Recycling of Molybdenum Slags by Comprehensive Utilization
Abstract
Molybdenum slag is a by-product of the chemical leaching process of molybdenum ore. In order to recycle the molybdenum slag, comprehensive utilization method can be employed. Firstly, the chemical composition of molybdenum slag is determined, and then the recovery of metallic molybdenum, silicon and phosphorus is concentrated by physical treatment methods. Finally, the phosphorus, silicon and metallic molybdenum are used as molybdenum materials, building materials, fertilizer and other products to obtain comprehensive economic and environmental benefits. This paper comprehensively summarizes the comprehensive utilization of molybdenum slag, and provides a reference for the research of molybdenum slag comprehensive utilization in the future.
Key words: molybdenum slag; comprehensive utilization; physical treatment
1 Introduction
Molybdenum is an important special steel product and its production technology is advanced. With the rapid development of the chemical industry and the increase of the demand for molybdenum, the production of molybdenum ore has increased, and the by-products of this process have also increased significantly. At present, the by-products of molybdenum production are mainly molybdenum slag and tailings. Due to the increasing amount of molybdenum slag, the problems of resource waste and environment pollution are caused in the process of molybdenum mining and smelting process. Therefore, it is of great significance to realize the comprehensive utilization of molybdenum slag.
The molybdenum slag is the residue of hydrogen dioxide in the leaching process of molybdenum sulfide ore by acid-alkali treatment, which contains molybdenum, iron, phosphorus, silicon and so on. According to the different treatment processes and raw material components, the composition of molybdenum slag varies greatly. Therefore, it is very important to study the chemical composition of molybdenum slag before its comprehensive utilization.
At present, the general comprehensive utilization process of molybdenum slag is as follows: firstly, determine the chemical composition of molybdenum slag, then adopt physical treatment method to concentrate and separate the valuable elements such as molybdenum, silicon and phosphorus, and finally convert it into molybdenum material, building material and fertilizer.
2 Chemical composition of molybdenum slag
The molybdenum slag is the residue of molybdenum sulfide ore leached by acid-alkali reaction. The chemical composition of molybdenum slag is complex and varied, and is closely related to the production process, raw materials and ore components. According to the actual production experience, molybdenum slag generally contains 2.4～4.0% of molybdenum, 1.3~2.2% of silicon, 0.04～0.26% of phosphorus, 0.1～0.5% of aluminum, 11.8～19.6% of iron, 4.5～11% of calcium, 0.14～2.6% of sulfur and other components.
3 Physical Treatment Process
The physical treatment process is one of the important links for comprehensive utilization of molybdenum slag. In the physical treatment process, the recovery of molybdenum, silicon and phosphorus is mainly concentrated. Generally, physical treatment technologies such as roasting, washing, magnetic separation, flotation and density separation are used[1].
1) Roasting
In this process, acid or basic sintering of molybdenum slag is performed, which can effectively separate and concentrate molybdenum, silicon, phosphorus and other valuabele elements. In the roasting process of molybdenum slag, the acidic reaction can release molybdenum, silicon and phosphorus in the slag, and makes them form molybdenum silises, molybdenum phosphate and molybdenum trisilicates. In the basic roasting process, most molybdenum, silicon and phosphorus in the molybdenum slag can be released, and could form molybdenum silicates and molybdenum silicates.
2) Washing
The main function of washing is to remove the soluble matter in the molybdenum slag and concentrate the valuable elements, so as to facilitate the subsequent physical separation process. After washing, the molybdenum, silicon, phosphorus and iron will increase, and the content of other elements such as calcium and sulfur will decrease.
3) Magnetic Separation
In the process of physical treatment, magnetic separation is mainly used for the separation of magnetic and non-magnetic elements in molybdenum slag, so as to achieve the purpose of enriching the magnetic components such as iron and molybdenum. During the magnetic separation process, the molybdenum concentrate with a grade of 55% - 62% and an iron grade of 22% - 28% can be obtained by magnetic selection method.
4) Flotation
In the physical treatment process, flotation can be used not only to remove black powder, but also to separate and remove more impurities and concentrate the molybdenum content in the molybdenum slag. After scrubbing, magnetic separation and flotation of molybdenum slag, the molybdenum concentrate with a grade of more than 76% and an iron grade of less than 5% can be obtained.
5) Density Separation
Density separation is also an effective method of physical treatment for molybdenum slag. The density separation method is mainly to classify the molybdenum slag by density difference, so as to enrich the high-density material and achieve the purpose of automatic separation.
4 Comprehensive Utilization
Molybdenum slag is a type of solid waste, which needs to be treated by comprehensive utilization method. The comprehensive utilization of the molybdenum slag mainly involves physical treatment, chemical treatment and conversion treatment according to its chemical components.
1) Molybdenum Mill Products
The physical treatment of molybdenum slag can concentrate and recover molybdenum, which can be further processed into molybdenum materrial, molybdenum wire, molybdenum bar and molybdenum alloy material.
2) Building Materials
The main component of molybdenum slag is silicon dioxide and phosphorus, which can be made into bricks, building tiles, calcium silicate boards and other building materials.
3) Fertilizer
The molybdenum slag is composed of silicon, phosphorus and other elements, which can be used to make fertilizer. This fertilizer can be used to improve soil fertility and promote the growth of crops.
4) Other Products
In addition to the above-mentioned products, molybdenum slag also can be made into catalysts, glass and other special materials or technical products with high value-added.
5 Conclusion
The comprehensive utilization of molybdenum slag can not only reduce the environmental pollution caused by the waste of resources, but also reduce the burden on the environment, achieve the goal of zero discharge, and achieve sustainable development of resources. In the process of molybdenum slag comprehensive utilization, it is necessary to determine the chemical composition of molybdenum slag, and then use physical treatment and other methods to concentrate and separate the valuable elements. Through this process, molybdenum materials, building materials, fertilizer and other products can be obtained to realize valuable utilization of resources and improve economic efficiency.
