Font Size: a A A

Study On Recovery Of Rare Earth By Rare Earth Waster/Residue Combined Alkali Roasting

Posted on:2021-01-16Degree:MasterType:Thesis
Country:ChinaCandidate:J Y HuFull Text:PDF
GTID:2381330611464054Subject:Metallurgical Engineering
Abstract/Summary:PDF Full Text Request
Because of its superior physical and chemical properties,rare earths are widely used in various fields of life,prompting the global demand for rare earth resources to gradually increase with the development of the rare earth industry.The primary rare earth resources are non-renewable,the continued development of the rare earth industry means that primary rare earth resources will continue to be consumed.Eventually forming an extreme phenomenon that the primary rare earth minerals cannot meet the world's demand for rare earths.For this reason,focusing on the recovery of secondary rare earth resources to form a perfect recycling pattern of rare earth resources is one of the major issues in the rare earth industry.This paper aims at the disadvantages of waste rare earth phosphor and rare earth molten salt electrolytic slag,such as high waste degree of secondary resources,difficult treatment,low recovery rate,and single enterprise recycling of single waste.Proposed combined alkaline roasting process of rare earth flotsam/slag.Taking into account the variable-value rare earth elements present in the waste rare earth phosphors,this paper proposes a rare earth waste/slag combined alkali roasting process under an inert atmosphere,and intends to realize the joint recovery of waste rare earth phosphors and rare earth molten salt electrolytic slag in industryThe research contents and results are as follows:?1?The conditions for extracting rare earths from waste rare earth p hosphors by combined alkaline roasting-acid leaching process under inert atmosphere were studied.The results showed that the ratio of sodium hydroxide mass to raw material mass is0.75,roasting temperature is 700°C,roasting time is 70 min,water washing temperature is 60°C,water washing time is 0.5 h,hydrochloric acid concentration is5 mol L-1,acid leaching time is 1 h.Under the conditions of acid leaching temperature of 50?and liquid-solid ratio of 10:1,the total extraction rate of rare earth can reach99.19%.?2?The forms of Ce3+,Eu3+,Gd3+,Tb3+,Y3+,Fe2+,Fe3+,and Al3+were studied in the oxalate system,and according to the principles of conservation of mass and chemical balance(Ce3+,Eu3+,Gd3+,Tb3+,Y3+)-C2O42--H2O co-precipitation system was thermodynamically analyzed,and the influence of impurities Fe2+,Fe3+and Al3+on the co-precipitation system was discussed.Analysis showed:In the absence of Fe???,Fe???and Al elements,the pH value corresponding to the minimum value of the total concentration of each rare earth element is relative to the presence of Al element in Fe???,Fe???.Under the condition that the minimum value of the total concentration of each rare earth element corresponds to a lower pH value;in the absence of Fe???,Fe???,Al elements,with the increase of the total oxalic acid concentration The minimum value of the total concentration shifts to the left;the presence of Fe???,Fe???,and Al will cause the optimal pH value of rare earth co-precipitation to be higher.In the absence of impurities,the optimal precipitation pH of the co-precipitation system is between 1 and 1.5.?3?Based on the analysis of the above results,this paper proposed to use H2O2 to pretreat the acid leaching solution,and then adjust the pH to remove iron and aluminum by alkali,and then carried out oxalic acid precipitation of rare earth and study the process conditions.The results showed that before adding 3.7 g/?100 mL H2O?NaOH to the acid leaching solution,pre-treat the acid leaching solution with 2ml H2O2.At this time,the pH of the solution is close to 5.1.After filtration,the iron ion concentration in the solution can be reduced to 98 ppm,and the aluminum ion concentration can be reduced to 109 ppm.After purification,under the conditions that the amount of oxalic acid 0.29g/?50 mL H2O?,precipitation time 40 min,precipitation temperature 25?,aging time 30min and stirring rate 300 r/min are the best process,the precipitation rate of each rare earth element is respectively Ce 96.85%,Eu98.03%,Gd 98.54%,Tb 94.81%,Y 97.90%.
Keywords/Search Tags:waste rare earth phosphor, rare earth molten salt electrolytic slag, combined alkali roasting, co-precipitation system, oxalic acid precipitation, rare earth secondary resources
PDF Full Text Request
Related items