scholarly journals Optimization of Roasting Parameters for Recovery of Vanadium and Tungsten from Spent SCR Catalyst with Composite Roasting

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1923
Author(s):  
Bo Wang ◽  
Qiaowen Yang
Keyword(s):  
Orthogonal Experiment ◽  
Weight Matrix ◽  
Matrix Analysis ◽  
Mass Ratio ◽  
Water Leaching ◽  
Scr Catalyst ◽  
Scr Catalysts ◽  
Roasting Temperature ◽  
Roasting Time ◽  
And Tungsten

Every year, large amounts of selective catalytic reduction (SCR) catalysts with losing catalytic activity and failing to be regenerated need to be regenerated, which will result in acute pollution. Recycling valuable metals from spent SCR catalysts can not only solve environmental problems, but also save resources. The process of sodium roasting and water leaching is able to effectively extract vanadium (V) and tungsten (W) from spent SCR catalysts. To improve the efficiencies of V and W, different sodium additives were first investigated in the roasting process. The results revealed that the process of NaCl-NaOH composite roasting and water leaching showed superior leaching efficiencies of V and W, which can reach 91.39% and 98.26%, respectively, and simultaneously, it can be found that adding low melting point NaOH promoted mass transfer as compared with the melting points of different sodium additives. Next, a single-factor experiment was conducted to investigate different roasting conditions, such as roasting temperature, roasting time, mass ratio of sodium additive and catalyst, and mass ratio of NaCl and NaOH, on the leaching efficiencies of V and W. Then, a three-level and four-factor orthogonal experiment and a weight matrix analysis were used to optimize the roasting parameters. The results showed that roasting temperature had the most significant effect on the leaching efficiencies of V and W, and the optimal roasting conditions were as follows: the roasting temperature was 750 °C, the roasting time was 2.5 h, the mass ratio of sodium additive and catalyst was 2.5, and the mass ratio of NaCl and NaOH was 1.5. Under the optimal roasting conditions, the leaching efficiencies of V and W were 93.25% and 99.17%, respectively. The results of XRD analysis inferred that VO2 coming from the decomposition of VOSO4 in spent SCR catalysts may first oxidize into V2O5 and then react with sodium additives to produce NaVO3. The formation of titanium-vanadium oxide ((Ti0.5V0.5)2O3) was a part reason of hindering the leaching of vanadium. With the increase of roasting temperature, TiO2 converted into Na2Ti3O7, which indicated that the main structure of the catalyst was destroyed, and simultaneously, more characteristic peaks of sodium metavanadate and sodium tungstate appeared, thus enhancing the leaching of V and W. Finally, it can be seen that the process of NaCl-NaOH roasting and water leaching remained higher leaching efficiencies of V and W and lower roasting temperature by comparing with leaching efficiencies of V and W in different processes of recycling SCR catalyst. The process of NaCl-NaOH composite roasting and water leaching provided a strategy with a highly efficient and clean route to leach V and W from spent SCR catalyst. The orthogonal experiment and weight matrix analysis in our study can be used as a reference to optimize the reaction conditions of a multiple indexes experiment.

Effective Extraction of Vanadium and Chromium from High Chromium Content Vanadium Slag by Sodium Roasting and Water Leaching

2016 ◽  
Vol 863 ◽  
pp. 144-148 ◽  
Author(s):  
Ming Li ◽  
Liang Xiao ◽  
Jing Jing Liu ◽  
Zhi Xin Shi ◽  
Zi Bi Fu ◽  
...  
Keyword(s):  
Chromium Content ◽  
Leaching Rate ◽  
Vanadium Slag ◽  
Water Leaching ◽  
Sodium Salts ◽  
High Chromium ◽  
Effective Factor ◽  
Roasting Process ◽  
Roasting Temperature ◽  
Roasting Time

The extraction of vanadium and chromium from high chromium content vanadium slag by salt roasting and water leaching process has been investigated, which uses mixed sodium salts (Na2CO3 and NaOH) as additive agent in roasting process. The mineralogical morphology was prospected by TG-DSC, XRD, SEM and EDS. The oxidation of slag and transversion of V/Cr-containing phase and sodium salts have been discussed. It has been demonstrated that the presence of NaOH contributes to decompose spinel and olivine phases, which is beneficial to reduce the roasting temperature and elevate V, Cr leaching ratio. The roasting parameters have been studied as a function of roasting temperature, roasting time and ratio of alkali, in which the roasting temperature is the most effective factor on the leaching rate of vanadium and chromium. Under the optimum condition, the leaching rates of V and Cr reached 95.8% and 97.6%, respectively.

Factors of Extracting Lithium from Lepidolite by Sulfate Roasting and Dilute Sulphuric Acid Leaching

2014 ◽  
Vol 522-524 ◽  
pp. 1467-1470 ◽  
Author(s):  
Xiang Zhong Kong ◽  
Hua Ye ◽  
Yu Qin
Keyword(s):  
Sulphuric Acid ◽  
Extraction Efficiency ◽  
Acid Leaching ◽  
Mass Ratio ◽  
Roasting Temperature ◽  
Roasting Time

Sulfate roasting and dilute sulphuric acid leaching were applied to extract lithium from lepidolite. Several conditions including roasting temperature, roasting time, K2SO4and CaO were investigated to improve the lithium extraction efficiency, the final lithium extraction efficiency could attain 94% with the conditions as follows: roasting temperature 850°C, roasting time 2 h, K2SO4to lepidolite mass ratio 0.15 and CaO to lepidolite mass ratio 0.75.

scholarly journals Hydrometallurgical process development to recycle valuable metals from spent SCR deNOX catalyst

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jong Hyuk Jeon ◽  
Ana Belen Cueva Sola ◽  
Jin-Young Lee ◽  
Rajesh Kumar Jyothi
Keyword(s):  
Process Development ◽  
Spent Catalyst ◽  
Water Leaching ◽  
Scr Catalyst ◽  
Silicon Compounds ◽  
Valuable Metals ◽  
Spent Catalysts ◽  
Increasing Demand ◽  
Leaching Efficiency ◽  
And Tungsten

AbstractSpent catalyst, containing vanadium and tungsten oxide in a TiO2 glass fiber matrix, pose a risk of environmental contamination due to the high toxicity of its metal oxides if leached into the soil when disposed in landfills. Due to the increasing demand of metals and the continuous depletion of primary resources there is an growing necessity for recycling and reprocessing of spent catalysts and other secondary metal sources for environmental and economical reasons. Study of spent SCR catalyst soda roasting process with dissolved NaOH compared with the usual NaOH dry roasting and its influence in the subsequent water leaching. After optimization, the ideal parameters are roasting using a 0.4 ratio of NaOH/spent SCR catalyst in solution for 2 h at 973 K and de-ionized water leaching for 30 min, at 298 K with a pulp density of 30%. The research results show an important reduction of the roasting temperature and leaching time during the processing of spent SCR catalyst obtaining a 95.4% W and 80.2% V leaching efficiency liquor. Silicon compounds are one of the main impurities leached alongside the valuable metals and in this work, the silicon compounds leached are reduced significantly with the aim of avoiding the de-silication post-processing of the leach liquor. The main advantage of the proposed process is the increase of the leaching efficiency of vanadium and tungsten with a minimization of silicon impurities in a shorter time regardless of the leaching temperature.

scholarly journals Investigation on the Effect of Roasting and Leaching Parameters on Recovery of Gallium from Solid Waste Coal Fly Ash

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1251 ◽  
Author(s):  
Jing Huang ◽  
Yingbin Wang ◽  
Guanxuan Zhou ◽  
Yu Gu
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Acid Leaching ◽  
Cost Effective ◽  
Mass Ratio ◽  
Leaching Process ◽  
Cost Effective Method ◽  
Roasting Temperature ◽  
Leaching Parameters ◽  
Roasting Time

Coal fly ash (CFA) provides important resources of gallium, which is regarded as an irreplaceable material in many technologies. A prospective roasting reagent assisted acid leaching process was proposed for the purpose of extracting gallium. The extraction efficiency of gallium by NaF (sodium fluoride) roasting followed by HNO3 (nitric acid) leaching process was demonstrated. The effect of roasting temperature, roasting time, the NaF-CFA mass ratio, acid leaching temperature, acid leaching time, and acid concentration were investigated. The results revealed that under optimal conditions (roasting temperature of 800 °C, roasting time of 10 min, acid leaching in 2 mol/L HNO3 for 1 h, and the NaF-CFA mass ratio of 0.75:1), 94% of gallium was extracted. Compared to previous studies, the process is a cost-effective method which can greatly shorten reaction time. It can reduce environmental pollution as it requires fewer acid reagents with low concentration and additives. It is expected to provide a method for the extraction of gallium from CFA.

scholarly journals Selective Leaching of Rare Earth Elements (REEs) from Eudialyte Concentrate after Sulfation and Thermal Decomposition of Non-REE Sulfates

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 522 ◽  
Author(s):  
Balinski ◽  
Atanasova ◽  
Wiche ◽  
Kelly ◽  
Reuter ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Produced Water ◽  
Ph Value ◽  
Selective Extraction ◽  
Water Leaching ◽  
Niobium Aluminum ◽  
Roasting Temperature ◽  
Eudialyte Concentrate ◽  
Roasting Time

Eudialyte, a sodium rich zirconosilicate, is one of the promising sources for REEs (rare earth elements), particularly for HREEs + Y (heavy rare earth elements and yttrium). The key challenge in hydrometallurgical processing is the prevention of silica gel formation and REE separation from resulting multi-element leach solutions. This study deals with the selective extraction of REE from eudialyte concentrate by selective roasting. In this method, metal ions are converted into sulfates, followed by the decomposition of non-REE sulfates in a roasting step and the water leaching of the calcine. The effect of acid addition, roasting temperature, roasting time, pulp density and leaching time is studied. For sufficient conversion of REEs into sulfates, sulfuric acid is added in excess. At a roasting temperature of ≥750 °C sulfates of zirconium, hafnium, niobium, aluminum and iron decompose into sparingly soluble compounds, while REE and manganese sulfates remain stable up to a roasting time of 120 min. The silica present in the calcine is found to be metastable even after roasting. The amount of leached Si4+ is dependent predominantly on the pH value of the leaching medium. Applying the method, REEs can be efficiently separated from zirconium, hafnium, niobium, aluminum and iron. However, only diluted solutions can be produced. Water leaching of calcine at high solid/liquid ratios causes REE losses resulting from formation of double sulfates and gypsum. The acid excess removed from the reaction mixture in the roasting stage can be simply recovered by treatment of the gas phase.

scholarly journals Recovery of Cerium Oxide Abrasive from an Abrasive–Glass Polishing Waste through Alkaline Roasting Followed by Water Leaching

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 752
Author(s):  
Li-Pang Wang ◽  
Pei-Hsin Liu ◽  
Yan-Jhang Chen
Keyword(s):  
Cerium Oxide ◽  
Polished Glass ◽  
Optimal Conditions ◽  
Mass Ratio ◽  
Polishing Process ◽  
Water Leaching ◽  
Solid Ratio ◽  
Roasting Temperature ◽  
Mineralogical Phases ◽  
Glass Polishing

Abrasive–glass polishing waste is generated from the polishing process of glass components by using cerium oxide abrasive, which contains the cerium oxide abrasive and the polished glass. This study attempted to recover the cerium oxide abrasive from the abrasive–glass polishing waste through removing the polished glass by alkaline roasting using sodium hydroxide (NaOH) followed by water leaching. The experimental results indicated that the polished glass in the abrasive–glass polishing waste could be fully removed under the optimal alkaline roasting and water leaching conditions of roasting temperature of 450 °C, mass ratio of polishing waste to NaOH of 1:1, roasting time of 30 min, leaching pH of 3, leaching temperature of 25 °C, and liquid–solid ratio of 25 mL/g. The characteristics including elemental composition, particle size distribution, mineralogical phases, and morphology of the recovered cerium oxide abrasive obtained under the optimal conditions were similar to those of the original unused one, which was suitable to be reused for polishing again.

scholarly journals Novel Eco-friendly Roasting and Leaching Process Development to Recycle Valuable Metals from Spent SCR deNOX Catalyst

2021 ◽  
Author(s):  
Jong Hyuk Jeon ◽  
Ana Belen Cueva Sola ◽  
Jin-Young Lee ◽  
Rajesh Kumar Jyothi
Keyword(s):  
Process Development ◽  
Spent Catalyst ◽  
Water Leaching ◽  
Scr Catalyst ◽  
Silicon Compounds ◽  
Valuable Metals ◽  
Naoh Solution ◽  
Spent Catalysts ◽  
Increasing Demand ◽  
And Tungsten

Abstract Spent catalyst, containing vanadium and tungsten oxide in a TiO2 glass fiber matrix, pose a risk of environmental contamination due to the high toxicity of its metal oxides if leached into the soil when disposed in landfills. Due to the increasing demand of metals and the continuous depletion of primary resources there is an growing necessity for recycling and reprocessing of spent catalysts and other secondary metal sources for environmental and economical reasons. Study of spent SCR catalyst soda roasting process with dissolved NaOH compared with the usual NaOH dry roasting and its influence in the subsequent water leaching. After optimization, the ideal parameters are roasting with 40% NaOH solution for 2h at 973K and DI water leaching for 30minutes, at 298K with a pulp density of 30%. The research results show an important reduction of the roasting temperature and leaching time during the processing of spent SCR catalyst with the objective to recover vanadium and tungsten. Silicon compounds are one of the main impurities leached alongside the valuable metals and in this work, the silicon compounds leached are reduced significantly avoiding the de-silication post-processing of the leach liquor. The main advantage of the proposed process is the increase of the leaching efficiency of vanadium and tungsten in a shorter time regardless of the leaching temperature.

scholarly journals Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K2CO3 roasting and water leaching followed by CaCl2 precipitation

2020 ◽  
Author(s):  
Xianghui Liu ◽  
Qiaowen Yang
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Environmental Hazards ◽  
Leaching Rate ◽  
Water Leaching ◽  
Scr Catalysts ◽  
Amorphous Si ◽  
Reduction Catalysts ◽  
And Tungsten

Abstract Waste selective catalytic reduction (SCR) catalysts are potential environmental hazards. In this study, the recovery of vanadium and tungsten from waste SCR catalysts by K2CO3 roasting and water leaching was investigated. The roasting and leaching conditions were optimized: the leaching efficiencies of vanadium and tungsten were 91.19% and 85.36%, respectively, when 18 equivalents of K2CO3 were added to perform the roasting at 900 °C for 2 h, followed by leaching at 90 °C for 1 h. Notably, in the described conditions, the leaching rate of silicon was only 28.55%. Titanates, including K2Ti6O13 and KTi8O17, were also produced. Si removal was achieved in 85% efficiency adjusting the pH to 9.5, and the Si impurity thus isolated was composed of amorphous Si. Tungsten and vanadium were precipitated using CaCl2. At pH 10 and following the addition of 0.10 mol of H2O2 and 16 equivalents of CaCl2, the precipitating efficiencies of tungsten and vanadium were 96.89% and 99.65%, respectively. The overall yield of tungsten and vanadium was 82.71% and 90.87%, respectively. Graphic abstract

Concentrating Pt from a spent alumina carrier catalyst by a roast-leach process

2019 ◽  
Vol 116 (2) ◽  
pp. 204
Author(s):  
Haigang Dong ◽  
Jiachun Zhao ◽  
Weifeng Tong ◽  
Hao Cui ◽  
Yuedong Wu
Keyword(s):  
Sulfuric Acid ◽  
Enrichment Factor ◽  
Xrd Analysis ◽  
Enrichment Factors ◽  
Mass Ratio ◽  
Spent Catalyst ◽  
Roasting Temperature ◽  
Optimized Conditions ◽  
Soluble Sulfates ◽  
Roasting Time

A roast-leach process has been developed for concentrating platinum (Pt) from a spent Pt-Al2O3 catalyst. The effects of (NH4)2SO4 to spent catalyst mass ratio, roasting temperature and roasting time on the Pt enrichment factors were investigated. The results showed that the optimized roasting conditions were (NH4)2SO4 to spent catalyst mass ratio of 7.5, roasting temperature of 350 °C and roasting time of 5 h. The roasted product was mainly comprised of soluble NH4Al(SO4)2 and Al2(SO4)3 according to XRD analysis. The roasted product was leached in sulfuric acid to remove the soluble sulfates, and meanwhile Pt was kept in the residue. Under optimized conditions, a Pt concentrate with Pt content of 73.2% could be obtained from the spent catalyst with 0.27% Pt, and the corresponding Pt enrichment factor was more than 270.

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