Three hundred years history of cyanide use, its environmental risks and mitigation technologies

For more than three centuries since the discovery of Prussian Blue i.e. ferric ferrocyanide in 1706, cyanide and its derivatives have been in use in paintings, in extraction of gold and silver, and for production of synthetic materials, drugs and pesticides. The industrial use of cyanide remains indispensable causing significant environmental and health risks owing to its high toxicity. Cyanide exposure occurs through smoke inhalation during industrial fires and from effluents of dyeing, electroplating, metal processing, fumigation, and photography industries. The cyanide-laden wastes, often co-disposed with heavy metals in artificial ponds, cause toxic environmental pollution due to leaching, accidental spills, or structural failure of extraction plant machineries. Once released into the environment, cyanide forms cyanide-metal complexes in soil and surface water contributing to long-term environmental contamination causing serious human and animal health hazards. Since complete degradation/removal of cyanide from the industrial effluents has not yet been possible, and considering its lethal effect on biota, it is essential that an economically viable and effective cyanide mitigation technology is urgently developed. In this review, we present a comprehensive overview of the historical and ongoing use and applications of cyanide and its derivatives in diverse industries, and associated adverse environmental impacts. To address cyanide pollution, different remediation strategies which are being currently deployed and their respective short-comings/application challenges have been discussed in a chronological order. The integration of current remediation approaches with advance biotechnology such as genetic engineering and omics-based technologies, has been proposed as an effective, scalable, and economically viable possible solution to the cyanide problem.