Zinc Ash Research Articles

Investigations of zinc recovery from metallurgical waste

Approximately 7 million tonnes of zinc is annually used for corrosion protection in processes of continuous galvanization and the hot dip processes. Two types of waste are obtained from the process: zinc ash and hard zinc and each of them constitute around 10% of the feed weight. Paper concerns the method of possible separation of metallic zinc from the non-metallic zinc compounds from the zinc ashes – the waste product of hot dip galvanization process. The investigative programme covered the comminution tests of the feed (zinc ash) in selected crushers: jaw crusher, roller crusher and impactor. Results of investigations show that application of individual crushing device results in various breakage of the feed sample. Impact force caused the highest increase in finest particles size fractions of the product, while metallic and non-metallic fractions were comminuted differently. The compression force, in turn, caused the selective comminution, i.e. the breakage of metallic zinc was observed in a higher degree.

Preliminary Investigation on Leaching Behavior of Zinc ash

Preliminary Investigation on Leaching Behavior of Zinc ash

Hydrometallurgical treatment of zinc ash from hot-dip galvanizing process

The oxide fraction of industrial zinc ash was characterized in terms of chemical and phase composition, leaching behavior in sulfuric acid solutions, and leaching thermal effect. The waste product contained about 68 percent zinc (Zn), 7 percent chlorine (Cl), 2 percent aluminum (Al) and less than 1 percent other metals, such as iron (Fe), manganese (Mn), calcium (Ca) and silicon (Si). It consisted mainly of zinc oxide contaminated with metallic zinc and zinc hydroxide chloride. The dissolution of metals from the zinc ash was determined for solid-to-liquid ratios ranging from 100 to 500 kg/m3, acid concentrations of 10 and 20 percent, and temperatures of 20 and 40 °C. The best result — 130 g/dm3 Zn(II) at 95 percent zinc recovery — was obtained at a solid-to-liquid ratio of 200 kg/m3, sulfuric acid concentration of 20 percent and initial temperature of 40 °C. The final solutions were contaminated mainly by Mn(II) and Fe(III) ions, but the presence of cadmium (Cd(II)) and lead (Pb(II)) ions enabled electrowinning of zinc of about 99 percent purity at high current efficiency of 85 to 99 percent. Leaching of the material was an exothermic process with reaction heat of about 520 kJ/kg.

Zn–Al–CO3 layered double hydroxides prepared from a waste of hot-dip galvanizing process

Hot-dip galvanizing process is used worldwide to protect the steel or iron pieces from corrosion. This process is a large generator of waste, considered one of the so-called dirty industries. One of the important wastes, in terms of quantity, is zinc ash that contains a mixture of metallic zinc and zinc oxide with a total content of zinc between 70 and 90%. The aim of this study is the preparation and characterization of a series of Zn R –Al–CO3 (R = 2–4) layered double hydroxides (LDH) by using as zinc precursor the zinc chloride obtained after hydrochloric acid leaching of fine-grained zinc ash. Results presented herein clearly demonstrated that characteristics of the synthesized samples are close to those of similar materials synthesized starting from analytical grade reagents. At the same time, it was observed that impurities existent in the zinc chloride solution prepared by zinc ash leaching (Pb, Fe, Ca), are found at traces in the synthesized LDH materials; therefore, they have no significant influence on the obtained LDH structure and properties. By this approach, several important benefits may be simultaneously achieved: (1) preventing the pollution associated with hot-dip galvanizing process wastes, (2) obtaining of valuable products with minimized costs, keeping in mind that LDH have multiple utilizations at industrial scale, (3) saving energy and material costs, and (4) increase of product competitiveness with respect to the circular economy.

Leaching of Zinc Ash with Hydrochloric Acid Solutions

Leaching of Zinc Ash with Hydrochloric Acid Solutions

Pathological and Biochemical Evaluation of Toxic Effects of Repeated Administration of Jasada Bhasma (Zinc Ash Formulation) in Wistar Albino Rats

Introduction: Jasada Bhasma is the well known potent zinc formulation commonly used in ‘Ayurveda’ medicine system. Its extensive usage in the health care sector is proved to be successful in the treatment of certain illness and is considered to be popular in its stability, lower dose, and its availability. Aim: To evaluate the toxicity profile of Jasada Bhasma with primary emphasis on haematological, biochemical and histopathological changes in Wistar albino rats. Materials and Methods: For toxicity study, Wistar albino rats of either sex, weighing from 150-225 gm of body weight were used, and they were divided into three groups, ten rats in each group. Group-I administered with carboxymethyl cellulose and considered as vehicle control. Group-II and III were administered with two levels of Jasada Bhasma, i.e., 10.8 mg/kg (Therapeutic dose) and 54 mg/kg (Five times of therapeutic dose) respectively for 28 consecutive days. On the 28th day, the animals were sacrificed. Blood sample and vital organs were collected for haematological, biochemical and histopathological examinations. Results: The repeated administration of Jasada Bhasma on Wistar albino rats didn’t produce remarkable toxicity changes at both the dose levels in most of the haematological parameters tested except there was a significant (p<0.01) increase in the mean cell haemoglobin concentration. Biochemically, the significant increase (p<0.01) in the serum creatinine but decrease in urea level has been shown in both levels of administration. The significant rise in potassium and total protein levels were also evident. Histopathologically, sections of liver and kidney showed pathological cytoarchitecture at both level dose exposures. However, sections of spleen showed mild to moderate increase in white pulp proportionate the five times of therapeutic dose level. Conclusion: The repeated administration of test drug Jasada Bhasma at therapeutic dose was relatively safer; however, at higher dose level it produces some functional changes in histopathological sections of kidney and liver.

Comparative studies on acid leaching of zinc waste materials

Three industrial waste materials were characterized in terms of their elemental and phase compositions, leaching behaviour in 10% sulfuric acid solution as well as leaching thermal effects. Slag from melting of mixed metallic scrap contained about 50% Zn and 10% Pb. It consisted mainly of various oxides and oxy-chlorides of metals. Zinc spray metallizing dust contained about 77% Zn in form of zinc and/or zinc-iron oxides, zinc metal and Zn-Fe intermetallic. Zinc ash from hot dip galvanizing was a mixture of zinc oxide, metallic zinc and zinc hydroxide chloride and contained about 80% Zn. Dissolution efficiency of zinc from the first material was 80% (independently on the solid to liquid ratio, 50–150 kg/m3), while decrease of the efficacy from 80% to 60% with increased solid to liquid ratio for the two remaining materials was observed. Both increase in the temperature (20 °C to 35 °C) and agitation rate (300 rpm to 900 rpm) did not improve seriously the leaching results. In all cases, transfer of zinc ions to the leachate was accompanied by different levels of solution contamination, depending on the type of the waste. Leaching of the materials was exothermic with the similar reaction heats for two high oxide-type products (slag, zinc ash) and higher values for the spray metallizing dust.

USE OF ZINC ASH FROM GALVANIZATION AS A SOURCE OF ZINC OXIDE

This paper reports the possibility of using zinc ash as a secondary source for zinc oxide, which can be further used as white pigment. For the extraction of zinc from zinc ash, sulphuric acid was used. The impact of different parameters (ash fraction, contact time, sulphuric acid concentration and liquid:solid (L:S) ratio) upon the extraction degree of metallic ions from zinc ash was studied. The optimum conditions for the metallic ions extraction are: 20 % H2SO4, 30 minutes contact time, 1:1 L:S ratio and the fraction of the ash <0.315 mm. The obtained solid zinc products were submitted to a complex study: chemical analysis, thermal analysis and X-ray diffractometry. It was established that from the resulting zinc ash from the hot-dip galvanizing process the zinc ions can be recovered and reused as useful products avoiding the negative impact of these wastes on the environment and at the same time it was shown that these wastes represent valuable zinc sources. Based on the experimental data, the non-polluting technological process scheme of reuse of zinc ashes in useful products was proposed.

The cationic dye removal by novel Si Zn composites prepared from zinc ash

Abstract Zinc ash, a waste in hot dip galvanizing, was firstly used for the successful synthesis of Si Zn composites (SZC) and for the removal of methylene blue (MB) from effluent. Materials were characterized by XRD, FE-SEM, FT-IR and XPS. The adsorption properties and optimum parameters were determined by operating different conditions (contact time, concentration of the dye, pH and temperature). Interestingly, the morphology was found to have significant impact on adsorption results. The adsorption quantities of SZC-1, SZC-2 and SZC-3 were 60.06 mg g−1, 20.13 mg g−1 and 11.76 mg g−1, respectively. The equilibrium data were analyzed by different isothermal models (Langmuir and Freundlich) and the mechanistic studies demonstrated that the pseudo-second-order kinetic model was fitted well to the adsorption. The increased values of enthalpy indicated an endothermic process. The result of XPS was discussed and the binding energy of Zn and S showed negative shifts, which suggested a chemisorption process due to the generation of the coordinate bond. The regeneration assessment was carried out by conducting a calcination method at 773 K and the material indicated a steady mass ratio (89%) and adsorption capacity (55.76 mg g−1) after four-time reuse.

Quantitative Leaching of Spent Galvanized Zinc Ash by Hydrochloric Acid

Leaching is an extractive metallurgy technique widely used in converting metal into soluble salt in aqueous media. In this study, experiments on quantitative leaching of spent galvanized zinc ash in hydrochloric acid solution were examined. Experimental parameters such as acid concentration and reaction temperature were varied. In addition, reaction residues at optimal leaching were examined by scanning electron micrography (SEM) and the products of reaction were identified by energy dispersive X-ray (EDXRF) and X-ray diffraction (XRD). The leaching results showed that the amount of zinc ash powder dissolved increases with increasing acid concentration and temperature. At optimal conditions (4 mol/L HCl, 75°C, 0.1mm), the dissolution reached 98.5% within 120 minutes. Also, the leaching results conform to a rate limiting diffusion controlled reaction. The calculated activation energy of 25.96 kJ/mol is reasonable for a rate limiting surface reaction and supported the proposed dissolution mechanism.

The pyrometallurgical recovery of zinc from the coarse-grained fraction of zinc ash by centrifugal force

Zinc ash generated during the hot dip galvanizing process is an important source of secondary zinc. The result of zinc ash processing technologies is the formation of zinc in the metallic form or in the form of zinc compounds. The present paper is aimed at possibilities of metallic zinc recovery from the coarse-grained fraction of zinc ash (d>1.25mm) from hot dip galvanizing by the pyrometallurgical process on designed laboratory equipment. Designed equipment for laboratory experiments used centrifugal force and protective atmosphere of a nitrogen flow during the process of melting and separation of zinc. The aim of the pyrometallurgical processing study on the designed equipment was to investigate the effect of time (30, 60, 90min) and temperature (480, 500, 550, 600, 650, 700°C) on recovery of smelted zinc. The most favourable conditions in terms of recovery of smelted zinc (88%) were obtained at the temperature of 500°C and the melting time of 30min. The influence of the melting time on zinc recovery was obvious only at the temperature of 480°C, where extension of time led to an increase of zinc recovery.

Hydrometallurgical Recovery of Zinc from Zinc Ash, Silver from Waste X-ray and Photographic Films

Hydrometallurgical Recovery of Zinc from Zinc Ash, Silver from Waste X-ray and Photographic Films

Precipitation and characterization of zinc borates from hydrometallurgical processing of zinc ash

Zinc ash has been used as a zinc source for precipitation of zinc borates through leaching–purification–precipitation route. Zinc ash containing about 71% Zn, 0.6% Fe, 28% Cl−, 0.2% Pb, and traces other elements such as Cu, Cd, As etc. in ppm level were leached in sulfuric acid. The leach solutions generated were purified by pH adjustment, followed by precipitation of borates using borax (Na2B4O7·10H2O). It has been observed that, the phase compositions of precipitated zinc borates as well as their morphologies are quite sensitive to B/Zn molar ratio, solution pH, precipitation temperature and ageing period. Precipitation of particular zinc borate phase of interest (3ZnO·3B2O3·3.5H2O) was found to be facilitated at higher precipitation temperature (≥95°C) and in the pH range 5.5–6.0 with B/Zn molar ratio >4.0.

Analysis Of Waste Production Management And Environmental Conditions On Coating Process Performancebefore And After The Implementation Of Environmental Management System (EMS)

The phenomenon of proactive environmental management began in the 1990's where manufacturing industries were aware the importance of corporate sustainability through sustainable environmental management. Various strategies can be done in a proactive environmental management. This study emphasized the development of conditions environmental performance companies in minimizing waste, especially in production process that contains a lot of waste. The company has trying to implement a standardized EMS, through its own sludge wastewater treatment as a raw material for making bricks, while for solid waste (zinc dross and zinc ash), had been sold to external parties from the beginning. There isn’t recycling process, Galva furnace repair and improvement work on the system setting WWT or the WWTP. EMS implementation is strengthened through the acceptance of ISO 14000 in 2007. The condition of Company's environmental performance related to waste minimization in the galvanizing process before and after implementing EMS was measured using input indicators (material), the input of water and energy use, and output of products in the form of waste (solid or sludge). The result did not correspond quantitatively with the indicators used in ISO 14000. Based on the quantitative result , a company processing waste , did not change significantly.

Incorporating Simulated Zinc Ash by Kaolinite- and Sludge-based Ceramics: Phase Transformation and Product Leachability

Zinc is one of the hazardous metals commonly found in municipal solid waste incineration (MSWI) ash, and this study reveals the stabilization mechanisms when sintering zinc-laden ash and ceramic precursors as a waste-to-resource strategy. Using ZnO to simulate the zinc-laden ash and sintering with kaolinite and mullite ceramic precursors, both zinc aluminate spinel (ZnAl2O4) and willemite (Zn2SiO4) phases were found in the products under the tested thermal conditions. The results also indicate that kaolinite and mullite precursors exhibit different incorporation behavior, and ZnAl2O4 and Zn2SiO4 were found to be competitive as the Zn-hosting phases in the system. A prolonged leaching test was used to evaluate the leachability of potential product phases in the system. The concentrations of zinc in ZnO and Zn2SiO4 leachates were about two orders of magnitude higher than that in ZnAl2O4 leachate, indicating the preference of forming ZnAl2O4 for zinc stabilization. Furthermore, the aluminum-rich sludge generated from waterworks could be beneficially used as a material resource to stabilize zinc in this study. The X-ray diffraction (XRD) pattern collected from the 1150 °C and 3-h sintered sample shows the success of incorporating zinc into the ZnAl2O4 spinel structure with waterworks sludge precursor. The formation of ZnAl2O4 indicates a strong potential for employing aluminum- and silicon-based materials to thermally immobilize zinc and achieve the beneficial use of metal-laden MSWI ash.

Caracterización de residuos sólidos procedentes de dos procesos distintos de galvanizado en caliente por inmersión

Zinc dust and zinc ash from hot-dip galvanizing industries located in Venezuela were characterized using atomic spectroscopy, scanning electron microscopy, X-Ray diffraction and infrared spectroscopy. Dust was formed during the high-pressure drying process of the galvanized pieces, in a plant that uses a steel kettle to hold the molten zinc. Ash identified as “A” came from the same plant as the dust, while ash identified as “B” came from a hot-dip galvanizing plant which use a ceramic lined galvanizing furnace. Dust contained 98 wt % Zn, in metallic form. Both ash samples contained: Zn and ZnO, while Zn 5 (OH) 8 Cl 2 —H 2 O and ZnCl 2 were only found in ash “B”. Globally, ash “A” and ash “B” contain 71 and 75 wt % Zn, respectively.

Cementation of copper from spent copper-pickle sulfate solution by zinc ash

The cementation of copper from sulfate medium using zinc ash was carried out by batch experiments. The effects of the different factors on the cementation process such as the pH of the solution, copper and zinc ash ratio, shaking time, copper concentration as well as temperature were separately studied. The results showed that about 99% of copper could be recovered from the sulfate solution of initial pH=2 with solid/liquid ratio=0.05 after 30min of continuous shaking. Kinetic investigations showed that the cementation reaction follows a first order reaction and the activation energy was calculated. A flow sheet was proposed and the investigated method was successfully applied for the recovery of copper from pickling solution resulting from a metal finishing plant which indicates the efficiency of zinc ash for the removal of copper from aqueous solutions.

A Small Amount of Alloying Additions Applied in Hot Dip Galvanizing

Investigating the changing quality of galvanized parts when pure zinc plated with other alloying additions. In the procedure of hot dip galvanizing, when pure zinc plated without other alloying additions, the corrosion resistance of zinc coating is poor, meanwhile the bath surface will produce a number of zinc dross, zinc ash, and this phenomenon will cause a waste of zinc, resulting in an increase in product costs, and the surface of product is relatively dark, the brightness is not enough, whilst sometimes even form a phenomenon of the formation of the Pan-color on the surface of the galvanized parts. However, when a proportion of aluminum or rare earth elements is added into melting zinc, the corrosion resistance of coating will be improved and much better than pure zinc galvanized parts;as the decrease of zinc ash, the cost will be reduced;synchronously the limititation of superficial quality above-mentioned will be improved. Via evaluating the superficial quality of galvanized parts and the corrosion resistance, the whole performance will be significantly improved when 0.5% aluminum and 1.5% rare earth elements is added into melting zinc.

Processing of Zinc-Based MgAl&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Composite and Effect of Fly Ash Addition

The properties of ceramic-metal (Cermet) composites as tensile strength, hardness and resistance to corrosion and high temperature are superior than ceramics and metals. Because of the enhanced characteristics of cermets, they are commonly used in various applications and industries. The main objective of this study is to produce a cheap, easy produced, strong and high corrosion resistant composite material. For these purposes, zinc is used for its natural capacity against corrosion, low density, low melting point and softness. Magnesium aluminates spinel oxide (MgAl2O4) is chosen because of its high melting point and low density. Fly ash is a waste from coal power plant having puzzolanic properties. In this study, the effect of various amounts of zinc and fly ash addition on density and hardness behaviour of zinc-based MgAl2O4 composites was investigated. The experimental results showed that zinc and fly ash addition improved the hardness behavior of zincbased MgAl2O4 composite.

Optical and Chemical Methods of Metal Ash Analysis and Tin Recovery

'Metal ash' presents a waste disposal problem in most of the developing countries as the industries employ obsolete technologies. In this paper we describe analysis of tin ash, zinc ash and aluminium ash by means of optical methods, such as X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), electron probe micro analysis (EPMA), scanning electron microscopy (SEM) and chemical methods. The results of tin ash obtained by XRD method matched well with the cassiterite, a naturally occurring mineral of tin. ICP-MS studies reveal the presence of a large number of tracer metals, which may cause pollution by tertiary dispersion and this aspect is discussed. Conversely, the data generated by chemical methods are limited. However, the methods are simple and cost-effective. Then, they can easily be adopted by low-budget industries. Simple and cost-effective process to recover tin from tin ash is described. It is based on heating tin ash with sodium cyanide to about 900 degrees C to separate tin component from the metal ash. The process recovers good quality tin and offers a very high yield. The process can be scaled up to small pilot plant.