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Cyanide Control in Petroleum Refineries
Published in Bell John W., Proceedings of the 44th Industrial Waste Conference May 9, 10, 11, 1989, 1990
Joseph M. Wong, Patrick M. Maroney
Cyanide toxicity is primarily attributable to HCN.5,6,7 HCN predominates (> 90%) in aqueous solutions at pH < 8.3 and is about two-thirds of the free cyanide at pH 9.O.5 The toxicity of metal-cyanide complexes is largely due to HCN released upon dissociation. Stable cyanide complexes such as ferricyanide and ferrocyanide generally do not produce significant toxicity. However, upon exposure to sunlight or ultraviolet (UV) light, part of the ferrocyanide may dissociate to liberate HCN, which could cause toxicity to fish.2,5 The rate of dissociation depends on exposure to ultraviolet radiation, and is therefore slow in deep, turbid, or shaded waters. Loss of HCN to the atmosphere and the bacterial and chemical destruction that occur at the same time as cyanide production tend to prevent increases of HCN concentrations to harmful levels.5
Water Pollutants and Water Pollution
Published in Stanley Manahan, Environmental Chemistry, 2017
Cyanide, a deadly poisonous substance, exists in water as HCN, a weak acid, Ka of 6 × 10−10. The cyanide ion has a strong affinity for many metal ions, forming relatively less-toxic ferrocyanide, Fe(CN)64−, with iron(II), for example. Volatile HCN is very toxic and has been used in gas chamber executions in the United States.
Water Pollutants and Water Pollution
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Cyanide, a deadly poisonous substance, exists in water as HCN, a weak acid, Ka of 6 × 10−10. The cyanide ion has a strong affinity for many metal ions, forming relatively less-toxic ferrocyanide, Fe(CN)64-, with iron(II), for example. Volatile HCN is very toxic and has been used in gas chamber executions in the United States.
The Leaching of Palladium from Polymetallic Oxide Ores using Alkaline Ferricyanide Solutions
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Huan Li, Elsayed Oraby, G. A. Bezuidenhout, Jacques Eksteen
It has been reported that both ferricyanide and ferrocyanide (hexacyanoferrate) can form complexes with transition metals, represented as MHCF (M=Mn, Cu, Ni, Co, Zn, etc.) with one of the most common MHCF being Prussian Blue (FeIII4[FeII(CN)6]3) (Geng et al. 2021; Wang et al. 2015; Wessells, Huggins, and Cui 2011). MHCF and its analogues have been intensively researched for their application as a battery electrode, absorbent, and catalyst. However, some of the MHCFs, including Mn, Ni, Co and Cu, are insoluble or have very limited solubility in water (which is why these MHCFs are commonly prepared by co-precipitation from aqueous solutions) (Jain, Singh, and Bala 1982; Wang et al. 2015), implying that they will not be leached into solution if their MHCFs are formed in the present study.