Galvanic Sludge Research Articles

Oily diatomite and galvanic wastes as raw materials for red ceramics fabrication

This work focused on the applicability and viability analysis of oil-contaminated diatomite waste and other two industrial residues (galvanic sludge and glass waste materials) in red ceramic fabrication. Red ceramic samples were produced varying the amount of waste materials. Diatomite content, galvanic sludge, and glass wastes in new materials ranged from 25% to 35%, 20% to 25%, and 5% to 20%, respectively. Natural clay was present by 30%. Mixtures of initial components were hydrated, compacted, dried and baked with different temperatures (950°C, 1000°C, 1050°C, and 1100°C) during 6h. The materials were analyzed by Scanning Electronic Microscopy (SEM), Electron Dispersive Spectroscopy (EDS), X-Ray Fluorescence Spectroscopy (XRF) and X-Ray Diffraction (XRD) techniques. Red ceramic samples were subjected to flexion resistance tests. High resistance, low dilatation values, water absorption, solubility and leaching of heavy metals could be observed in the obtained ceramic samples. Those outcomes can be explained by melting of some crystal structures of raw components (completely of Illite and partly of Quartz) and partial transition to amorphous glassy formations, well visible by SEM micrographs. The developed materials can be highly economically attractive because of the utilization of industrial wastes to produce construction materials. The wide-scale use of the method can be environmentally effective.

Development of a Process for Copper Recovering from Galvanic Sludges

Galvanic coating processes are based on metal plating baths and are responsible for the production of large amounts of wastewaters. Subsequent physical-chemical treatment of the wastewaters generates solid wastes called galvanic sludges. These sludges have a hazardous character and are often disposed, mainly on landfills, without any economical or environmental benefits. The development of alternatives and viable ways to reduce the environmental impact and recover the valuable metals contained in those sludges such as copper, chromium, nickel or zinc, which content might reach 30% (wt.%, dry weight) are of utmost importance. The present work has been developed in the aim of the project VALMETAIS and proposes a hydrometallurgical process for copper recovery from galvanic sludges produced by Ni/Cr plating plants. This procedure has been developed on laboratory scale and is based on leaching of sludges in sulphuric acid solution followed by copper cementation step, using iron scrap as a precipitating agent. The sludge has been characterized for its chemical and physical properties. Chemical analysis showed a copper concentration of more than 10% (dry base). Preliminary leaching tests in both sulphuric acid and ammoniacal media were performed in order to determine the best operating conditions for this step of the process and to assure the best metal recovery conditions in subsequent separation methods. Sulphuric acid yielded much higher metal ion dissolution when compared with ammoniacal leaching. Optimal experimental leaching parameters were defined as follows: sulphuric acid solution 100 g/l, a solid to liquid ratio of 1:10, stirring speed of 400 rpm at room temperature and under atmospheric pressure. It was found that metals dissolution was almost complete in 30 minutes of reaction time. Extraction rates of 99% for Cu and Ni were obtained under the leaching conditions above mentioned. The solid residue separated from the leaching solution is mostly constituted by gypsum (CaSO4), and presents a metal content below 1%. The subsequent extraction of cooper from the obtained solution is achieved by a cementation step with iron scrap. Copper precipitation was performed at a pH of 2 which was achieved through adding new sludge to the filtered leaching solution. Such pH level led to insignificant precipitation of other metals present in the leaching solution, namely chromium. The recovery rate of copper is about 90% and the purity grade of the resulting copper cement enables its application as a commercial product.

Inertisation of galvanic sludge with calcium oxide, activated carbon, and phosphoric acid

In this study we compared three methods for the treatment of electroplating sludge highly loaded with zinc and iron: (1) calcium oxide-based solidification/stabilisation; (2) conversion into inert material by adsorption of organic and inorganic pollutants onto activated carbon; and (3) conversion of mobile waste components into insoluble phosphates. All three methods proved highly efficient in the conversion of hazardous waste into inert material. Under optimum treatment conditions zinc concentration in the leachate of solidified waste was reduced by 99.7 % compared to untreated sludge. Zinc retention efficiency in the waste treated with activated carbon and phosphoric acid was 99.9 % and 98.7 %, respectively. The advantages of electroplating sludge treatment with activated carbon over the other two methods are high sorption capacity, insignificant pH and volume changes of the sludge, and simple use.

Procedure for treatment of hazardous waste by MID-MIX procedure in Serbia

This paper presents adequate treatment characteristics of the problem of hazardous waste while providing a specific example of the problem. Hazardous waste being discussed here is galvanic sludge. Furthermore, not only is the hazardous waste problem within a company discussed, but also on a national level. The MID-MIX® procedure was chosen and described as an optimal solution for adequate hazardous waste treatment, as well as activities and listed documentation on a possible procedure of transporting the waste discussed here to the treatment plant. With a view to demonstrate the problem solving procedure, a flowchart has been used as a graphical representation technique of a realization of a process. Improper waste disposal, especially of hazardous waste, has a tremendously negative effect on the environment. In this particular example it impacts the agriculture, and thereby the food production. Finally, directions for future work on this subject and solutions for the hazardous waste problem on a national level are provided here. Key words: Best available technology not entailing excessive cost (BATNEEC), MID-MIX® procedure, waste management, hazardous waste, waste generator, sustainability.

Extraction of heavy metals from galvanic sludges

Extraction of copper, nickel, zinc, and chromium from galvanic sludges by various complexons (pyrocatechol, phenanthroline, disodium ethylendiaminetetraacetate, and nitrilotrimethylenephosphonic acid) was considered.

Adsorption of heavy metal ions on galvanic sludges and disposal of the sludges in soil

The sorption capacity of ferritized galvanic sludge toward nickel(II), zinc(II), and copper(II) ions was studied. Sorption isotherms were plotted, and quantitative characteristics of adsorption were determined. Ferritized sludges are stable in the natural environment and thus can be disposed of in soil in an environmentally friendly way.

Electromigration purification of galvanic sludge of copper ions

We have investigated the process of electromigration copper extraction from solid wastes when treating wastewaters of printed board production. We have determined conditions making it possible, when applying an external electric field on a wetted sludge dispersion, to extract > 80% of copper contained in the sludge with the copper efficiency > 50% and power consumption 5 to 10 kW h per 1 kg of the extracted copper at the voltage across the unit 3–10 V.

Eco-technological process of glass-ceramic production from galvanic sludge and aluminium slag

Methods of purification of waste water which are most commonly used in the Republic of Serbia belong to the type of conventional systems for purification such as chemical oxidation and reduction, neutralization, sedimentation, coagulation, and flocculation. Consequently, these methods generate waste sludge which, unless adequately stabilized, represents hazardous matter. The aluminium slag generated by melting or diecasting aluminium and its alloys is also hazardous matter. In this sense, this paper establishes ecological risk of galvanic waste sludge and aluminium slag and then describes the process of stabilization of these waste materials by means of transformation into a glass-ceramic structure through sintering. The obtained product was analyzed with Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray diffraction (XRD). The object of the paper is the eco-technological process of producing glass-ceramics from galvanic sludge and aluminium slag. The aim of the paper is to incorporate toxic metals from galvanic sludge and aluminium slag into the glass-ceramic product, in the form of solid solutions.

Incorporation of solid wastes in red ceramics: an updated review

A review on the fundamentals and technological advances in the incorporation of industrial solid wastes into red ceramics was updated since 1997, when the first overview on this subject was published by Dondi, Marsigli and Fabbri. Other works conducted before this period, but not covered by that overview were also reviewed. Modifications were introduced in the original categories of wastes to permit a wider variety to be considered. In addition to fuel and fluxing wastes, a category of property affecting wastes substituted the originally proposed fly-ash and plasticity reducing/ plastifying wastes categories. In order to be more comprehensive, this updated review considered industrially relevant subdivisions within each category. Accordingly, fuel wastes encompass: oily residues, blast furnace sludge, and paper industry residues. Fluxing wastes encompass: rejects from ornamental rocks, glassy residues and fluxing ashes. Property affecting wastes encompass: grog, water treatment sludge, steel-refining sludge/slag, non-fluxing ashes, mineral processing tails, galvanic sludge, spent catalyst reject, textile slurry, foundry reject sands, tannery sludge and construction and demolition leftovers.

Preliminary evaluation of galvanic sludge immobilization in clay-based matrix as an environmentally safe process

This study attempts to determine the possibilities and limitations of the immobilization of galvanic wastes by their incorporation into clay-based materials. It focuses on the effects of several processing parameters such as the temperature of thermal treatment, the relative amount of sludge, and the physico-chemical aspects of the sample, on the fixing level of relevant metals (Zn, Ni, Fe, Mn, Pb, Cu, Cr) in thermally treated clay-based samples. The effectiveness of sludge inactivation was assessed by water-leaching test and conductivity measurements. In view of the potential use of the sludge stabilization products as construction materials, the linear shrinkage and bending strain of the fired samples was investigated. To characterize their morphology, mineralogy and composition, fired samples of clay and its mixtures with galvanic sludge were studied on a scanning electron microscope (SEM) coupled with an energy dispersive X-ray analyser (EDS) and X-ray diffractometer (XRD). It was found that the efficiency of metal immobilization is dependent on the clay composition and the temperature of the thermal treatment of the prepared mixtures. The thermal treatment of all samples at all temperatures resulted in the stabilization of all heavy metal ions (copper, nickel, iron, lead, manganese and zinc) with the exception of chromium.

Synthesis of chromium containing pigments from chromium galvanic sludges

In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium(III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to color ceramic material. Two different pigments pink CaCr 0.04Sn 0.97SiO 5 and green Ca 3Cr 2(SiO 4) 3 were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furthermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr 2O 3. The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr–Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr 2O 3.

Malayaite ceramic pigments prepared with galvanic sludge

The synthesis and characterisation of chrome-tin red malayaite Ca(Cr,Sn)SiO 5 pigments are reported. The novel approach of using a galvanizing sludge from the Cr/Ni plating process as colouring agent is investigated. The ceramic pigments were prepared using a common, solid state reaction process, with optimisation of milling and firing conditions. Characterisation was undertaken using X-ray powder diffraction, diffuse reflectance spectroscopy and application in standard ceramic glazes. The ceramic pigments were of high purity (≥96% malayaite) and developed a burgundy colour due to the occurrence of Cr 4+ and Cr 3+ and also Ni 2+ in the sludge-bearing samples. The hue of the pigments agreed with standard expectations and optimal formulations showed better performance than some commercial pigments, perhaps due to the contribution of nickel.

Heavy metal-rich wastes sequester in mineral phases through a glass–ceramic process

Certain sludges generated by industry are rich in contaminating elements and are a major environmental problem. In this study, we determine the ability of these contaminating elements to be incorporated into a glass-matrix and in various mineral phases after a crystallization process. The contaminating elements studied were obtained from sewage sludges (SS) and galvanic sludges (GS), our raw materials. The sludge samples were taken from urban wastewater treatment plant in Catalonia (NE Spain) with high levels of phosphorus oxide (P(2)O(5)). In silica glasses, P(2)O(5) acts as a network former. We determined the chemical composition of both the SS and GS, as well as their thermal behaviour by differential thermal analysis and thermal gravimetric analysis (DTA-TG) to obtain their melting curves. The vitreous transition temperature of the obtained glass was established by dilatometer technique at 725 degrees C. The DTA-TG curve of the glass obtained has an exothermal wide peak at 860 degrees C corresponding to crystallization of the two phases: a spinel phase and a phosphate phase. A second exothermal wide peak at 960 degrees C was attributed to the crystallization of aluminium pyroxene, anorthite and fluor-apatite, with two exothermal phenomena attributed to the evolution of these phases. An exothermal peak at 1100 degrees C was attributed to gehlenite crystallization. Scanning electron microscope observations and energy-dispersed X-ray spectroscopy microanalyses of glass-ceramic showed that the contaminating elements were concentrated in the spinel phases, which are the first phases to crystallize during the cooling of glass. Finally, the spinel structure permits the incorporation of all the contaminating elements into it.

Studies on solidification of wastes from metal coating

Studies on solidification of wastes from metal coating There are over 1000 electroplating workshops functioning in Poland; they are agglomerated in automotive industry, agricultural and construction machines industry, precision instruments industry, electronics, electrotechnics, etc.2. The chemical composition of wastes from galvanizing plants strictly depends on the technological processes as well as the methods of neutralization of industrial wastewaters. The wastes mentioned can be neutralized, among other possibilities, using cement, fly ashes or lime. The material that gains the widest applicability for treating a wide spectrum of hazardous wastes is Portland cement. Using cement enables an improvement of the physical (solidifying) and chemical characteristics of various kinds of wastes, that ensures a decrease in the mobility of contaminants (stabilization). The process using Portland cement (CEM I 32,5 R) was used towards galvanic sludges. The results presented in this article allow for the assesment of the applicability of mixture of cement with mortar sand, as well as the mixture of cement and flotation tailings for the stabilizing and solidifying galvanic sludge, containing mainly Cr, Cu, Zn and Ni. The presented study was also concentrated on the limitation in the transport of leached contaminants to the environment, the reduction of the solubility of hazardous contaminants, as well as a change in the physical structure of the waste - in other words, derivation of the product that could be mechanically durable during transport and storage.

Use of sulfoaluminate cement and bottom ash in the solidification/stabilization of galvanic sludge

Solidification/stabilization (S/S) process can improve the physical characteristics of wastes, reduce their leaching and limit the solubility of their heavy metals. The identification of binders able to assume the fixation of contaminants is essential for the success of the technique. In this study, calcium sulfoaluminate cement was added to another waste, bottom ash, in order to treat galvanic sludge. The properties of the resultant solid matrix (MS) were determined: setting time, compressive strength and products of hydration. Solid matrix composed of 77% waste and only 23% cement presented initial setting time lower than 4 h and 28 day-strength of 6 MPa. SEM investigations showed that contaminants present in the galvanic sludge (Cr) were encapsulated in the hydrated phases and particles of bottom ash.

Galvanic sludge metals recovery by pyrometallurgical and hydrometallurgical treatment

This paper reports a study, on laboratory scale, of sulphating roasting to perform a treatment for a selective recovery of valuable metals from galvanic sludge. The target metals were copper, zinc and nickel and the sulphating agent used was pyrite, from coal wastes. The particularity of this treatment is the use of two hazardous wastes as raw material. They are generated in large quantities at coal extraction sites (coal wastes) and at plating shops (galvanic sludge). The wastes were characterized by X-ray fluorescence (XRF), particle size distribution and water contents. The chemical characterization showed sludges with high copper concentration, with more than 14% (dry base). In the roasting step, the galvanic sludge was mixed with pyritic waste and the parameters evaluated were galvanic sludge/pyrite ratio, roasting temperature and roasting time. After roasting, the product of reaction was leached with water in room temperature for 15 min. Considering that other studies have already demonstrated that the pyrometallurgical step determines the process efficiency, this paper only reports the influence of pyrometallurgical parameters. Hydrometallurgical processes will be better evaluated in further studies. The conditions that best reflect a compromise between the valuable metal recover and the economical viability of the process were achieved for 1:0.4 galvanic sludge/pyrite ratio, 90 min of roasting time and 550 °C of roasting temperature. These conditions lead to a recovery of 60% zinc, 43% nickel and 50% copper.

Characterization of Raw and Stabilized Waste in Relation to Toxic Metals Mobility in Realistic Landfilling Scenarios

Toxic metal release in simple leaching tests has been studied in this paper to assess waste behaviour in realistic landfilling scenarios. The waste is a galvanic sludge, raw or cement stabilized. Six different leachants were taken into account: distilled water, CO2-saturated solution, Olsen solution, Mehlich No. 3 solution, acid or alkaline soil circulating solution. Dynamic leaching tests of different duration were used for raw and stabilized waste. The results have shown that, with the exception of Mehlich No. 3 solution, when the waste comes into contact with waters of composition similar to that of the solutions studied, the potential environmental contamination should not be of concern.

Stabilization/solidification of galvanic sludges by asphalt emulsions

A combination of two-aqueous asphalt emulsions was proposed for stabilization/solidification treatment of galvanic sludges prior to landfilling. The presented procedure comprises mixing the galvanic sludge with a slow setting nonionic asphalt emulsion and subsequently forming a secondary asphalt barrier by means of a rapid setting anionic asphalt emulsion. The method was tested on four samples of galvanic sludge from various galvanizing plants, with various water and pollutant contents. Stabilization efficiency was assessed by water-leaching test, TCLP test and by determining ecotoxicity of leachates. Leachate parameters exhibited very low values and favorable results of ecotoxicological tests indicate high efficiency of the developed procedure for galvanic sludge disposal.

Leaching behaviour of a galvanic sludge in sulphuric acid and ammoniacal media

Leaching studies of a sludge produced by the physico-chemical treatment of wastewaters generated by a Ni/Cr plating plant were carried out in both sulphuric acid and ammoniacal media aiming to decide which of them would be the best treatment for this kind of waste material. The dissolution behaviour of some metals (Cu, Ni, Cr and Zn) was studied in order to assure the best metal recovery conditions in subsequent processes by the use of some separation methods such as solvent extraction and precipitation techniques. Therefore, the study here presented deals with the first chemical stage of an integrated treatment process. For the sulphuric acid leaching, maximal conversions obtained were 88.6% Cu, 98.0% Ni and 99.2% Zn for the following experimental conditions: a 100 g L −1 acid concentration, a 5:1 liquid-to-solid ratio (L/S), a particle size less than 1 mm, a digestion time of 1 h, a stirring speed of 700 rpm (all at room temperature and under atmospheric pressure). As expected, no selectivity was achieved for the sulphuric acid leaching, despite this option yielding much higher metal ion dissolution when compared with that reached by ammoniacal leaching. The use of this latter medium allowed the extraction of Cu and Ni without Cr species, but rates of conversion were only about 70% for Cu and 50% for Ni, much lower than those obtained for sulphuric acid leaching.

Kinetic study of the immobilization of galvanic sludge in clay-based matrix

The viability of inertization of galvanic wastes through their incorporation in clay-based materials, such as common formulations for tiles and bricks, is here studied by determining the leaching kinetics in different media. Metals immobilization is assured by firing at reasonably high temperatures, since intimately contact and/or reaction between residue and clay particles is promoted but also due to formation of insoluble metal oxides that rest unreactive towards clay grains. For most metals, leaching rate follows a zero-order kinetic law, with values between 0.001 to 0.1 mg/(g day cm 2). Leaching velocity tends to increase with rising atomic numbers: Zn < Cu < Ni < Cr. These values depend exponentially on the relative sludge content.