other. The optimum pyrolysis temperature of organic binders in electrode materials is 500 °C and the main pyrolysis products are fluorine-containing benzene and ester electrolyte. The liberation efficiency of cathode increases from 82.88% to 99.78% by pyrolysis, while that of anode increases from 88.08% to 99.60%. Meanwhile, adequate liberation of pyrolytic electrode materials requires a shorter period of time. Electrode materials from pyrolytic electrode are mainly concentrated in −0.045 mm size fraction, and they are up to 82.49% and 78.91% respectively for cathode and anode materials. 5106.

Thermal decomposition was used to enrich indium tin oxide (ITO) from waste colour filter glass. The colour layer was destroyed through oxidation, and the ITO layer was separated from the glass substrate. With the increase in the temperature and time of thermal decomposition, the yield of ITO concentrate decreased, but the ITO recovery and enrichment ratio increased. Furthermore, the ITO could be effectively enriched at 600 °C and 8 min, where the yield, recovery and enrichment ratio of ITO were 0.06 %, 98 % and 1669, respectively. The particle size distribution of the ITO concentrate was mainly distributed in 0.1–1.3 and 2.6–42.0 μm, with cumulative percentages of 4.33 % and 95.55 %, respectively. Moreover, the crystal structure of recycled ITO was not changed. Substantial poisonous and harmful mixed flue gas are produced during thermal decomposition. After condensation and adsorption by activated carbon, the emission of mixed flue gas could be effectively controlled to avoid serious pollution to the atmospheric environment.

An environmentally-friendly technology of pyrolysis-ultrasonic-assisted flotation for recovering graphite and LiCoO2 from spent lithium-ion batteries has been evaluated in this paper. Surface prope...

Flotation is used to enrich indium tin oxide from the colour filter glass of waste liquid crystal display panels. Contact angle measurement and infrared spectroscopy analysis indicated that colour filter contained hydrophobic methyl groups and aromatic ring. Crushing experiment and backscatter imaging analysis revealed that the colour filter with indium tin oxide almost separated from the glass substrate with size fraction of −0.032 mm. The proportion of particles in the −0.032 mm fraction increased with increasing grinding time. A sufficient dissociation was found between the colour filter with indium tin oxide and the glass substrate, and the indium content in the fine size fraction also increased. Moreover, the indium content, indium tin oxide concentrate yield and indium tin oxide recovery increased with decreasing feed size. The indium content of the indium tin oxide concentrate reached 0.61%, the indium tin oxide recovery peaked at 85.21% and the enrichment ratio was 16.6 in particles with size below 0.025 mm. Furthermore, the indium content, indium tin oxide concentrate yield and indium tin oxide recovery increased with increasing grinding time. After 80 min of grinding, the indium tin oxide recovery peaked at 92.51%, the indium content of the indium tin oxide concentrate reached 0.60% and the enrichment ratio was 18.4.

Mixture breakage of particles in various sizes is common in industrial mills, and breakage behavior is influenced by size composition. But studies on particle breakage are conducted to narrowly sized samples. In this paper, tentative works are made to investigate interaction among super clean coal in mixture breakage from aspects of breakage rate, energy consumed characteristics and energy split factors. Experimental results demonstrate that breakage rate of coarse particles in mixture breakage increases if compared with that in single breakage. Particle size is modelled into classical breakage equation, and the modified model is successfully applied to mixture breakage. Energy split factor of component is determined based on the balance of specific energies of components in heterogeneous breakage and energy-size equation, and consumed energy (W) of component in multi-component grinding is calculated. Calculated energy split factors of components are all above one in various mixed conditions, so energy efficiency (value of product t10 at the same specific energy) decreases if compared with that of single breakage. Energy split analyses are also conducted for mixture breakage of middling coals, which illustrates that the method is robustness for energy-size reduction process influenced by associated minerals in coal.

Breakage behaviors and energy consumed characteristics of coal are directly influenced by properties, such as particle size, ash content or density. It is essential to model these effects and conduct quantitative evaluation. In this study, samples of 4 particle sizes × 4 ash contents were ground in a Hardgrove mill for 9 energy levels, respectively. Breakage rate of particles in the top size and t10 were determined and effects of coal properties on two parameters were also discussed. Though the relation between consumed energies and t10 of each sample can be described by classical breakage model, experimental data of all samples were scatter. In this case, particle size and ash content were modelled into breakage equation in exponential term, namely t10 = A × (1 − e−b∙x∙Ecs/eYa). This modified model gave good fitting results to experimental data. Introduce of coal properties into energy-size reduction model helps to compare grinding energy efficiency of various coals. Confidence analyses of repeat experiments demonstrated the repeatability of test results and indicated the reliability of new breakage model.

In this study, the strengthening of the density segregation in a gas-solid fluidized bed is evaluated by applying an external electric field to recover residual metals from fine particles of the non-metallic fraction of waste printed circuit boards. The results demonstrate that large amounts of metals remain in the fine non-metallic fraction of the waste printed circuit boards and account for 21.93 wt%. The main residual metals are Fe, Cu, Sn, Zn, Mg, and Pb, and their contents are 6.06 wt%, 5.35 wt%, 2.92 wt%, 1.99 wt%, 1.36 wt%, and 1.31 wt%, respectively. The external electric field apparently influences the fluidization characteristics by changing the hydrodynamics and the bubble motions in the gas-solid fluidized bed. The minimum fluidized air flow velocity is larger in a fluidized bed with an electric field than in a common fluidized bed. After applying the electric field, the bed expansion increases from 1.15 to 1.21, the gas is well-distributed, and the interaction between the gas and the solid is enhanced. The horizontal motion of the particles can break the agglomeration of glass fibers and loosen the gas-solid bed, which results in an increase in the metal recovery from 67.61% to 76.61%. Based on this research, a novel recycling flowchart of fine waste printed circuit boards is proposed.

In this paper, a mechanical separation and thermal treatment process is developed to recover valuable metals and graphite from the −0.25 mm crushed products of spent lithium-ion batteries (LiBs). Effect of key parameters for roasting such as the temperature and roasting time are investigated to determine the most efficient conditions for surface modification of the mixed electrode materials by roasting. The roasted mixed electrode materials are separated by flotation operation to recover the cathode material and anode materials respectively. The results show that most of the organic outer layer coated on the surface of the mixed electrode materials can be removed at the temperature of 450 °C for 15 min. After roasting treatment, the original wettability of LiCoO2 and graphite is regained. The −0.25 mm crushed products of spent LiBs can be separated into LiCoO2 concentrate and graphite concentrate by flotation process efficiently. The enrichment ratios of Co, Mn, Cu and Al are 1.35, 1.29, 1.25 and 1.19, their recovery rates are 97.66%, 93.66%, 90.14% and 86.29%, respectively. This process proposed for the recovery of valuable materials is simple and of high efficient for the spent lithium-ion batteries recycling industry.

To investigate the effect of size and density on the segregation of particles in the static classifier of vertical spindle mill, classification tests of coal were conducted in a lab-scale classifie...

Triboelectric separation, as an entirely dry technology, is a prospective method to process fine minerals. The aim of this paper is to investigate the performance of triboelectric separation of ilmenite and quartz minerals in a lab unit and to get ready for the separation of ilmenite ore. A tribocharge measurement system was used to test the triboelectric properties of ilmenite and quartz particles with tribochargers respectively made of PVC, PPR, PMMA, Teflon, copper, stainless steel and quartz glass. The results show that the ilmenite particles charged positively while quartz charged negatively when tribocharged with PVC tribocharger. The mixture of 12% ilmenite and 88% quartz was prepared for the triboelectric separation. The recovery of ilmenite increases with the increase of airflow rate, decreases with the increasing feed rate, and grows up firstly and then decreases with the increasing voltage. A maximum ilmenite recovery of 51.71% with ilmenite content 32.72% was obtained at 40 m3/h airflow rate, 6 g/s feed rate and 20 kV voltage. According to the optimal parameters of the separation of ilmenite and quartz mixture, fine ilmenite ore with 7.55% Ti content was beneficiated using the unit and the Ti content increased to12.32% in concentrate product. Keywords: Triboelectric separation, Tribocharge, Ilmenite, Quartz, Ilmenite ore

Raw coal was ground in a Hardgrove mill, and mineral liberation from coal was investigated by float-sink test and electron probe microanalyzer (EPMA). Based on EPMA, associated conditions of mineral were determined. Analyses of energy-size reduction show that energy efficiency decreases with time. For +0.074 mm progenies, yields of particles in −1.5 g.cm−3 decrease with the increase of size and time, and products in +1.8 g.cm−3 show the opposite trend. EPMA of 0.25–0.125 mm, 1.5–1.8 g.cm−3 products ground for 10 min indicates that only part of minerals are liberated. For −0.074 mm products, the yield of particles in −1.5 g.cm−3 decreases by 23.36% in last several minutes, but ash content of +1.8 g.cm−3 also decreases by 13.18%. Since breakage of raw coal in last 9 min does not reduce particle size obviously, and liberation degree cannot be improved dramatically, closed grinding of 10 min in Hardgrove mill is proper to balance the size reduction and mineral liberation.

Due to the limitation of secondary pollution and high equipment investment, the industrial-scale recycling technology for electrode materials from spent lithium-ion batteries (LIBs) needs urgent breakthrough. In this paper, a physical recycling method, grinding flotation, is creatively proposed for the separation and recovery of LiCoO 2 and graphite from spent LIBs. According to the exploratory experiments, if the mixed electrode materials is ground in the hardgrove machine for 5 min before reverse flotation, the concentrate grade of LiCoO 2 sinks and graphite floats can reach 97.13% and 73.56%, respectively. Moreover, with the help of advanced analytical technologies, the surface morphology, elemental chemical states and element distribution on the very surface of electrode particles before and after grinding were systematically analyzed to reveal the mechanism of dry surface modification. Results indicate that the mechanical grinding destroys the lamellar structure of graphite, exposing massive newborn hydrophobic surfaces. Meanwhile, the abrasion of organic film coating the LiCoO 2 particles causes its original hydrophilic surface partially regained. Hence, the great wettability difference between LiCoO 2 and graphite contributes to an excellent flotation separation. This grinding flotation method is a promising separation method without any toxic emissions or introducing other impurities in industrial application.

The recovery of resources from waste printed circuit boards is of growing importance in parallel with the rapid increase of waste printed circuit boards as a result of the shorter product life cycles and upgrade of electronic equipment. As a byproduct of the recycling process of waste printed circuit boards, the nonmetallic fractions have an urgent requirement for recycling from the perspective of environment protection and resource recovery. In this paper, morphology, mineralogy and separation characteristics of nonmetallic fractions collected from the recycling line of waste printed circuit boards were analyzed by application of multi-analytical techniques, which lay the foundation for the recycling of nonmetallic fractions. Analysis results demonstrate that organic materials account for 60.03 wt% in raw nonmetallic fractions while the concentration of residual metals is up to 16.68 wt%. The concentration of magnetic production is 5.92 wt% in raw nonmetallic fractions and presents increasing trend with the size decreasing. The metal components in nonmagnetic part are mainly in single substance forms, while compound forms are presented in magnetic parts. Scanning electron microscope images demonstrate that there is an adequate liberation between metals and nonmetals, but glass fibers did not liberate from epoxy resin in +0.125 mm size fraction. There is an obvious difference in the components of different size fraction; and the metals were mainly concentrated in fine size fraction. Based on the mineralogical characteristics of each size fraction of nonmetallic fractions, the optimal recycling process of nonmetallic fractions including several processing operations is proposed.

In this study, the flotation technology is used for the separation and purification of cathode and anode material after removing organics by pyrolysis. Effects of surface microscopic properties on the flotation efficiency of spent electrode materials are investigated, and on this basis, surface analysis combined with flotation foundation tests are conducted to reveal pyrolysis-assisted surface modification mechanism. Residual electrolyte and organic binders decrease the difference in wettability of cathode and anode material, and hinder the interaction between electrode particles and collecting agent. Organics and their pyrolysis products can be adequately removed at the optimum pyrolysis temperature of 550 °C. After pyrolysis, the change of Zeta potential and surface free energy demonstrates that hydrophilic components of cathode material increase while the hydrophobic components of the anode material increase. The induction time of cathode material rises from 190 ms to 650 ms while the induction time of the anode material decrease from 145 ms to 37 ms. Collector adsorption capacity of anode material is obviously improved and anode material is easy to incorporate with bubbles and will be collected in the froth product. After one stage flotation, the recovery rate of cathode material is 83.75% with a high grade of 94.72%.

Lignite is difficult to be effectively separated by traditional preparation techniques because of its sliming property and difficulty of subsequent dewatering. A dry separation method of using a pulsing air classifier is applied to decrease the ash content of lignite for improving its effective utilization. The lignite sample used in this study was collected from Inner Mongolia, China. Mineralogical characteristics of the lignite sample were analyzed, and the effects of airflow rate, pulse frequency, and feed rate on the separation efficiency of −6 + 3 and −3 + 1 mm size fractions were determined using the lab pulsing air classifier system. The results demonstrated that the ash content of the product was reduced by 10.18% and 30.98% for the −3 + 1 mm and −6 + 3 mm size fractions, respectively, and the pulsing air classifier has a better separation efficiency for a larger size fraction.

Different lignite submacerals have complex physical and chemical properties, and exploring their molecular structures are of great significance for enrichment the evolution mechanism of coal microstructure and efficient utilization. In this paper, raw lignite with rich-(eu-ulminite) (FJ) and rich-leviglinite (FW), respectively, were selected on the basis of petrographic identification. The proximate analysis and ultimate analysis, FTIR, XPS, 13C NMR, HRTEM and molecular simulation technique were used to construct the molecular structure of FJ and FW. The experimental data and molecular structural models show that FW has a higher aromaticity, larger size of the aromatic layer, and more pronounced directional arrangement. In a single stable molecular configuration, aromatic rings and the aliphatic ring are arranged in a wrapped arrangement. Furthermore, the type of hydrogen bond mainly depends on the type of oxygen-containing functional group of the molecular structure. In addition, the length and angle of the hydrogen bond tend to be polarized. There is a little difference on the value of experimental and simulated density.

Efficient liberation is a key to the recycling of the electrode materials in spent lithium-ion batteries (LIBs). To improve the liberation of the electrode materials, a novel cryogenic grinding method of high selectivity was proposed. The low temperature characteristics of the traditional binder material PVDF and the current collector materials were tested. The results show that the glassy transition temperature of the binder PVDF is about 235 K. The binder would change from a high elastic state to a brittle state thus is easy to be crushed at a lower temperature. On the contrary, the impact strength of the current collector materials increases with the decrease of the temperature. Therefore, the grinding of electrode plates at low temperatures would be more selective grinding. The cryogenic grinding tests results show that, compared with that of room temperature, the content of the nickel-cobalt-manganese-lithium in the −0.15 mm particle size was increased from about 16–84%, the graphite content from 31.55% to 90.58%, and the content of aluminum and copper in the +1 mm grain size increased from 79.32% and 74.62–95.42% and 97.75%，respectively. This research may provide a new method to the recycling of spent LIBs.

Electrostatic charge accumulation in a gas–solid fluidized bed is considered an adverse effect. However, with the presence of an external electrical field, we can take advantage of electrostatic charging to separate charged particles according to their polarity. In this paper, we proposed a bench-scale two-dimensional fluidized bed with an external electrical field. We then systematically investigated the tribo-charging behavior of anthracite-quartz mixture in the fluidized bed at different conditions and the effect of the external electrical field on their fluidization characteristics. Subsequently, an orthogonal design of experiments analysis was implemented to find the optimized parameters of gas velocity, plate voltage, and initial bed height to separate bituminous coal particles. These findings provide a dry method to separate coal particles from their associated minerals using the proposed two-dimensional fluidized bed with an external electrical field and have general implications for the triboelectric separation of various materials.

Colloid mill attrition can remove the oxidized layer from oxidized coal surface. The effects of colloid mill gap space and milled pulp density were investigated according to the flotation response. It was found that both particle size reduction and flotation recovery enhancement were higher at higher pulp density and smaller gap space. When colloid mill worked at higher pulp density and smaller gap space, oxidized layers of coal particles could be removed more thoroughly. In addition, the greater reduction in particle size at higher pulp density and smaller gap space should be conductive to the flotation of oxidized coal because large particle size of oxidized coal is considered not suitable for its flotation. Because colloid mill was successfully applied in improving oxidized coal flotation, the results of this paper will promote the industrial application of colloid mill into effective flotation of oxidized coal in coal preparation plants.

Traditional air classifiers produce binary splits based on the terminal velocity rather than the density of the feed. In this study, a pulsating air with a sine-like shape wave was introduced into a vertical column air classifier to achieve the density dominant separation on −6+3 mm fine coal. A lab-scale separation device was used to investigate the effects of pulsating characteristics (amplitude and frequency) and particles volumetric concentration on pulsating airflow separation in a batch process. The optimum operating conditions of 34.1 cm pulsation amplitude, 2.45 Hz frequency and 500 g feed amount achieved 48.08% separation efficiency, 68.22% combustible matter recovery and produced a clean coal with 17.98% ash (from a feed containing 42.02% ash), 47.73% yield and Ep value of 0.17. The results showed that the pulsating air classifier has a potential for fine coal dry beneficiation. The motion of particles in a pulsating airflow field under a hindered settling condition has been presented.

In this paper, a Fenton reagent assisted flotation process is developed to recover valuable electrode materials LiCoO 2 and graphite from spent lithium-ion batteries (LiBs). At room temperature, effect of key parameters for Fenton reaction such as the ratios of H 2 O 2 /Fe 2+ (40–280) and liquid-solid (25–100) are investigated to determine the most efficient conditions of surface modification of electrode materials by Fenton reagent. The modified electrode materials are separated by flotation operation to recover the cathode material and anode materials respectively. The results show that in the optimum conditions that the Fe 2+ /H 2 O 2 ratio is 1:120, and the liquid-solid ratio is 75:1, most of the organic outer layer coated on the surface of electrode materials can be removed. After modified by Fenton reagent, the original wettability of LiCoO 2 and graphite is regained. The −0.25 mm crushed products of spent LiBs can be separated into LiCoO 2 concentrate and graphite concentrate by flotation process efficiently.

The recovery of metals from waste printed circuit boards (WPCBs) has been studied for a long time because of the high economic value of these metals. The low usability of the nonmetallic fraction (NMF) of WPCBs caused by inorganics makes its industrial reuse difficult. Removal of inorganics by triboelectric separation with the aim of improving the usability of NMF was investigated using a lab triboelectric separation system. After separation, a new composite was produced by compounding 20 wt% NMF and 80 wt% high-density polyethylene (HDPE). The mechanical properties of each composite were compared, and the surface morphology was analyzed with a scanning electron microscope (SEM). The separation results demonstrated that inorganics were removed and collected in a groove that was closed to a negative plate. Mechanical property testing showed that the removal of inorganics could improve the usability of NMF. Both the flexural and impact strengths of the composites that were filled by NMF without inorganics were obviously improved. The SEM image indicated that air holes and faultage caused by glass fiber agglomerations and poor compatibility between HDPE and inorganics were the main features contributing to composites with poor mechanical properties.

An environmentally friendly technology of cryogenic grinding for recovering cathode materials from spent lithium-ion batteries was has been investigated in this paper. Differential Scanning Calorimeter was used to test the glass transition temperature of the organic binder. Advanced analysis techniques, a microcomputer-controlled electronic universal material-testing machine, a low-temperature impact testing machine, scanning electron microscopy and high-resolution 3 Dimension-X-ray microscopy, were utilized to analyze the effect of low temperature on the mechanical properties and morphology of cathode. Results show that the yield strength, tensile strength and impact strength of the current collector is significantly increased at low temperature, that the glass transition temperature of the organic binder is approximately 235 K. Low temperature enhances the strength of the current collector and causes the organic binder to fail. Therefore, cryogenic grinding could realize the selective grinding of the cathode and significantly improve the peel-off of the electrode materials. The peel-off efficiency of cathode materials was improved from 25.03% to 87.29% at the optimum conditions of low temperature pretreatment for 5 min and cryogenic grinding for 30 s. The experiments demonstrate that the cryogenic grinding can obviously facilitate the efficient recovery of cathode materials, revealing a great application prospective for the recycling of spent lithium-ion batteries.

The increasing market size of high-energy storage systems due to the booming of not only portable electronic devices but also electrical vehicles and renewable energy sources has promoted battery technologies, resulting in many spent lithium-ion batteries (LIBs). This study focuses on proposing a closed-loop process to recycle the full valuable metals from spent LiNi1/3Co1/3Mn1/3O2 material. Reduction roasting and hydrometallurgy were combined and used for de-agglomeration of cathode composites and enhanced recycling of valuable metals. Experimental results showed the cathode material was reduced to Ni, Co, Li2CO3, and MnO under microwave carbothermic reduction, and lithium carbonate was directly recovered after dissolved in water with a high yield of 99%. Afterward, transition metals (Ni, Co, Mn) enriched residues can be dissolved in fumaric acid with leaching efficiencies of more than 96% under optimized leaching conditions, and finally recovered as single compounds by step-wise addition of chemicals. The mechanism of the nonthermal effect of microwave on the leaching of metals was analyzed by kinetic studies, and the decreased Ea values for metals demonstrate that microwave treatment is beneficial for metals leaching through decreasing their apparent energies. Besides, the characterization results of X-ray diffraction and scanning electron microscope indicate the destruction of the layered crystal structure and an increased liberation degree after microwave treatment, which is also beneficial for the enhancement of metals leaching. Therefore, the microwave reductive-assisted process is found in a green and effective industrial process to recycle valuable metals from spent LIBs.

It is well known that fine particles have a negative influence on the energy size reduction of other materials in the grinding chamber. But a quantitative evaluation about it is relatively less. In this article, a Hardgrove mill was used to investigate the effect of fine coal on the grinding energy, specific rate of breakage of the top size, and the production of fine coal in -0.074 mm size fraction. A qualitative description of the friction coefficient between coal and grinding media demonstrates that this index drops with more fines added in the particle bed. The decreasing degree of grinding energy increases 2.5 times if added level of fine coal changes from 2.5 g to 10 g. Breakage of the top size at different added levels of fine coal still follows the first-order law. But due to the decrease of grinding energy and the cushion effect of added fine coal, the breakage rate of coarse particles decreases 2% to 25% if compared with the single breakage. Decreases of grinding energy and breakage rate...

Interactions among components in the heterogeneous grinding would change energy consumed characteristics of components if compared with those in the single-component breakage. In this paper, energy split phenomenon for the coarse grinding of super clean anthracite coal (SCAC)/calcite mixture of 2.8–2 mm in the ball-and-race mill is investigated. Before the analysis of experimental results, accuracy of energy split function in terms of time-dependent breakage rate is first discussed. Energy consumed characteristics of grinding in the ball mill and ball-and-race mill are also compared. Breakage model of product t 10 (yield of progenies in −0.237 mm) vs specific energy is used to describe the energy-size reduction of the single-component and multi-component grinding. Interaction between components is reflected by the comparison of specific energy of components in mixture and single breakage to yield the same product t 10 . Based on the energy balance, energy split factors of components in different time and mixed conditions are first determined. This parameter shows no change with time. Calcite increases the grinding efficiency of SCAC significantly, with the energy split factor for SCAC ranging from 0.68 to 0.73, which means less specific energy is consumed by SCAC to yield the same t 10 if compared with the single breakage. As the volumetric ratio of calcite increases in mixture, grinding energy efficiency decreases and energy split factor of calcite increases from 1.70 to 1.83. Soft material reduces the grinding energy efficiency of hard one in the multi-component breakage.

Dry triboelectric separation of coal depends on tribocharge difference of the coal and gangue minerals. A suitable tribocharger material which makes the coal and minerals tribocharged of opposite polarity is of great importance for triboelectric separation. In this paper, the composition of coal was analyzed by x-ray diffraction (XRD), and the triboelectric characteristics of coal and other ash-forming minerals were tested using stainless steel (SS), polyvinyl chloride (PVC), pentatricopeptide repeats (PPR), polyfluortetraethylene (PPFT), and polymethyl methacrylate (PMMA) tribochargers in lab triboelectric unit. The charge−mass ratio of coal and mineral particles were presented and evaluated. Infrared spectroscopy was adopted to analyze the different tribocharge properties between clean coal and minerals. The results show that the gangue minerals in coal are mainly pyrite, kaolin, calcite, dolomite, and quartz. The conductive mineral had the lowest chargeability, especially tribocharged with cond...

Experimental and simulation approaches were combined to investigate the fluidization characteristics of a dense-medium gas–solid fluidized bed (DMGFB) for coal cleaning. Results indicated that the static bed height should be adjusted by maintaining a stable height of 150–300 mm to avoid its harmful effect on fluidization stability. Bed pressure drops presented favorable stability with slight fluctuations at a superficial gas velocity of 11.68 cm/s (1.6 U mf ). The uniform density distributions with slight variations throughout the whole bed were verified by comparing the experimental, simulated and calculated results. A fluidization index, U mb / U mf , was used to conduct stability-region analysis for DMGFB. On the basis of fluidization stability, a successive beneficiation flowsheet via a DMGFB separator was used to perform density-based separation of 6–50 mm sized run-of-mine coal. Results demonstrated that the low-ash clean coal with a yield of 61.36% was efficiently obtained with the ash content reduced from 39.64% to 10.18% and sulfur content rejected from 1.36% to 0.85%. Probable error E values were 0.06 and 0.075 g/cm 3 in high- and low-density separation stages, indicating efficient separation performance. The dry coal beneficiation technique has great potential for utilization in arid and water-deficient areas and countries.

Vibrational energy was introduced to a dense medium gas–solid fluidized bed to improve the separation performance of 1–6 mm fine low-rank coal. The setup was termed a vibrated gas–solid fluidized bed and could provide a stable fluidization state and uniform density distribution for dry coal beneficiation by the transfer of vibrational energy and the interaction between vibrations and the gas phase. Favorable segregation of the ash content of the 1–6-mm-sized lignite samples is achieved under suitable operating conditions. Higher yields of cleaning coal were acquired when the ash content was reduced. The probable error values were 0.065 and 0.055 at separating densities of 1.68 and 1.75 g/cm 3 for the 1–3- and 3–6-mm-sized lignite samples, respectively. Effective beneficiation of 1–6-mm-sized fine lignite could be achieved using the vibrated gas–solid fluidized bed, which provides an alternative technique for the separation of fine low-rank coal in arid areas.

The growing demand for high-quality batteries has promoted frequent upgrading of Lithium-Ion Batteries (LIBs), resulting in a large number of spent LIBs entering into the waste stream. Grinding flotation may be a promising physical recycling method to help dispose of this waste. This study provides theoretical support for this technology by exploring the physical and chemical changes in the grinding modification process. To study physical grinding behavior, an interaction model between LiCoO2 and graphite particles was proposed; it shows that a mixed grinding process successively undergoes peeling of the graphite lamellar structure, abrasion of the LiCoO2 particles, and bending fracture of the graphite sheets. This process effectively avoids excessive pulverization of feed particles and guarantees a good flotation environment. As for surface hydrophobic changes, the contact angle difference significantly increased, from 5° to 53.34°, after mixed grinding. Further chemical composition analysis suggests that the active lithium element robs the F element from the C–F bond to form LiF, which reduces about 25% surfactant organic impurities and ultimately increases the hydrophobicity differential in the electrode materials. It is the synergistic effect of a good feeding environment and great hydrophobicity differential that contributes most to excellent flotation separation (LiCoO2 94.38%).

The growing demand for high-energy lithium-ion batteries (LIBs) has promoted the production of LiNixCoyMnZO2 cathode, which results in many spent LIBs to resolve. A novel method that employs microwave carbothermic reduction was used to enhance the leaching of metals from layered LiNi1/3Co1/3Mn1/3O2 of spent LIBs. The thermodynamic analysis showed that LiNi1/3Co1/3Mn1/3O2 could be theoretically reduced to single metals in the presence of graphite. Then experimental results demonstrated that the transition metals can be effectively reduced under the parameters of 500 W microwave energy and 30min time. Afterward, multiscale characterizations revealed that microwave irradiation leads to the disorderly crystal structure and lattice cracks of LiNi1/3Co1/3Mn1/3O2 materials, which is more efficient to facilitate their interparticle liberation and destruction of crystal structure compared with the conventional heating process. Based on the characterization of the reduction products and their leaching performance, the mechanism for microwave carbothermic reduction was accordingly raised. Finally, the leaching experimental results show the optimal efficiencies of 97% transition metals (Co Ni, and Mn) and 99% Li were obtained under microwave carbothermic reduction, which is found more efficient in comparison to the samples without microwave treated. The whole process is found to be effective and sustainable for recovery of valuable metals from the industrial electrode of spent LIBs.

Heterogeneous breakage is common in industrial production processes, and the quantification of components in the product mixtures is essential for the fundamental research of breakage behavior and interaction among constituents. In this paper, methods to quantify the heterogeneous grinding of minerals are summarized, and some potential ways to determine component yields in ground products of coal mixtures are discussed. The characteristic ratio of diffraction images and organic sulfur content were selected to monitor the breakage. A relation between those two parameters and the yield of components in mixtures was established. This study provides basic information on the heterogeneous grinding of coals of various ash contents, coalification degrees and grindabilities.

A novel method of cryogenic grinding and froth flotation is proposed to recover LiCoO2 and graphite from spent lithium-ion batteries. After 9 min of cryogenic grinding, the grade of LiCoO2 concentrate was up to 91.75%, with a recovery rate of 89.83% after flotation, but the materials that have not been cryogenic grinding, the grade and recovery rate of LiCoO2 after flotation only 55.36% and 72.8%, respectively. Analysis of the surface properties and morphology of electrode particles was performed using scanning electron microscopy, X-ray photoelectron spectroscopy, and field emission-electron probe micro-analysis. Results indicate that the organic binder on the surface of the raw materials resulted in a poor recovery rate and grade of the flotation concentrate. Cryogenic grinding, on the other hand, caused the organic binder on the surface of electrode materials to peel off, with spherical graphite changing into a scaly layer structure that revealed a new surface. The hydrophilicity of LiCoO2 and hydrophobicity of graphite were obviously improved by cryogenic grinding, and in turn contributed to an excellent flotation separation. This work provides an efficient and environmentally-friendly process for recovering LiCoO2 and graphite from spent lithium-ion batteries.

Aiming to maximize the utilization of coal resource, heterogeneous grinding of coal in various coalification degrees is common. Interaction among particles of different coals in mixture breakage results in changes of energy-size reduction characteristics if compared with that of single grinding. In this paper, anthracite and coking coals of low ash are ground together in a Hardgrove mill, and resistance to be broken is compared based on the classical breakage model. Product t10 of component after mixture breakage are determined by the relation between characteristic ratio (ratio of height and full width at half maximum of 002 peak) and yield of anthracite coal in mixture. Results indicate that product t10 of anthracite coal increases as more coking coal is added, and that of coking coal shows the contrary trend. A new method is proposed for the determination of energy split factors of components based on the assumption that the relation t10 and spilt energy of component still can be modelled by the classical breakage model. Besides energy split factors of components, breakage indictors are also determined according to above assumption and energy balance by genetic algorithm. Soft coking coal promote the energy-size reduction of hard anthracite coal in mixture breakage, with the increase of breakage indicator (A and b) and energy efficiency compared with those of single breakage. Energy split factors of anthracite coal is above one, and increases with the product fineness. And coking coal shows the contrary trend.

A vibrated gas-solid fluidized bed was proposed and tested to improve and upgrade fine lignite. A broad particle size (0.074–0.3 mm) of magnetite powder was prepared and used as main separating medium solids for coal improvement. The fluidization stability of the bed, including the fluidization index, fluctuations of bed pressure drop, and uniformity of bed density, was greatly enhanced by introducing the vibration energy to the static bed. The vibrated separation shows positive effects to improve the surface morphology of lignite and upgrade its quality to a certain degree. Ash-content segregation of fine lignite samples obviously occurs by the joint effects of fluidized gas and vibration. The optimal segregation degree Sash values of 0.73 and 0.70 were achieved with suitable operating factors. The density-dependent separation performance indicates that the ash and sulfur contents of lignite were sharply reduced with the probable error E values of 0.060 and 0.065 g/cm3. However, the overall E value for 6–1 mm sized fine lignite increases to 0.12 g/cm3 due to the shift in the D50 with particle size. The products of low-ash clean coal, middlings, and high-ash gangue were effectively obtained by successive separations. The dry coal improvement technology provides an alternative approach for the clean utilization of fine coal.

The hydrodynamic characteristics of the dense medium gas–solid (DMGS) fluidized bed for coal beneficiation and cleaning were analyzed and discussed by the experimental measurement and numerical simulation. The magnetite powder with a wide particle size of 0.3–0.15 mm was selected as the major fluidized medium in this study. The simulation and experiment results indicate that the bed pressure drop can reach stable condition in a relatively short period with the increase of superficial gas velocity. Afterwards, the bed pressure drop shows minor fluctuations within the gas velocity of 1.8Umf ≤ U ≤ 2.2Umf. Meanwhile, the bed density shows good homogeneity at various bed heights and axial directions with slight density fluctuation. Therefore, the results clearly demonstrate that the hydrodynamic characteristics of the fluidized bed, including the bed pressure drop and separating density distribution, overall maintain stable and uniform conditions without intense fluctuations. It provides favorable flui...

In this work, detailed surface analysis on the fine crushed products of spent lithium-ion batteries is investigated by X-ray photoelectron spectroscopy. The results showed that although LiCoO2 was a main composition of the fine crushed products, the surface atomic abundance of cobalt was only 1.69%, but the surface atomic abundance of organic compounds was more than 75%. During the crushing process, LiPF6 decomposed and harmful and toxic substances such as HF, POF3 were generated, it is necessary to take appropriate measures to avoid the secondary pollution in the crushing process of spent LiBs. Metallics such as Co, Cu, and Al were fluoridated and oxidized, and the organic compounds were oxidized and decomposed, too. The surface composition and microstructure of the fine particles were presented, which showed that the fine particles in the crushed products were lithium cobalt oxides and graphite cores coated inside by organic compounds. Flotation test pointed out that if the outer layer was removed, the flotation selectivity would be greatly improved: the enrichment ratio could be increased from 1.16 up to 3.24. Based on the surface analysis, potential ways for removal of the outer layer were proposed.