A novel separation process for detoxifying cadmium-containing residues from zinc purification plants

A novel separation process for detoxifying cadmium-containing residues arising from zinc hydrometallurgical processes has been developed. The solution of sulfuric acid and ammonium citrate ((NH₄)₃C₆H₅O₇) is used as the lixiviant to partially extract copper and other metals from the residue at room temperature. Copper in the leachate is recovered by solvent extraction (SX) with LIX 973. Cobalt in the raffinate from the copper SX process is recovered by precipitation with α-nitroso-β-naphthol. Zinc remaining in the solution, at high concentrations, is further separated from cadmium by solvent extraction with P204 (di(2-ethylhexly)phosphoric acid, D2EHPA). The results show that around 50% of the copper and virtually all the zinc, cadmium and cobalt in the residue can be leached under the experimental conditions used here. Virtually all dissolved copper and cobalt can be recovered in the subsequent solvent extraction and precipitation processes. The presence of (NH₄)₃C₆H₅O₇ could significantly facilitate the extraction of zinc by D2EHPA. More than 97% of the dissolved zinc can be recovered through a two-stage counter current solvent extraction process. After separating copper, cobalt and zinc, cadmium can easily be recovered from the solution either by cementation with zinc powder or by electrowinning, while the purified solution can be recycled back to the leaching process.     

电弧炉烟尘湿法提锌研究

江苏苏钢集团电弧炉炼钢烟尘含锌15.4%,并主要分布在铁酸锌中。对该炼钢烟尘进行浸出试验,结果表明：以氢氧化钠为浸出剂进行碱性浸出时,锌的浸出率仅为34.0%;以硫酸为浸出剂进行酸性浸出时,在搅拌转速为420 r/min,硫酸浓度为200 g/L,液固比为10∶1,反应温度为90 ℃,浸出时间为2 h的条件下,锌的浸出率达到98.7%。     

含铟锌渣氧粉加压氧化浸铟的工艺研究

研究了含铟锌渣氧粉在加压和加入氧化剂的条件下与工业硫酸反应时硫酸初浓度、浸出时间、反应温度、氧化剂用量等工艺条件对铟浸出效果的影响。研究结果表明,加压和加入氧化剂高锰酸钾对锌渣氧粉的浸出有较好的强化作用,能明显提高铟浸出率。其最佳工艺条件：硫酸初浓度为400 g/L,反应时间为120 min,反应温度为120 ℃,高锰酸钾用量为矿样量的4%,液固比为8,反应压强为0.5 MPa,搅拌器转速为400 r/min。在此条件下,锌渣氧粉的铟浸出率可达到90.6%。     

在密闭鼓风炉熔炼过程中锗铟的富集及综合回收

在密闭鼓风炉炼铅锌过程中 ,锗和铟富集于真空炉渣中 ,铟富集于B塔底铅和粗铅中 .先采用氯化蒸馏从真空炉渣中回收锗 ,再从其残液中用TBP和P2 0 4 萃取回收铟 ,锗、铟的回收率分别高于 78%,83%;采用碱熔造渣捕集铟、水洗除碱、混酸浸出铟的工艺从B塔底铅中回收铟 ,回收率85 %;采用硫酸熟化浸出、铁屑置换除杂、P2 0 4 萃取富集的工艺从反射炉烟尘中回收铟 ,铟的回收率约 85 %.     

加压氧化对锌渣氧粉中铟浸出率影响的试验研究

以含铟的锌渣氧粉为原料,以硫酸为浸出剂,研究了锌渣氧粉在高压釜中浸铟时氧化剂种类和用量、酸初始浓度等工艺条件对铟浸出率的影响。结果表明,加压和氧化对铟的浸出过程都有较好的强化效果。在液固比为8、反应时间为150min、搅拌速度为575r/min、反应温度为90℃、空气压力为0.5MPa(表)和硫酸初浓度为500g/L的浸出条件下,在双氧水用量为0.5mL/(g矿)、高锰酸钾用量为0.025g/(g矿)时,铟浸出率可达到90%以上,比无氧化剂常压浸出提高了13个百分点。     

以废旧NCM523型电池正极材料浸出液制备NiCo2O4和Li2CO3研究

采用湿法冶金方法回收废旧NCM523型锂离子电池正极材料中的镍、钴和锂, 正极材料的硫酸浸出液经净化除杂后, 采用“水热沉淀-煅烧法”制备NiCo₂O₄, 再采用化学沉淀法回收锂。研究了添加剂种类、水热温度及时间、煅烧温度对产物形貌的影响。结果表明, 以电极材料硫酸浸出液为原料, 以草酸作沉淀剂、六次甲基四胺作表面活性剂, 在140 ℃下水热反应4 h, 得到NiCo₂O₄前驱体; 前驱体在300 ℃下煅烧2 h, 得到形貌均匀的棒条状NiCo₂O₄材料; 采用饱和Na₂CO₃溶液沉淀水热反应母液中的锂, 得到Li₂CO₃。该工艺初步实现了废旧电池正极材料中有价金属镍、钴和锂的回收利用。     

有机除钴剂（OACR剂）在湿法炼锌工艺中的应用

为提高湿法炼锌净化工序中除钴效率,开展了有机除钴剂（OACR剂）在不同的净化工艺条件下的除钴实验,测试了活性炭吸附残余OACR剂后,吸附后液的粘度、表面张力等物理性质、红外透过光谱以及阴极极化曲线,并用吸附后液配制电解液进行了模拟电解实验。结果表明：OACR剂可在较宽的工艺范围内高效除去净化前液中钴,适当的活性炭吸附操作可大部分除去净化后液中残余的OACR剂。吸附后液的析锌电位与硫酸锌溶液的析锌电位相当,析氢过电位略有增大,说明吸附后液进入锌电解沉积工序不会对电解过程带来不利影响。模拟电解实验中,吸附后液配制电解液的电积锌电流效率不低于纯硫酸锌配制电解液的电积锌电流效率。将OACR剂应用于湿法炼锌净化工序可提高除钴效率并对电解无负面影响。     

用萃铟余液生产氧化锌的试验研究

以某厂铟冶炼生产过程中产生的废液--萃铟余液为原料,进行了生产氧化锌的小型联合试验。萃铟余液先经中和残酸和射流空气法初步除铁,再用高锰酸钾和锌粉通过4段净化除去残铁及锰、砷、锑、铜、镉等杂质,然后用碳酸钠沉锌,生成的碱式碳酸锌经3次洗涤后进行干燥、煅烧、破碎,得到氧化锌产品。经检测,产品达到工业活性氧化锌的一等品标准。     

烟化炉烟灰制备高等级氧化锌的研究

本文介绍了利用氨法处理杂质成分复杂的某大型冶炼厂炼铅系统烟化炉氧化锌烟灰制备高等级氧化锌的工艺。该工艺采用硫酸铵-氨混合浸出体系,浸出液经过净化后利用蒸氨及复盐沉淀的方法沉锌,得到的氢氧化锌经煅烧制得高级氧化锌。采用该工艺产出的高等级氧化锌的氧化锌含量达到99.7%,并且整个工艺过程简单。     

湿法炼锌协同处置富氧顶吹炼铅烟尘分离回收镉的生产实践

针对富氧顶吹炼铅工艺铅烟尘中镉不断富集的难题,为充分发挥铅锌冶炼联合工艺流程的优势,利用湿法炼锌中的浸出工序实现烟尘中镉与铅的分离,再采用锌粉置换、净化,实现镉的分离和回收。结果表明：在初始硫酸浓度为20 g/L、液固比4∶1、浸出温度70℃、浸出时间3 h的优化条件下,铅烟尘硫酸浸出段镉浸出率为85.7%;烟尘中铅、银进入浸出渣,可返回铅系统实现铅的回收,浸出液可采用铜渣除,氯控制氯离子浓度小于200 mg/L;除氯后液并入锌冶炼湿法浸出、净化流程回收镉,实现镉的资源化利用,使铅烟尘中镉形成有效开路,整个工艺经济环保、可操作性强。     

利用湿法炼锌赤铁矿法沉铁渣制备铁红

湿法炼锌工业中产生的沉铁渣的资源化利用,长期以来是备受关注的问题,渣的堆积容易对环境产生污染。目前主流的三种沉铁方法中的赤铁矿法所产生的赤铁矿渣具有较高的利用回收价值,对其的资源化利用,具有较高的研究价值。本文以湿法炼锌赤铁矿渣为实验对象,探究其在一定条件下使用酸洗浸出的方法制备高纯度铁红颜料的可行性,针对其中主要的杂质硫、锌等,以及不同含铁物相的去除与转化,研究了温度、时间、酸度、液固比对杂质脱除效果的影响。结果表明,在酸度8 g/L硫酸、温度220 ℃、时间3 h、液固比为6 mL/g工艺条件下可获得较好的脱杂提纯效果,可将沉铁渣铁含量由58%提高至66.5%以上,渣中主要杂质硫脱杂率在70%以上,锌等其余杂质脱除率在90%以上。     

Cadmium removal from diluted aqueous solutions by electrowinning in a flow-by cell

Mineral processing and metal finishing industries produce large amounts of effluents containing a host of heavy metals - cadmium, lead, nickel and chromium - with cadmium as a heavy hazard, since, even in mild concentrations, it may give rise to serious environmental problems. Effluents from electroplating industries and from zinc ore hydrometallurgical processing may contain this metal in the range of 15 to 100 ppm. Cadmium harm to all living systems is aggravated by its strong cumulative effect, because of the long number of years required for its elimination. The electrolytic waste treatment has shown advantages over the classical chemical precipitations by alkalis or carbonates, because it does not produce bulky sludges, which require land for its accumulation, and which may have a retarded pollution effect, due to the redissolution by rain; a great advantage comes from the possibility of the metal recovery in a commercially pure form. In this paper, a laboratory scale electrolytic flow-by cell with a reticulated vitreous carbon (RVC) cathode, developed in our laboratory, is described, which permitted the purification of aqueous solutions containing cadmium ion on the usual order of concentration of metallurgical industries effluents; with this cell, operating in a mass transport regime, it has been possible to decrease cadmium concentration of solutions of 2 liters volume from 200 to 0.1 ppm, with current efficiencies up to 40%, in a matter of 85 minutes.     

Recovery of zinc and cadmium from industrial waste by leaching/cementation

Metallic zinc production from sulfide zinc ore is comprised by the stages of ore concentration, roasting, leaching, liquor purification, electrolysis and melting. During the leaching stage with sulfuric acid, other metals present in the ore in addition to zinc are also leached. The sulfuric liquor obtained in the leaching step is purified through impurities cementation. This step produces a residue with a high content of zinc, cadmium and copper, in addition to lead, cobalt and nickel. This paper describes the study of selective dissolution of zinc and cadmium present in the residue, followed by the segregation of those metals by cementation. The actual sulfuric solution, depleted from the electrolysis stage of metallic zinc production, was used as leaching agent. Once the leaching process variables were optimized, a liquor containing 141 g/L Zn, 53 g/L Cd, 0.002 g/L Cu, 0.01 g/L Co and 0.003 g/L Ni was obtained from a residue containing 30 wt.% Zn, 26 wt.% Cd, 7 wt.% Cu, 0.35 wt.% Co and 0.32 wt.% Ni. The residue mass reduction exceeded 80 wt.%. Cementation studies investigated the influence of temperature, reaction time, zinc concentration in feeding solution, pH of feeding solution and metallic zinc excess. After that such variables were optimized, more than 99.9% of cadmium present in liquor was recovered in the form of metallic cadmium with 97 wt.% purity. A filtrate (ZnSO₄ solution) containing 150 g/L Zn and 0.005 g/L Cd capable of feeding the electrolysis zinc stage was also obtained.     

大洋多金属结核低温氢还原-湿法冶金联用回收有价金属

以大洋多金属结核为原料, 采用低温氢还原-湿法冶金联用工艺回收有价金属, 湿法冶金过程包括硫酸浸出、M5640萃取铜、针铁矿法除铁、P204萃取除锌、HBL110萃取回收镍。在HBL110萃取回收镍过程中, 考察了平衡pH值、相比O/A等因素对萃取镍的影响, 并绘制了镍萃取与反萃平衡等温线。结果表明, 采用50%HBL110+50%磺化煤油组成的有机相, 经过6级逆流萃取-4级逆流洗涤, 镍萃取率达99.85%, 除钴外, 杂质金属Mn、Ca、Mg、Al基本不被萃取。负载有机相经5级逆流反萃, 镍反萃率达98.53%。     

Thermodynamic modelling of the multiphase pyrometallurgical processing of electric arc furnace dust

Electric arc furnace (EAF) dust is produced when automobile scrap is remelted in an electric arc furnace and about 10–20 kilograms are generated per ton of steel. The major elements present in the dust are usually zinc, iron and calcium with smaller amounts of numerous other elements such as lead, copper and nickel. Typically, in the pyrometallurgical EAF dust treatment processes, the lead and zinc are separated as a crude zinc oxide while the iron is generally not worth recovering. Copper and nickel are usually not recovered as they report either to the oxide residue or to any metallic iron that is produced. In the present research, the recovery of the non-ferrous metals in a multiphase system consisting of gas, slag, matte, metal and solid carbon phases was investigated. The equilibrium compositions of the various phases, resulting from the smelting of the dust, were calculated using the SOLGASMIX module of Outokumpu HSC Chemistry. The effects of the following operating variables were investigated; carbon additions, sulphur additions, nitrogen and oxygen additions, temperature and dust composition. The thermodynamic modelling results show that the majority of the non-ferrous metals can be recovered, with the zinc and lead concentrating in the gas phase and the nickel and copper concentrating in the matte phase.     

硫酸浸出转底炉高锌铅粉尘的研究

研究了硫酸浸出转底炉高锌铅粉尘提取锌的工艺条件和参数。最佳浸出工艺条件为: 搅拌速度400 r/min, 硫酸浓度为1.0 mol/L, 浸出温度为25 ℃, 固液比为1∶8, 浸出时间为0.5 h。在此条件下, 锌的浸出率可达96%以上。采用针铁矿-氧化水解法除铁、过硫酸铵深度除铁锰、锌粉置换除杂的方法对浸出液净化处理, 得到高纯度硫酸锌溶液, 该溶液可直接电解制取锌或制取碱式碳酸锌和氧化锌。     

金川低品位氧化镍矿的酸法制粒堆浸工艺研究

对于金川有色金属公司低品位的氧化镍矿,目前的火法和湿法冶金工艺,生产成本高,难以回收利用。通过制粒预处理,加入润湿液与矿石中的耗酸组分作用,可以预先破坏碳酸盐和Ca、Mg的氧化物,降低硫酸浸出过程中CO2气体逸出对颗粒的损害。选择N603作为低品位氧化镍矿的黏合剂,有效地改善了堆浸的渗透性,浸出过程中,矿石颗粒未发现严重的破裂和泥化现象。预处理后矿石浸出,每t矿石总用酸量258.8kg,镍浸出率85%以上。如果利用该公司硫酸厂大量的低浓度硫酸来堆浸,则在经济上和环境保护方面都比较合理。     

Hydrometallurgical process development for the production of a zinc sulphate liquor suitable for electrowinning

This study deals with the development of an innovative hydrometallurgical process for zinc recovery from Waelz Oxide, a concentrate of zinc and lead oxides obtained pyrometallurgically from the treatment of EAF dusts.Its main objective is the production of a zinc sulphate liquor to be used as feedstock in electrolytic processes. The process requires different stages to achieve this goal. The first stage consists of a double-sulphuric-acid-leaching, achieving a 88% lixiviation of the zinc present in the Waelz Oxide. After the leaching, to fulfil the strict requirements of an electrolysis feed, some purifying stages, such as oxidation, removing more than the 99% of the iron present in the leach liquor, and cementation to remove cadmium, lead and copper were investigated. Finally, if the concentration of some metallic impurity is above the accepted level for electrolytic processes, an additional purification stage could be considered.Through this process, sulphate zinc liquors with a zinc purity of around 99.75%, containing less than 135 ppm of metallic impurities, could be obtained.     

Microwave caustic leaching of electric arc furnace dust

Electric arc furnace (EAF) dust is a waste product which is generated when steel scrap is melted in an electric arc furnace. It contains high concentrations of iron, zinc and lead. Numerous pyrometallurgical and hydrometallurgical processes have been developed to treat this material. Only a limited number of these have reached commercialization and the majority have been pyrometallurgical. However, the hydrometallurgical processes, such as caustic leaching, offer some potential advantages.In the present research, the application of microwave radiation at 2.45 GHz was employed, as the energy source, in the hydrometallurgical caustic leaching process for EAF dust treatment. The variables which were investigated were: leaching time, microwave power, caustic concentration and the solid to liquid ratio. The experimental results showed that the zinc recovery from the dust increased with a decrease in the solid to liquid ratio and an increase in the microwave power. The optimum caustic concentration for the maximum zinc recovery was 8M. The rates of zinc recovery were significantly higher under microwave conditions as compared to those observed with conventional leaching. Some possible mechanisms to explain this behaviour are discussed.     

Recovery of zinc from an industrial zinc leach residue by solvent extraction using D2EHPA

A hydrometallurgical treatment involving solvent extraction of zinc using di-2-ethylhexyl phosphoric acid (D2EHPA) has been investigated to recover zinc from an industrial leach residue. The residue was leached with sulfuric acid producing leach liquor which was subjected to solvent extraction for enrichment of zinc and removal of impurities. Operating variables, such as pH, D2EHPA concentration, temperature, aqueous/organic (A/O) phase ratio, tri-butyl phosphate (TBP) concentration and sodium sulfate (Na₂SO₄) concentration in aqueous phase were studied. Practically, all zinc was extracted from the aqueous solution at pH 2.5 with 20% w/w D2EHPA in kerosene. Increasing either TBP concentration up to 5%, or Na₂SO₄ concentration up to 0.2 M, increased the zinc extraction. Zinc could be extracted at one theoretical stage at A/O of 1/1, as calculated by McCabe–Thiele method.