In order to avoid excessive mercury cyanide, it should be thoroughly dried. The residue after ethanol treatment is dark red rhodium salt and sodium salt powder. Rhodium can be produced without heating the powder in a hydrogen stream.
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Alkaline compounds, such as NaOH, Na2CO3, Na3PO4, Na2SiO3, etc. Organic solvents such as kerosene, gasoline, acetone, toluene, trichloroethylene and carbon tetrachloride are also commonly used in degreasing process. Sometimes it is used to remove oil from parts with particularly serious oil pollution, and then chemically alkaline degreasing is carried out. In order to remove some mineral oil, a certain amount of emulsifier is usually added to the degreasing solution.
Such as OP emulsifier, AE emulsifier, triethanolamine oleic acid soap, etc. Therefore, the cleaning wastewater and regeneration wastewater generated in the degreasing process are alkaline wastewater, which often contains oils and other organic compounds.
Hydrochloric acid and sulfuric acid are commonly used in pickling and derusting. In order to prevent the corrosion of the substrate, thiourea, sulfonated coal tar, urotropine benzidine and other corrosion inhibitors are often added. The cleaning water produced in the process of pickling and rust removal is generally high in acidity and contains heavy metal ions and a small amount of organic additives.
Pretreatment wastewater is an important part of electroplating wastewater treatment, accounting for about 50% of the total electroplating wastewater. Wastewater contains some salts, free acids, organic compounds, etc. Its composition varies greatly with the type of coating, pretreatment process and factory management level.
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