Application of surfactant for improving leaching process of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores(WREOs)in China are the main source of medium and heavy rare earths in the world.In order to improve the seepage and the mass transfer of traditional ammonium salt leaching process of WREOs,surfactants were added in the ammonium sulfate leaching solution and the ammonium chloride leaching solution.The leaching kinetics,the mass transfer process,and the adhesion work reduction factor calculated from the interfacial properties were studied to reveal the strengthening mechanism of surfactant.In the presence of the tested five surfactants,cetyl trimethyl ammonium bromide(CTAB),dodecyl trimethyl ammonium bromide(DTAB),sodium dodecyl sulfate(SDS),sodium oleate and oleic acid,the permeability of WREOs is improved,the rare earth(RE)leaching efficiency increase and the impurity aluminum(Al)leaching efficiency decrease,indicating its promotional effect on the leaching process of WREOs.Furthermore,CTAB shows a better leaching enhancement,and the optimal addition dosage is 0.4 g/L for the two ammonium salt leaching agent systems.The kinetics analysis shows the internal diffusion controls model of RE and Al leaching process,and the leaching kinetics equations of RE and Al related to CTAB concentration were obtained for the two ammonium salt leaching systems.According to the chromatographic plate theory,the mass transfer efficiency of RE increases with the CTAB concentration increasing until 0.4 g/L,which confirms that the optimal CTAB addition is 0.4 g/L.Smaller adhesion work and adhesion work reduction factor indicate more favorable permeation as well as the leaching process.

Leaching kinetics and permeability of polyethyleneimine added ammonium sulfate on weathered crust elution-deposited rare earth ores

At present,in-situ leaching of weathered crust elution-deposited rare earth ores(WCE-DREOs) encounter with problems such as long leaching cycles,slow infiltration rate and low product purity.In order to solve the above problems,the conventional leaching agent ammonium sulfate((NH_(4))_(2)SO_(4)) was compounded with polymeric surfactant polyethyleneimine(PEI) to form a composite leaching agent.The effects of leaching temperature,PEI concentration.flow rate and pH on leaching kinetics and permeability of rare earths(RE) and aluminum(AI) in orebody were studied.It is found that with temperature increasing,the time required to reach leaching equilibrium for both RE and Al is shortened,the apparent activation energies of RE and AI are 14.79 and 13.45 kJ/mol,respectively,and the leaching processes are in accordance with the outer diffusion control,When the concentrations of(NH_(4))_(2)SO_(4) and PEI in the composite leaching agent are 2.0 wt% and 0.4 wt%;the time required to reach leaching equilibrium for RE and AI is about 50% shorter than that using(NH_(4))_(2)SO_(4) alone,and the leaching efficiencies of RE are slightly higher than that of Al.Properly increasing the temperature and flow rate of the composite leaching agent can improve the leaching efficiencies of RE and Al,but pH has neglected effects on the leaching efficiencies of RE.At PEI concentrations below 0,4 wt%, the addition of PEI promotes the leaching of RE and AI.In column leaching studies of the WCE-DREO,the addition of 0.4 wt% PEI to the traditional leaching agent(NH_(4))_(2)SO_(4) has no impact on the leaching efficiencies of RE.However,it can significantly increase the infiltration rate of WCE-DREO,shortening the leaching time per 10 mL effluent from about 30 min for(NH_(4))_(2)SO_(4) leaching system to 20 min for the composite leaching system.The leaching time is shortened by one-third,and the leaching cost is reduced,which can provide theoretical guidance for the development and commercial implementation of novel composite leaching agent for WCE-DREO.

Process mineralogy of Weishan rare earth ore by MLA

Mineral liberation analyser(MLA) was applied to quantitatively analyze the rare earth ore from Weishan in Shandong. Mineralogy parameters, such as mineral composition, occurrence states of rare earth elements(REEs) and valuable elements, mineral embedded grain size distribution, mineral association and liberation, are obtained. Results show that the contents of REEs and other valuable elements mainly contained in the ore were La 1.02 wt%, Ce 4.29 wt%, Pr 0.34 wt%, Nd 0.84 wt%, Sr 3.4 wt%and Ba 26.53 wt%, respectively. The REEs mainly occur in bastnaesite and carbocernaite in the form of independent mineral and the contents of bastnaesite and carbocernaite in the ore were 5.96 wt% and12.30 wt%, respectively. 67.34% of strontium occurs in carbocernaite and the rest occurs in celestobarite and strontianite mineral. 92.71% of barium occurs in barite. Liberation of main rare-earth minerals such as bastnaesite and carbocernaite is more than 80% when the grinding fineness is78.42% passing 74 μm. The research results could be employed to provide detailed basic theoretical data for further improvement of the beneficiation process flow and the processing index of rare earth ore, the recycling of other valuable minerals and the comprehensive utilization of tailings.

Local concentration of middle and heavy rare earth elements in the col on the weathered crust elution-deposited rare earth ores

This present study focused on investigating the content and relative enrichment multiple of rare earth elements（REEs） in different terrain of weathered ore body, and the value of light rare earth elements/middle and heavy rare earth elements（LREEs/HREEs）, in order to understand the mobilization and redistribution of HREEs, Furthermore, the abrasion pH was investigated as well, The results show that the average contents of HREEs in the knap, ridge and col are 37.26, 61.71, and 271.3 μg/g, respectively. The value of LREEs/HREEs is decreased from 16.78 to 7.914 between knap and col and the relative enrichment multiple of HREEs is as follows： CCol-HREEs 〉 CRidge-HREEs 〉 0. It is indicated the HREEs is concentrated in the col and the enrichment degree of HREEs is stronger than the ridge and the knap. Rare earth elements fractionation is exhibited in the different terrain of weathered ore body. Based on this study, the finding that HREEs concentrate in the lower terrain of weathered crust elution-deposited rare earth ores, such as in the col, would become a marker or indicator to search for middle and heavy rare earth enriched zone.

Enhancing mineral liberation of a Canadian rare earth are with microwave pretreatment

Liberation. as an attribute of mineralogy characteristic. whose impacts on finely disseminated Canadian rare earth ore was studied with microwave pretreatment. Samples of a light rare earth ore along with mostly ankerite and biotite as dominant gangue minerals as well as bastnaesite, strontianite and goethite as dominated minerals were exposed to further comminution by ball mill and microwave pretreatment fragmentation. Mineralogical characteristics were analyzed by using a mineral liberation analyzer（MLA）.The results indicated that tight association mutually penetrates among dominated minerals in the range size of -300 ＋ 212 μm and 212 ＋ 150 μm and gangue minerals in the form of adjacent type. fine vein type. shell type and packing type. Temperature in the ore samples pre-treated by microwave can rapidly rise to 250 ℃ with microwave power of 0-1.5 kW and microwave time of 0-2 min. Applying the microwave pretreatment merely reduces the hardness of the ore causing the fracture of rare earth ore, but this does not transform or change the original mineralogy characteristics of the ore samples. On the basis of above study. the liberation value of bastnaesite, strontianite and goethite with microwave pretreatment is greater than with conventional comminution when the liberation class is above 75%. The distribution of particle size of rare earth ore samples is better with microwave pretreatment than with conventional comminution for particle size of 7.4 × 10^（-5） m. With microwave pretreatment, the theoretical grade-recovery of bastnaesite. strontianite and goethite in the rare earth ore attains better results than with conventional comminution at a given grade.

Influences of CeO_(2)morphology on enhanced performance of electro-Fenton for wastewater treatment

As a kind of rare-earth oxide,CeO_(2)has been considered as a great potential material for its abundant oxygen vacancies and catalysis activity in wastewater treatment.In this study,three ceria samples with different morphological structure were prepared,and their effect on contaminates degradation in electro-Fenton(E-Fenton)system was investigated.It is found that the morphology of CeO_(2)has great influence on promoting the performance of E-Fenton process.The rod-like CeO_(2)(R-CeO_(2))induced EFenton system shows higher azo dye X3 B removal and mineralization rates than cubs(C-CeO_(2))and octahedrons(O-CeO_(2)),and the degradation kinetic rate constants are 0.28,0.169 and 0.181 min^(-1)respectively,already surpass that of the blank one(0.120 min^(-1)).The H_(2)O_(2)generation capacity of R-CeO_(2)induced E-Fenton system is also superior to the others,and the corresponding Faraday current efficiency even increases to 166.2%at 2.5 min.Characterizations by scanning-transmission electron microscopy(STEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),electron spin resonance(ESR),Raman spectroscopy were conducted to disclose the mystery behind this phenomenon.The results indicate that the difference of surface oxygen vacancy density in different shaped CeO_(2)acts as a magic driving force for the accelerated oxygen reduction,and then leads to the enhanced degradation efficiency of E-Fenton system.This work provides a new insight into the development and application of rare-earth elements based catalyst in E-Fenton technology.