Vulcanization Of Molybdenum In W-Mo-SH 2 O System And Extraction Behavior Of Each Component

With the continuous consumption of high quality tungsten resources in China,the molybdenum content in tungsten ore is increasing.There are many problems when the mainstream technology is used to treat high molybdenum solution,such as the large consumption of copper salt,difference in removal of molybdenum and the treatment of copper and molybdenum slag.In comparison,quaternary ammonium salt extraction has great potential in dealing with molybdenum solution due to its high processing capacity,fast reaction time and rapid phase splitting rate.At present,the quaternary ammonium salt extraction is mainly aimed at the separation of tungsten and molybdenum in sodium tungstate solution with small molybdenum content,therefore,this paper chooses the solution of high molybdenum tungstate as the object,studies the vulcanization process of molybdenum in the solution and the extraction behavior of each element of the sulfide solution in quaternary ammonium salt extraction system,which provides a reference for the separation of tungsten and molybdenum in the high molybdenum tungstate solution.?1?The sulfuration is a key factor of affecting the separation result of tungsten and molybdenum.It is necessary to study the distribution behavior of sulfur in the extraction process under the condition that the excessive dosage of sulphide.Because of the lack of literature on the detection of negative sulphur in the process of sulfuration about removing molybdenum,the paper studied the determination of negative valence sulfur in the mixed liquor of tungsten and molybdenum,and the effects of the content of tungsten acid root,molybdate and sodium hydroxide on the determination of negative sulphur by direct iodine method and indirect iodic method.The results show that the direct iodine method is less interfered,and is suitable for the detection of negative sulfur in the extraction and stripping process of W-Mo-S-H₂O system.?2?Through the study of the extraction behavior of each component in the W-Mo-H₂O and W-S-H₂O systems,it is known that the binding capacity of normal molybdenum root and normal tungsten acid root is basically the same.to quaternary ammonium salt.However,when pH<8,the tungstate root will be polymerized,resulting in a significant increase in the extraction of tungsten,we should avoid the loss of tungsten in the process of sulfuration because of high acidity On the other hand,the extraction ability of quaternary ammonium salt to negative sulphur is significantly stronger than normal tungsten acid root,so the excess of negative sulfur in the solution can help to the extraction of tungsten.?3?By studying of the sulfuration and the extraction behavior of the Mo-S-H₂O system,it can be known that the dosage of vulcanizing agent and pH are the key factors that influencing the degree of sulphation,and increasing the curing temperature can shorten the time of sulfuration.When the pH is 9.5,the ratio of sulfur and molybdenum is greater than 8,and the reaction is 2 h at 65°C,the molybdenum is basically vulcanized to thiomolybdate.The higher the degree of molybdenum sulfuration,the higher the extraction rate,but it is more difficult to stripping;And free negative sulphur can be extracted together in organic phase and difficult to be extracted.?4?When studying the extraction behavior of each component in W-Mo-S-H₂O system,it is found that the presence of tungsten is not conducive to molybdenum sulfuration,so the deep sulfuration of molybdenum can be achieved under the higher dosage of sulfurizing agent.When the tungsten is 0.5 mol·L^-1,pH is 9.5,the reaction is 2 h at 65°C,the sulfur and molybdenum ratio needs to be more than 26,molybdenum only to be completely vulcanized to thiomolybdate,and the excess of sulfur has an adverse effect on the depth of removing molybdenum by subsequent extraction.Therefore,this paper puts forward to the idea of stepwise sulfuration extraction.That is,when the dosage of vulcanizing agent is low,reducing molybdenum from 5 g·L^-1 down to about 1 g·L^-1,molybdenum in the form of low thiosulfate is mainly extracted to organic phase,then we can deeply removal molybdenum in the case of high sulfur and molybdenum.Further,we also studied the recovery of excess negative sulfur in the vulcanized liquid,and the vacuum evaporation method is proposed to recover the partial free negative sulfur in the solution.The experimental results show that the recovery of free negative sulfur can be over 90%when the vacuum is-80 kPa,the volatilization temperature is 60°C,NH₄⁺/S^2-=3:1,and the volatilization time is 1 h.