Leaching Kinetics And Mechanism Of Extracting Vanadium By Oxidizing Leaching From The Prepared Single-valence Stone Coal Samples

The technology of oxidizing extracting vanadium from stone coal belongs to the whole wet process.The addition of oxidant as the auxiliary agent in the leaching process can greatly improve the leaching effect of vanadium and realize the purpose of efficient and clean production.Leaching operation is a key link in the process of extracting vanadium from stone coal,which directly affects the recovery rate of the product and the control of environmental pollution.The detailed study on oxidizing leaching kinetics of vanadium from stone coal can provide a theoretical basis for the selection of clean,efficient,cheap,widely used oxidants and efficiently reasonable leaching measures,and it is of great significance to improve the practical operation and improve the productivity.In view of the above problems,leaching kinetics and mechanism of extracting vanadium from stone coal by oxidizing leaching was investigated in this paper,of which the experimental materials was from the west of Hunan province.The study mainly included three parts:1?Preparation of single-valence stone coal samples: Raw materials of preparation for single-valence stone coal samples were selected by analyzing the valence distribution of vanadium in the stone coal materials and the change of the vanadium valence in the roasting process of materials.The forms and dissolution of vanadium in materials determined methods of preparing single-valence stone coal samples.The results show that the sample of stone coal with V(?)is prepared by direct acid leaching,of which the experimental material is from Guzhang county.The sample of stone coal with V(?)and V(?)are prepared by roasting-alkali leaching and two-stage roasting method,respectively,of which the experimental materials were from Baojing county.According to the study and analysis of single factor experiment,the single-valence stone coal samples that vanadium content of each valence is more than 98% can be prepared by controlling appropriate leaching conditions and roasting conditions.2 ? Study on oxidation leaching experiments: The appropriate oxidants for single-valence stone coal and ore samples were picked out.Effects of oxidant dosage,liquid-solid ratio,sulfuric acid concentration,leaching temperature and leaching time on the leaching rate were investigated by single factor experiment and orthogonal test,and the best leaching conditions was obtained.The results show that sulfuric acid concentration and leaching temperature are the main factors of affecting the leaching rate.3?Study on leaching kinetics and mechanism of extracting vanadium: Based on the best experimental conditions,the leaching kinetics of extracting vanadium from single-valence stone coal and ore samples was studied by adopting the shrinking core model.According to the dynamic experiments and calculations,solid membrane diffusion is the rate limiting step in the leaching process of extracting vanadium from stone coal with V(?).The apparent activation energy is 63.22 kJ/mol and the apparent reaction series is 1.303.The results indicate that the leaching process of vanadium for stone coal with V(?)is controlled by chemical reaction within the selected temperature of 35 ~ 60?,and the apparent activation energy is 32.32 kJ/mol.At 65~95?,the leaching process of vanadium is controlled by solid membrane diffusion with the apparent activation energy of 49.04 kJ/mol.The apparent reaction series is calculated to be 1.018 within the selected sulfuric acid concentration.The leaching process of vanadium is controlled by chemical reaction into solid membrane diffusion when the sulfuric acid concentration is more than 30%.Chemical reaction is the rate limiting step in the direct leaching process of vanadium for the stone coal with V(?).The apparent activation energy is 28.28 kJ/mol and the apparent reaction series is 1.015.Vanadium has a similar state of occurrence in the stone coal from country of Guzhang and Baojing.The leaching process of vanadium is controlled by solid membrane diffusion.The apparent activation energy and apparent reaction series of the oxidative leaching reaction vary with the distribution of vanadium at each valence.Their apparent activation energies are 64.81 kJ/mol and 58.68 kJ/mol,respectively.Their apparent reaction series are 1.414 and 1.326,respectively.The leaching kinetics of extracting vanadium is closely related to the valence distribution of vanadium: V(?)is more difficult to leach,followed by V(?),and V(?)is the most easy to leach.The leaching rate of vanadium can be effectively improved by promoting the oxidation of low-valent vanadium.The kinetics and mechanism of the leaching process of vanadium can be predicted and the key factors that affecting the leaching effect of vanadium can be deduced by analyzing the distribution of vanadium at each valence state,which will be able to initially select the process of extracting vanadium from stone coal.