Application And Basic Research On The Utilization Of The Waste Residue Removal Of Phosphorus

Phosphorus removal residue is a by-product from the chemical and hydrometallurgical process after phosphorus removal.It often contains phosphorus,calcium,silicon,aluminum,etc.Phosphorus,aluminum and vanadium are valuable elements,and the recycling of such elements is significant.It is difficult to recycle such elements as the result of the variable composition of the residue.Therefore,it is of great practical significance to develop an efficient phosphorus recovery process.In this paper,we developed a new method of phosphorus slag utilization based on the composition and structure analysis of phosphorus slag from the vanadium-chemical industry;we used the phosphorus removal residue as the raw materials,and got the new technology of recovery of vanadium.First of all,the principle and technology of sulfuric acid leaching,aluminum phosphate preparation and recovery of vanadium are studied.Secondly,the change of standard Gibbs free energy in the reaction of the main components of phosphorus removal slag and sulfuric acid is analyzed from the thermodynamic point of view.The effects of the amount of sulfuric acid,the ratio of leaching liquid to solid,reaction temperature,reaction time and pH value on the recovery process of phosphorus removal waste residue were investigated.On this basis,the influence of reaction system alkalinity and reaction temperature on the recovery rate of phosphorus,aluminum and vanadium in the process of neutralization and desulfurization of calcium oxide was investigated.Finally,the effect of pH value and reaction temperature on the impurity removal efficiency of aluminum phosphate was also discussed.The following results were obtained:(1)A new process for the preparation of aluminum phosphate and recovery of vanadium from the waste residue of phosphorus is developed.The phosphorus removal residue is prepared by acid leaching,neutralization,precipitation of aluminum phosphate,dissolution of aluminum phosphate,two precipitation and transformation of aluminum phosphate.After the aluminum phosphate precipitation is completed,the vanadium can be precipitated into polyoxovanadate by adding vanadium removing agent in the solution,and vanadium pentoxide products are prepared by calcining.(2)The process parameters of acid leaching,aluminum phosphate preparation and recovery of vanadium were optimized.The optimum conditions for the leaching of main elements in the waste residue of phosphorus removal are as follows:the mass ratio of 98%concentrated sulfuric acid and phosphorus removal residue is 1:1,the mass ratio of liquid to solid volume is 3:1,stirring speed is 300r/min,reaction temperature is 90’C and reaction time is 3 hours.Under this condition,the leaching rate of phosphorus,aluminum and vanadium is more than 95%.(3)For the process of neutralization and desulfurization,when the selection of terminal pH is 0.5 can effectively eliminate the loss of phosphorus,aluminum and vanadium.Studies on the separation of phosphorus,aluminum and vanadium show that the selection of pH is 8.0 can effectively eliminate the adsorption of vanadium by aluminum phosphate and improve the separation efficiency.(4)In the process of purification and impurity removal,when the pH is 12,reaction time is 2h and reaction temperature is 80℃ are the best conditions for impurity removal.The results of the preparation of aluminum phosphate show that the pH is 8.0,the ratio of phosphorus to aluminum is the best,the high temperature transformation treatment at 130℃can improve the filtration performance of aluminum phosphate slurry by 30 times.The main innovation of this paper is to develop a new way to utilize the waste residue of phosphorus removal.The phosphate waste residue is used as the raw material to prepare aluminum phosphate and the vanadium can be recovered at the same time.