Knowledge Management System Of Institute of process engineering,CAS
钒、铬是我国重要的稀缺资源和战略金属，也是国家重点防控的重金属。钒产量的90%来源于钒钛磁铁矿及其火法冶炼产生的钒渣。因铬、钒性质相近，钒渣提钒过程中，部分铬与钒同步浸出至液相，沉钒后废水中含有未能沉淀的钒及大量的铬，经还原、调碱、过滤后会产生钒铬泥。钒铬泥现已被列为重金属危险固废，目前尚无有效处理方法，严重制约钒产业的可持续发展。中科院过程所基于铬/钒/铁的络合深度分离特性的发现，提出钒铬泥高效酸解—铬钒铁络合分离—钒铬产品高值制备新技术，可实现钒铬泥的资源化利用，但其络合深度分离机理尚不清晰。本论文在分析铬、钒、铁及络合剂（二烷基二硫代氨基甲酸盐）络合性质的基础上，系统研究了铬、钒、铁与络合剂的反应原理、络合反应发生的主要pH区间、钒/铁络合反应动力学，优化了酸性体系铬/钒/铁络合分离工艺，并探明了碱性条件下络合物解离机理及络合剂再生工艺，从而为钒铬泥资源化利用技术的进一步推广和优化提供理论基础。主要研究结论如下：（1）通过对络合产物的分析表征，查明了铬、钒、铁络合反应原理。制备并纯化了铬(III)、钒(V)、铁(III)与络合剂反应的络合产物，采用热重、XRD、FT-IR及元素分析等多种分析手段，查明了铬(III)、钒(V)、铁(III)络合物的组成分别为Cr(CS2NR2)3、VO(CS2NR2)3、Fe(CS2NR2)3，获得了三种络合物的分子结构图。在此基础上，通过实验进一步获得了铬钒铁络合反应的络合比及络合常数，络合比均为3，络合常数分别为3.05×1014，8.18×1013和2.19×1014。（2）通过对络合反应前后的溶液pH值、金属离子浓度以及生成的固体产物进行分析，查明了水溶液中铬(III)、钒(V)、铁(III)与络合剂反应的pH区间。结果表明，铬(III)与络合剂的络合反应主要发生在pH 6~8区间，钒(V)与络合剂的络合反应主要发生在pH 1.0~5.5区间，铁(III)与络合剂的络合反应主要发生在pH 2~6区间。（3）研究了溶液pH值、温度、络合剂加入量以及时间、铬钒（或铬铁）浓度比对络合分离效果的影响规律，发现pH值和温度对络合分离效果影响较大，获得了钒/铬、铁/铬络合分离的优化工艺条件。在优化工艺条件下，沉钒率达97%，沉铁率达99%，铬损失率为3%。（4）采用连续电导率法获得了钒(V)、铁(III)络合反应动力学模型及表观活化能。钒(V)、铁(III)络合物沉淀的成核及晶体长大均满足一级反应模型，钒(V)络合物沉淀的成核及晶体长大的表观活化能分别为7.47 kJ/mol、17.75 kJ/mol，铁(III)络合物沉淀的成核及晶体长大的表观活化能分别为11.01 kJ/mol、77.31 kJ/mol。（5）研究了溶液pH值、反应温度、反应时间以及CaO加入量对钒、铁络合物解离及络合剂再生效果的影响规律，获得了络合剂再生的优化工艺条件。在优化工艺条件下，络合剂再生率达95%以上。(6)基于铬钒铁络合性质差异，构建了铬/钒/铁络合分离体系，并在钒铬泥资源化利用获得产业化应用验证，铬、钒回收率超过85%，所得产品Cr2O3的纯度可达98%。;Vanadium and chromium are important scarce resources and strategic metals in China, and they are also the national key prevention and control heavy metals. 90% of vanadium production comes from vanadium-titanium magnetite and its vanadium slag produced by pyrometallurgical smelting. Due to the similar properties of chromium and vanadium, some chromium and vanadium are simultaneously leached into the liquid phase during vanadium slag extraction. After the vanadium precipitation, the waste water contains unrecovered vanadium and a large amount of chromium, which will be produced into V-Cr-bearing reducing slag after reduction, alkali adjustment and filtration. V-Cr-bearing reducing slag has been classified as a heavy metal hazardous solid waste. Currently, there is no effective treatment method to treat V-Cr-bearing reducing slag, which seriously restricts the sustainable development of the vanadium industry. Based on the discovery of complexation deep separation characteristics of chromium, vanadium and iron in the Institute of Process Engineering, Chinese Academy of Sciences, a new high-value preparation technology of V-Cr-bearing reducing slag high efficiency acid leaching-chromium vanadium iron complexation separation-vanadium,chromium product was proposed, which can realize the resource utilization of V-Cr-bearing reducing slag. However, the mechanism of complexation separation is not clear. Based on the analysis of the complexation properties of chromium, vanadium, iron and complexing agent (dialkyldithiocarbamate), the reaction principle of chromium, vanadium, iron and complexing agent, the main pH range of complexation reaction and the kinetics of vanadium and iron complexation reaction were studied systematically. The chromium, vanadium and iron complexation separation process of acid system was optimized and explored. The mechanism of the dissociation of vanadium and iron complexes and the regeneration process of the complexing agent under alkaline conditions are clarified. It is believed that those studies will provide a theoretical basis for the optimization of V-Cr-bearing reducing slag resource utilization technology. The main findings are as follows:(1) The principle of complexation reaction of chromium, vanadium and iron was ascertained by analysis and characterization of complexation products. The complexation products of chromium (III), vanadium (V) and iron (III) with complexing agent were prepared and purified. The chromium (III), vanadium (V) and iron (III) complexes was identified by various analytical methods such as thermogravimetry, XRD, FT-IR and elemental analysis. The composition of chromium (III), vanadium (V) and iron (III) complexes are Cr(CS2NR2)3, VO(CS2NR2)3, Fe(CS2NR2)3, respectively, and the molecular structure diagrams of the three complexes are obtained. On this basis, the complexation ratio and complexation constant of the complexation reaction of chromium, vanadium and iron were obtained by experiments. The complexation ratio both were 3, and the complexation constants were 3.05×1014, 8.18×1013 and 2.19×1014, respectively.(2) By analyzing the pH value of the solution, the concentration of metal ions and the solid product formed before and after the complexation reaction, the main reaction pH range of chromium (III), vanadium (V) and iron (III) with the complexing agent in the aqueous solution was determined. The results show that the complexation reaction of chromium (III) with complexing agent mainly occurs in the range of pH 6~8. The complexation reaction of vanadium (V) with complexing agent mainly occurs in the range of pH 1.0~5.5. The complexation reaction of iron (III) with complexing agent mainly occurs in the pH range of 2~6.(3) The effects of pH value, temperature, the addition amount of complexing agent, time, and the concentration ratio of chromium to vanadium (or to iron) on complexation separation were studied. It was found that the pH value and temperature had a great influence on the complexation separation effect. The optimized process conditions for vanadium/chromium and iron/chromium complexation separation. Under the optimized process conditions, the vanadium precipitation rate is 97%, the iron precipitation rate is 99%, and the chromium loss rate is 3%.(4) The kinetic model and apparent activation energy of vanadium (V) and iron (III) complexation reaction were obtained by continuous conductivity method. The nucleation and crystal growth of vanadium (V) and iron (III) complexes all satisfy the first-order reaction model. The apparent activation energy of nucleation and the of crystal growth of vanadium (V) complexes precipitation are 7.47 kJ/mol and 17.75 kJ/mol, respectively. The apparent activation energy of nucleation and the of crystal growth of iron (III) complexes precipitation are 11.01 kJ/mol and 77.31 kJ/mol, respectively.(5) The effects of solution pH, reaction temperature, reaction time and the addition amount on vanadium, iron complex dissociation and complexing agent regeneration were studied. The optimized complexing agent regeneration conditions were obtained. Under the optimized process conditions, the regeneration rate of the complexing agent is over 95%.(6) Based on the difference of complexation properties of chromium vanadium iron, a chromium, vanadium and iron complexation separation system was constructed, and the industrial application of V-Cr-bearing reducing slag resource utilization was verified. The recovery rate of chromium and vanadium was over 85%. The purity of the product Cr2O3 can reach 98%.
|彭雪枫. 钒铬泥资源化利用中铬/钒/铁络合深度分离机理研究[D]. 中国科学院大学,2019.|
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