Research of heavy metals leaching from sediments after feritization processing of galvanic sludge

Possibility of environmental safety increasing for industrial enterprises as a result of resource-saving technology implementation for processing galvanic sludge is considered. An experimental study of stability for sediments after ferritization processing of galvanic sludge and exhausted technological solutions was carried out. As a result of dynamic leaching of heavy metal ions, the immobilization properties of sediments were determined, which were obtained at different technological parameters of the ferritization process. It is shown that the level of immobilization of heavy metals in ferritic sediments has significantly higher values in comparison with sediments of traditional wastewater neutralization. It was found, that the precipitate obtained at following key parameters of reaction mixture for the ferritization process: the total concentration of heavy metal ions 10.41 g/dm3; ratio of concentrations of iron ions to total concentration of other heavy metals ions 4/1 and pH value of 10.5, is characterized by the highest degree of immobilization of heavy metals in the sediments of 99.96% mass. Using the results of a complete factorial experiment, regression equation for the leaching of heavy metal ions (iron, nickel, copper and zinc) from ferrite sediments was obtained: ratio of iron concentrations to the total concentration of other heavy metals and the pH value of reaction mixture. The adequacy of coefficients of regression equations was evaluated according to the criteria of Student and Fisher, which with 95% reliability correspond to the experimental results of the study. The proposed calculation algorithm provides an opportunity to increase efficiency and automation of ferritization process. Subsequent use of the research results will allow to implement reliable utilization of ferritized galvanic waste by application them into the row materials for obtaining alkaline cements for special purposes.

Determination of influence of pH on reaction mixture of ferritation process with electromagnetic pulse activation on the processing of galvanic sludge

This paper considers prospects for increasing the level of environmental safety of industrial enterprises as a result of the implementation of resource-saving technology of processing galvanic sludge using the ferritization method. The effectiveness of the use of electromagnetic pulse discharges for resource-saving activation of the ferritization process with the extraction of heavy metal ions from sludge (Fe, Ni, Cu, Zn) has been confirmed. The influence of key parameters of the process such as the pH value of the reaction mixture and the initial concentrations of metals in the solution on the quality of processing galvanic sludge by ferritization has been experimentally investigated. It was determined that with an increase in the pH value from 8.5 to 10.5 the residual concentrations of metal ions decrease to the values of 0.1÷0.25 mg/dm3 regardless of the total initial concentrations. It has been established that the technique of electromagnetic pulse activation ensures an adequate degree of extraction of metal ions of 99.9 %; it also has indisputable energy advantages compared to the thermal method: energy costs are reduced by more than 60 %. That indicates the suitability of purified water for reuse in galvanic production in terms of the requirements for the content of heavy metal ions in it. In addition, the structural studies of ferritization sediment samples have been carried out. The sediment is characterized by the maximum content of crystalline ferromagnetic phases of ferrite. It was established that an increase in the pH of the initial reaction mixture leads to an increase in the ferrite phase in sedimentation: at pH=10.5, phases were detected, which are characterized by a maximum ferrite content (exceeding 76 %). The proposed resource-saving ferritization process prevents environmental pollution, ensures efficient and rational utilization of raw materials and energy in the industry; it also makes it possible to obtain commodity products from industrial waste.

Recovery of Zinc from Treatment of Spent Acid Solutions from the Pickling Stage of Galvanizing Plants

Typical methods for the treatment of waste pickling solutions include precipitation by alkaline reagents, most commonly calcium hydroxide. As a result, large volumes of galvanic sludge form, containing iron, calcium, sulphates, and a relatively small quantity of zinc (<20%), making Zn recovery not profitable. In summary, state-of-the-art Zn galvanization processes entail the loss of valuable metals and the irrational and expensive handling of spent pickling solutions (SPSs). The resulting conclusion is that there is room for a significant improvement in the way SPSs are treated, with the double goal of enhancing Zn galvanization methods’ economic viability and achieving a lesser impact on the environment’s processes. The experimental results show that it is possible to use SPS as a coagulant to treat the process wastewaters, kept separated, and added with sodium hydroxide. The results in obtaining precipitates with Zn contents higher than 40%, increasing the added advantage of making Zn recovery profitable. The results show the possibility of using SPS as a coagulant in the process of physical-chemical wastewater treatment and sodium hydroxide to obtain a precipitate with a zinc content of more than 40%.

Wastewater Treatment from Galvanization Industry with Zinc recovery

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (<20 %), which makes Zn recovery not profitable. The experimental results presented in this article show that it is possible to use as a coagulant to treat the process wastewaters the spent pickling solution (SPS) from the process, kept separated and added with sodium hydroxide. This results in obtaining precipitates with Zn contents higher than 40%, which brings the further advantage of making Zn recovery profitable.

INFLUENCE OF THE PYROKATEKHIN COMPLEX FORMING AGENT ON THE EXTRACTION OF NICKEL AND NICKEL HYDROXIDE FROM GALVANO SLIDES AND THE STUDY OF CHARACTERISTICS OF ELECTRODES MADE FROM Ni(OH)2

The problems of enterprises of the chemical and machine-building industries, which have a negative impact on the state of the natural environment, are considered. The galvanic workshops and areas available in their structure belong to categories 1-3 of hazard classes due to the use of solutions and the resulting wastewater containing various heavy metals.On the territory of these workshops, a large amount of galvanic sludge (GS) is formed and accumulates, containing such toxic components as nickel, zinc, iron, copper, chromium, lead, cadmium, etc., which have a high toxic, carcinogenic and mutagenic effect on living organisms. However, when finding an effective method for processing, GS can serve as a source of obtaining valuable components, in particular metals and their compounds. The work carried out selective extraction of nickel ions contained in galvanic sludge into a solution with addition of pyrocatekhin (PC) in the concentration range of 50-250 g/l (step 50 g/l). It was found that the optimal concentration of catechol for the extraction of Ni2+ ions was Cpc = 50 g/l. With an increase in the concentration of PC, the concentration of extracted nickel ions increases (from 12.4 to 18.2 mg / ml), however, at high concentrations of PC (100–250 g / L), a thick suspension is formed, which is practically not amenable to filtration. During the subsequent processing of the resulting solution of 40% NaOH in the range of pH = 7.2 ÷ 9.5, Ni(OH)2 hydroxide was precipitated, which met the requirements of TU 48 3 63 90 "Nickel nitrous hydrate". It was used as a component of the active mass of nickel-cadmium (iron) battery cathodes. The electrochemical characteristics of the obtained cathodes have been studied and it has been shown that, in terms of their operating parameters, they are not inferior to industrial Ni(OH)2 electrodes. As a result of the experiments, it was found that the proposed technology for extracting nickel hydroxide from metal-containing galvanic sludge can be used to manufacture the active mass of nickel-cadmium (iron) batteries cathodes and is promising.

Obtaining effective oil sorbents based on chemical industry waste for water treatment

It was proposed new technologies for producing effective oil sorbents based on chemical industry waste. It was shown the possibility of using PET waste as a binder in the produc- tion of oil sorbents with specific properties (hydrophobicity, oleophilicity, magnetic proper- ties) using thermally expanded and oxidized graphite (TEG and OG) and ferritized iron- containing galvanic sludge (FGS). The presence of iron ions in the galvanic sludge allows one to obtain magnetite and ferrites during ferritization, which leads to the appearance of magnetic properties in FGS, established using a vibration magnetometer, the saturation induction was ~ 0.02 T. Electroplating sludge was carried out at t ≈ 1000 oC and τ = 1.5 hr with preliminary mechanical activation. The physicomechanical, chemical, and sorption properties of the obtained oil sorbents (bulk density, abrasion, grindability, particle size distribution, oil capacity, moisture capacity, wettability, buoyancy, specific surface area, chemical composition, adsorption capacity of materials under static and dynamic conditions) are studied. It was found that sorption ma- terials have 100% buoyancy, are highly active in cleaning water surface from films of oil products with different thicknesses (1–5 mm). It was shown that sorption capacity increases with increasing film thickness and reaches a maximum value at a thickness of 3 mm. The cleaning efficiency is 99.0%. It has been established that the sorption capacity of the sorption material (SM) depends on the nature of oil products, its viscosity, solubility and initial concentration in water. It is proved that the processes of sorption of oil products proceed by the physical mechanism, which can be represented as the oleophilic interaction of particles of the Sorption material and oil products, which is confirmed by the type of sorption isotherms, which are type II and IV according to the BDT theory and type L according to the Hills classification char- acteristic of polymolecular adsorption. The obtained adsorption isotherms were processed in the framework of the Langmuir and Dubinin – Radushkevich models, and the constants of the adsorption equations were calculated.

Hydrometallurgical Technology for Processing of Galvanic Sludges

The problem of processing galvanic sludges, formed as a result of neutralization of technological solutions and wastewater containing heavy non-ferrous metals is considered in this study. At present, sludges are transported to disposal area and are not used in any way. Typically, such sludges contain significant amounts of chromium and nickel, which creates environmental hazard. Investigated sludge contains up to 6,6% Ni and up to 7,4% Cr. The hydrometallurgical process to treatment of these sludges is carried out. Solutions of sulfuric acid and ammonia were used as lixiviants. It is shown that when using a solution of sulfuric acid with pH=1,5, extraction of up to 93,3% Cu, 70,2 Ni, 90,3 Zn is achieved. For selective nickel recovery sorption concentration by Lewatit TP207 is proposed. Keywords: Galvanic sludge, hydrometallurgy leaching, nickel, ion-exchange resin