黄铜矿表面性质及CN~-在其表面吸附的密度泛函理论研究

发布时间：2018-11-05 20:57

【摘要】：我国金银矿山氰化尾渣中的黄铜矿由于受到氰化物的强烈抑制,未能有效地综合回收,造成了严重的资源浪费和环境污染问题,且目前我国对氰化尾渣中铜资源的综合利用水平较低,关于黄铜矿氰化抑制机理的研究不足,为这部分铜矿物的回收带来困难。论文采用基于密度泛函理论的平面波赝势法,系统地研究了黄铜矿表面性质及氰根离子的吸附,讨论了CN~-在其表面的吸附机理,并采用单矿物浮选试验、XPS测试对密度泛函理论计算结果进行了验证分析。密度泛函理论研究结果显示,黄铜矿晶体属于直接带隙的p型半导体,Fe原子与Cu原子的化合价之比接近3:1,S-Fe键的稳定性较S-Cu键高。结构优化后,黄铜矿(0 0 1)-M、(0 0 1)-S、(1 1 2)-M、(1 1 2)-S和(1 1-2)-M面都发生了明显的表面重构现象,仅(1 1-2)-S面发生小幅的表面驰豫,表面重构使黄铜矿表面生成了S_2~(2-)和S_n~(2-),并出现不同程度的S元素富集现象,使黄铜矿表现出良好的天然可浮性。在各计算表面中,黄铜矿(1 1 2)-M面的表面能最低,具有较高的热力学稳定性,因此(1 1 2)-M面是黄铜矿的最稳定解理面。CN~-能够自发地吸附在黄铜矿(1 1 2)-M面上,其中最稳定的吸附位点为表面Fe-Fe穴位,吸附能达-335.90 kJ/mol,为化学吸附。氰根离子通过C原子与黄铜矿表面的Fe原子相互作用,C原子的2s轨道与Fe原子的4s轨道和4p轨道形成共价s键,Fe原子3d轨道的电子转移到C原子上,占据了C原子空的反键p轨道,形成d-p反馈p键。单矿物浮选结果表明,当氰化钠浓度较低时,对黄铜矿的浮选影响较小,当氰化钠浓度达到0.8%时,黄铜矿的浮选回收率下降到20%以下,对其产生了强烈的抑制作用。黄铜矿回收率随着浸出时间的延长出现小幅增长的趋势,这主要是由于黄铜矿表面Cu~(2+)的溶解,消耗了一部分氰化钠,对黄铜矿产生了一定的活化作用。XPS分析结果表明,黄铜矿各原子化合价构型为Cu~+Fe~(3+)(S~(2-))_2,且黄铜矿表面存在S_2~(2-)和S_n~(2-),这与黄铜矿表面性质的理论计算结果相一致。氰化钠在黄铜矿表面吸附后,表面O元素的相对含量大幅降低,表明氰化钠的吸附阻碍了氧分子与矿物表面的作用。氰化钠能够与黄铜矿表面的金属原子形成亲水性物质铁氰络合物和氰化亚铜,并且优先与Fe原子作用,当氰化钠浓度较高时,能够与表面Cu原子反应,对黄铜矿产生显著的抑制作用。
[Abstract]:Chalcopyrite in cyanide tailings of gold and silver mines in our country has been restrained strongly by cyanide and has not been recovered effectively, which has caused serious waste of resources and environmental pollution. At present, the comprehensive utilization of copper in cyanide tailings in China is relatively low, and the research on the mechanism of cyanidation inhibition of chalcopyrite is insufficient, which brings difficulties to the recovery of copper ore. In this paper, the surface properties of chalcopyrite and the adsorption of cyanide ions on the surface of chalcopyrite are systematically studied by using the plane wave pseudopotential method based on density functional theory. The adsorption mechanism of CN~- on its surface is discussed, and the flotation test of single mineral is used. The results of density functional theory (DFT) are verified by XPS test. The results of density functional theory show that chalcopyrite crystal belongs to p-type semiconductor with direct band gap, and the valence ratio of Fe atom to Cu atom is close to 3: 1, the stability of S-Fe bond is higher than that of S-Cu bond. After structural optimization, the surface reconstruction of chalcopyrite (0.01) -M, (0.01) -S, (112) -M, (112) -S and (1.1-2) -M has been observed. Only a small surface relaxation occurred on the (11-2) -S surface, and the surface reconstruction resulted in the formation of S2- and Sn2- on the chalcopyrite surface, and the enrichment of S elements in the surface of chalcopyrite was observed in varying degrees. Chalcopyrite shows good natural floatability. Among the calculated surfaces, chalcopyrite (112) -M plane has the lowest surface energy and high thermodynamic stability. Therefore, the (112) -M plane is the most stable cleavage surface of chalcopyrite. CN~- can spontaneously adsorb on the chalcopyrite (112) -M surface, and the most stable site is the surface Fe-Fe acupoint, and the adsorption energy is up to-335.90 kJ/mol,. For chemisorption. The C atom interacts with the Fe atom on the surface of chalcopyrite. The 2s orbital of the C atom forms a covalent s bond with the 4s orbital and 4p orbital of the Fe atom, and the electrons of the 3D orbital of the Fe atom transfer to the C atom. The d-p feedback p bond is formed by occupying the antibond p orbital of the C atom space. The results of single mineral flotation show that when the concentration of sodium cyanide is low, the effect on the flotation of chalcopyrite is small. When the concentration of sodium cyanide reaches 0.8, the flotation recovery of chalcopyrite decreases to less than 20%, which has a strong inhibitory effect on the flotation of chalcopyrite. The recovery rate of chalcopyrite increases slightly with the prolongation of leaching time, which is mainly due to the dissolution of Cu~ (2) on the surface of chalcopyrite, which consumes a part of sodium cyanide and activates chalcopyrite to some extent. The results of XPS analysis show that, The valence configuration of each atom of chalcopyrite is Cu~ Fe~ (3) (S2-) 2, and there are S2- and Sn- on the surface of chalcopyrite, which is in agreement with the theoretical calculation results of surface properties of chalcopyrite. After the adsorption of sodium cyanide on the surface of chalcopyrite, the relative content of O element on the surface of chalcopyrite decreases significantly, which indicates that the adsorption of sodium cyanide hinders the interaction between oxygen molecule and mineral surface. Sodium cyanide can form a hydrophilic iron cyanide complex and copper cyanide with metal atoms on the surface of chalcopyrite, and react with Fe atoms preferentially. When the concentration of sodium cyanide is high, it can react with Cu atoms on the surface. It has significant inhibitory effect on chalcopyrite.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD952;O647.31

【参考文献】