Extraction of lithium from lepidolite using chlorination roasting-water leaching process

Chlorination roasting followed by water leaching process was used to extract lithium from lepidolite.The microstructure of the lepidolite and roasted materials were characterized by X-ray diffraction（XRD）.Various parameters including chlorination roasting temperature,time,type and amount of chlorinating agents were optimized.The conditional experiments indicate that the best mass ratio of lepidolite to NaCl to CaCl2 is 1：0.6：0.4 during the roasting process.The extraction of lithium reaches peak value of 92.86% at 880 °C,potassium,rubidium,and cesium 88.49%,93.60% and 93.01%,respectively.The XRD result indicates that the major phases of the product after roasting lepidolite with mixture of chlorinating agents（CaCl2 and NaCl） are SiO2,CaF2,KCl,CaSiO3,CaAl2Si2O8,NaCl and NaAlSi3O8.

Fe extraction from high-silicon and aluminum cyanide tailings by pretreatment of water leaching before magnetic separation

Pretreatment of high content of Si- and Al-containing cyanide tailings by water leaching to remove some impurities, such as the major impurities minerals of Si and A1, as well as its effect on Fe extraction in the water leaching process was investigated. The effects of different parameters on iron recovery were studied, and the reaction parameters were proposed as follows： sodium carbonate content of 30%, water leaching at 60 ~C for 5 min, liquid/solid ratio of 15：1, and exciting current of 2 A. Under these optimal conditions, magnetic concentrate containing 59.11% total iron and a total iron recovery rate of 76.12% was obtained. In addition, the microstructure and phase transformation of the process of water leaching were studied by X-ray powder diffraction technique （XRD）, Electronic image of backscattering （BEI）, X-ray fluorescence （XRF）, and energy dispersive spectrometry （EDS）. The results indicate that the soluble compound impurities generated in the roasting process are washed out, and the dissoluble substances enter into nonmagnetic materials by water leaching, realizing the effective separation of impurities and Fe.

Extraction of molybdenum and nickel from roasted Ni-Mo ore by hydrochloric acid leaching, sulphation roasting and water leaching

To extract molybdenum and nickel from the roasted Ni-Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leaching rate of Mo and Ni. Under the optimum conditions of hydrochloric acid leaching （roasted Ni-Mo ore leached with 0.219 mL/g hydrochloric acid addition at 65 ℃ for 30 min with a L/S ratio of 3 mL/g）, sulphation roasting （51.9% sulfiaric acid addition, roasting temperature 240 ℃ for 1 h）, followed by leaching with the first stage hydrochloric acid leaching solution at 95 ℃ for 2 h, the leaching rates of Mo and Ni reached 95.8% and 91.3%, respectively.

Recovery of valuable metals from zinc leaching residue by sulfate roasting and water leaching

Zinc leaching residue(ZLR),produced from traditional zinc hydrometallurgy process,is not only a hazardous waste but also a potential valuable solid.The combination of sulfate roasting and water leaching was employed to recover the valuable metals from ZLR.The ZLR was initially roasted with ferric sulfate at640°C for1h with ferric sulfate/zinc ferrite mole ratio of1.2.In this process,the valuable metals were efficiently transformed into water soluble sulfate,while iron remains as ferric oxide.Thereafter,water leaching was conducted to extract the valuable metals sulfate for recovery.The recovery rates of zinc,manganese,copper,cadmium and iron were92.4%,93.3%,99.3%,91.4%and1.1%,respectively.A leaching toxicity test for ZLR was performed after water leaching.The results indicated that the final residue was effectively detoxified and all of the heavy metal leaching concentrations were under the allowable limit.

Migration and distribution of saline ions in bauxite residue during water leaching

Bauxite residue,a highly saline solid waste produced from digestion of bauxite for alumina production,is hazardous to the environment and restricts vegetation establishment in bauxite residue disposal areas.A novel water leaching process proposed here was used to investigate the dynamic migration and vertical distribution of saline ions in bauxite residue.The results show that water leaching significantly reduced the salinity of bauxite residue,leaching both saline cations Na+,K+,Ca2+and anions CO32-,SO42-,HCO3-.Na+and K+migrated from 40-50 to 20-30 cm of the column,presenting a high migration capacity.The migration capacity of Ca2+was lower and accumulated at 30-40 cm of the column.CO32-initially distributed at 20-30 cm of the column,subsequently transported to 30-40 cm of the column,and finally returned to 20-30 cm of the column along with evaporation.SO42-was originally distributed at 40-50 cm,but finally migrated to 20-30 cm of the column.Nevertheless,HCO3-remained at the bottom of the column,and its migratory was less affected by evaporation.

Chlorination roasting-coupled water leaching process for potash recovery from waste mica scrap using dry marble sludge powder and sodium chloride

The present paper reports the effective utilization of marble sludge powder(MSP)for the recovery of potash values from waste mica scrap using chlorination roasting-water leaching method.Characterization studies indicated the presence of dolomite as the major mineral phase in MSP,whereas muscovite and quartz were observed in the mica sample.The acid leaching studies suggest a maximum of 22%potash recovery under conditions:4 M H2SO4 acid,particle size of^100μm,stirring speed of 600 r/min,leaching temperature of 75℃,and leaching time of 90 min.The chlorination roasting-water leaching process was adopted to achieve the lowest level of 80%-90%potash recovery.The optimum conditions for the recovery of^93%potash from mica(~8.6wt%K2O)requires 900℃ roasting temperature,30 min roasting time,and 1:1:0.75 mass ratio of mica:MSP:NaCl.The roasting temperature and amount of NaCl are found to be the most important factors for the recovery process.The reaction mechanism suggests the formation of different mineral phases,including sylvite(KCl),wollastonite,kyanite,and enstatite,during roasting,which were confirmed by X-ray diffraction(XRD)analyses and scanning electron microscopy(SEM)morphologies.The MSP-blended NaCl additive is more effective for potash recovery compared with the other reported commercial roasting additives.

Recovery of vanadium and tungsten from waste selective catalytic reduction catalysts by K_(2)CO_(3) roasting and water leaching followed by CaCl_(2) precipitation

Waste selective catalytic reduction(SCR)catalysts are potential environmental hazards.In this study,the recovery of vanadium and tungsten from waste SCR catalysts by K_(2)CO_(3)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 K_(2)CO_(3)were added to perform the roasting at 900℃ 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 K_(2)Ti_(6)O_(13)and KTi8017,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 CaCl_(2).At pH 10 and following the addition of 0.10 mol of H_(2)O_(2)and 16 equivalents of CaCl_(2),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.

Zinc extraction from zinc oxidized ore using(NH4)2SO4 roasting−leaching process

An improved method of(NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied.The operating parameters were obtained by investigating the effects of the molar ratio of(NH4)2SO4 to zinc,roasting temperature,and holding time on zinc extraction.The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol^−1.The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry–differential thermal analysis curves.The water leaching conditions,including the leaching temperature,leaching time,stirring velocity,and liquid-to-solid ratio,were discussed,and the leaching kinetics was studied.The reaction rate was obtained under outer diffusion without product layer control;the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol^−1.The maximum zinc extraction ratio reached 96%while the efficiency of iron extraction was approximately 32%under appropriate conditions.This work offers an effective method for the comprehensive use of zinc oxidized ores.

Intensifying recovery of metallic aluminum in secondary aluminum dross by alkali roasting−water leaching

An innovative process was proposed to recover metallic aluminum from secondary aluminum dross(SAD)by alkali roasting−water leaching.Thermodynamic calculations and experimental results were used to illustrate the phase transformation and reaction mechanism of the alkali roasting process.The leaching behaviors of roasted residue were also analyzed.Under optimal conditions,the aluminum extraction rate reached 93.08%.In addition,the kinetics of the water leaching of roasted products was studied through shrinking core model,and it was revealed that the leaching process of aluminum was in accord with diffusion control.The apparent activation energy of the leaching process was calculated to be 3.44 kJ/mol.Based on the above study,the underlying mechanism of the alkali roasting−water leaching was clarified.

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting(SCS)dust using a sulfating roasting−water leaching process were investigated.The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl.Under the sulfating roasting conditions of the roasting temperature of 250℃ and the sulfuric acid excess coefficient of 1.8,over 74 wt.%of F and 98 wt.%of Cl were volatilized into flue gas.Approximately 98.6 wt.%of Zn and 96.5 wt.%of Cu in the roasting product were dissolved into the leaching solution after the water leaching process,while the leaching efficiencies of Pb and Sn were only 0.12%and 0.22%,respectively.The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

A method for recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures： low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.

A two-step zircon decomposition method to produce zirconium oxychloride:alkali fusion and water leaching

In this work,a two-step zircon method to produce zirconium oxychloride was introduced,and the alkali fusion technique with NaOH and water leaching process were investigated.The effects of the operating conditions on the decomposition of zircon were determined,and the optimal conditions are as follows:alkali/zircon mass ratio of 0.7 at the first step and 0.6 at the second step(0.7+0.6),fusion temperature of 700℃and fusion time of 0.5 h at the first step and 0.5 h at the second step(0.5+0.5 h).Under these conditions,the decomposition alloy of zircon sand can reach 97.25%.In the fusion process of zircon sand,the products of first step are mainly Na2ZrO3 and ZrSiO4,the products of second step are Na2ZrO3 and Na2SiO3,and the diffraction peaks of Na2ZrSiO5 are not observed.The conditions of water leaching process were investigated as well,and the optimal conditions are as follows:liquid-solid ratio of 5:1,leaching time of 0.5 h,leaching temperature of 50℃and leaching three times.Under these conditions,the contents of leaching products SiO2 and Na2O are 3.51%(40%ZrO2)and 4.46%(40%ZrO2),respectively.The crystal phase structures of Na2ZrO3 and Na2SiO3 are formed in water leaching process.

Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida

Water quality in Florida is significantly impacted by nitrate(NO_(3)-N)leaching losses from agriculture in a large part of the state.Horticultural crops are planted across large areas of Florida on coarse sandy soils with low soil water retention and soil organic matter,increasing the potential for NO_(3)-N leaching.Nitrate leaching losses from the root zone of vegetable cropping systems can negatively impact groundwater.New tools such as the Nitrogen Index(N-Index)are able to quickly assess N use efficiency and losses via NO_(3)-N leaching from agricultural systems.Furthermore,the N-Index provides technical information about N losses pathways tied to agricultural management practices with a great level of confidence;this information has been used by researchers,growers and policymakers as a decision support system.However,the current version of the NIndex that has been used for different field crops has not been calibrated to be used in plastic-mulched horticultural cropping systems.The aim of this work was to calibrate and validate the N-Index for plasticmulched horticultural cropping systems of Florida.This study found that the N-Index tool accurately identified and ranked the risk of N losses in the evaluated horticultural systems.The N-Index was calibrated for Florida's plastic-mulched horticultural cropping systems using a sensitivity analysis.The adjusted N-Index was validated using compiled data of vegetables grown under plastic mulching systems during three consecutive seasons.Results from these studies suggest that the N-Index can be an easy-to-use tool capable of assessing nitrogen management practices for vegetable systems.The tool can be used to guide nutrient managers in the implementation of best nitrogen management practices that could contribute to reduced NO_(3)-N leaching losses from vegetable systems in Florida,contributing to a smaller environmental footprint and conservation of water quality.

Recovery of titanium and vanadium from titanium–vanadium slag obtained by direct reduction of titanomagnetite concentrates

A process of NaOH molten salt roasting-water leaching to treat titanium-vanadium slag obtained by direct reduction of titanomagnetite concentrates was investigated.X-ray diffraction(XRD), scanning electron microscopy(SEM) equipped with energy dispersive spectroscopy(EDS), and thermogravimetry-differential scanning calorimetry(TG-DSC) techniques were used to characterize the samples. The results show that anosovite(Mg_(x)Ti_(3-x)O_(5))and clinopyroxene [Ca(Ti,MgAl)(SiAl)_(2)O_(6)] are the major phases of titanium-vanadium slag. In the NaOH molten salt roasting process, titanium is converted to intermediate product Na_(2)TiO_(3) and vanadium is converted to water-soluble vanadate. The response surface methodology(RSM) was used to optimize the roasting process conditions. NaOH to slag mass ratio(N/S) and roasting temperature are the main influential factors. Under the optimal roasting conditions,i.e., roasting temperature of 550℃, N/S of 1.20, and roasting time of 80 min, the conversions of titanium and vanadium are 96.5 % and 93.0 %, respectively. In the water leaching process, Na_(2)TiO_(3) is converted to amorphous structure of H_(2)TiO_(3) since Na^(+)is exchanged with H^(+). Up to 93.0 % vanadium is leached out under the optimal leaching conditions. Titanium and vanadium in the titanium-vanadium slag can be separated and then recovered.