Abstract
The aeration rate for the degree of purification of highly concentrated galvanic wastewater from zinc and ferrum ions was investigated using various activation methods. It is shown that the intensity of aeration has a significant effect on the quality of wastewater treatment and the characteristics of water treatment sludge. The efficiency of the use of an energy-saving method for activating the ferritization process with the use of electromagnetic pulses for the extraction of zinc ions from wastewater has been confirmed. It was determined that with an increase in the aeration rate to 3.5 dm3/min per 1 dm3 of the reaction mixture and the use of thermal activation of the process, the residual concentration of zinc ions remains within the range of 0.12÷0.2 mg/dm3. In this case, the concentration of ferrum ions decreases to values of 0.08÷0.14 mg/dm3. It was found that at an aeration rate of 2.5 dm3/min and the use of pulsed electromagnetic (EMP) activation, the residual concentrations of heavy metal ions decrease to values of 0.08÷0.16 mg/dm3. Comparison of the results indicates the advisability of using low rates of aeration of the reaction mixture. This, together with the use of resource-saving EMR process activation, allows to achieve a significant reduction in energy costs. The quantitative phase composition of ferritization precipitates was determined, in which the crystalline phases of zinc ferrite Zn2Fe2O4 and magnetite Fe3O4, as well as ferrum oxyhydroxide FeO (OH) and sodium sulfate Na2SO4, prevail. It is found that with an increase in the volumetric aeration rate, the proportion of the ferrite phase increases. At an aeration rate of 2.0 dm3/min, more than 85 % of the zinc ferrite phase was found in the sediments. Taking into account the qualitative and quantitative composition of precipitates, it is recommended to use them in the production of building materials. The experimental results obtained make it possible to provide a comprehensive processing of liquid galvanic waste.
Highlights
Among many environmental problems, a special place is occupied by the release of pollutants into the environment, including compounds of heavy metals, the main sources of which are industrial enterprises [1]
It is relevant in the future to determine the optimal technological parameters of electromagnetic pulse (EMP) activation using the rational values of the aeration rate proposed in this work
As a result of experimental studies, it has been shown that the best indicators of water purification from zinc and ferrum ions with traditional thermal activation of ferritization are achieved with aeration from 2.0 to 2.5 dm3/min
Summary
A special place is occupied by the release of pollutants into the environment, including compounds of heavy metals, the main sources of which are industrial enterprises [1]. Galvanic production is one of the most environmentally hazardous, characterized by hazardous working conditions, a large amount of waste, significant volumes of wastewater containing highly toxic chemical pollution [2]. Sources of environmental pollution in galvanic production are flushing waste water, but highly concentrated waste solutions, in particular electrolytes. Discharges of these solutions are 10–15 % of the total amount of wastewater in size, and 70 % in terms of the total pollution content [3]. With insufficiently treated galvanic wastewater, thousands of tons of highly toxic compounds containing zinc ions (Zn2+) enter water bodies annually. The urgent task of developing effective methods for the treatment of toxic wastewater containing valuable zinc compounds, with the rational use of water, raw materials and energy in the system of galvanic production
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