Column leaching of lanthanides from Abu Tartur phosphate ore with kinetic study

The dynamic leaching of lanthanides from a west desert phosphate ore, Egypt (Abu Tartur) by hydrochloric acid, nitric acid and sulfuric acid solutions was investigated in this study as a function of acid concentration, flow rate and the presence of some additives such as boric acid. Also the kinetics of leaching of lanthanides was investigated as a function of temperature. It was found that the leaching process could be described by a shrinking-core model, with activation energy about 5.9, 13.8 and 21.9 kJ/...

Leaching of rare earth elements from contaminated soils using saponin and rhamnolipid bio-surfactant

The effective leaching of rare earth elements（La, Ce, Y and Eu） from simulated contaminated soil using bio-surfactant was investigated in a lab-scale column leaching experiment, where anionic biosurfactant rhamnolipid and non-ionic biosurfactant saponin were used as washing solutions. Soil properties and the rare earth element fractions were analysed to define the effect of leaching on soil and elemental speciation. Column leaching results showed that saponin solution was more effective than rhamnolipid in the removal of the four rare earth elements tested, with the accumulative removal efficiency of La, Ce, Y and Eu following flushing with 400 mL of 25 g/L saponin, reaching 35.258%, 26.072%, 31.476% and 30.849%, respectively. The change in REE speciation showed that REE removed from soils were mainly derived from the acid-soluble and residual fractions released when rhamnolipid solution was used as a leaching agent. However, for saponin leaching, removed REE amounts were derived from acid-soluble and reducible fractions. Complexation interactions were identified between saponin and REEs, according to infrared spectroscopy and ion exchange data, with saponin complexing with La, Ce, Y, and Eu at a complex ratio of 1：1.

Pyrite oxidation in column at controlled redox potential of 900 mV with and without bacteria

Comparisons on the bioleaching and sterile oxidation of pyrite were performed at controlled redox potential of 900 mV(vs.SHE) and different temperatures of 30 and 60℃.For sterile experiments,the redox potential of irrigation solution was controlled by adding hydrogen peroxide solution(15 wt%),while the redox potential of irrigation solution for bioleaching was elevated by flowing through the packed bed in which bacteria were activated and colonized.The rate of pyrite bioleaching is faster than that of sterile oxidation at temperature of 30℃.The reason is that the potential gradient of leaching solution in bioleaching column is much smaller than that in sterile column.The redox potentials of irrigation solution and leaching solution are similar for bioleaching;however,the redox potential difference of irrigation solution and leaching solution for sterile oxidation is about 150 mV.When temperature increases to 60℃ for sterile oxidation,the rate of pyrite leaching is faster than that of bioleaching at temperature of 30℃,even though the redox potential gradient of leaching solution is great.The mineralogy analyses of pyrite residue were performed by scanning electron microscopy-energy-dispersive spectroscopy(SEM-EDS),X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) analyses.The results confirm that pyrite oxidation might only occur at specific sites with high surface energy on surface and obeys the "indirect mechanism" whether there are bacteria or not.The pyrite oxidation rate is not inhibited by inert sulfur on residue surface at elevated redox potential.According to the conclusions,the way to accelerate pyrite oxidation is proposed.

Adsorption ability of rare earth elements on clay minerals and its practical performance

The adsorption behaviors of rare earth elements on clay minerals would have great influence on the mineralization process and the leaching process of the ion-adsorption type rare earths ore.In this work,the adsorption thermodynamics of REEs on kaolin were investigated thoroughly and systematically.The experimental results showed that the adsorption characteristics of La,Nd,Y on kaolin did fit well with the Langmuir isotherm model and their saturated adsorption capacities were 1.731,1.587 and 0.971 mg/g,respectively.The free energy change（ΔG）values were –16.91 kJ/mol（La）,–16.05 kJ/mol（Nd）and –15.58 kJ/mol（Y）,respectively.The negative values of ΔG demonstrated that the adsorption of rare earth on kaolin was a spontaneously physisorption process.The deposit characteristic of the volcanic ion-adsorption type rare earths ore and the behavior of the rare earth in the column leaching process were also developed here.With the increase of the ore body depth,the distribution of the LREEs decreased and the HREEs increased.And the slight differences in the adsorption ability of REEs on clay minerals led to the fractionation effect in the column leaching process.These developed more evidences and better understanding of metallogenic regularity,and provided a theoretical basis and scientific approach to separation of the HREEs and LREEs in the leaching process.