The treatment of sewage sludge from electroplating plants

In the process of wastewater treatment in the electroplating industry there is always sludge, the composition and amount of which depend on the chemical composition and flow of wastewater and methods of its processing. The paper covers approved in the practice methods for sludge utilization. The authors describe preparation of himalaica, electroplating and battery electrolytes for wood and the two-component composition for simultaneous preservation and toning of wood to look like mahogany. The authors provide a method of processing sewage sludge from electroplating plants into concentrates of non-ferrous metals, pigment paste, and deoxidizing additives for metallurgical smelting of copper. The study also presents a technology of extracting non-ferrous metals from sewage sludge by leaching with hydrochloric acid and ammonia water. In the process of such processing, a suspension with a certain ratio of solid phase to liquid is originally prepared from the sludge, and then it is sequentially treated with hydrochloric acid and ammonia water. After the formation of soluble ammonia complexes of copper, zinc, iron the suspension is fed into the filter, where it is separated into a precipitate and a filtrate containing the above-mentioned ammonia complexes. After that the filtrate is heated to remove ammonia gas and form the slurry containing oxides and hydroxides of non-ferrous metals. The obtained suspension is filtered. The residue (concentrate of metals) is dried, and then it's sent to the finished goods warehouse and further o enterprises of non-ferrous metallurgy. The filtrate is discharged to wastewater treatment facilities for neutralization.