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Application of Advanced Oxidation Processes to Treat Industrial Wastewaters: Sustainability and Other Recent Challenges
Published in Maulin P. Shah, Sweta Parimita Bera, Günay Yıldız Töre, Advanced Oxidation Processes for Wastewater Treatment, 2022
Idil Arslan-Alaton, Fatos Germirli Babuna, Gulen Iskender
Cyanide (CN−) originates from mining activities and electroplating processes. Free cyanide (KCN, NaCN) is easily oxidizable, but complex cyanides (FeCN) cannot be oxidized by conventional oxidants (H2O2, HOCl, ClO2, O3). Recommended AOPs for cyanide treatment are H2O2/UV (40–80 kWh/m3/order for full H2O2/UV oxidation), photo-Fenton treatment (10–20 kWh/m3/order; but requires acidification to pH = 2–5). Free CN− is further oxidized to cyanate (CNO−) and ultimately to CO2, NO2, or N2 (g) by H2O2 or HOCl.
Plant Security
Published in Frank R. Spellman, Fundamentals of Public Utilities Management, 2020
Cyanide (CN-) is a toxic carbon-nitrogen organic compound that is the functional portion of the lethal gas hydrogen cyanide (HCN). The toxicity of aqueous cyanide varies depending on its form. At near-neutral pH, “free cyanide” (which is commonly designated as “CN-,” although it is actually defined as the total of HCN and CN-) is the predominant cyanide form in water. Free cyanide is potentially toxic in its aqueous form, although the primary concern regarding aqueous cyanide is that it could volatilize. Free cyanide is not highly volatile (it is less volatile than most volatile organic compounds (VOCs), but its volatility increases as the pH decreases below 8). However, when free cyanide does volatilize, it volatilizes in its highly toxic gaseous form (gaseous HCN). As a general rule, metal-cyanide complexes are much less toxic than free cyanide because they do not volatilize unless the pH is low.
Plant Security
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
Cyanide (CN−) is a toxic carbon-nitrogen organic compound that is the functional portion of the lethal gas hydrogen cyanide (HCN). The toxicity of aqueous cyanide varies depending on its form. At near-neutral pH, “free cyanide” (which is commonly designated as “CN−,”although it is actually defined as the total of HCN and CN−) is the predominant cyanide form in water. Free cyanide is potentially toxic in its aqueous form, although the primary concern regarding aqueous cyanide is that it could volatilize. Free cyanide is not highly volatile (it is less volatile than most VOCs, but its volatility increases as the pH decreases below 8). However, when free cyanide does volatilize, it volatilizes in its highly toxic gaseous form (gaseous HCN). As a general rule, metal-cyanide complexes are much less toxic than free cyanide because they do not volatilize unless the pH is low.
Processing of Refractory Gold-Bearing Sulfide Concentrates: A Review
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Bauyrzhan Surimbayev, Ata Akcil, Lyudmila Bolotova, Serikbol Shalgymbayev, Aliya Baikonurova
Recently, significant efforts have been made to develop new and improved reagents for leaching ‘difficult-to-process’ concentrates. Much of this effort is focused on finding alternative leaching reagents that could compete with conventional cyanide (Konyratbekova, Baikonurova, and Akcil 2015; Surimbayev et al. 2018, 2019; Yessengarayev, Baimbetov, and Surimbayev 2020). In addition, current studies are directed towards the development of nontoxic environmental friendly cyanide substitutes. There are several reagents that can form stable complexes with gold and silver, for example, thiourea, thiosulfate, halides, malononitrile, acetonitrile, polysulfides, and others (González-Anaya, Nava-Alonso, and Pecina-Treviño 2011; Olyaei et al. 2019; Piervandi 2023; Zhang and Senanayake 2016).
Physiologically based pharmacokinetic modeling of hydrogen cyanide in humans following the oral administration of potassium cyanide and cyanogenic glycosides from food
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Quoc Ba Tran, Tanapon Phenrat, Manupat Lohitnavy
Dietary exposure to CGs in food has the potential to cause acute cyanide poisoning (Bolarinwa et al. 2016). Longer periods of intake of subacute amounts of CGs in daily food have led to chronic toxification (Gleadow and M⊘ller 2014). Many studies have revealed convincing evidence that exposure to foods containing CGs leads to cyanide poisoning in humans in several regions throughout the world, where the usual symptoms are vomiting, abdominal pain, dizziness, diarrhea, nausea, fever, agitation, dermal irritation, drowsiness, oral irritation, pruritis, or even death (Akil et al. 2013; Akyildiz et al. 2010; Forrester 2018; Hung et al. 2007; Konstantatos et al. 2017; Nyirenda et al. 2011; Sauer et al. 2015; Sriapha et al. 2015; Srisuma et al. 2018; Vlad et al. 2015). The hazard potential of foods containing CGs on humans has been summarized in some recent studies (Abraham et al. 2016; Bolarinwa et al. 2016). In addition, Srisuma et al. (2018) showed that, from 2007 to 2015, 245 people in Thailand exhibited symptoms after exposure to foods containing CGs, and six of them died. Similarly, another study conducted in Thailand by Sriapha et al. (2015) revealed that 13 people died from ingestion of cassava in the period from 2001 to 2010.
Gold extraction from biosolid sludge obtained by sewage treatment
Published in Environmental Technology, 2019
Sara AlKetbi, Hussain Elsayed, Sulaiman Al-Zuhair
Gold is a precious metal, which if found among the heavy metals extracted from the biosolids would make the treatment process more advantageous. A survey of metal concentrations found in the sludge treated in the biosolid treatment facilities of Texas indicated the presence of gold in the biosolids [24]. Gold extraction by potassium cyanide solution is an old method, which is used at a large scale for extracting gold from its ores. After extraction, the extracted gold is precipitated using zinc shavings. Potassium cyanide has a high extraction selectivity for gold, allowing only gold to be extracted leaving behind other metals. However, this technique is not suitable for heavy metal extraction from biomass meant to be used as a fertilizer, because it is more desirable to extract all heavy metals and not only gold. In addition, cyanide is highly poisonous and harmful to the environment. Thiourea has been suggested as an alternative safer solvent [25]. A solution containing 24 g/L of thiourea and 0.6% of Fe3+ was found to be effective, and within 2 h, over 90% of gold was extracted from mobile phone scraps. However, the main disadvantages of this technique are the high cost of the oxidant (ferric ion) and the need for large volumes of reagents [26].