Deep Purification of Zinc Ammoniacal Leaching Solution by Cementation with Zinc Dust

Deep purification of zinc ammoniacal leaching solution by cementation using zinc dust was studied.The effects of relative amount of metallic impurities,dosage of zinc dust,purification time,temperature,pH value and total ammonia concentration in the solution on the purification of the solution were investigated.The results indicate that total ammonia concentration in the solution had no effect on the purification,but relative amount of metallic impurities,dosage of zinc dust,purification time,temperature and pH value of the solution were the main factors influencing the purification.Keeping appropriate molar ratio of copper to cadmium or nickel to cadmium was beneficial to the cementation of cadmium.Nevertheless,the presence of cobalt went against the cementation of cadmium and cobalt.All metallic impurities could be decreased to acceptable levels under the optimized conditions of 2 g/L of zinc dust dosage,1 h of purification time,35℃,pH value 9.03 of zinc ammoniacal leaching solution.The deeply purified zinc ammoniacal solution obtained by one-stage purification meets the requirements of zinc electrowinning.

Reduction of Aromatic α-Keto Esters by Commercially Available Zinc Dust and Ammonium Formate: Formation of Aromatic α-Hydroxy Esters

Various aromatic α-keto esters were rapidly and selectively reduced to aromatic α-hydroxy esters by commercially available zinc dust and ammonium formate in the presence of other functional groups such as halogens, methoxy and esters.

Selective recovery of lead from zinc oxide dust with alkaline Na_2EDTA solution

The selective recovery of lead from the zinc oxide dust using an alkaline Na2EDTA solution was investigated. The effects of temperature, leaching time, Na2EDTA concentration and initial NaOH concentration on the leaching rates of lead and zinc were studied. The following optimized leaching conditions were obtained： liquid-to-solid ratio 5：1 mL/g, stirring speed 650 r/min, Na2EDTA concentration 0.12 mol/L, initial NaOH concentration 0.5 mol/L, leaching temperature 70 ℃, leaching time 120 min. Under the optimized conditions, the average leaching rates of lead, zinc, fluoride and chloride are 89.92%, 0.94%, 62.84% and 90.02%, respectively. The filtrate was used to electrowin lead powders. The average current efficiency of electrowinning is about 93% and lead content is higher than 98% under the conditions of temperature of 60 ℃, current density of 200 A/m2, H3PO4 concentration of 1.5 g/L, and lead ion concentration of above 5 g/L. The consumption of Na2EDTA and the direct current are about respectively 0.218 kg and 0.958 kW·h for per kilogram of lead powder.

Preparation of high purity cadmium with micro-spherical architecture from zinc flue dust

This research has focused on the treatment of zinc flue dust by an acid leach process, combining an environmentally suitable impurity removal process to recover cadmium. Optimum conditions were found as follows： H2SO4 concentration 90 g/L, liquid/solid ratio 6：1, leaching temperature 60 ℃ and leaching time 1.0 h. Under these conditions, 95.8% cadmium was recovered. FeAsO4 and Fe（OH）3 precipitates with FeCI3 are found to be highly effective to obtain a high degree of separation of heavy metals and the oxyanions of arsenic from the leachate. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at n（Fe）/n（As） ratio of 3：l and pH 6. The removal rates ofFe, Pb and Cu from the solution were greater than 98.9%, and As removal rate was 99.6%. A solvent extraction with P204 was used for the separation of zinc and cadmium. Optimum conditions are obtained as follows： 20% P204 （volume fraction） diluted with kerosene at room temperature, pH 3.0, and varying organic/aqueous （O/A） phase ratio 1：1. The extraction rate of zinc is 99.2% under these conditions. Spherical cadmium particles showing nearly uniform size were produced by hydrogen reduction at 310 ℃ and the crystal structure was cubic. In addition, the purity of the recovered cadmium powder is more than 99.99%.

Dielectric properties and temperature increase characteristics of zinc oxide dust from fuming furnace

Cavity perturbation method was used to determine the dielectric properties （ε′,ε″, and tanδ） of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 ＆#176;C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.

Selective recovery of zinc from zinc oxide dust using choline chloride based deep eutectic solvents

Deep eutectic solvents(DESs) are a kind of potential lixiviant for selective metal processing due to their versatile complexation properties. In this study, we investigated the recovery of zinc from zinc oxide dust using choline chloride-ureaethylene glycol(ChCl-urea-EG) DESs. The zinc extraction efficiency can be up to 85.2% when the slurry concentration is 50 g/L, leaching temperature is 80 °C and stirring speed is 600 r/min. The leaching process is controlled by the diffusion and the corresponding activation energy is 32.1 k J/mol. The resultant solution was directly used for the electrodeposition of zinc. The pure zinc deposit is obtained with a current efficiency of 82.6%. Furthermore, the ChCl-urea-EG DESs can be recycled. This approach is shown to be promising for the recycling of zinc from the zinc-containing dust.

Indium recovery from zinc oxide flue dust by oxidative pressure leaching

Indium was recovered from zinc oxide flue dust(ZOFD)with sulfuric acid by oxidative pressure leaching in an autoclave, and the effects of different technological conditions on indium leaching were studied.Potassium permanganate and hydrogen peroxide were used as oxidants.The atmospheric pressure leaching experiments were also carried out.The experimental results show that the leaching rate of indium can be effectively improved by oxidative pressure leaching.The optimum conditions of pressure leaching are determined as sulfuric 5.10 mol/L acid,leaching time 150 min,temperature 90℃,and the H2O2 dosage of 0.5 mL/g or 2.5%KMnO4.The leaching rate of indium is more than 90%,which is increased by 13%compared with that of atmospheric pressure leaching process without oxidant under the optimum conditions.

Leaching behavior of zinc from crude zinc oxide dust in ammonia leaching

Zinc extraction from crude zinc oxide(CZO)is beneficial to the full utilization of secondary resources and environmental protection.In this paper,a systematic investigation was carried out to study the leaching behavior of CZO by using ammonia-ammonium carbonate solution.It was found that the maximum leaching rate of zinc from CZO dust was 95.7%under the conditions of[Zn]T:[NH 3]T:[CO_(3)^(2−)]=1:7.00:1.75,liquid to solid ratio 5:1,leaching temperature 30℃ and leaching time 60 min.Compared with pure zinc oxide(PZO)leaching,the CZO leaching required longer time and more leaching agents,which is caused by the Cd^(2+),Pb^(2+) and other metal cationic impurities in CZO.The metal cationic impurities dissolved in the leaching solution and combined with ammonium to form complexes,consuming leaching agents and affecting zinc leaching.

A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

A novel hydrothermal process was developed to extract zinc from pure zinc ferrite（ZnFe2O4） nanopowder and zinc-containing electric arc furnace（EAF） dust using hexahydrated ferric chloride（FeCl3-6H2O） as a decomposing agent.The effects of solid FeCl3-6H2O to ZnFe2O4 ratio by mass（RF/Z）,hydrothermal reaction temperature,and time on zinc extraction were systematically investigated.In the results,when the hydrothermal reaction is conducted at 150℃ for 2 h with RF/Z of 15：20,the efficiency of zinc extraction from ZnFe2O4 reaches97.2%,and the concentration of ferric ions（Fe^3＋） in the leaching solution is nearly zero,indicating a high selectivity for zinc.In addition,the zinc extraction efficiency from the EAF dust reaches 94.5%in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl3-6H2O to EAF dust ratio by mass（RF/EAF dust） of 15：10.Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.

Mathematical model of the direct reduction of dust composite pellets containing zinc and iron

Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace （RHF） in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.

Ultrasound effects on zinc recovery from EAF dust by sulfuric acid leaching

In this work, an ultrasound-assisted leaching process was studied for the recovery of zinc from electric arc furnace （EAF） dust, in which zinc was mainly present in the form of franklinite （60%）. HydrometaUurgy is emerging as a preferred process for the recovery of a va- riety of metals, and the use of ultrasound could offer advantages over the conventional leaching process, especially for the dissolution of franklinite. Franklinite is a refractory phase that is difficult to leach and represents the main obstacle in conventional hydrometallurgy proc- essing. Atmospheric leaching with different sulfuric acid concentrations （0.2-2.0 M） at two temperatures （323 and 353 K） was performed. The tests were conducted using both conventional and ultrasound-assisted leaching. After the leaching tests, the solid residues were charac- terized by scanning electron microscopy （SEM） and X-ray diffraction （XRD） techniques, whereas the leach liquor was analyzed by induc- tively coupled plasma spectroscopy OCP）. The use of ultrasound facilitated the dissolution of franklinite at low acid concentrations and re- suited in a greater zinc recovery under all of the investigated operating conditions.

Study on the volatilization kinetics of zinc in carbon-containing pellets made of Zn-bearing dusts

A study was carried out on the volatilization kinetics of Zn in the pellets made of Zn-bearing dusts mixed with coal powder in a nitrogen atmosphere and within the temperature range between 1 100℃and 1 300℃. The study shows that the reduction temperature has a significant effect on the volatilization rate of zinc and that either the coal particle size or the excess carbon content has no effect on the volatilization rate. The obtained activation energy for the volatilization of zinc is 79.42 kJ/mol. The volatilization rate of zinc is controlled by the reaction between the zinc oxides and CO.

Wetting agent investigation for controlling dust of lead-zinc ores

The purpose of this project is to control the pollution of dust,which occurred in a typical lead-zinc mine.Two kinds of surfactants and water glass were chosen as the wetting agents to study the behaviours of suppressing the dust.The performances of the wetting agents of various sizes and water content of dust and their compositions among different weting agents were investigated. Firstly,the chemical compounds,dispersity,water content,bulk density and other relevant physico-chemical properties of the choiced dust of lead-zinc ore were mensurated.A great number of down-ward penetrating tests were conducted to different partical sizes of dust and to analyze the dust wetting behaviour respectively.The optimal compositions of wetting agents were obtained in accordance with different water contents and partical sizes of the dust after analyzing and statisting the achieved experimental data. The data show that the efficiency of chemical dust suppression of weting agents is much better than that of water.The results of the research work prove that the partical size and the water content of the dust are very important factors to the dust suppression.The results are also proved validly by the dropping experiment,which takes the penetrating diameter and penetrating time as the major factors.The superfine dust is much more difficult to be wetted.Since increasing the water content of dust is the best approach to control it,the choice of wetting agents for improving dispensation is significant.

Reduction process and zinc removal from composite briquettes composed of dust and sludge from a steel enterprise

In this study, composite briquettes were prepared using gravity dust and converter sludge as the main materials; these briquettes were subsequently reduced in a tube furnace at 1000-1300℃ for 5-30 min under a nitrogen atmosphere. The effects of reaction temperature, reaction time, and carbon content on the metallization and dezincification ratios of the composite briquettes were studied. The reduced com- posite briquettes were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and energy-dispersive spectroscopy （EDS）. The results show that the gravity dust and converter sludge are combined into the composite briquettes and a reasonable combination not only improves the performance of the composite briquettes, but also leads to the reduction with no or little reductant and flux. As the re- action temperature is increased and the reaction time is extended, the metallization and dezincification ratios of the composite briquettes in- crease gradually. When the composite briquettes are roasted at 1300℃ for 30 rain, the metallization ratio and dezineification ratio reaches 91.35% and 99.25%, respectively, indicating that most of the iron oxide is reduced and the zinc is almost completely removed. The carbon content is observed to exert a lesser effect on the reduction process; as the C/O molar ratio increases, the metallization and dezincification ra- tios first increase and then decrease.

Volatilization of zinc and lead in direct recycling of stainless steel making dust

The volatilization of zinc and lead from the stainless steel making dust pellets in the direct recycling procedure was conducted by using a thermo-gravimetric analyzer and a Tamman furnace in the nitrogen atmosphere respectively. The results show that the temperature has a significant effect on the volatilization rates of zinc and lead, and the carbon content in the pellets has no effect on the volatilization process. The volatilization of zinc is controlled by the chemical reaction between zinc oxide and carbon monoxide, while the volatilization of lead is controlled by the evaporation from liquid phase to the atmosphere. The volatilization of zinc and lead mainly happen at about 1 000 ℃ according to non-isothermal experiment.

Alkaline leaching of metal melting industry wastes and separation of zinc and lead in the leach solution

In this work, a thorough examinations on the extractability of zinc and lead present in the steelmaking dusts using alkaline leaching process and the effectiveness of the zinc and lead separation in the resultant leaching solutions using sulfide precipitation method were made. It was found that only about 53% of zinc and over 70% of the lead could be leached out of the dusts, while the other 47% of zinc and 30% of lead were left in the leaching residues. The zinc and lead in the resultant leaching solution can be effectively and selectively separated. When the weight ratio of sodium sulfide (M.W. = 222-240) to Pb was kept at 1.8, the lead in the solution could be precipitated out quantitatively while all the zinc was remained in the solution. The zinc left in the solution can be further recovered by the addition of extra sodium sulfide with a weight ratio of sodium sulfide to the zinc over 2.6. The resultant filtrate can be recycled to the leaching of dust in the next leaching process.

氧化锌烟尘中锗的浸出行为

针对锌浸渣烟化挥发产生的氧化锌烟尘中锗浸出率低、氧化锌烟尘浸出渣中锗含量高的问题,开展了锌浸渣烟化挥发过程不同收尘器收集的氧化锌烟尘中锗的浸出行为研究,分析了锗、铁、硅浸出的相关性,考察了锗的浸出行为、渣中锗的赋存状态,揭示了渣中锗难以被进一步浸出的原因。并在此基础上,对氧化锌烟尘浸出渣进行硫酸浸出分解铁酸盐−盐酸浸出解离硫酸铅−氢氟酸浸出解离硅酸盐的梯级强化浸出。结果表明:混合氧化锌烟尘中锗主要赋存于硅酸盐及固溶体中,尤其是锅炉尘中铁酸盐和硅酸盐较高,制约了锗浸出率的提高;影响锗浸出率的关键因素是氧化锌烟尘中铁、硅含量,渣中不溶锗主要赋存于难溶硅酸盐矿物及固溶体中,提高锗浸出率的关键是硅酸盐的解离;在硫酸体系下,采取高温高酸浸出解离难溶铁酸锌及含硅矿物,控制过程硅的浸出与沉淀,可进一步提高锗的浸出率。

含锌冶金尘泥还原焙烧-磁选分离试验

为实现钢铁企业含锌冶金尘泥低碳环保高效的资源化利用,对铁含量为30.38%、锌含量为4.79%的含锌冶金尘泥进行还原焙烧-磁选分离研究。结果表明,该含锌冶金尘泥直接磁选难以实现锌铁有效分离,在焙烧温度950℃、焙烧时间20 min、磁选强度100 mT等条件下,磁选精矿铁回收率为79.50%、铁含量为57.00%、锌含量为2.45%,磁选尾矿锌回收率为71.06%、锌含量为9.92%、铁含量为16.81%,锌铁分离效果较好。磁选产物中精矿主要以单质Fe为主,尾矿主要由SiO_(2)与ZnO等物相组成。

微波焙烧对钢铁行业含锌冶金尘泥锌铁分离的影响

为推进钢铁行业含锌冶金尘泥的资源化利用,对铁含量为30.38%、锌含量为4.79%的含锌冶金尘泥进行微波还原焙烧-磁选分离试验研究。结果表明:含锌冶金尘泥未焙烧直接磁选以及常规马弗炉还原焙烧-磁选的方式均难以较好实现含锌冶金尘泥中锌铁的有效分离;在微波马弗炉700℃、15 min时,焙烧产物中主要存在的物相为单质Fe,焙烧产物在磁场强度为150 mT时,含锌冶金尘泥中锌铁能够达到较好的分离,所得磁选的精矿指标:锌含量为2.73%、铁含量为57.84%、铁回收率为88.67%,磁选的尾矿指标:铁含量为9.54%、锌含量为9.85%、锌回收率为61.72%。

从铁矾渣侧吹熔炼—烟化法烟灰中回收锌镉及其净化除杂

研究了采用酸性浸出—硫化除杂法从铁矾渣侧吹熔炼—烟化法产出的烟灰中回收锌、镉,并选择性除去浸出液中的铜,产物用以制备镉掺杂硫化锌;在热力学分析基础上,探明了硫酸体系下锌浸出率影响因素及其浸出动力学;通过正交试验明确了各参数对硫化钠选择性除杂的影响。结果表明:烟灰中锌主要以氧化锌形式存在,其浸出过程符合混合控制,表观活化能为73.70 kJ/mol;在最佳条件下,锌浸出率达98.99%。以Na_(2)S用量为理论添加量的3.2倍,控制体系pH=2.0,铜去除率可达95.97%,同时有效保留锌、镉,实现了铜与锌、镉的选择性分离。