Disposal of solid waste from electroplating production for applying zinc coatings

One of the main reasons for the contamination of natural objects with zinc compounds is the waste of production for applying zinc coatings. One of the types of such waste is solid waste, which is obtained as a result of neutralization of acid-base industrial wastewater, separation of the resulting sludge and its drying. This type of waste is classified as hazard class III. Currently, in Udmurtia it is planning to build a facility for the decontamination and disposal of industrial waste of hazard class I and II at repurposed facilities for the destruction of chemical weapons. Due to the lower toxicity, waste of hazard class III is not expected to be disposed of at this facility. Such waste can enter municipal solid waste landfills and can cause contamination of various environmental objects. We have developed a method kir recycling such waste using hydrometallurgical processing using a solution of sulfuric acid. At the first stage, the waste is treated with an acid solution and converted into soluble compounds at pH = 1.0-1.5. The insoluble part is separated and sent for disposal as inert filler of building materials. Then, using a 20% suspension of chlorinated lime, the obtained substances are oxidized and neutralized to pH = 3.0-3.5. In this case, a precipitate is formed, which is a mixture of iron( III) hydroxide and calcium sulfate. This precipitate is separated, dried and heated to a temperature of 180 degrees C. The resulting material can be disposed of as a component of building materials based on gypsum binder. The filtrate was then neutralized to pH = 8-9. The precipitate was separated and additional processing was carried out to obtain zinc and chromium concentrates in the form of their oxides. Such concentrates can be a valuable raw material for obtaining various economic products.