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Metal Recovery Processes
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2017
The commercial form of sulfate salt of nickel is nickel sulfate hexahydrate (NiSO4·6 H2O). It is emerald green in color and decomposes to NiO and SO3 when heated to above 800°C. The principal use of nickel sulfate is in the making of electrolytes for electroplating of Ni, electrorefining of crude Ni metal, electroextraction of Ni from sulfide anodes, and electroless plating of nickel.
Short-Bed Ion Exchange
Published in Arup K. SenGupta, Ion Exchange and Solvent Extraction, 2007
After loading, the resin is regenerated with acid, producing a recovered nickel salt solution. If sulfuric acid is used, nickel sulfate will be produced. If a mixed nickel sulfate-chloride product is preferable, the resin can be regenerated with a sulfuric-hydrochloric acid mixture.
Electrodeposition: three steps towards sustainability
Published in Transactions of the IMF, 2020
A. Mulone, J. Hildenbrand, U. Klement
Since December 2006, the European Union launched REACH with the aim of addressing the production and use of chemical substances and their impact on both environment and human health.19 In 2008, ECHA (European Chemicals Agency), formed in 2007 as the administrative body of REACH, published the first list of SVHC and since then the list has been regularly updated with new candidates.8 If a compound from the SVHC list is also included in the Annex XIV of REACH (also known as ‘Authorisation List’), it is given a latest application date referred to as the ‘sunset date’.20 Chromium is not listed as an SVHC, but the compounds containing hexavalent chromium (e.g. chromic and dichromic acid) for the electrodeposition of chromium coatings are listed as SVHC and included in the Annex XIV as they are highly carcinogenic and toxic to aquatic life with long-lasting effects. The health risks associated with the chromium plating from hexavalent chromium baths have triggered the development of trivalent chromium plating (i.e. from Cr3+ solutions) which is less harmful, and it is considered an established technology for the production of decorative chromium. However, the deposition of hard chromium coatings from trivalent chromium electrolytes is less widely known. Cobalt salts are not included in the Annex XIV, but they are listed as SVHC because they are carcinogenic and toxic for reproduction.8 As compared to Co or Cr6+, the health hazards associated with Ni electrodeposition are less prominent. Nickel is not listed as SVHC but, as previously mentioned, Ni is highly allergenic, and its use is restricted according to Annex XVII. Also, the inhalation during the manufacturing process may lead to respiratory diseases and increase the risk of carcinogenicity.21,22 Health risks are also associated with nickel sulphate-based electrolytes, often used for nickel electrodeposition, because nickel sulphate may cause cancer by inhalation and it is very toxic to aquatic life.23 Thus, it is a registered substance according to REACH regulation and it is also subject to classification and labelling. As compared to the other materials (Cr, Co and Ni), there are no restrictions for Fe and Fe compounds when it comes to electrodeposition, yet.