难处理铀矿外场预处理强化生物浸出研究进展

External Field Pretreatment to Enhance Bioleaching of Refractory Uranium Ore:A Review

在当前能源紧缺、碳达峰与碳中和的背景下,核电因具有清洁、低碳、经济等特点而备受关注,而天然铀的安全稳定供给是核电持续发展的重要保障。随着中国铀矿资源开采日趋贫化,复杂难处理铀矿所占比例逐年增加,传统酸法水冶工艺由于工艺复杂、成本高及环境污染等不足,难以经济开采此类矿石,生物浸出技术为难处理矿石及废弃资源中有价金属的提取回收提供了新方向。本综述讨论了铀矿生物浸出技术的最新进展,总结了影响和阻碍生物堆浸技术推广应用的关键技术问题,探讨了微波、超声波、电磁场、电场等非常规外场预处理强化铀矿浸出优势和不足。最后,结合当前铀矿生物浸出技术的进展,提出了难处理铀矿生物强化浸出的研究方向,为今后该领域的研究提供借鉴。

Under the background of the current energy shortage,“Carbon Peak”and“Carbon Neutralization”,nuclear power has at⁃tracted much attention due to its clean,low-carbon and economical characteristics,and the safe and stable supply of natural uranium is an important guarantee for the sustainable development of nuclear power.With the increasing scarcity of uranium resources in Chi⁃na,the proportion of complex and refractory uranium ore increases yearly.The traditional wet acid leaching process is difficult to eco⁃nomically exploit such ore due to its complex process,high cost and environmental pollution.Bioleaching technology provides a new di⁃rection for extracting and recovering valuable metals in refractory ores and waste resources.However,the bioleaching of uranium ore still has shortcomings such as long leaching time and low uranium leaching efficiency,which restrict its industrial application.There are mainly the following technical problems that need to be solved urgently:the uranium minerals and sulfide minerals with large ex⁃posed surface in the ore are easy to leach,while the uranium wrapped in the ore is difficult to leach.Due to the weak oxidation activity of bacteria in the heap,the leaching rate of uranium is reduced.The ore with fine particle size is prone to compaction and precipita⁃tion,resulting in poor permeability of the ore heap and uneven distribution of the solution in the ore heap,reducing the leaching effi⁃ciency of uranium.Therefore,further expanding the ore micro-crack structure,increasing the exposed surface of uranium minerals,and improving the bacterial activity of growth and reproduction in the ore heap has become key technical problems to solve the bottle⁃neck of bioleaching technology.This review discussed the latest progress of uranium bioleaching technology,summarized the key tech⁃nical issues that hinder the popularization and application of biological heap leaching technology,and pointed out that the field pre⁃treatment technology with high efficiency,energy saving and short research cycle was an important technology for enhancing uranium ore bioleaching in the future.The field pretreatment technology mainly referred to the use of microwave field,ultrasonic wave,electro⁃magnetic field,electric field and other unconventional technical conditions to strengthen the leaching process,so as to improve the treatment effect,reduce energy consumption,and improve the comprehensive utilization of complex resources.This paper reviewed the advantages and disadvantages of enhanced uranium leaching with field pretreatment technologies such as microwave,ultrasonic,electromagnetic and electric field.Microwave heating of minerals had the advantages of selective heating,high efficiency,controllable heating process,and low energy consumption.The use of microwave pretreatment of ore could cause different degrees of strain in the mineral lattice,destroy the mineral structure,and generate micro-cracks in the mineral interface,which would increase the exposed area of minerals,shorten the reaction time,reduce the dosage of chemical leaching agent,and improve the metal leaching rate.Ultra⁃sonic-assisted bioleaching could effectively strengthen the bioleaching process compared with traditional bioleaching.By ultrasonic pre⁃treatment,the exposed area of encapsulated minerals could be increased,generation of organic acid could be increased,improving the extraction rate of metals.It is worth noting that Aspergillus niger was the dominant microorganism in the study of ultrasonic bioleach⁃ing reported at present.When a new microbial strain used for ultrasonic bioleaching,the effect of ultrasonics on biological growth should be further explored.Although the mechanical and chemical effects of ultrasonication increased the efficiency of bioleaching of target minerals,the microscopic mechanism of ultrasonic bioleaching needed to be further investigated.Electromagnetic field could change the physical and chemical properties of the leaching solution,enhancing the oxidation activity and growth and reproduction rate of A.ferrooxidans,thereby accelerating the reaction rate of bioleaching of uranium ore,shortening the leaching time,and improv⁃ing the leaching rate.The technology and mechanism of electromagnetic field enhanced bioleaching needed to be further studied.The growth activity and reproduction rate of A.ferrooxidans could be improved by applying an external voltage,thus the bioleaching reaction process could be strengthened,the metal recovery ratio could be improved,and the leaching time could be shortened.So far,the effect of external voltage on the bacterial activity for the uranium ore bioleaching system had not been reported.In a word,field pretreatment technology was an important technology to strengthen the bioleaching of uranium ore.In the future,research should be strengthened in the following aspects:First,the mechanism of bioleaching enhanced by the pretreatment technology should be deeply explored and fur⁃ther improve the leaching efficiency,reduce production costs.Second,it was necessary to further study the technology and mechanism concerning enhancing and maintaining bacterial activity and oxidation rate in the mine heap by the methods such as electromagnetic field and external voltage,providing strong support for bioleaching applications.Third,it was necessary to strengthen the research and development of efficient field pretreatment-leaching processes and related equipment to achieve wider industrial applications.