Desorption Of Rare Earth Elements Research Articles

Chemical modification of zeolites for the recovery of rare earth elements evaluated by machine learning algorithms

Rare earth elements (REE) are a significant group of valuable elements used in diverse and relevant applications in our daily lives. The mining and processing of the original ores, as well as the final wastes disposal, produce wastewater with variable concentrations of REE to be recovered. Sorbent materials like zeolites have been employed in adsorption processes to capture diverse pollutants from wastewater. The objective of this study is to identify the most effective modified zeolite for the adsorption and desorption of REE from aqueous solutions. To achieve this, the processes evaluation by machine learning (ML) algorithms was explored through both supervised and unsupervised analyses. The purpose of the usage of such tools was to assist in the selection of the optimal zeolite for REE recovery and to assess the predictive capabilities of the models. Modified zeolites were obtained by acid and alkali treatments in order to increase their sorption capacity compared to the controls and they were characterized by SEM/EDS, FTIR and pH zero point charge. Kinetic modelling and desorption assays were also performed, these last ones to evaluate the REE leaching from the sorbent for the best suitable modified zeolites. An overall removal of 80% for adsorption and over 90% recovery for desorption were achieved for the best modified zeolites. ML algorithms helped to classify the adsorption results and allowed the selection of the best suitable modified zeolites. It is concluded that alkali modification of the zeolites surfaces increases their natural adsorption capacity for recovering REE.

Adsorption of rare earth elements in carboxylated mesoporous carbon

The separation of Rare Earth Elements (REEs) from various non-conventional sources is critically important to maintain the supply–demand balance of REEs in the western world. In this research, we have investigated coal Fly Ash (CFA) as the non-conventional source of REEs. In order to recover REEs, we have synthesized carboxylate-functionalized mesoporous carbon (CMC) to harness the chelation-induced adsorption of REEs. These adsorbents were characterized with pore textural properties, FTIR spectroscopy, and SEM-EDX mapping. In the initial study with single-component La(III) Dy(III) and Lu(III), it was revealed that CMC can adsorb those REEs 2–4 times more than that of pristine mesoporous carbon confirming the effective role of the carboxylate group in the REE separation. Furthermore, the affiliation of the carboxylate group towards heavier REEs (Lu > Dy > La, when present is equal amounts) provides an added benefit of this adsorbent owing to the high demand for heavier REEs in the technology sectors. The leachate solution produced from CFA contained sixteen REEs in the range of 50–200 ppb for most of the REEs. It was revealed that CMC can extract 80–90% of all the REEs thereby further confirming the success of the CMC as an effective REE sorbent. Three successive cycles of adsorption and desorption of REEs with the same CMC revealed the consistent adsorption capacity of REEs. In-situ X-ray Absorption Near Edge Spectroscopy (XANES) analysis confirmed the + 3 oxidation states of La, Dy, and Lu within CMC. In-situ Extended X-ray Absorption Fine Structure (EXAFS) analysis revealed the shortening of mean La-O, Dy-O, and Lu-O bond distance by 0.03–0.05 Å thereby confirming the coordination of these REEs with carboxylate groups present on CMC.

Desorption of REEs from Halloysite and Illite: A Link to the Exploitation of Ion-Adsorption RE Ore Based on Clay Species

The adsorption/desorption characteristics for light and heavy rare earth elements (REEs) on halloysite and illite (which are beneficial for the utilization of ion-adsorption RE ore) were systematically investigated and compared. Additionally, halloysite and illite were fully charactered by XRD, SEM, microscope, zeta potential, nitrogen adsorption–desorption isotherms and buffer pH to build the relationship between adsorption/desorption mechanisms and the minerals’ properties. The results of experiments show that the adsorption rate of halloysite is higher than illite, although they are both very fast and follow the pseudo-second-order kinetic model. The adsorption capacity of halloysite and illite increases with an increase in adsorption pH and remains constant when pH is higher than 4. Due to the narrow interlamellar spacing of halloysite and the fact that it is a nanotube, RE ions are adsorbed only through electrostatic attraction, whereas the adsorption and desorption pH have a significant effect on the recovery of RE ions from illite, because of the diverse adsorption mechanism. The results illustrated that the structure and surface properties of clays are also the key factors that affect RE ions leaching.

EXTRACTION OF RARE EARTH ELEMENTS FROM SOLID WASTE OF PRODUCTION OF PHOSPHORIC ACID FOLLOWED BY SORPTION ON CATION EXCHANGE RESINS

The basis of production of extraction phosphoric acid is two simultaneous processes: dissolving phosphate raw material in a mixture of sulfuric and phosphoric (formed in the process) acids and crystallization of calcium sulfate (phosphogypsum). Phosphogypsum is an inevitable large-tonnage and cumbersome waste at sulfuric acid processing of apatite, which is of interest not only as a source of building gypsum, but also as an alternative rare earth raw material does not have a natural activity and containing rare-earth elements as a cerium and yttrium groups. As a raw material for the production of rare earth elements, calcium sulfate of three types has been used: phosphogypsum from a sludge accumulator, calcium phosphate phospho-hemihydrate and calcium sulfate phosphate dihydrate from a carousel filter produced by extraction phosphoric acid at JSC "PhosAgro-Cherepovets". The extraction of rare-earth elements from phosphogypsum from a sludge accumulator by leaching (percolation) with inorganic acids with subsequent sorption on cation-exchange resins is considered. As an adsorbent for extracting REE from leach solutions, cationite "Purolite" S-150 is used. A static exchange capacitance of cation exchanger is found that is the capacity of the resin when equilibrium is reached with a solution of a certain volume and composition. The static capacity of cation exchanger for rare-earth elements is 1.57%, which indicates a good absorbing capacity. Desorption of rare-earth elements from the cation exchanger is carried out with a solution of ammonium nitrate. The optimal solution for leaching was found to be sulfuric acid with a concentration of 5% by weight. The degree of extraction of rare-earth elements from phosphogypsum with sulfuric acid is about 82%.Forcitation:Artamonov A.V., Smirnova D.N., Smirnov N.N., Ilyin A.P. Extraction of rare earth elements from solid waste of production of phosphoric acid followed by sorption on cation exchange resins. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 87-93

Adsorption of rare earth ions using carbonized polydopamine nano carbon shells

AbstractHerein we reported the structure effects of carbon nano-shells prepared by the carbonization of polydopamine for the adsorption of rare earth elements (REEs) for the first time. Solid carbon spheres, 60 nm carbon shells and 500 nm carbon shells were prepared and evaluated for adsorption and desorption of REEs. The adsorption performance of carbon nano-shells for REEs was far superior to the solid carbon spheres. In addition, the effect of acidity on the adsorption and desorption properties was discussed. The good adsorption performance of the carbon nano-shells could be attributed to their pore structure, specific surface area, and the presence of both amine and carbonyl groups from the grafted dopamine.

Application of rare-earth elements in the agriculture of China and its environmental behavior in soil.

Rare-earth elements (REEs) have been used in fertilizers in the agriculture of China for about 20 years. They have been shown to be beneficial elements for plants. For example, they have improved the yield and quality for several kinds of crops. This paper reviews the current literature on studies of REEs being used as fertilizers. Some studies have focused on the effects of REEs on metabolic nutrients, photosynthesis and stress resistance of plants. Other studies have shown that the environmental behaviors of REEs in soil are dominated by their low solubility. Fluorides, carbonates, phosphates and hydroxides may form neutral complexes containing REEs with a low solubility. The amount of extraneous REEs demonstrate the following relationship: residual >> bound to organic matter > bound to Fe-Mn oxides > bound to carbonate >> exchangeable and water soluble forms. The adsorption capacity of REEs depends on the clay type and the content of amorphous and manganese oxides, whereas the desorption of REEs is usually very low. At the end of the paper, authors discuss the needs for future environmental research on REEs, which would shed new light on the effects of REEs on agriculture, environment and human health.

Effect of organic acids on adsorption and desorption of rare earth elements

Effect of citric, malic, tartaric and acetic acids on adsorption of La, Ce, Pr and Nd by and desorption from four typical Chinese soils was studied. Generally, adsorption capacities of rare earth elements (REEs) were significantly correlated with the cation exchange capacity (CEC) of soils. In the presence of acetic acids adsorption of REEs was similar to that in the presence of Ca(NO 3) 2. However, in the presence of citric, malic and tartaric acids adsorption of REEs by Heilongjiang, Zhejiang and Guangdong soils decreased to varying extents if compared with that in the presence of nitrate and acetic acid. The significance of suppression followed the order of citric acid > malic acid > tartaric acid > acetic acid , which was consistent with the order of stability of complexes of REEs with these organic acids. However, the adsorption increased with increasing equilibrium solution pH. For Jiangxi soil with low soil pH, CEC and organic matter these organic acids exerted an even more serious suppression effect on the adsorption of REEs. Another feature of the relationship between the adsorption of REEs and equilibrium solution pH was that the adsorption of REEs decreased with increase of pH from 2 to 4.5 and then slightly increased with further increase of pH. Desorption of REEs varied with soils and with organic acids as well. REEs were released easily from Heilongjiang, Zhejiang and Guangdong soils in the presence of organic acid. Generally, desorption of REEs decreased with increasing equilibrium solution pH. Effect of organic acids on desorption of REEs from Jiangxi soil was more complicated. In the presence of citric and malic acids no decrement and/or slight increase in desorption of REEs were observed over the equilibrium solution pH from 3 to 6.5. The reasons for this were ascribed to the strong complexing capacity of citric and malic acids and low soil pH, CEC and organic matter of Jiangxi soil.

Application of rare-earth elements in the agriculture of china and its environmental behavior in soil

Rare-earth elements (REEs) have been used in fertilizers in the agriculture of China for about 20 years. They have been shown to be beneficial elements for plants. For example, they have improved the yield and quality for several kinds of crops. This paper reviews the current literature on studies of REEs being used as fertilizers. Some studies have focused on the effects of REEs on metabolic nutrients, photosynthesis and stress resistance of plants. Other studies have shown that the environmental behaviors of REEs in soil are dominated by their low solubility. Fluorides, carbonates, phosphates and hydroxides may form neutral complexes containing REEs with a low solubility. The amount of extraneous REEs demonstrate the following relationship: residual>>bound to organic matter>bound to Fe-Mn oxides>bound to carbonate>>exchangeable and water soluble forms. The adsorption capacity of REEs depends on the clay type and the content of amorphous and manganese oxides, whereas the desorption of REEs is usually very low. At the end of the paper, authors discussed the needs for future environmental research on REEs, which would shed new light on the effects of REEs on agriculture, environment and human health.

Partial Dissolution of Lithogenic Nd and Global Isotopic Distribution in the Ocean

In marine geochemistry, Nd isotopic ratios are used as water mass tracer, scavenging tracer and source tracer of lithogenic component in the sediment. In spite of its usefulness, Nd behaviour in the marine environment has not clearly been understood yet. The Nd residence time estimated from concentration gradient (104 yr.) does not agree with the one based on a heterogeneous isotopic distribution in the world ocean (< 1500 yr.). Dissolved-particulate Nd exchange is likely to be a key term to solve this 'Nd paradox'. The local scale studies suggest that exchange occurs intensively at the continental margin and atmosphere/ocean interface: Mediterranean Sea (Henry et al., 1994); Sargasso Sea (Jeandel et al., 1995); tropical NE Atlantic (Tachikawa et al., 1997). The purpose of this paper is to clarify the mechanism of this exchange and impact of the exchange to Nd isotopic distribution in the world ocean. The Nd exchange includes a partial dissolution (and desorption) of lithogenic Nd and replacement by scavenged Nd from seawater (authigenic Nd). On the basis of the measurements of marine particles from the tropical NE Atlantic (Tachikawa et al., 1997) and Nd budget in the Mediterranean Sea (Henry et aL, 1994), we estimate lithogenic Nd dissolution at 30%. This value is surprisingly higher compared to the previous estimate (2%) based on a laboratory experience (Oreaves et al., 1994). Biological activity may play a significant role in dissolution of lithogenic material. It is well known that desorption of Rare Earth Elements (including Nd) from particulate matter occurs intensively under acid condition. The higher dissolution is probably due to a passage through the guts of zooplankton. The scavenging of dissolved Nd is related to occurrence of Mn oxides which are produced microbially (Sunda and Huntsman, 1987). We will discuss how Nd isotopic distribution varies in the global ocean if this exchange is under consideration.

Adsorption and desorption of rare earth elements with synthesized polyacrylamide.

Polyacrylamide (PAAM) was synthesized by plasma-initiated polymerization of acrylamide and N, N'-methylenebisacrylamide. Batchwise adsorption experiments demonstrated that PAAM had the characteristics to adsorb rare earth elements {Y(III), Ce(III), Eu(III), Ho(III) and Er(III)} and the adsorption of the rare earth elements onto PAAM depended on pH. The 50% adsorption pH for each element is as follows: Ce(III), 3.4; Y(III), 3.6; Er(III), 3.7; Ho(III), 3.9; Eu(III), 4.0. Adsorption equilibrium of the rare earth elements onto PAAM was attained within 15 min. These elements were released from the resin quantitatively by treatment of the PAAM with 0.1 M (mol/dm3) EDTA (pH 8.5) solution. A column packed with PAAM was used for the adsorption and desorption of the elements. As a result, the elements except Er(III) were adsorbed and desorbed quantitatively. Further, influence of co-existing anions on adsorption of cerium and europium was studied. From above results, it was found that PAAM had the possibility for being used as an adsorbent of rare earth elements.