Study On The Properties Of Rare Earth Extraction By Alkylphosphinic Acid In Acidic System

The rare earth elements in domestic phosphates associated with rare earths are mainly lanthanum,cerium,lanthanum and cerium.These rare earth elements are irreplaceable strategic resources.Solvent extraction method is widely used in rare earth separation because of its high recovery rate of rare earth,good product purity,low production cost and easy control of reaction process.At present,the widely used extractants P₂₀₄,P₅₀₇ and Cyanex272have many problems such as high acidity of rare earth stripping,small separation coefficient of rare earth extraction,low selectivity,small extraction capacity and easy emulsification.Aiming at the deficiencies of the existing rare earth extraction process and research,this paper synthesized a new type of extractant?diisobutylphosphinic acid?,studied the properties of self-made new extractant for rare earth extraction,and explored the extraction mechanism.Further research in the field provides theoretical support.The research shows that the novel compounds of diisobutylphosphinic acid are synthesized by using sodium hypophosphite and tert-butanol as raw materials.The optimized synthesis conditions are:sodium hypophosphite 10g,solvent 10.05mL,mixed solution(tert-butanol 22.1mL,3.8 mL of acetic acid and 0.9 mL of t-butyl peroxide,0.75mol of catalyst,and 0.08 mol of initiator were reacted at 110°C for 48 h,and the highest conversion was>96%.The structure of the newly synthesized compound was characterized by infrared spectroscopy,nuclear magnetic resonance spectroscopy and phosphorus spectroscopy.It was proved that the synthesized new compound was the desired target product.The self-made new extractant?diisobutylphosphinic acid?has good extraction and separation effects on rare earth elements yttrium?Y?,yttrium?Nd?,cerium?Ce?and cerium?Nd?.By comparing the effects of extraction and stripping rare earth under phosphoric acid,nitric acid and hydrochloric acid system,it is known that the hydrochloric acid medium is more suitable for the new extractant to exert the ability to extract rare earth.In the hydrochloric acid system,in the 0.1mol/L hydrochloric acid medium,compared with O/A=5:1,40%extractant concentration,extraction at room temperature for 15min,the extraction rates of Y,Ce and Nd are all greater than 97%,and the extraction rate of La is greater than80%;the stripping agent is 5mol/L hydrochloric acid.Compared with O/A=1:6,after stripping for 10min,the stripping rate is over 90%,and the cerium is almost completely stripped.In the study of rare earth properties,it is found that the initial aqueous phase acidity is inversely proportional to the rare earth extraction rate and the stripping rate.The extraction?back stripping?,extraction?back stripping?time,and extraction?back stripping?concentration are beneficial.The extraction effect is improved,but the higher the better,the better the extraction range is required to achieve a good extraction effect.Under the phosphoric acid,nitric acid and hydrochloric acid systems,the infrared spectrum test analysis and the calculation of the coordination number of the extraction reaction indicated that the extraction reaction was carried out by replacing the rare earth ions with P-OH and proceeding according to the cation exchange mechanism.The reaction equations for extracting four rare earths are Y³⁺+3?HA?_2?O?=Y?HA₂?_3?O?+3H⁺,La³⁺+3?HA?_2?O?=La?HA₂?_3?O?+3H⁺,Nd³⁺+3?HA?_2?O?=Nd?HA₂?_3?O?+3H⁺,Ce⁴⁺+4?HA?_2?O?=Ce?HA₂?_4?O?+4H⁺.