Recovery of aluminium, nickel-copper alloys and salts from spent fluorescent lamps

This study explores a combined pyro-hydrometallurgical method to recover pure aluminium, nickel-copper alloy(s), and some valuable salts from spent fluorescent lamps (SFLs). It also examines the safe recycling of clean glass tubes for the fluorescent lamp industry. Spent lamps were decapped under water containing 35% acetone to achieve safe capture of mercury vapour. Cleaned glass tubes, if broken, were cut using a rotating diamond disc to a standard shorter length. Aluminium and copper-nickel alloys in the separated metallic parts were recovered using suitable flux to decrease metal losses going to slag. Operation variables affecting the quality of the products and the extent of recovery with the suggested method were investigated. Results revealed that total loss in the glass tube recycling operation was 2% of the SFLs. Pure aluminium meeting standard specification DIN 1712 was recovered by melting at 800 degrees C under sodium chloride/carbon flux for 20 min. Standard nickel-copper alloys with less than 0.1% tin were prepared by melting at 1250 degrees C using a sodium borate/carbon flux. De-tinning of the molten nickel-copper alloy was carried out using oxygen gas. Tin in the slag as oxide was recovered by reduction using carbon or hydrogen gas at 650-700 degrees C. Different valuable chloride salts were also obtained in good quality. Further research is recommended on the thermodynamics of nickel-copper recovery, yttrium and europium recovery, and process economics.     

氯化铵浸取法回收盐泥中的镁

以盐泥为原料,采用氯化铵浸取回收盐泥中的Mg²⁺,以浸取液和回收的氨反应制取氢氧化镁产品。考察了盐泥浆液固含量、浸取时间、物料比（氯化铵与盐泥中氢氧化镁的摩尔比）等工艺条件对Mg²⁺浸取率的影响,并以比表面积为考察指标进行正交实验,确定氢氧化镁的最佳制备条件。实验结果表明：在盐泥浆液固含量为248 g/L、浸取时间为100 min、物料比为2.3的条件下,Mg²⁺浸取率为75.0%;在n（MgCl₂）:n（NH₄Cl）=0.5、氨水浓度3 mol/L、氨水滴加速率 0.8 mL/min、反应温度 90 ℃的最佳条件下,制备的氢氧化镁的比表面积为17.87 m²/g,粒径约为3 μm。该工艺简单可行,为盐泥的综合利用提供了新的思路。     

Recyclables recovery of europium and yttrium metals and some salts from spent fluorescent lamps

Europium and yttrium metals and some valuable salts were recovered from the powder coating the inner surface of the glass tubes of fluorescent lamps. The tubes were broken under 30% aqueous acetone to avoid emission of mercury vapor to the atmosphere, and the powder was collected by brushing. Metals available in the powder were pressure leached using sulfuric/nitric acid mixture. Sulphate salt of europium and yttrium so obtained was converted to thiocyanate. Trimethyl-benzylammonium chloride solvent was used to selectively extract Eu and Y from the thiocyanate solution. The metal loaded in the organic solvent was recovered by N-tributylphosphate in 1M nitric acid to produce nitrate salts of Eu and Y. Europium nitrate was separated from yttrium nitrate by dissolving in ethyl alcohol. The isolated powder contained 1.62% europium oxide, 1.65% yttrium oxide, 34.48% calcium sulphate, 61.52% Ca orthophosphate and 0.65% other impurity metals by weight. Autoclave digestion of the powder in the acid mixture for 4h at approximately 125 degrees C and 5 MPa dissolved 96.4% of the yttrium and 92.8% of the europium. Conversion of the sulphate to thiocyanate is favoured at low temperature. Extraction of Eu and Y from the thiocyanate solution attained its maximum at approximately 80 degrees C. N-tributylphosphate in 1N nitric acid at 125 degrees C achieved a stripping extent of 99%. Thermal reduction using hydrogen gas at 850 degrees C and 1575 degrees C produced europium and yttrium metals, respectively. A metal separation factor of 9.4 was achieved. Economic estimation revealed that the suggested method seemed feasible for industrial applications.     

Processing of copper converter slag for metal reclamation. Part I: Extraction and recovery of copper and cobalt.

Clean processing of copper converter slag to reclaim cobalt and copper could be a challenge. An innovative and environmentally sound approach for recovering valuable metals from such a slag has been developed in the present study. Curing the slag with strong sulphuric acid, without re-smelting or roasting as practiced currently in the industry, render it accessible to leaching, and more than 95% of cobalt and up to 90% of copper was extracted together with iron by water leaching, leaving silica behind in a residue. The copper in the leach liquor was recovered by cementation with iron and the dissolved iron crystallized as ferrous sulphate monohydrate. The cobalt in the mother-liquor rich in iron was recovered by either cementation or sulphide precipitation. Operation variables in the new process were also investigated and optimized.     

Recovery of copper and cobalt from ancient slag.

About 2.5 million tonnes of copper smelter slag are available in Küre, northern part of Turkey. This slag contains large amounts of metallic values such as copper and cobalt. A representative slag sample containing 0.98% Cu, 0.49% Co and 51.47% Fe was used in the experimental studies. Two different methods, direct acid leaching and acid baking followed by hot water leaching were used for recovering Cu and Co from the slag. The effects of leaching time, temperature and acid concentration on Cu- and Co-dissolving efficiencies were investigated in the direct acid leaching tests. The optimum leaching conditions were found to be a leaching time of 2 h, acid concentration of 120 g L(-1), and temperature of 60 degrees C. Under these conditions, 78% Cu and 90% Co were extracted. In the acid baking + hot water leaching tests, 74% Co was dissolved after 1 h of roasting at 200 degrees C using a 3:1 acid:slag ratio, whereas the Cu-dissolving efficiency was 79% and the total slag weight loss was approximately 50%.     

An overview on the production of pigment grade titania from titania-rich slag.

To recover pigment grade TiO2, operating plants all over the world use chemical processes. Slag-based technology is considered to be attractive because of low waste generation and low chemical cost due to high titanium content and is poised to replace the conventional technology. This paper provides a review of the slag-based technology with the specific aim to produce leachable slag and achieving high titania yield from recovered wastes. Leachable oxides of the lower oxidation state, such as TiO and Ti2O3, facilitate the leaching process. However, during smelting these oxides increase the viscosity of the slag. Formation of titanium carbide or carbonitride is also not desirable as it leads to resistance to the leaching of titanium. This report highlights the problems and their possible solutions to obtain leachable slag.     

Ammoniacal leaching and recovery of copper from alloyed low-grade e-waste

The paper concerns a hydrometallurgical method for selective recovery of copper from low-grade electric and electronic wastes. The following consecutive stages were proposed: smelting of the scraps to produce Cu–Zn–Ag alloy, leaching of the alloy in ammoniacal solution, and selective copper electrowinning. Cu–Zn–Ag alloy was a polymetallic and five-phase system. It was leached in chloride, carbonate, sulfate and thiosulfate solutions. This resulted in the separation of the metals, wherein metallic tin and silver as well as lead salts remained in the slimes, while copper and zinc were transferred to the electrolyte. Copper was selectively recovered from the ammoniacal solutions by the electrolysis, leaving zinc ions in the electrolyte. The best conditions of the alloy treatment were obtained in the ammonia–carbonate system, where the final product was copper of high purity (99.9 %) at the current efficiency of 60 %. Thiosulfate solution was not applicable for the leaching of the copper alloy due to secondary reactions of the formation of copper(I) thiosulfate complexes and precipitation of copper(I) sulfide, both inhibiting dissolution of the metallic material.     

从废甲醇合成催化剂中回收铜锌

将废RK-05甲醇合成催化剂经过煅烧、浸取、精制等工序回收其中的铜和锌。经正交实验得到煅烧废催化剂的最优工艺参数为:废催化剂筛目100目,煅烧温度950℃,煅烧时间60 min。最佳浸取工艺条件为:废催化剂加入量约4 g/L,浸取温度75℃,浸取剂用量与理论用量体积比2.0~3.0,浸取剂浓度4.0 mol/L,浸取时间10min。精制工序制备CuO的最佳工艺条件为:锌粒与滤渣质量比为1.00,反应时间3 h,煅烧温度450℃,煅烧时间4 h。制备ZnO的最佳工艺条件为:煅烧温度800℃,煅烧时间60 min。回收的产品CuO纯度为99.1%,满足GB/T674—2003《化学试剂粉状氧化铜》中优级品的标准。回收的产品ZnO纯度为99.6%,满足GB/T3185—1992《氧化锌(间接法)》中一级品的标准。     

废硅电池片表面银的回收

采用氨-肼联合还原法回收废硅电池片上的银,优化了回收的工艺条件。实验得到的最佳回收工艺条件为：室温下采用硝酸2次浸取废硅电池片上的银,其中硝酸质量分数30%,硝酸浸取时间6 min;氯化银粉体用氨水和水合肼还原,n（Ag）∶n（N₂H₄）=0.5,水合肼还原反应温度50 ℃。回收的银粉纯度很高,结晶性较好,无需提纯。     

Petrogenetic characteristics of molten slag from the pyrolysis/melting treatment of MSW

MSW slag materials derived from four pyrolysis melting plants in Japan were studied from the viewpoint of petrology in order to discriminate the glass and mineral phases and to propose a petrogenetic model for the formation process of molten slag. Slag material is composed of two major components: melt and refractory products. The melt products that formed during the melting process comprise silicate glass, and a suite of minerals as major constituents. The silicate glass is essentially composed of low and high silica glass members (typically 30% and 50% of SiO(2), respectively), from which minerals such as spinels, melilite, pseudowollastonite, and metallic inclusions have been precipitated. The refractory products consist mainly of pieces of metals, minerals and lithic fragments that survived through the melting process. Investigations demonstrated that the low silica melts (higher Ca and Al contents) were produced at upper levels of high temperature combustion chamber HTCC, at narrower temperature ranges (1250-1350 degrees C), while the high silica melts formed at broader temperature ranges (1250-1450 degrees C), at the lower levels of HTCC. The recent temperature ranges were estimated by using CaOAl(2)O(3)SiO(2) (CAS) ternary liquidus diagram that are reasonably consistent with those reported for a typical combustor. It was also understood that the samples with a higher CaO/SiO(2) ratio (>0.74-0.75) have undergone improved melting, incipient crystallization of minerals, and extensive homogenization. The combined mineralogical and geochemical examinations provided evidence to accept the concept of stepwise generation of different melt phases within the HTCC. The petrogenesis of the melt products may therefore be described as a two-phase melt system with immiscible characteristics that have been successively generated during the melting process of MSW.     

Hydrometallurgical processing of Nd–Fe–B magnets for Nd purification

An evaluation of various metal purification processes subsequent to the leaching processing of the neodymium (Nd) product from neodymium–iron–boron (Nd–Fe–B) magnets has been conducted. These post-leaching purification processes included precipitation; replacement and electrolysis were studied in order to check the purity of the recovered neodymium. A hydrometallurgical investigation was adopted to digest the metal content of the scrap Nd–Fe–B magnets for the recovery of valuable Nd metal and other metals such as Fe, B, Co and Ni. The effect of leaching conditions such as solid-to-liquid ratio and temperature were optimized and 100 % Nd, 100 % Fe, 100 % B and 85.87 % Co leaching efficiencies were achieved under these conditions. The coating material of the magnet, Ni, achieved 50 % impregnation after increasing the reaction temperature to 70 °C. The metals present in the optimal leaching solution were recovered 99 % by pH adjustment. However, the replacement had the highest separation efficiency for the recovery of Nd metal. Further, the optimal leaching Nd–Fe–B solution was subjected to the electrolysis processes in order to verify the recovery efficiency for all metals.     

防腐漆涂装含锌废水中锌粉的回收与利用

从水性环氧富锌涂料工业涂装废水中回收废锌粉,通过加热二甲基亚砜来溶解包覆于废锌粉表面的环氧树脂漆膜,得到回收锌粉,并将其再利用制防腐漆。在沉降时间12 h、热处理温度110 ℃、热处理时间60 min的条件下,废锌粉表面上的环氧树脂被去除,可直接以金属锌粉的形态加以回收利用,回收锌粉达到GB/T 6890—2012《锌粉》中的二级标准。使用后的溶剂经旋转蒸发后可再次使用,对锌粉的回收效果无影响。回收锌粉制备的防腐漆,其防腐蚀性能良好,可比市售锌粉。     

Physicochemical properties of slags produced at various amounts of iron addition in lead smelting

In the process of lead production from lead-bearing materials generated in copper metallurgy, a large amount of hazardous waste in the form of slag is produced. To assess the effect of the slag on the environment, its physicochemical properties were determined. In this study, the following methods were used: wavelength dispersive X-ray fluorescence (WD XRF), X-ray diffraction (XRD), and Bunte-Baum-Reerink method to determine softening and melting points, as well as viscosity examination and leaching tests. The measurements were performed on the slag produced with two different amounts of iron addition to the lead smelting process. The resulting slags, an oxide rich phase slag and a sulfide rich phase slag have different compositions and physicochemical properties. It was found that the increase in iron addition causes an increase in the softening melting point of the oxide rich phase slag by about 100 °C, and a twofold increase in the viscosity of both slag phases. The increase in iron addition also results in the decrease in As leachability and increase in Zn, Fe, and Cu leachability from the slags. Slag produced with increased iron addition has a greater impact on the environment.

     

Stabilization and utilization of hospital waste as road and asphalt aggregate

This article reports the operational results of the effective utilization of hospital waste molten slag produced using a high-temperature melting system, and being operated at a hospital in Selangor, Malaysia. The hospital waste is incinerated and subsequently melted at 1200°C. Scanning election microscope (SEM)/EDX results showed that the slag produced after melting contained amounts of SiO₂, CaO, and Al₂O₃ in excess of 53%, 9%, and 16%, respectively. The results from a leaching analysis on the slag produced proved that the melting process had successfully stabilized the heavy metals. The use of this slag as an alternative material to replace conventional aggregates for road construction was studied. The results from aggregate and asphalt mix tests showed that the slag produced fulfills all the requirements of an alternative aggregate. The average asphalt content, or the optimum asphalt content to be mixed with hospital waste molten slag, was found to be about 5.53%.     

Characteristics of bricks made from waste steel slag

The characteristics of bricks made from steel slag were investigated in this research. Slag addition was shown to reduce the required firing temperature. When the firing temperature was greater than 1050 degrees C and the slag addition less than 10%, the bricks met ROC national standard CNS 3319 third-class brick for builders. The percentage of slag increased as the quartz and kaolin decreased in the sintered samples while the magnesium aluminum silicate and calcium silicate increased. There were no new crystal phases observed in these samples.     

酸浸出法回收冶金污泥中的有价金属

采用二次酸浸出的方法回收镍钴湿法冶金工业污泥中的有价金属。先采用水和硫酸作为浸出剂浸出Mg和Na,最佳工艺条件为浸出液的pH 7.5、浸出时间5 min、浸出剂体积与干污泥质量的比(ω)为10 mL/g。再采用硫酸作为浸出剂、焦亚硫酸钠作为还原剂进行二次酸浸,在硫酸与污泥质量比为1.3、焦亚硫酸钠与污泥质量比为0.3、ω为5 mL/g、浸出温度85℃、浸出时间20 min的最佳工艺条件下,Co、Ni、Cu、Mn和Zn的浸出率分别达92.45%、93.48%、89.52%、97.78%和94.79%。经XRD表征,浸出后污泥中未见原污泥中的矿物相,说明原污泥中的矿物几乎全部被溶解。     

Recovery of nickel, cobalt and some salts from spent Ni-MH batteries

This work provides a method to help recover nickel, cobalt metals and some of their salts having market value from spent nickel-metal hydride batteries (SNiB). The methodology used benefits the solubility of the battery electrode materials in sulfuric or hydrochloric acids. The results obtained showed that sulfuric acid was slightly less powerful in leaching SNiB compared to HCl acid. Despite that, sulfuric acid was extremely applied on economic basis. The highest level of solubility attained 93.5% using 3N sulfuric acid at 90 degrees C for 3h. The addition of hydrogen peroxide to the reacting acid solution improved the level of solubility and enhanced the process in a shorter time. The maximum recovery of nickel and cobalt metals was 99.9% and 99.4%, respectively. Results were explained in the light of a model assuming that solubility was a first order reaction. It involved a multi-step sequence, the first step of which was the rate determining step of the overall solubility. Nickel salts such as hydroxide, chloride, hexamminenickel chloride, hexamminenickel nitrate, oxalate and nickel oleate were prepared. With cobalt, basic carbonate, chloride, nitrate, citrate, oleate and acetate salts were prepared from cobalt hydroxide Cost estimates showed that the prices of the end products were nearly 30% lower compared to the prices of the same chemicals prepared from primary resources.     

Thermal behaviour of chromium electroplating sludge

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.     

Recovery of valuable metals from electronic and galvanic industrial wastes by leaching and electrowinning

In the present paper, a study on laboratory scale to perform a treatment for valuable metals recovery from electronic and galvanic industrial wastes, is reported. The characterisation of the waste, performed by XRD, SEM, EDX and chemical analysis, showed a high metals content in the sludge, such as Cu, Ni, Mn, Pb, Sn, W. A leaching process, coupled by electrowinning, is then proposed in order to reduce the volume of the waste material and to recover selectively valuable metals, such as Cu and Ni. During the leaching step, carried out by using H(2)SO(4), several factors were investigated (acid concentration, temperature and time of treatment). The leached liquor has been successfully treated with an electrowinning process, to recover copper and nickel. The copper and nickel depositions, were performed in acid and alkaline conditions, respectively. The Faraday yield was of about 95%. The energy consumption was 2.13 and 4.43 kWh per kg of copper and nickel recovered, respectively. At the end of the process, about 94-99% of the initial content of Cu and Ni was recovered at the cathode. The experimental results obtained, showed the technical feasibility of the process.     

Effect of exposure test conditions on leaching behavior of inorganic contaminants from recycled materials for roadbeds

Throughout the utilization of recycled materials, weathering factors such as humidity, gas composition and temperature have the potential to change the material properties and enhance the release of inorganic contaminants. In this research, the effects of weathering factors on recycled gravel materials for roadbeds were evaluated by applying three kinds of accelerating exposure tests: freezing–melting cycle test, carbonation test, and dry–humid cycle test. The effects of exposure tests were determined by X-ray diffraction (XRD) analysis and serial batch leaching test, making it possible to identify the change in release mechanisms. Sixteen elements, mainly metals, were investigated. Tested samples were molten slag from municipal solid waste, molten slag from automobile shredded residue, and crushed natural stone.After the exposure tests, the increase of cumulative release in the leaching test was generally less than 2.0 times that of the samples without the exposure test. Among the three test conditions, freezing–melting showed a slightly higher effect of enhancing the release of constituents. XRD analysis showed no change in chemical species. From these results, it was determined that the stony samples were stable enough so that their properties were not significantly changed by the exposure tests.