Lamp Phosphors Research Articles

Highly efficient separation of Sc3+ and Y3+ in acid solution by a graphene oxide membrane with interlayer sieving

Sc and Y are key rare earth elements and are widely used in lamp phosphors, lasers and high-performance alloys. However, highly efficient extraction and separation of Sc3+ and Y3+ is laborious, harmful, slow, and costly, strongly necessitating more efficient extraction and separation techniques. Here, we produced hydrated Sc3+- and hydrated Y3+-controlled graphene oxide (GO) membranes and find that both hydrated cations were completely self-rejected by the membrane. By combining this self-rejection effect of the larger hydrated Y3+-controlled GO membrane and the rapid passage of the membrane through the smaller hydrated Sc3+, we proposed a strategy to separate Sc3+ and Y3+ by using a hydrated Y3+-controlled GO membrane. The experimental results show that the permeation rate of Sc3+ exceeds that of Y3+ when the separation factor reaches 4.02, which can be attributed to the interlayer sieving effects of the GO membrane. Our finding illustrates the use of a forward osmosis process with a GO membrane for the efficient separation of Sc3+ and Y3+ by interlayer sieving, which provides a new effective and eco-friendly method for the separation of rare earth elements.

Recovery of rare earth elements from waste phosphors using phosphonic acid-functionalized silica adsorbent

Recovery of rare earth elements from secondary sources is crucial to promote environmental sustainability and ensure the responsible utilization of natural resources. In this study, we showed a potential application of a silica-based adsorbent with immobilized fragments of aminobis(methylenephosphonic acid) for selective recovery of rare earth elements from acidic solutions, such as leaching solution of red lamp phosphor waste. The adsorption behavior of the material was studied in the dispersive solid phase extraction mode from model aqueous solutions that had an excess of 22 interfering ions in 0.5 mol/L NaCl. The results demonstrate reversible adsorption and outstanding kinetic characteristics of the adsorbent. The complete absorption of 14 rare earth elements occurs in less than 5 min under acidic conditions (with pH above 2.0). This method resulted in a 100-fold increase in the content of rare earth elements extracted from leachate.

A highly efficient sensor for europium(III) estimation using a poly(propylene imine) diaminobutane diglycolamide dendrimer as the ionophore: Potentiometric and photoluminescence studies

Multiple-diglycolamide (DGA) based ligands are known as highly promising extractants for the selective and efficient extraction of trivalent lanthanides/actinides from acidic feed solutions and therefore they have a great potential for the low level detection of these metal ions when used as ionophores in a potentiometric sensor. However, their use as ionophores in a potentiometric sensor is not much explored. Here in, we report the potentiometric sensing of Eu(III) ion in acidic medium using three novel multiple DGA-functionalized dendrimers: viz., generation zero (G0), one (G1) and two (G2) poly(propylene imine) diaminobutane dendrimers as ionophores doped in a polyvinyl chloride (PVC) matrix containing 2-nitrophenyl octyl ether (NPOE) as the plasticizer and sodium tetraphenylborate (NaTPB) as the ionic additive. Out of these three dendrimers, the G1 membrane gave very encouraging results and the G2 membrane did not work properly. On the other hand, the G0 membrane showed a narrower linear dynamic range (LDR), and a higher limit of detection (LOD) than the G1 membrane. The membrane with 4.1 % G1, 31.1 % PVC, 62.2 % NPOE, 2.6 % NaTPB exhibited a linear response behaviour from 6.6 × 10-7m to 1.5 × 10-2m Eu(III) with a slope of 15.6 ± 0.2 mV/decade and a LOD of 5.0 × 10-7m. The response time and lifetime of this sensor were found to be < 10 s and more than three months, respectively, and showed reasonably high selectivity with respect to mono- and divalent cations as well as the uranyl ion. All the sensor membranes contained two types of Eu(III) species as seen by luminescence spectroscopy. The sensor efficiency was checked by the ‘spike recovery method’. The G1 membrane sensor was also employed for the potentiometric titration of Eu(III) as an indicator electrode. Both methods showed more than 95 % recovery with excellent matching with the X-ray fluorescence (XRF) results. The sensor can also be used in the estimation of europium ion in a laboratory bearing waste and in a lamp phosphor waste leached which compared well with XRF and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) results, respectively.

Technoeconomic analysis of supercritical fluid extraction process for recycling rare earth elements from neodymium iron boron magnets and fluorescent lamp phosphors

This study offers a comprehensive and rigorous analysis of the technoeconomics of supercritical fluid extraction (SCFE) technology as applied to the recovery of rare earth elements (REEs) from end-of-life neodymium iron boron magnets and fluorescent lamp phosphors. Drawing on an array of data sources including laboratory results, literature data, scaling models, scenario analysis, and sensitivity analysis, this study conducts a sound economic analysis of the SCFE process at an industrial scale. The study renders a detailed estimation of the costs and revenues associated with the process and identifies the primary factors that impact its profitability. The findings demonstrate that the SCFE of REEs from these feedstocks can be economically viable under certain circumstances, with the efficiency of extracting terbium, dysprosium, and neodymium and the price of their respective oxides emerging as key drivers of profitability. By providing valuable insights into the feasibility of the SCFE process for REEs recovery, this study informs future research and development activities in the field.

The Influence of Optically Active Impurities on the Performance of Phosphors and Scintillators

This paper provides examples of a strategy employed to improve specific properties of phosphors and scintillators which would otherwise have limited their performance in lighting, cathode-ray tubes, and medical imaging technologies. When electron-hole pairs are produced by the exposure to high-energy radiation, the activator ion in the lattice preferentially captures one of the charge carriers. The subsequent capture of the carrier of opposite charge yields the activator ion luminescence. The carrier of the opposite charge can also be diverted to defects in the lattice. The trapping by defects reduces the brightness of phosphors and is responsible for the unwanted afterglow in scintillators. The strategy that is adopted to suppress the trapping by defects is to deliberately introduce an impurity ion that can compete successfully with the defects for the charge carrier. Since the impurity ion traps charge of the opposite sign to the activator ion, we label them as “anti-activators.” While the use of anti-activators gained importance in the field of scintillators in the 1990’s, results on their use for improving brightness of lamp and cathode-ray phosphors were available in the literature of the 1960’s and 1970’s.

Physicochemical properties of Li3Ba2La3(MoO4)8:Eu,Tb red-emitting phosphor for solid state white lamps

In this work, combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps. We synthesized a material with emission wavelength at λem = 617 nm, excited under long UV-blue wavelength based on Eu3+, Tb3+-activated molybdates Li3Ba2(La1–x–yEuxTby)3(MoO4)8 with 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1. A series of powder samples were produced by the combustion method and post-annealed at 800 °C in air. The crystalline phase formation was investigated by X-ray diffraction, which reveals the monoclinic C2/c (15) space group. It is observed that crystalline structure and morphology are preserved when the host lattice is doped with Eu3+ or Tb3+ single ions and co-doped with both ions at different doping concentrations. A detailed characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) shows a similar morphology in all samples: rather large (1–7 μm) agglomerate particles with irregular shapes and surrounded by smaller nanoparticles of 50 nm in size. UV–visible absorption spectra confirm the presence of Eu3+ and Tb3+ ions. The luminescent properties of the obtained phosphors were studied in detail. Cathodoluminescence measurements indicate that the best emission intensity is for Eu3+:Tb3+ doping ratios of 80:0, 90:0 and 20:80. On the other hand, samples with 80:0, 60:40, and 20:80 doping ratios show the highest intensity in a detailed photoluminescence analysis and they exhibit the highest quantum yield values. A complete and efficient energy transfer from the sensitizer Tb3+ to the activator Eu3+ is observed in all co-doped phosphors post-annealed at 800 °C for 4 h. Thus, the Li3Ba2La3(MoO4)8:Eu3+,Tb3+ materials fabricated by combustion synthesis are excellent phosphors for being applied as red-emitting component in solid-state white-light lamps due to an improved color rendering index (CRI) that can be obtained under long UV-blue excitation wavelengths.

Peptide functionalized Dynabeads for the magnetic carrier separation of rare-earth fluorescent lamp phosphors

Novel separation processes for end of life fluorescent lamp phosphors could greatly contribute towards a more sustainable rare-earth element market. Furthermore, surface-binding peptides bound to magnetic carriers are a promising biotechnological tool for selective particle separation processes. In this work, we investigate the magnetic carrier separation of the three most common rare-earth fluorescent lamp phosphors, facilitated by Dynabeads functionalized with previously identified selectively surface-binding peptides. We present an active ester-mediated coupling to chemically immobilize the peptides on amine and carboxylic acid coated beads. We report on the impact of the peptide functionalization on the surface properties of the beads, based on zeta potential investigations of variously functionalized beads and a Raman spectroscopic structural study of the investigated peptides. Fluorometrically, we show that the phosphor removal strongly depends on the medium and the surface coating of the beads. Furthermore, the Raman spectroscopic evidence of various simultaneously present disulfide bond conformations indicates an equilibrium of multiple peptide conformations and/or the presence of intermolecular disulfide bonds. Moreover, we found that carboxylic acid coated Dynabeads have a high affinity for the red phosphor Y2O3:Eu3+and based on the determined isoelectric points we hypothesize that this is driven by electrostatic surface interactions. This work can contribute towards novel rare-earth phosphor separation processes and towards a better understanding of magnetic carrier separation processes facilitated by surface-binding peptides.

Comparison of processing routes for recovery of rare earth elements from discarded fluorescent lamp phosphors

This study investigates two phosphor samples with three processing routes to extract rare earth elements (REE). Acid leaching in 2 M HCl, 80 °C, 1 h yielded higher REE extraction in the compact fluorescent lamp (CFL) feed (82% Eu), with varying rare earth (RE) purity (77–97%) compared to fluorescent tubelight (TL) feed (69% Eu, 98–95% purity). Mechanical activation (MA) of 30 and 60 min caused partial dissociation of the LAP (LaPO4:Ce3+Tb3+) phase and yielded 34% Ce, 36% Tb, and 40% La. Transmission electron microscopy results revealed the formation of polycrystalline sites, which improved RE recovery. Alkali baking showed better REE extraction for both phosphors. 86.5% Y, 69% Eu was selectively extracted in feed acid leaching, and 100% La, 60% Tb, 20.6% Eu after alkali baking with 97% purity and CeO2 in the leach residue. The acid baking route was preferred for CFL phosphor with 91% REE (43 % Tb) extraction and 98% purity. TL phosphor was better for Tb extraction. The alkali baking of TL feed and acid baking of CFL feed yields 37.7% and ∼30% rare earth oxides, respectively.

Optimizing Leaching of Rare Earth Elements from Red Mud and Spent Fluorescent Lamp Phosphors Using Levulinic Acid

Although various hydrometallurgical and solvometallurgical efforts have been made to extract REEs from end-of-life (EoL) products and waste, a systematic and statistical analysis of the impacts of leaching parameters to optimize the leaching process using organic acids is necessary, but lacking in the literature. This study employed the response surface methodology to develop mathematical models for optimal leaching by levulinic acid (LevA) of REEs in two waste materials, namely red mud and spent fluorescent lamp phosphors. The established models exhibited excellent statistical properties, in terms of significance, fitting, prediction, and error distribution. For red mud, the optimal conditions of liquid-to-solid ratio (L/S; v/w) of 40, temperature of 70 °C, and duration of 60 h led to 100% leaching of REEs excluding Sc. At the same L/S and temperature, &gt;98.7% of REEs were leached from fluorescent phosphors after 96 h. The SEM–EDS analysis of the waste materials revealed and confirmed morphological and compositional changes after leaching under the optimal conditions.

Leaching of yttrium and europium from fluorescent lamp phosphor powder using nitric acid: kinetics and optimization

ABSTRACT Rare earth elements (REEs) are recognized as one of the most critical elements and considered essential for the development of sustainable energy technologies, lasers, electronics, alloys, catalysts, and other applications. In order to meet the increasing demand to ensure those essential usages, the supply of REEs is however limited from the primary sources. Recovery of REEs from secondary resources, such as discarded electrical and electronic equipment, referred to as electronic waste (e-waste) is consequently crucial. Fluorescent lamps among such wastes are of special concern due to the high quantity of REEs present in them. This article discusses a potential hydrometallurgical method for recovering REEs (yttrium and europium) from fluorescent lamp waste via nitric acid leaching. The effects of leaching factors including acid concentration and temperature were examined. To assist the leaching yields of those metals, the effect of alkaline fusion was specifically examined. The kinetics of both processes, direct- and alkaline fusion-assisted leaching were investigated based on the shrinking core model. In the case of direct leaching, the metal dissolution was controlled by surface chemical reaction with apparent activation energies of 43.9 and 48.1 kJ/mol for yttrium and europium, respectively, in the temperature range 303–333 K. Pretreatment, viz., the alkaline fusion changed the subsequent leaching mechanism to diffusion control with apparent activation energies of 7.4 and 9.5 kJ/mol for the respective metal in the same temperature range. Optimization of the alkaline fusion-assisted acid leaching process was undertaken by applying response surface methodology (RSM) based on the central composite design (CCD). Under the alkaline fusion conditions such as soda/fluorescent powder mass ratio of 0.65 g/g, temperature of 1223 K and reaction time of 7200 s followed by acid leaching (nitric acid concentration – 3.5 M, temperature-323 K, pulp density – 30 g/L and leaching duration – 1200 s), the leaching efficiencies of 92.6% and 99.5% for yttrium and europium, respectively, could be achieved.

E-waste mining and the transition toward a bio-based economy: The case of lamp phosphor powder.

Replacement of conventional hydrometallurgical and pyrometallurgical process used in E-waste recycling to recover metals can be possible. The metallurgical industry has been considered biohydrometallurgical-based technologies for E-waste recycling. Biorecovery of critical metals from phosphor powder from spent lamps is an example of transition to a bio-based circular economy. E-waste contains economically significant levels of precious, critical metals and rare-earth elements (REE), apart from base metals and other toxic compounds. Recycling and recovery of critical elements from E-waste using a cost-effective technology are now among the top priorities in metallurgy due to the rapid depletion of their natural resources. This paper focuses on the perceptions of recovery of REE from phosphor powder from spent fluorescent lamps regarding a possible transition toward a bio-based economy. An overview of the worldwide E-waste and REE is also demonstrated to reinforce the arguments for the importance of E-waste as a secondary source of some critical metals. Based on the use of bioprocesses, we argue that the replacement of conventional steps used in E-waste recycling by bio-based technological processes can be possible. The bio-recycling of E-waste follows a typical sequence of industrial processes intensely used in classic pyro- and hydrometallurgy with the addition of bio-hydrometallurgical processes such as bioleaching and biosorption. We use the case study of REE biosorption as a new technology based on biological principles to exemplify the potential of urban biomining. The perspective of transition between conventional processes for the recovery of valuable metals for biohydrometallurgy defines which issues related to urban mining can influence the mineral bioeconomy. This assessment is necessary to outline future directions for sustainable recycling development to achieve United Nations Sustainable Development Goals.Graphical

Separation and Recycling Potential of Rare Earth Elements from Energy Systems: Feed and Economic Viability Review

This review explores the potential of separating and recycling rare earth elements (REEs) from different energy conversion systems, such as wind turbines, electric vehicles batteries, or lighting devices. The REEs include 17 elements (with global production of 242 kilometric tons in 2020) that can be found abundantly in nature. However, they are expensive and complicated to extract and separate with many environmental challenges. The overall demand for REEs is continuously growing (with a 10% yearly increase) and it is quite clear that recycling has to be developed as a supply strategy in addition to conventional mining. However, the success of both mining and recycling depends on appropriate separation and processing technologies. The overall REE recycling situation today is very weak (only 2% of REEs are recovered by recycling processes compared with 90% for iron and steel). The biggest recycling potentials rely on the sectors of lamp phosphors (17%), permanent magnets (7%), and NiMH batteries (10%) mainly at the end-of-life stage of the products. The profitability of rare earth recycling mostly depends on the prices of the elements to accommodate the processing costs. Therefore, end-of-life REE recycling should focus on the most valuable and critical REEs. Thus, the relevant processes, feed, and economic viability warrant the detailed review as reported here.

Recovery of Rare Earth Elements from Acidic Leaching Solution of the Red Lamp Phosphor Waste Using Phosphonic Acid-Functionalized Silica Adsorbent

Recovery of Rare Earth Elements from Acidic Leaching Solution of the Red Lamp Phosphor Waste Using Phosphonic Acid-Functionalized Silica Adsorbent

Potential application of graphene oxide and Aspergillus niger spores with high adsorption capacity for recovery of europium from red phosphor, compact fluorescent lamp and simulated radioactive waste

The recovery of rare earth elements (REEs) is a global challenge and the mining of rare earths has serious environmental implications due to the toxic waste released post mining. Hence, the rising demand for rare earths and their far reaching electronic applications necessitates an effective strategy to recover the REEs from more viable sources. In this work, the graphene oxide–Aspergillus niger spores (GO–A. niger spores) blend was utilized for adsorptive recovery of a precious rare earth Eu(III) and the adsorption variables like pH of the medium, adsorbent dosage, sorption kinetics, thermodynamics, and isotherm were optimized for the developed biosorbent. The adsorption process suits the Langmuir isotherm model with a maximum adsorption capacity of 147.3 mg/g. The pseudo–second–order kinetics is a perfect fit to describe the adsorption process. The results obtained through the Van't Hoff plot show negative free energy change (ΔG0) which implies the spontaneity of the adsorption process. The negative standard enthalpy change (ΔH0) values show that the nature of the adsorption process is exothermic. The analytical characterizations including Fourier transform infrared spectroscopy (FTIR), Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), thermal gravimetric analysis (TGA), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) were employed to study the biosorbent. The features of GO–A. niger spores biosorbent were applied to recover Eu(III) from real samples such as fluorescent lamp phosphor, red phosphor powder, and a simulated radioactive waste solution.

Co-solvent-assisted sintering and thermal stability investment of BaMgAl10O17:Eu2+ by cationic substitution

Thermal quenching is one of the most critical challenges for the application of materials under high temperatures. Particularly, BaMgAl10O17:Eu2+ (BAM) has been well considered the preferred blue-emitting phosphor in tricolor fluorescent lamps, plasma display panels (PDP), and many other lighting and display devices due to its excellent luminescence efficiency and satisfactory chromaticity. However, its wide application range is still constrained by two major problems. Firstly, the synthesis temperature for BAM is too high. Commercial BAM materials are typically prepared with high-temperature solid-phase methods over 1550°Ctemperatures. Secondly, co-solvent, which is added during the synthetic process to dissolve the solid phases, is prone to thermal deterioration. To tackle these problems, we propose the cationic substitution method combined with co-solvent-assisted sintering to improve the thermal stability of BAM. In the end, we obtained a novel BAM material with a comparably lower synthesis temperature and satisfactory thermal stability. In our work, the thermal stability of BAM synthesized with 5% boric acid substituted by 0.08 mol Ca2+ was significantly higher compared with that synthesized without calcium substitution. Additionally, the activation energies (ΔE) of Ba0.92Ca0.08MgAl10O17:Eu2+ and Ba0.92Sr0.08MgAl10O17:Eu2+ were calculated to be approximately 0.26 eV and 0.35 eV, respectively, indicating that the BAM substituted with Sr2+ is more thermally stable.

Broadening the excitation spectrum of BaMgAl10O17:Cr3+ using Eu2+ as a codopant

BAM:Eu is a very well known, commercial phosphor that is used for tricolor fluorescent lamps and plasma display panels. In recent years, Cr3+ doped BAM had been suggested as a phosphor for LED lamps for plant growth. However, excitation spectrum of Cr3+ is narrow. To overcome this problem, we have attempted co-doping by Eu2+. Eu2+ → Cr3+ energy transfer was observed in BaMgAl10O17:Eu2+,Cr3+ phosphor. The energy transfer was established by photoluminescence emission, excitation and lifetime measurements. Efficiency of the energy transfer is 40.2%. By virtue of this energy transfer, the excitation spectrum corresponding to Cr3+ emission covers a broad spectral region 340–430 nm. These phosphors were prepared by facile combustion synthesis which is a fast method. It is suggested that this phosphor will be useful for preparing LED lamps based on near ultraviolet, violet and blue chips.

High-Gradient Magnetic Separation of Compact Fluorescent Lamp Phosphors: Elucidation of the Removal Dynamics in a Rotary Permanent Magnet Separator

In an ongoing effort towards a more sustainable rare-earth element market, there is a high potential for an efficient recycling of rare-earth elements from end-of-life compact fluorescent lamps by physical separation of the individual phosphors. In this study, we investigate the separation of five fluorescent lamp particles by high-gradient magnetic separation in a rotary permanent magnet separator. We thoroughly characterize the phosphors by ICP-MS, laser diffraction analysis, gas displacement pycnometry, surface area analysis, SQUID-VSM, and Time-Resolved Laser-Induced Fluorescence Spectroscopy. We present a fast and reliable quantification method for mixtures of the investigated phosphors, based on a combination of Time-Resolved Laser-Induced Fluorescence Spectroscopy and parallel factor analysis. With this method, we were able to monitor each phosphors’ removal dynamics in the high-gradient magnetic separator and we estimate that the particles’ removal efficiencies are proportional to (d2·χ)1/3. Finally, we have found that the removed phosphors can readily be recovered easily from the separation cell by backwashing with an intermittent air–water flow. This work should contribute to a better understanding of the phosphors’ separability by high-gradient magnetic separation and can simultaneously be considered to be an important preparation for an upscalable separation process with (bio)functionalized superparamagnetic carriers.

Integrated Process for Recovery of Rare-Earth Elements from Lamp Phosphor Waste Using Methanesulfonic Acid

Integrated Process for Recovery of Rare-Earth Elements from Lamp Phosphor Waste Using Methanesulfonic Acid

Enhancement of photoluminescence emission of Gd3+ activated borate phosphors for phototherapy lamps: A review

In this review paper, we discuss about photoluminescence emission of Gd3+ in various inorganic phosphors. Narrow band UVB (NB-UVB) emission of Gd 3+ in 312-315 nm is well sought after in medical field to treat photo-responsive diseases like atopic dermatitis, vitiligo, psoriasis, etc. However, this 4f-4f, 6Pj → 8S7/2 intra-configurational transition of Gd3+ is weak and hence needs to be sensitized. Suitable sensitizers like Bi3+, Pr3+ are found to enhance the PL emission of Gd3+. Such phosphors with sensitized Gd3+ emission is highly suitable for phototherapy lamps.

Malonamide-Functionalized Ionic Liquid for Recovery of Rare-Earth Metals from End-Of-Life Products (Lamp Phosphors)

A novel functionalized ionic liquid, namely, malonamide-functionalized ionic liquid (MFIL) was synthesized and evaluated for the liquid–liquid extraction of rare-earth metals (REMs), transition, and other base metals from a hydrochloric acid medium. Theoretical calculations coupled with FT-IR studies were used to establish the mode of complexation between metal ions and the extracting moiety of MFIL. Uptake studies with multimetal feed solutions showed very good selectivity for REMs over other transition and base metals. Quantitative back extraction of REMs from loaded MFIL was accomplished using an acidic solution. MFIL showed preferential uptake of REMs over base and transition metals typically found in lamp phosphors.