Scientists Turn Spent Fluorescent Lamps Into a Rare Earth Goldmine With Shrimp-Shell Chemistry

Billions of fluorescent lamps have flickered their last over the past decades, and most of them are sitting in landfills. That is not just a waste-management problem; it is a squandering of some of the most strategically valuable materials on the planet. Inside the white phosphor coating of every spent tube lies a blend of rare earth elements — yttrium, lanthanum, cerium, europium and terbium — that modern industry increasingly cannot get enough of. A new study published in Environmental Science and Pollution Research by researchers at the Indian Institute of Technology Kanpur now describes a carefully engineered, two-part process that pulls these elements out of lamp waste and concentrates them using an adsorbent built from one of the most abundant biopolymers on Earth: chitosan, derived from shrimp and crab shells.

The stakes are high. Rare earth elements underpin LEDs, wind turbines, electric vehicle motors, mobile phones and defense technologies, and analysts expect demand to outstrip current supply in the coming years. Mining new rare earths is difficult, geographically concentrated and environmentally fraught, so recycling end-of-life products has become a central strategy in the push toward a circular economy. Waste fluorescent lamps are an especially attractive feedstock because their phosphor powder contains roughly six weight percent rare earths — a far richer grade than many natural ores, where individual rare earth concentrations can be orders of magnitude lower. The catch is that the powder also carries a heavy load of unwanted calcium and other impurities that complicate downstream separation.

The research team, led by Pallabi Roy and Musthaq Mohammad Syed under the supervision of Arunabh Meshram and Krishanu Biswas, attacked that problem with an integrated enrichment-and-adsorption strategy. Their first move was thermal rather than chemical: a three-cycle alkali roasting process at 800 degrees Celsius. This treatment transforms the stubborn phosphate phases in the phosphor powder — crystalline compounds that resist ordinary dissolution — into far more reactive oxides. It is a decisive preprocessing step, because the chemistry of the rare earth phosphates used in lamp coatings makes them notoriously reluctant to give up their metal atoms under mild leaching conditions. Converting them to oxides opens the door to hydrometallurgical recovery with weaker, cheaper reagents.

Once roasted, the powder went through a sequential two-stage leaching protocol designed to dissolve the useful elements while stripping away calcium, the main contaminant. The first stage used 2 moles per liter sulfuric acid at 40 degrees Celsius to attack the oxide matrix. The second stage was more unusual: a brine leach using 2.5 moles per liter sodium chloride solution held at pH 5, 90 degrees Celsius, for 90 minutes. The high chloride concentration leverages salt solubility chemistry to pull calcium out of the solid, while the near-neutral pH avoids dissolving more of the rare earth fraction than necessary. The combined effect was dramatic: calcium content dropped from 36.74 to 8.06 weight percent, a 78.1 percent decrease, leaving behind a solid substantially enriched in the target rare earths.

With the pre-concentrated material in hand, the team turned to the adsorption stage, which is where the study’s most distinctive chemistry lives. Chitosan is a polysaccharide obtained by deacetylating chitin, the structural polymer of crustacean shells, and it is prized in materials science for its abundance, biodegradability and dense array of amine groups that naturally bind metal ions. On its own, however, chitosan’s affinity for rare earths is limited. The researchers therefore grafted EDTA — ethylenediaminetetraacetic acid, the workhorse chelating agent of analytical chemistry — onto the chitosan backbone. EDTA’s carboxylate and amine groups wrap around metal ions in stable coordination complexes, and when anchored to a solid polymer, they act as molecular fishing lines that pluck dissolved rare earth cations out of solution.

The adsorption experiments were run under optimized conditions of pH 5, 50 degrees Celsius and 24 hours of contact time. The performance varied across the five elements, and the pattern is chemically telling. Terbium, the heaviest and most valuable of the set, was captured most efficiently at 82.4 percent, followed by yttrium at 79.15 percent, cerium at 74.10 percent, lanthanum at 60.13 percent and europium at 31.87 percent. Adsorption efficiency generally tracks ionic radius and hydration chemistry: smaller, more highly charged rare earth cations form stronger complexes with EDTA ligands, so the heavy elements win out. Europium’s comparatively modest uptake reflects the specific speciation and competition among ions in the leach liquor rather than a failure of the material itself.

To quantify the adsorbent’s true capacity, the team fitted their equilibrium data to the Langmuir isotherm, a classical adsorption model that assumes a finite number of identical binding sites forming a single molecular layer on the surface. The fitted maximum capacities were 179.54 milligrams of terbium per gram of adsorbent, 115.35 milligrams for cerium, 106.45 for yttrium, 77.68 for lanthanum and 28.47 for europium. Good Langmuir fits indicate monolayer adsorption and site saturation — in other words, the EDTA groups behave in a predictable, well-behaved manner rather than showing the erratic multi-layer accumulation that plagues many crude sorbents. For a bio-derived material, capacities approaching 180 milligrams per gram for terbium are competitively strong against synthetic ion-exchange resins.

The choice of a biopolymer adsorbent is more than an aesthetic nod to green chemistry. Conventional rare earth separation relies on solvent extraction circuits that consume large volumes of organic solvents and generate acidic wastewater, and on ion-exchange resins derived from petrochemical feedstocks. Chitosan-based sorbents are renewable, biodegradable and inexpensive, and earlier work by other groups — including EDTA- and DTPA-functionalized chitosan for chromatographic rare earth separation, and magnetic chitosan composites for heavy metal capture — has established the platform’s versatility. The IIT Kanpur team’s own previous study demonstrated the same functionalized chitosan recovering neodymium and dysprosium from discarded hard disk magnets, and the present work extends the concept to a fundamentally different waste stream with a messier, calcium-laden chemistry.

What makes the study notable is less any single step than the integration. Alkali roasting, selective sequential leaching and bio-based adsorption are each known techniques, but combining them into one coherent flowsheet that takes raw lamp phosphor powder from six percent rare earths to a pre-concentrated, selectively adsorbed product is the kind of process-level engineering that determines whether lab chemistry can ever scale. The authors frame the approach as a technically efficient route for selective rare earth recovery that contributes to sustainable and circular economic development, and the framing is fair: the strategy replaces aggressive, solvent-intensive separation with a sequence that leans on heat, table salt, dilute acid and a shrimp-shell polymer.

Challenges remain before such a process could feed industrial supply chains. Adsorption selectivity among the five elements is incomplete — europium lags considerably — so a full recovery scheme would still need downstream polishing or fractional desorption to deliver separated, high-purity oxides. Adsorbent regeneration and reuse over many cycles, process economics at tonne scale, and the logistics of collecting spent lamps all remain open questions that the published data do not fully resolve. Yet as a demonstration, the work lands at a consequential moment. The fluorescent lamp is a fading technology being replaced by LEDs worldwide, which means the stock of phosphor-rich waste is peaking right now and will gradually become the legacy inventory of a bygone lighting era. Harvesting its rare earths before they disperse irretrievably is exactly the kind of urban mining that resource security strategists have been calling for, and this study shows a credible, greener path for doing it — one grounded not in exotic chemistry but in sulfuric acid, brine and the shells of the seafood industry.

Subject of Research: Recovery of rare earth elements from waste fluorescent lamp phosphor powder using integrated leaching and bio-based adsorption

Article Title: Recovery of rare earth elements (Y, La, Ce, Eu and Tb) from waste fluorescent lamps via integrated leaching and EDTA-functionalized Chitosan adsorption

Article References: Recovery of rare earth elements (Y, La, Ce, Eu and Tb) from waste fluorescent lamps via integrated leaching and EDTA-functionalized Chitosan adsorption. (n.d.). https://doi.org/10.1007/s11356-026-38276-9

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38276-9

Keywords: rare earth elements, fluorescent lamps, yttrium, terbium, europium, lanthanum, cerium, EDTA-functionalized chitosan, adsorption, leaching, urban mining, circular economy