Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 377, Issue -, Pages 284-289Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jhazmat.2019.05.051
Keywords
Glycine metabolism; Biological catalysis; Cyanid; E synthesis; WPCBs
Categories
Funding
- National Key R&D Program of China [2018YFD0800700]
- 111 Project [B18060]
- Science and Technology Planning Project of Guangdong Province, China [20158020237005, 2016A020221014]
- Pearl River Star of Science and Technology [201710010032]
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Precious metals were lost in the current technologies of recovering waste printed circuit boards (WPCBs). Microbe-produced cyanide is considered as an important lixiviant in bioleaching of precious metals from WPCBs. Enhancing cyanide production is the key to industrialization of bioleaching technology. This study identified the precursor form of biogenic cyanide, investigated the energy characteristics of cyanide synthesis, thermal change characteristics of cyanogenic culture, and the potential kinetic relationship between cyanide production and thermal change. We firstly found glycine anion [H2NCH2CO2]- was the precursor form of cyanide in microbial biocatalysis. The bond cleavage pathways from glycine anion to cyanide were analyzed by computation chemical. Results showed decomposition of glycine anion into cyanide was endothermic and non-spontaneous. Formations of [HN = CHCO2]- and-C N have an average energy barrier of 34.05 and 9.15 kcal/mol respectively, while formations of free radicals from anionic intermediates have an average barrier of 71.05 kcal/mol. Cyanide concentration began to increase from 0.48 to 5.27 mg/L when heat production was strongest. Temperature difference between sterile medium and cyanogenic culture reached 0.3 C. Therefore, metabolic heat brought positive effect on cyanide biosynthesis.
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