Abstract
The study reports results of experimental studies into processing highly concentrated metal-containing wastes (HCMW) from galvanic production with obtaining precipitates of the predefined chemical composition, specified physical-and-chemical properties and with copper ions content. We defined the following precipitate properties in the study of copper-iron containing sludges obtained by coprecipitation of copper and iron-containing spent technological solutions (STS): humidity ‒ 89.7 %, density ‒ 1.17 kg/dm 3 , specific precipitate resistance ‒ 15–16∙10 11 m 2 /kg. It is easy to filter such precipitate. Therefore, it reduces consumption of reagents, increases purification efficiency, and makes it possible to obtain the precipitate, which is ready for transportation. Therefore, it is advisable to obtain copper-containing precipitates (sludges) with iron content for easier separation and avoiding of the conditioning operation. A technological scheme was developed for processing and subsequent disposal of copper-containing HCMW. It included transformation of copper- and iron-containing precipitate into a solution by addition of sulfuric acid; precipitation of iron ions with 25 % ammonia solution; separation of the obtained precipitate of iron hydroxide (ІІІ) by filtration for disposal; sending the obtained copper-containing filtrate for electrochemical removal of copper in the form of a metal precipitate or for disposal by the reagent method. We established in the processing of copper-containing HCMW in a diaphragm electrolyzer to extract copper in the form of a metal precipitate that the current consumption decreases with an increase in the initial metal concentration. Therefore, it is possible to ensure the degree of transformation of a=0.9 with current efficiency >80 % at the concentration of copper ions >0.1 mol/dm 3 . For reagent copper precipitation, it is optimal to use KOH and К 2 СО 3 mixtures рН=9.5–10 as reagents to obtain a hydroxocarbonate precipitate. Precipitates obtained in this way are suitable for further disposal by processing or they can be raw materials for production of ready-to-use products, which may be a final stage of galvanic production
Highlights
Galvanic production is one of the most dangerous sources of environmental pollution due to formation of large volumes of wastewater (WW) and waste technological solutions (WTS), which belong to the category of concentrated water systems
2) In the study of cuprum-ferrum sludges obtained by coprecipitation of cuprum- and ferrum-containing WTS, vНОН/vel
The advantages of the conducted studies are: – technological solutions obtained during the studies provide a closed cycle of resource consumption, which minimizes waste discharges into the environment and expenditures of galvanic and PCB enterprises; – the obtained technological solutions and technologies make it possible to ensure the ecological safety of galvanic waste by elimination of formation of sludge discharges after neutralization of WTS and WW for this type of production; – there is a large amount of experimental data on the electrochemical extraction of copper of WTS for obtaining of a precipitate on a cathode in a metallic form
Summary
Galvanic production is one of the most dangerous sources of environmental pollution due to formation of large volumes of wastewater (WW) and waste technological solutions (WTS), which belong to the category of concentrated water systems. They include a large variety of metal ions (Al3+, Cr3+, Zn2+, Ni2+, Cu2+, Co2+) and Cu2+ ions prevail among them. Sludges (precipitates) of the galvanic industries is a highly concentrated metal-containing waste generated in purification of wastewater and spent technological solutions usually with the use of chemical reagents with subsequent separation during settling and flotation [2]. The density of the precipitates is 1.16‒1.24 g/cm (at moisture content of 60‒85 %), with pH=3.2‒7.9 [4]
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