Precision Engineering of 2D Protein Layers as Chelating Biogenic Scaffolds for Selective Recovery of Rare-Earth Elements.

Rare-earth elements, which include the lanthanide series, are key components of many clean energy technologies, including wind turbines and photovoltaics. Because most of these 4f metals are at high risk of supply chain disruption, the development of new recovery technologies is necessary to avoid future shortages, which may impact renewable energy production. This paper reports the synthesis of a non-natural biogenic material as a potential platform for bioinspired lanthanide extraction. The biogenic material takes advantage of the atomically precise structure of a 2D crystalline protein lattice with the high lanthanide binding affinity of hydroxypyridinonate chelators. Luminescence titration data demonstrated that the engineered protein layers have affinities for all tested lanthanides in the micromolar-range (dissociation constants) and a higher binding affinity for the lanthanide ions with a smaller ionic radius. Furthermore, competitive titrations confirmed the higher selectivity (up to several orders of magnitude) of the biogenic material for lanthanides compared to other cations commonly found in f-element sources. Lastly, the functionalized protein layers could be reused in several cycles by desorbing the bound metal with citrate solutions. Taken together, these results highlight biogenic materials as promising bioadsorption platforms for the selective binding of lanthanides, with potential applications in the recovery of these critical elements from waste.

Elemental composition, rare earths and minority elements in organic and conventional wines from volcanic areas: The Canary Islands (Spain).

The organic wine market is rapidly growing worldwide, both in terms of production and consumption. However, the scientific literature is not conclusive regarding differences in the elemental composition of wines according to their production method, including both major and trace elements. Minerals can be present in wine as a result of both anthropogenic and environmental factors. To date, this has not been evaluated in volcanic contexts, neither has the emergent issue of rare earths and other minority elements as potential sources of food contamination. This study using inductively coupled plasma mass spectrometry (ICP-MS) analyses organic and conventional wines produced in the Canary Islands (Spain), an archipelago of volcanic origin, to compare their content of 49 elements, including rare earths and minority elements. Our results showed that organic wines presented lower potential toxic element content on average than their conventional counterparts, but differences were not significant. Geographical origin of the wine samples (island) was the only significant variable differentiating wine samples by their composition profiles. By comparing our data with the literature, no agreement was found in terms of differences between organic and conventionally-produced wines. This confirms that other factors prevail over elemental composition when considering differences between wine production methods. Regarding the toxicological profile of the wines, five samples (three organic and two conventional) exceeded the maximum limits established by international legislation. This highlights the need for stricter analytical monitoring in the Canary Islands, with a particular focus on Cu and Ni concentration, and potentially in other volcanic areas.

Biohydrometallurgy for Rare Earth Elements Recovery from Industrial Wastes.

Biohydrometallurgy recovers metals through microbially mediated processes and has been traditionally applied for the extraction of base metals from low-grade sulfidic ores. New investigations explore its potential for other types of critical resources, such as rare earth elements. In recent times, the interest in rare earth elements (REEs) is growing due to of their applications in novel technologies and green economy. The use of biohydrometallurgy for extracting resources from waste streams is also gaining attention to support innovative mining and promote a circular economy. The increase in wastes containing REEs turns them into a valuable alternative source. Most REE ores and industrial residues do not contain sulfides, and bioleaching processes use autotrophic or heterotrophic microorganisms to generate acids that dissolve the metals. This review gathers information towards the recycling of REE-bearing wastes (fluorescent lamp powder, spent cracking catalysts, e-wastes, etc.) using a more sustainable and environmentally friendly technology that reduces the impact on the environment.

A short critique on biomining technology for critical materials.

Being around for several decades, there is a vast amount of academic research on biomining, and yet it contributes less to the mining industry compared to other conventional technologies. This critique briefly comments on the current status of biomining research, enumerates a number of primary challenges, and elaborates on some kinetically-oriented strategies and bottom-up policies to sustain biomining with focus on critical material extraction and rare earth elements (REEs). Finally, we present some edge cutting developments which may promote new potentials in biomining.

Recent Materials Developed for Dispersive Solid Phase Extraction.

Solid phase extraction (SPE) is an analytical procedure developed with the purpose of separating a target analyte from a complex sample matrix prior to quantitative or qualitative determination. The purpose of such treatment is twofold: elimination of matrix constituents that could interfere with the detection process or even damage analytical equipment as well as enriching the analyte in the sample so that it is readily available for detection. Dispersive solid phase extraction (dSPE) is a recent development of the standard SPE technique that is attracting growing attention due to its remarkable simplicity, short extraction time and low requirement for solvent expenditure, accompanied by high effectiveness and wide applicability. This review aims to thoroughly survey recently conducted analytical studies focusing on methods utilizing novel, interesting nanomaterials as dSPE sorbents, as well as known materials that have been only recently successfully applied in dSPE techniques, and evaluate their performance and suitability based on comparison with previously reported analytical procedures.

Molecular tests support the viability of rare earth elements as proxies for fossil biomolecule preservation.

The rare earth element (REE) composition of a fossil bone reflects its chemical alteration during diagenesis. Consequently, fossils presenting low REE concentrations and/or REE profiles indicative of simple diffusion, signifying minimal alteration, have been proposed as ideal candidates for paleomolecular investigation. We directly tested this prediction by conducting multiple biomolecular assays on a well-preserved fibula of the dinosaur Edmontosaurus from the Cretaceous Hell Creek Formation previously found to exhibit low REE concentrations and steeply-declining REE profiles. Gel electrophoresis identified the presence of organic material in this specimen, and subsequent immunofluorescence and enzyme-linked immunosorbant assays identified preservation of epitopes of the structural protein collagen I. Our results thereby support the utility of REE profiles as proxies for soft tissue and biomolecular preservation in fossil bones. Based on considerations of trace element taphonomy, we also draw predictions as to the biomolecular recovery potential of additional REE profile types exhibited by fossil bones.

Selective extraction and column separation for 16 kinds of rare earth element ions by using N, N-dioctyl diglycolacid grafted silica gel particles as the stationary phase.

The selective extraction and column separation rear earth elements (REEs) were investigated in the present work. Herein, the functional ligand of N, N-dioctyldiglycolic acid (DODGA) was synthesized and chemically grafted on the silica gel (SG) particles to give the novel material SG@DODGA. The obtained SG@DODGA was fully characterized by NMR, BET (Brunauer-Emmett-Teller) N2 physisorption analysis, atom force microscopy (AFM), scanning electronic microscopy (SEM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). After investigating the adsorption capability of the SG@DODGA towards 16 kinds of REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Td, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc), the results showed that the adsorption kinetic data was better fitted with pseudo-second-order model and Elovich model, the adsorption isotherms data was suitable for Freundlich model. The above result also indicated that the adsorption mechanism between the SG@DODGA and REEs was chemical ion exchange. Moreover, choose SG@DODGA as the column chromatography stationary phase and packed in a glass column for the column studies to obtain breakthroughs profile of each REEs. Furthermore, the column was used to try to separate the mixed 16 kinds of REEs. The first attempt to preliminary separate REEs result showed that this column could be applied for simply separating REEs. The light REEs La, Ce, Pr, Nd exhibited better separation effect than the other REEs.

Biological leaching of rare earth elements.

The distinctive physico-chemical features of rare earth elements (REEs) have led to an increase in demand by the global market due to their multiple uses in industrial, medical and agricultural implementations. However, the scarcity of REEs and the harsh eco-unfriendly leaching processes from primary sources beside obliviousness to their recycling from secondary sources, together with the geopolitical situation, have created the need to develop a more sustainable mining strategy. Therefore, there is a growing interest in bio-hydrometallurgy, which may contribute to the scavenging of these strategic elements from low-grade resources in an environmentally friendly and economically feasible way as with copper and gold. Several prokaryotes and eukaryotes show the ability to leach REEs, however, the success in employing these microorganisms or their products in this process relays on several biotic and abiotic factors. This review focuses on the differences made by microorganisms in REEs leaching and fundamentally explains microbes-REEs interaction.

Biosorption as green technology for the recovery and separation of rare earth elements.

Rare earth elements (REE) have great demand for sustainable energy and the high-end technology sector. The high similarity of REE owing to the nature of their electronic configurations increases the difficulty and costs of the development of chemical processes for their separation and recovery. In this way, the development of green technologies is highly relevant for replacing conventional unit operations of extractive metallurgy, viz. precipitation, liquid-liquid and solid-liquid extraction, and ion-exchange. Biosorption is a physicochemical and metabolically-independent biological process based on a variety of mechanisms including absorption, adsorption, ion-exchange, surface complexation and precipitation that represents a biotechnological cost-effective innovative way for the recovery of REE from aqueous solutions. This mini-review provides an overview and current scenario of biosorption technologies existing to recover REE, seeking to address the possibilities of using a green technology approach for wastewater treatment, as well as for the recovery of these high valued elements in the REE production chain.

Direct Recovery of the Rare Earth Elements Using a Silk Displaying a Metal-Recognizing Peptide.

Rare earth elements (RE) are indispensable metallic resources in the production of advanced materials; hence, a cost- and energy-effective recovery process is required to meet the rapidly increasing RE demand. Here, we propose an artificial RE recovery approach that uses a functional silk displaying a RE-recognizing peptide. Using the piggyBac system, we constructed a transgenic silkworm in which one or two copies of the gene coding for the RE-recognizing peptide (Lamp1) was fused with that of the fibroin L (FibL) protein. The purified FibL-Lamp1 fusion protein from the transgenic silkworm was able to recognize dysprosium (Dy3+), a RE, under physiological conditions. This method can also be used with silk from which sericin has been removed. Furthermore, the Dy-recovery ability of this silk was significantly improved by crushing the silk. Our simple approach is expected to facilitate the direct recovery of RE from an actual mixed solution of metal ions, such as seawater and industrial wastewater, under mild conditions without additional energy input.

Synthesis and application of alginate immobilised banana peels nanocomposite in rare earth and radioactive minerals removal from mine water.

This study describes the preparation, characterisation and application of pelletised immobilised alginate/montmorillonite/banana peels nanocomposite (BPNC) in a fixed-bed column for continuous adsorption of rare earth elements and radioactive minerals from water. The materials was characterised by Fourier transform infrared, X-ray diffraction and scanning electron microscopy analyses. Analyses indicated that the pellets are porous and spherical in shape. FT-IR analysis showed that the functional groups responsible for the coordination of metal ions were the carboxylic (-COO-) and siloxane (Si-O-Si and Si-O-Al) groups. XRD analysis showed two additional peaks which were attributed to alginate and montmorillonite. The influence of the initial concentration, bed depth and flow rate were investigated using synthetic and real mine water in order to determine the breakthrough behaviour of both minerals. The processed bed volume, adsorbent exhaustion rate and service time, were also explored as performance indices for the adsorbent material. Furthermore, the breakthrough data were fitted to both the Thomas and Bohart-Adams models. The BPNC exhibited high affinity for U, Th, Gd and La in the real mine water sample. However, studies may still be required using waters from different environments in order to determine the robustness of BPNC.

Recovery of Rare Earth Elements from Wastewater Towards a Circular Economy.

The use of rare earth elements is a growing trend in diverse industrial activities, leading to the need for eco-friendly approaches to their efficient recovery and reuse. The aim of this work is the development of an environmentally friendly and competitive technology for the recovery of those elements from wastewater. Kinetic and equilibria batch assays were performed with zeolite, with and without bacterial biofilm, to entrap rare earth ions from aqueous solution. Continuous assays were also performed in column setups. Over 90% removal of lanthanum and cerium was achieved using zeolite as sorbent, with and without biofilm, decreasing to 70% and 80%, respectively, when suspended Bacillus cereus was used. Desorption from the zeolite reached over 60%, regardless of the tested conditions. When in continuous flow in columns, the removal yield was similar for all of the rare earth elements tested. Lanthanum and cerium were the elements most easily removed by all tested sorbents when tested in single- or multi-solute solutions, in batch and column assays. Rare earth removal from wastewater in open setups is possible, as well as their recovery by desorption processes, allowing a continuous mode of operation.

Constant-pattern design method for the separation of ternary mixtures of rare earth elements using ligand-assisted displacement chromatography.

A constant-pattern design method for separating ternary mixtures using ligand-assisted displacement chromatography was developed for non-ideal systems. The general correlation for the minimum column length required to achieve the constant-pattern state for binary separations from our previous study was extended to ternary separations. Additionally, an equation for the yield of a target component as a function of key dimensionless groups was derived based on the constant-pattern mass transfer zone lengths. The column length and operating velocity solved from the two equations ensured the yields and the constant-pattern state for the target components. A selectivity weighted composition factor was developed to allow the design method to specify a minimum target yield for one or multiple components. The design method was verified using simulations and experiments for different targeted yields (70-95%), ligand concentrations (0.03-0.06 M), and feed compositions (1/12-5/6). The targeted yields were achieved or exceeded in all cases tested. The minimum column length required to achieve a constant pattern-state and the productivity of LAD are limited by the lowest selectivity or by a minority component with a low concentration in the feed, even when it does not have the lowest selectivity. Sacrificing the yields of minor components can increase the total productivity significantly. The productivities achieved using this design method are 839 times higher than literature results for ternary separations with the same purity and similar yields.

Industrial countercurrent chromatography separations based on a cascade of centrifugal mixer-settler extractors.

In hydrometallurgy, traditional extraction technologies, in particular, for isolation and purification of rare-earth metals include a number of processing steps using up to hundreds of mixer-settler extractors. These technologies could be greatly simplified by using the methods of countercurrent chromatography (CCC) separation. However, the current CCC equipment cannot process large volumes of feed material formed during the industrial production of these metals. In this paper, the cascade of centrifugal mixer-settler extractors assembled as a multi-stage unit is suggested for industrial application of CCC and discussed.

Application of a functionalized ionic liquid extractant tributylmethylammonium dibutyldiglycolamate ([A336][BDGA]) in light rare earth extraction and separation.

A type of functionalized ionic liquid extractant, tributylmethylammonium dibutyldiglycolamate ([A336][BDGA]), was synthesized, and its extraction ability of light rare earth elements, namely, La(III), Ce(III), Pr(III) and Nd(III), wascompared with that of other functionalized ionic liquid extractants, including tributylmethylammonium dioctyldiglycolamate and diglycolic amide extractants N,N,N,N-tetrabutyl-3-oxapentane-diamide (TBDGA) and N,N,N,N-tetraoctyl-3-oxapentane-diamide (TODGA). The study of extraction behavior indicated that the ionic liquids exhibited better extraction properties than the amides under lower acidity conditions. The effects of the pH and concentration of the extractant on the extraction behavior of [A336][BDGA] on light rare earths were determined. A separation strategy of mixed light rare earths was investigated by means of extraction chromatography using [A336][BDGA] as the stationary phase. As a result, nearly pure La(III), Ce(III), Pr(III) and Nd(III) were obtained, respectively. A new strategy of separating mixed light rare earths was established by means of extraction chromatography. The stationary phase of [A336][BDGA] was used in this strategy. The four rare earths elements, La(III), Ce(III), Pr(III) and Nd(III), achieved baseline separation.

Key parameters controlling the development of constant-pattern isotachic trains of two rare earth elements in ligand-assisted displacement chromatography.

Ligand-assisted displacement chromatography (LAD) has been developed for separating rare earth elements since the 1950's. Isotachic displacement trains, which are similar to those in conventional displacement chromatography, were reported previously. However, there has been no general theory delineating the conditions required to form constant-pattern displacement trains for non-ideal systems (or systems with significant mass transfer resistance). The constant-pattern state is critical for obtaining pure products with high yield and high productivity. Without theoretical guidance, all the previous studies found the constant-pattern state by experimental trial and error, which was time consuming and costly. In this study, an efficient rate model and simulations of LAD were developed and verified with experimental data for non-ideal systems. Verified simulations were used to understand the mechanisms of separations and the transition from the transient state to the constant-pattern state. The key dimensionless factors affecting the transition for binary non-ideal systems were identified. Dimensionless groups were developed to reduce the number of variables. Simulations were used to find the transition points fromthe transient state to the constant-pattern state, which indicates the minimum dimensionless column lengths in the multi-parameter space. Strategic combination of the key dimensionless groups allows the minimum dimensionless column lengths to correlate with the combined groups in a two-dimensional diagram (or a map). The correlation curve divides the multi-dimensional space into the transient region and the constant-pattern region. The correlation was further verified with five sets of experiments. It can be used to find, without process simulations or experiments, the minimum column lengths for developing constant-pattern isotachic trains for non-ideal systems, which is useful for designing efficient ligand-assisted displacement chromatography at any scale.

Bioleaching of metals from WEEE shredding dust.

A bioleaching process developed in two separate steps was investigated for the recovery of base metals, precious metals and rare earth elements from dusts generated by Waste Electrical and Electronic Equipment (WEEE) shredding. In the first step, base metals were almost completely leached from the dust in 8 days by Acidithiobacillus thiooxidans (DSM 9463) that lowered the pH of the leaching solution from 3.5 to 1.0. During this step, cerium, europium and neodymium were mobilized at high percentages (>99%), whereas lanthanum and yttrium reached an extraction yield of 80%. In the second step, the cyanide producing Pseudomonas putida WSC361 mobilized 48% of gold within 3 h from the A. thiooxidans leached shredding dust. This work demonstrated the potential application of biohydrometallurgy for resource recovery from WEEE shredding dust, destined to landfill disposal, and its effectiveness in the extraction of valuable substances, including elements at high supply risk as rare earths.