Browsing by Author "Li, Yun"

Filter results by typing the first few letters
Now showing 1 - 12 of 12
  • Clean antimony production from stibnite concentrate with goethite residue co-treatment for zinc, iron, sulfur conservation
    (2021-09-01) Li, Yun; Xue, Haotian; Taskinen, Pekka; Jokilaakso, Ari; Tang, Chaobo; Jin, Wei; Rämä, Minna; Chen, Yongming; Yang, Shenghai
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In view of the issues of low efficiency and environmental pollution existing in current antimony production, this work proposes an innovative and cleaner process to extract antimony from stibnite concentrate and co-treat goethite residues. The mechanisms of antimony extraction and zinc, iron, sulfur conservation was thermodynamically and experimentally investigated. The results show that iron- and zinc-bearing components in the goethite residue firstly reacted and releasing FexOy and ZnO, then stibnite (Sb2S3) quickly converted to senarmontite (Sb2O3) in the presence of FexOy and ZnO. Intermediate Sb2O3 was subsequently reduced to metallic Sb. Bench-scale experiments of antimony extraction from stibnite concentrate with goethite residue as sulfur-fixing agent validated that 85.7% of Sb was directly recovered as crude antimony bullion, only around 7.4% antimony volatilized to fume. Pb, As, Au, and Ag tended to also be co-enriched in the bullion. 97.4% of sulfur, 88.8% of zinc and 86.1% of iron were recovered and fixed simultaneously. Sulfur in Sb2S3, iron and zinc contained in goethite residues was conserved in matte as marketable Fe2Zn3S5, FeS, and ZnS, instead of forming gaseous SO2. This novel process is a promising recycling and co-treatment alternative for various secondary iron- and zinc-containing materials.
  • Cleaner extraction of lead from complex lead-containing wastes by reductive sulfur-fixing smelting with low SO 2 emission
    (2019-02-01) Li, Yun; Yang, Shenghai; Lin, Wenrong; Taskinen, Pekka; He, Jing; Wang, Yuejun; Shi, Junjie; Chen, Yongming; Tang, Chaobo; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A novel and cleaner process for lead and silver recycling from multiple lead-containing wastes, e.g., lead ash, lead sludge, lead slag, and ferric sludge, by reductive sulfur-fixing smelting was proposed. In this process, coke and iron-containing wastes were employed as reductive agent and sulfur-fixing agent, respectively. A Na 2 CO 3 -Na 2 SO 4 mixture was added as flux. The feasibility of this process was detected from thermodynamic and experimental perspectives. The influence of Fe/SiO 2 and CaO/SiO 2 , composition of the molten salt, coke addition, smelting temperature, and smelting time on direct Pb recovery and sulfur-fixation efficiency were investigated. The optimal process conditions were determined as follows: W Coke = 15%W Pb wastes ,W Na2CO3 /W Na2SO4 = 0.7/0.3, Fe/SiO2 = 1.10, CaO/SiO 2 = 0.30, smelting temperature 1200 °C, and smelting time 2 h, where W represents weight. Under these optimum conditions, 92.4% Pb and 98.8% Ag were directly recovered in crude lead bullion in one step treatment, and total 98.6% sulfur was fixed. The generation and emissions of SO2 can be avoided. The main phases in ferrous matte obtained were FeS, NaFeS 2 , Fe 2 Zn 3 S 5 , and a little entrained Pb. The slag was a FeO-SiO 2 -CaO-Na 2 O quaternary melt.
  • Cleaner Recycling of Spent Lead-Acid Battery Paste and Co-Treatment of Pyrite Cinder via a Reductive Sulfur-Fixing Method for Valuable Metal Recovery and Sulfur Conservation
    (2019-08) Li, Yun; Yang, Shenghai; Taskinen, Pekka; Chen, Yongming; Tang, Chaobo; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study proposes a cleaner lead-acid battery (LAB) paste and pyrite cinder (PyC) recycling method without excessive generation of SO2. PyCs were employed as sulfur-fixing reagents to conserve sulfur as condensed sulfides, which prevented SO2 emissions. In this work, the phase transformation mechanisms in a PbSO4-Na2CO3-Fe3O4-C reaction system were studied in detail. Furthermore, the co-treatment of spent LAB and PyCs was conducted to determine the optimal recycling conditions and to detect the influences of different processing parameters on lead recovery and sulfur fixation. In addition, a bench-scale experiment was carried out to confirm the feasibility and reliability of this novel process. The results reveal that the products were separated into three distinct layers: slag, ferrous matte, and crude lead. 98.3% of lead and 99% of silver in the feed materials were directly enriched in crude lead. Crude lead with purity of more than 98 wt.% (weight percent) was obtained by a one-step extraction. Lead contents in the produced matte and slag were below 2.7 wt.% and 0.6 wt.%, respectively. At the same time, 99.2% total sulfur was fixed and recovered.
  • Experimental thermodynamic and kinetic studies on extraction and recycling of lead from spent lead-acid battery paste
    (2019) Li, Yun
     School of Chemical Technology | Doctoral dissertation (article-based)
    Lead recycling from complex secondary materials has gained increasing interest in recent years. Around 80-85% of the total secondary lead is recycled from lead paste. Due to the high toxicity of lead and increasingly stringent environmental regulations, cleaner and efficient processing of such materials and development of industrial processes are urgently required. In the present work, an innovative and clean lead-acid battery paste recycling technique is proposed. Iron-containing waste materials are utilized as sulfur-fixing agents to capture sulfur as FeS, instead of generating excessive amount of SO2. Na2CO3 or Na2CO3-Na2SO4 salt mixture is added to the smelting system to promote the reactions and improve valuable metals' recovery and sulfur-fixation efficiency.Thermodynamic calculations and experimental determination of the reaction mechanisms in the PbSO4-Fe2O3-C, PbSO4-Na2CO3-C, and PbSO4-Fe2O3-Na2CO3-C systems are carried out to build the fundamental knowledge. Thermogravimetric analysis and quenching method coupled with a direct spectroscopic analysis of the phase and chemical compositions of the resulting phases, i.e. XRD and SEM-EDS, are employed to investigate the phase transformation mechanism. The results indicate that without Na2CO3 addition, lead in lead paste is shown to be extracted mainly through the sequence of PbSO4→PbS→PbO→Pb. Sulfur in PbSO4 is thus first transferred to PbS and finally fixed as FeS. In the presence of Na2CO3, at low temperatures and in weakly reductive atmospheres, lead is extracted mainly through the sequence of PbSO4→PbO→Pb. Na2CO3 helps to transform SO3 from PbSO4 to Na2SO4. At high temperatures and strong reducing atmospheres, PbSO4→PbS dominates the reactions, and lead and sulfur are conserved as PbS. Lead can not be effectively extracted from PbS without a sulfur-fixing agent. When Fe2O3 is presented, lead in PbS will further be extracted through the sequence of PbS→PbO→Pb. Finally, sulfur is fixed as FeS, NaFeS2 and Na2S. A series of bench-scale experiments are conducted to detect the influence mechanisms of smelting conditions on lead extraction and sulfur fixation efficiency. The optimum smelting parameters obtained are integrated to an industrial pilot campaign. Under the optimum conditions, three smelting products, crude lead, ferrous matte, and slag, are formed. 91%-96% lead in the initial raw materials is found to be enriched in crude lead bullion. 97%-99% sulfur is fixed in the sulfide matte and slag. Purity of the crude lead reaches 96%-98%. Lead concentrations in the matte and slag are below 2.4%-4.1% and 0.5-1.2%, respectively, without subsequent matte and slag cleaning. The addition of sodium salts, e.g. Na2CO3 and a Na2CO3-Na2SO4 mixture, is seen to promote the reductive sulfur-fixing reactions and improve extraction and sulfur-fixation efficiency.
  • A New Pyrometallurgical Recycling Technique for Lead Battery Paste without SO2 Generation: A Thermodynamic and Experimental Investigation
    (2018) Li, Yun; Chen, Yongming; Tang, Chaobo; Yang, Shenghai; Klemettinen, Lassi; Rämä, Minna; Wan, Xingbang; Jokilaakso, Ari
     A4 Artikkeli konferenssijulkaisussa
    An innovative lead recycling process from scrap lead-acid battery paste is presented. The novelty in the process is avoiding SO2 generation and emission by using reductive sulfur-fixing technique. Iron-bearing secondary wastes produced from metallurgical industry were utilized as sulfur-fixing agent to capture sulfur in the form of FeS (s) instead of generation of SO2 (g). Molten Na2CO3 salt was added to the smelting system to speed the reactions and improve valuable metals’ recovery and sulfur-fixation efficiency. Furthermore, this process can simultaneously co-treat various lead and iron-bearing wastes. At the same time, some precious metals, such as Au and Ag, contained in iron-bearing wastes can be recovered. The feasibility and reliability of this process was investigated thermodynamically and experimentally with the help of HSC 9.0 database and XRD and SEM-EDS analysis. A possible reaction mechanism and path in PbSO4-Fe2O3-Na2CO3-C smelting system was also clarified.
  • Novel recycling process for lead-acid battery paste without SO2 generation - Reaction mechanism and industrial pilot campaign
    (2019-04-20) Li, Yun; Yang, Shenghai; Taskinen, Pekka; He, Jing; Liao, Fangwen; Zhu, Rongbo; Chen, Yongming; Tang, Chaobo; Wang, Yuejun; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study proposes an innovative and environment-friendly method for recycling spent lead-acid batteries without SO2 generation. Iron-containing waste was employed as a sulfur-fixing agent to retain sulfur as ferrous matte, which eliminated the generation and emissions of gaseous SO2. This work investigated the thermodynamic and experimental feasibility and conversion mechanism of the method, and evaluated its industrial applicability. A bench-scale test showed direct recoveries of 93.5% and 97.7% in crude lead and ferrous matte for lead and sulfur, respectively. The phase transformation mechanism study indicated that metallic lead from the lead paste was extracted mainly through the sequence of PbSO4 →C/CO PbS →Fe3O4 PbO →C/CO Pb. Sulfur in PbSO4 was thus first transferred to PbS and finally fixed as FeS. An industrial-scale pilot campaign was also conducted to confirm the feasibility and reliability of the new process.
  • Oxidizing roasting behavior and leaching performance for the recovery of spent LiFePO4 batteries
    (2020-11) Jie, Yafei; Yang, Shenghai; Li, Yun; Zhao, Duoqiang; Lai, Yanqing; Chen, Yongming
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this study, the effects of oxidizing roasting process on the liberation of cathode materials from Al foil under different conditions were investigated systematically. The mineralogical characteristics of the cathode materials before and after thermal treatment were extensively characterized using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) as well as Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results indicated that the increase in roasting temperature, oxygen concentration, and air flow rate enhanced the liberation of cathode materials. The cathode materials were gradually oxidized to Li3Fe2(PO4)3 and Fe2O3. Further, the carbon and fluorine content in the cathode materials decreased slowly during the thermal treatment, while the Al content increased. When the roasting temperature exceeded the melting point of Al, the Al foils were ablated and the cathode materials adhered to the Al foils again, resulting in difficulty in separation. The cathode materials leaching performance test results demonstrated that the oxidation of cathode materials had a negative effect on the leaching of Fe in sulfuric acid leaching system.
  • PbSO4 Reduction Mechanism and Gas Composition at 600–1000°C
    (2021-03) Li, Yun; Taskinen, Pekka; Wang, Yuejun; Yang, Shenghai; Tang, Chaobo; Chen, Yongming; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A promising lead-containing waste recycling method, with sulfur conservation and reductive sulfur-fixing co-smelting process (RSFCS), is proposed. This work investigated the PbSO4 reduction equilibrium composition, phase conversions, and microscopic transformation mechanisms during the RSFCS process at different temperatures, times, and CO-CO2 mixtures using thermodynamic modeling, thermogravimetric analysis, x-ray diffraction, and SEM-EDS analysis techniques. At the same time, the gaseous products were collected and analyzed. The results showed that three reduction paths existed: (1) PbSO4→CO/CO2 PbO·PbSO4+SO2→CO/CO2 2PbO·PbSO4+SO2→CO/CO2 4PbO·PbSO4+SO2→CO/CO2 PbO+SO2→CO/CO2 Pb; (2) PbSO4→CO/CO2 PbS; (3) PbSO4 → PbO·PbSO4+SO3 → 2PbO·PbSO4+SO3 → 4PbO·PbSO4+SO3 → PbO+SO3. Reduction temperature and CO concentration were determined as major factors in the PbSO4 reduction. In a relatively weak reductive atmosphere and at low temperature, xPbO·PbSO4 (x = 1, 2, 4), PbO, Pb, and SO2 were the major products. When temperature and the CO concentration increased, PbSO4 was selectively reduced to PbS, with sulfur in the PbSO4 fixed in PbS, instead of emitting SO2/SO3.
  • Recycling of Spent Lead-Acid Battery for Lead Extraction with Sulfur Conservation
    (2020-09-01) Li, Yun; Yang, Shenghai; Taskinen, Pekka; He, Jing; Chen, Yongming; Tang, Chaobo; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study proposed a cleaner pyrometallurgical lead-acid battery (LAB) recycling method for lead extraction and sulfur conservation without an excessive amount of SO2 generation. A reducing atmosphere was introduced to the lead paste recycling system to selectively reduce PbSO4 to PbS. At the same time, PbO and PbO2 components contained in the lead paste were also reduced to metallic Pb. Then, the intermediate PbS further reacted with a sulfur-fixing agent, typically Fe3O4, to generate PbO and FeS. Sulfur was transformed from PbSO4 to PbS and finally conserved as FeS. Thus, SO2 emissions and pollution were significantly eliminated. This work investigated the thermodynamic and experimental feasibility and phase conversion mechanism of this proposed method, the detailed lead extraction and sulfur fixing mechanisms were clarified, and the phase transformation and microstructural evolution processes were characterized. Additionally, a bench experiment of industrial, end-of-life LAB paste was conducted to detect the lead recovery and sulfur fixation efficiency.
  • Spent Lead-Acid Battery Recycling via Reductive Sulfur-Fixing Smelting and Its Reaction Mechanism in the PbSO 4 -Fe 3 O 4 -Na 2 CO 3 -C System
    (2019-07-15) Li, Yun; Yang, Shenghai; Taskinen, Pekka; He, Jing; Chen, Yongming; Tang, Chaobo; Wang, Yuejun; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    An innovative and environmentally friendly lead-acid battery paste recycling method is proposed. The reductive sulfur-fixing recycling technique was used to simultaneously extract lead and immobilize sulfur. SO 2 emissions and pollution were significantly eliminated. In this work, the detailed lead extraction and sulfur-fixing mechanisms in the PbSO 4 -Fe 3 O 4 -Na 2 CO 3 -C system were investigated thermodynamically and experimentally, and the phase transformation and microstructural evolution processes characterized. In addition, a series of bench-scale pilot experiments were carried out to confirm the feasibility of the technique. The results show that the lead extraction and sulfur-fixing reactions followed the shrinking unreacted-core model. The recycling products were separated into three distinct layers: slag, matte, and crude lead bullion. Primary recoveries of 96.2% for lead and 98.9% for sulfur were obtained. The purity of the crude lead bullion was 98.6 wt.%. Sulfur was fixed in the solidified matte as FeS and NaFeS 2 .
  • Sulfation Roasting Mechanism for Spent Lithium-Ion Battery Metal Oxides Under SO2-O2-Ar Atmosphere
    (2019) Shi, Junjie; Peng, Chao; Chen, Min; Li, Yun; Eric, Hurman; Klemettinen, Lassi; Lundström, Mari; Taskinen, Pekka; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Sulfation roasting followed by water leaching has been proposed as an alternative route for recycling valuable metals from spent lithium-ion batteries (LIBs). In the present work, the reaction mechanism of the sulfation roasting of synthetic LiCoO2 was investigated by both thermodynamic calculations and roasting experiments under flowing 10% SO2-1% O2-89% Ar gas atmosphere at 700°C. The products and microstructural evolution processes were characterized by x-ray diffraction, scanning electron microscope and energy dispersive x-ray spectrometer, and atomic absorption spectroscopy. It was confirmed that Co3O4 was formed as an intermedia product, and the final roasted products were composed by Li2SO4, Li2Co(SO4)2, and CoO. The leaching results indicated that 99.5% Li and 17.4% Co could be recovered into water after 120 min of roasting. The present results will provide the basis and solid guidelines for recycling of Li and Co from spent LIBs.
  • Sustainable phase-conversion method for antimony extraction and sulfur conservation and waste treatment at low temperature
    (2020-09-20) Li, Yun; Xue, Haotian; Taskinen, Pekka; Yang, Shenghai; Tang, Chaobo; Jin, Wei; Chen, Yongming; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This work proposes a novel environmentally-friendly, low temperature phase-conversion method for antimony extraction and studies its experimental application and feasibility in pyrite cinder waste co-treatment. The detailed phase transformations and microstructural evolution mechanisms during antimony extraction and sulfur fixation process were investigated. The results show that stibnite (Sb2S3) can quickly transform to senarmontite (Sb2O3) in the presence of Fe2O3 and Na2CO3, and then Sb2O3 will be continuously reduced into metallic Sb. Sulfur in Sb2S3 was conserved as FeS and Na2SxOy (Na2S, Na2SO4 and/or Na2S2O3). As a result, sulfur was immobilized and recycled in the solid state resource, instead of emitting SO2 gas. Laboratory-scale batch experiments employed pyrite cinder as sulfur-fixing agent indicate that more than 92.6% of antimony can be extracted and recovered by one step conversion from stibnite at 1123 K (850 °C) by this new technique. 97.3% of sulfur was fixed and converted to sulfide as matte and sulfate. In other words, SO2 emissions were reduced by 97.3%. By-product elemental sulfur was produced after the water-leaching step, and finally producing industrial H2SO4. Iron contained in pyrite cinder waste will also be recycled. This novel method is an energy-saving, environmentally friendly and promising alternative for antimony extraction and waste treatment.