【作者】 王大伟；

【导师】 邱定蕃；

【作者基本信息】 中南大学 ， 冶金环境工程， 2022， 博士

【摘要】 随着高品位铜矿石的日渐枯竭,大量低品位、高含砷的铜矿将成为未来铜冶炼的主要原料之一。高砷原料不仅会严重影响铜冶炼系统的正常运行,同时对生态环境产生极大威胁。如何有效控制冶炼过程砷的迁移与转化,是铜冶炼绿色发展的关键。冰铜是铜火法过程的重要中间产物,其中的砷直接影响后续铜电解精炼的效率,是铜冶炼全过程砷污染防控的关键环节。本文在查明冰铜中砷物相赋存特征的基础上,阐明了冰铜中难分解砷关键相的形成规律,揭示了高温过程中Cu-As合金相形成及分解机制,开发基于钠盐调控的冰铜中砷调控新工艺,取得了以下研究成果:（1）系统分析了冰铜中砷赋存特征,为冰铜相中砷定向调控提供数据基础。冰铜的主要物相是硫化亚铜和硫化亚铁组成的斑铜矿相,冰铜品位越高砷含量也越高。冰铜中砷赋存态依次为残渣态砷>砷酸盐>砷硫化物>砷氧化物,绝大多数的砷都是以残渣态赋存,稳定性极强。高砷冰铜中,砷主要以金属键的作用与其它金属形成复杂金属间化合物。采用扫描电镜（SEM）,背散射电子区分（MLA）等手段对砷的主要负载物相进行分析,发现砷主要存在于斑铜矿相、磁铁矿相、铜基合金相以及其它合金相等四个相区域。其中含砷总量最大的是铜基合金化合物相,其砷浓度约为1%-10%,砷分配比例为60%-80%。由于Cu-As之间的金属键极为稳定,高温下砷分离较难,因此铜砷合金化合物是冰铜中砷调控的关键相。（2）揭示了冰铜中铜砷合金化合物的形成机制及冶炼条件对砷在冰铜中残留的影响。砷在氧化气氛下与冰铜中的硫化亚铜相反应,生成残渣态砷物相-Cu₃As相是冰铜中砷难去除的关键原因。高温、氧化气氛及高品位的冰铜促进Cu₃As相的产生。砷与硫化亚铜在高温下反应时,更优先富集在铜单质相中。冶炼条件对砷在冰铜体系中溶解影响的实验表明,提高温度、缩短反应时间及增高冰铜品位促使砷在冰铜体系中的残留;冰铜体系需要适量的氧化气氛和单独硫化亚铜相存在才能使体系内产生单质铜相,从而与砷反应将砷固定在冰铜体系中。过量的氧及四氧化三铁的存在都会在冰铜体系中产生铜铁尖晶石,抑制单质铜的产生,从而减少砷在冰铜体系中的残留。（3）阐明了碳酸钠转化铜砷合金的机制及过程特征,明确了冶炼条件对碳酸钠转化冰铜中残渣态砷的影响。铜砷合金中的Cu-As结构在碳酸钠及氧气的作用下被破坏,转化为单质铜和砷酸钠/亚砷酸钠,新生成的砷酸钠会在铜砷合金表面阻碍其被过氧化。在8wt.%的碳酸钠添加量、反应温度1250℃和反应60min的实验条件下,冰铜中超过98%的砷转化为非残渣态。研究了不同碳酸钠添加量对冰铜中砷转化行为的影响,在0至1 wt.%的碳酸钠添加量下,碳酸钠由于其低熔点的特性,能有效降低反应的熔点,增强样品的流动性,从而提高反应体系的氧化气氛,促进冰铜中斑铜矿相的分解及氧化;当碳酸钠的添加量达到2 wt.%后,首先碳酸钠会在冰铜表面形成一层钠盐,这些钠盐会减少冰铜与空气发生氧化反应,阻碍其发生分解及氧化;另一方面冰铜中的铜砷合金化合物相可以在碳酸钠的作用下被转化为砷酸钠相,完成由残渣态向非残渣态的转变。（4）探索了钠盐调控后,铁橄榄石型铜渣高温下与砷酸钠的反应机制。砷酸钠与铁橄榄石反应的过程中,同时存在挥发反应（70wt.%）和溶解反应（30 wt.%）;铁橄榄石在砷酸钠的作用下,硅酸盐网络结构被破坏,释放出Fe O和Si O₂,其中Si O₂与Na₂O结合生成Na₂O·Si O₂（无定型）,而Fe O则与[As O₄]反应生成单质金属砷和无定形的铁氧四面体（[Fe O₄]）,使部分晶体态的硅酸铁转化为了无定形硅酸铁玻璃体,砷酸钠在此过程中主要以挥发反应为主。没有挥发的砷酸钠进入到铁橄榄石结构中后,铁橄榄石被转化的[Si O₄]和溶解进铁橄榄石相中的[As O₄]通过桥氧键结合,形成新的网络结构,无定形铁橄榄石玻璃体中的（Q²+Q³）相对含量达到41.12%,增强了铁橄榄石结构的稳定性;样品的浸出毒性实验表明,铁橄榄石与砷酸钠反应前后砷的浸出毒性由3025.52 mg/L降低至12.8 mg/L,铁橄榄石能有效降低砷酸钠的浸出毒性。图81幅,表23个,参考文献179篇更多还原

【Abstract】 With the depletion of high-grade copper ores,a large amount of low-grade and high-arsenic copper ores will become one of the main raw materials for copper smelting in the future.The high-arsenic raw materials will not only seriously affect the normal operation of copper smelting system,but also pose a great threat to the ecological environment.How to effectively control the migration and transformation of arsenic in copper smelting process is the key to the green development of copper smelting.Copper matte is an important intermediate product in copper pyrometallurgy process.The arsenic content in matte affects the efficiency of copper electrorefining directly.Based on finding out the occurrence characteristics of arsenic phase in copper matte,the paper elucidates the formation law of the key phase of arsenic in copper matte which is difficult to be decomposed,reveals the formation and decomposition mechanism of Cu-As alloy phase in high temperature process,and develops the new control technology of arsenic in matte on the basis of sodium salt regulation,and has made the following research achievements:（1）The occurrence characteristics of arsenic in copper matte were analyzed,which provided data for the directional regulation of arsenic in copper matte phase.The main phase of copper matte is bornite phase composed of cuprous sulfide and ferrous sulfide.The higher the grade of copper matte,the higher the arsenic content.The chemical states of arsenic in copper matte are in the order of residue arsenic,arsenate,arsenic sulfide and arsenic oxide.Most arsenic is in residue state and is very stable.In copper matte with high arsenic content,arsenic forms complex intermetallic compounds mainly by means of metallic bonding.By means of scanning electron microscopy（SEM）and backscattered electron analysis（MLA）,it is found that arsenic mainly exists in bornite phase,magnetite phase,copper-based alloy phase and other alloy phases.Among them,the copper-based alloy compound phase contains the largest amount of arsenic,and its arsenic concentration is about 1%-10%,and the arsenic distribution ratio is 60%-80%.Because the metal bond between Cu-As is extremely stable,it is difficult to separate arsenic at high temperature,which is the key of arsenic control in copper-based matte.（2）The formation mechanism of Cu-As alloy compounds in copper matte and the effect of smelting conditions on the residue of Arsenic in copper matte are revealed.Arsenic reacts with cuprous sulfide phase in copper matte under oxidizing atmosphere to form residual arsenic phase-Cu3As phase,which is the key reason for the residue of Arsenic in copper matte phase.The formation mechanism of Cu-As alloy compounds in copper matte and the effect of smelting conditions on the residue of Arsenic in copper matte are revealed.Arsenic reacts with cuprous sulfide phase in copper matte under oxidizing atmosphere to form residual arsenic phase-Cu3As phase,which is the key reason for the residue of Arsenic in copper matte phase.High temperature,proper oxidizing atmosphere and high grade of copper matte promote the formation of Cu₃As phase,while excessively high oxygen concentration will inhibit the formation of Cu₃As phase.When Arsenic reacts with cuprous sulfide at high temperature,it is preferentially enriched in the copper phase,and less in the cuprous sulfide phase.The experiments on the effect of smelting conditions on the dissolution of arsenic in the copper matte system show that the increase of smelting temperature,the reduction of reaction time and the increase of copper matte grade will promote the retention of arsenic in the copper matte system,and the copper matte system needs proper oxidation atmosphere and the existence of cuprous sulfide phase to produce elemental copper phase,which reacts with arsenic and fixes it in the copper matte system.Excessive oxygen and Fe₂O₄ can produce Cu-Fe spinel in copper matte system,inhibit the formation of copper element,and reduce the retention of Arsenic in copper matte system.（3）The mechanism and process characteristics of sodium carbonate transforming Cu-As alloy were clarified,and the effect of smelting conditions on the transformation of residual arsenic in Cu-As matte with sodium carbonate was studied.The Cu-As structure in Cu-As alloy is destroyed by sodium carbonate and oxygen and transformed into elemental copper and sodium arsenate/sodium arsenite.The newly formed sodium arsenate resists peroxidation on the surface of the copper-arsenic alloy.Under the experimental conditions of 8 wt.%sodium carbonate,reaction temperature 1250℃and reaction time 60 min,more than 98%of arsenic in matte was transformed to non-residual form.The effect of sodium carbonate on arsenic transformation in copper matte was studied.At the addition of sodium carbonate from 0 to 1 wt.%,sodium carbonate can effectively lower the melting point of the reaction,enhance the fluidity of the sample,and thus increase the oxidation atmosphere of the reaction system,and promote the decomposition and oxidation of bornite phase in copper matte.When the addition of sodium carbonate reaches 2 wt.%,sodium carbonate plays two roles in the transformation of arsenic phase in copper matte.Firstly,sodium carbonate can form a layer of sodium salts on the surface of copper matte,which can reduce the oxidation reaction of copper matte with air and hinder its decomposition and oxidation.On the other hand,copper-arsenic alloy phase in copper matte can be transformed into sodium arsenate phase by the action of sodium carbonate,completing the transformation from residue state to non-residue state.（4）The reaction mechanism of fayalite copper slag with sodium arsenate at high temperature was explored.In the reaction process of sodium arsenate with fayalite,there were both volatilization reaction（70wt.%）and dissolution reaction（30 wt.%）.Under the action of sodium arsenate,the silicate network structure of fayalite was destroyed and Fe O and Si O₂ were released.Si O₂ combined with Na₂O to form Na₂O·Si O₂（amorphous）,and Fe O reacted with[As O₄]to form arsenic and amorphous tetrahedron of iron oxide（[Fe O₄]）,which transformed part of the crystalline iron silicate into amorphous iron silicate glass.The volatilization reaction of sodium arsenate was the main reaction in this process.After the non-volatilized sodium arsenate enters into the structure of fayalite,the transformed[Si O₄]in fayalite and[As O₄]dissolved in fayalite phase combine through bridging oxygen bonds to form a new network structure,and the relative content of（Q²+Q³）in amorphous fayalite-type glass body reaches 41.12%,which enhances the stability of fayalite structure.The leaching toxicity test of the samples showed that the leaching toxicity of arsenic before and after the reaction of fayalite and sodium arsenate was reduced from 3025.52 mg/L to 12.8mg/L,and fayalite could effectively reduce the toxicity of sodium arsenate.更多还原