Erbium

Typical wastewaters

• rare earth separation and processing (saponification wastewater) Er³⁺ carried with the whole lanthanide row in ammonia rich separation plant wastewater (ammonia nitrogen 300 to 5,000 mg/L in Chinese saponification wastewater, 2005 estimate) no erbium specific concentration read
• coal mine drainage (acid) Er³⁺ and the ErSO₄⁺ ion pair dissolved at low pH in sulfate rich drainage; total rare earths averaged 282 µg/L over 141 Appalachian sites, per-element values not read co-precipitates into the iron, aluminium and manganese hydroxide sludge when the drainage is neutralised

1 · Identity

Symbol, number

Er, 68

Oxidation states in water

+3 only (Er³⁺)

Note

The metal's reactions are in the book entry; in water erbium shares the trivalent carbonate and phosphate chemistry of the lanthanide row.

2 · Occurrence in water

Natural sources

Weathering of monazite, bastnaesite and xenotime; heavy lanthanide, carbonate complexed in neutral to alkaline water; used with Yb to interpolate thulium in REE patterns.

Anthropogenic sources

None read. Rare earth separation wastewater carries the whole row.

3 · Speciation

Trivalent Er³⁺ throughout the natural pH and Eh range. Below about pH 6, and in sulfate rich water such as mine drainage, the free ion and the ErSO₄⁺ ion pair dominate (sulfate complexes above 90 percent at pH 3.1 to 3.4 in the EPA groundwater study). From neutral to alkaline pH the carbonate complexes ErCO₃⁺ and Er(CO₃)₂⁻ take over, and they bind the heavy lanthanides more strongly than the light ones (at pH 5.1 to 6.1 the carbonate share rose from 5.0 percent for La to 19.2 percent for Lu). Phosphate, carbonate and fluoride solids and sorption to iron and manganese oxides cap the dissolved concentration at ng/L in oxic neutral water, and the light lanthanides ride partly on colloids.

Solubility

Controlled by the phosphate, carbonate and fluoride solids and by sorption; the RIVM report puts total dissolved lanthanum and cerium in Dutch surface water at about 1 µg/L or less and the free ion fraction at 0.3 fM to 9 pM. No solubility product for a erbium solid was read this session.

Hydrolysis

Hydrolysis of Er³⁺ is minor in natural water; the hydroxide Er(OH)₃ forms only at high pH, so lime or caustic neutralisation of acid mine water strips the element with the iron and aluminium hydroxides rather than as its own hydroxide (no hydrolysis constant read this session).

Complexation

Sulfate at low pH, carbonate at neutral to alkaline pH (the sources read); humic substances compete for the element in organic rich water and are out-competed by carbonate in alkaline water. No stability constants were read this session.

Precipitates

ErPO₄ (hydrated phosphate), Er₂(CO₃)₃, ErF₃ near fluoride rich discharges, Er(OH)₃ at high pH; co-precipitated on iron, aluminium and manganese hydroxides.

4 · Role in treatment

Not relevant or not given for this element.

5 · Removal and control

6 · Analytics

Sampling pitfalls

Filtration defines the result: 0.2 or 0.45 µm filtrates still carry colloid bound lanthanides, and only ultrafiltration (10 kDa) separates the truly dissolved pool, which matters most for the light lanthanides. Acidify after filtration. Report the shale-normalised pattern so that anthropogenic anomalies (gadolinium, lanthanum, samarium) are visible.

7 · Regulatory limits

Limits change, and many are set locally. Treat these as the published values to start from, not as your compliance target: check the standard in force at your site and the numbers written into your own permit.

8 · Health and environmental effects

Toxicity

No human health guideline anywhere read; no acute or chronic human toxicity data for this element were read this session.

Bioaccumulation

Field bioconcentration factors in Rhine estuary amphipods fall from the light to the heavy lanthanides (La 28,840 to Lu 4,786; Er 7,413); carp muscle takes up little (BCF 0.22 to 1.10 for Ce, La, Nd, Pr, Sm) while internal organs reach 634 to 978. Anthropogenic La and Sm in the Rhine are taken into mussel shells, anthropogenic Gd is not, so speciation decides bioavailability.

Ecotoxicity

No MPC was derived for erbium: the RIVM report set risk limits only for Y, La, Ce, Pr, Nd, Sm, Gd and Dy. The one erbium number it carries is a field bioconcentration factor in amphipods of 7,413 (porewater basis).

Flags

• The RIVM MPCs, where they exist, are environmental risk limits from a 2000 report (LC₅₀ divided by 1000, background at the detection limit), not permit limits.
• The seawater range is one western Pacific station.

Gaps

• WHO GDWQ and EU DWD 2020/2184 Annex I were not read this session (eur-lex returned the articles without the annexes), so their absence of a rare earth parameter is not asserted here; only the US EPA table was read.
• No GCC discharge standard was read; no GCC row is written.
• World average river water concentrations (Gaillardet et al. 2003) were not reachable; river figures come from the Rhine and Dutch waters only.
• No source read this session gives municipal wastewater concentrations for this element beyond the gadolinium literature.
• ICP-MS oxide interference corrections between lanthanides are standard practice but no method text describing them was read, so none is written.
• No stability constants or solubility products for this element's carbonate, phosphate or hydroxide were read; the speciation is qualitative, taken from the EPA groundwater study and the RIVM report.
• No erbium specific river, groundwater or wastewater concentration was read, and no toxicity test.

Sources

Identity

Name and symbol

Erbium, Er

Atomic number

68 protons

Position

no group (f-block) · period 6 · f-block · lanthanide

CAS number

7440-52-0

Atomic structure

Atomic mass

167.259 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹²
[Xe] 6s²⁴f¹²

Electrons per shell

2, 8, 18, 30, 8, 2

Valence electrons

14 ns, (n-1)d and (n-2)f

Physical properties

State at room temperature

Solid

Melting point

1,802 K (1,528.85 °C)

Boiling point

3,141 K (2,867.85 °C)

Density

9.07 g/cm3

Appearance

silvery white

Thermal conductivity

14.5 W/(m·K)

Electrical resistivity

poly: 0.860 µΩ·m

Electrical conductivity

1.16 MS/m

Crystal structure

hexagonal close packed

Molar heat capacity

28.12 J/(mol·K)

Chemical properties

Oxidation states

+3

Electronegativity

1.24 (Pauling Scale)

Ionisation energy

6.108 eV
1st 589.3, 2nd 1,150, 3rd 2,194 kJ/mol

Electron affinity

not in sources

Atomic radius

empirical 189, covalent 189, van der Waals 235 pm

Ionic radius

Er³⁺ 89 pm

Reactivity

A late lanthanide (4f12 6s2) trivalent in all its ordinary chemistry, with rose-pink Er3+ salts; the metal is fairly stable in air and oxidises less quickly than the lighter rare earths, but it reacts with water, acids and the halogens.

with water

Reacts slowly with cold water and quickly with hot water to the hydroxide and hydrogen: $\ce{2 Er + 6 H2O -> 2 Er(OH)3 + 3 H2}$, like its neighbours.

with oxygen, air

Keeps its lustre in dry air, tarnishes slowly in moist air and burns readily on heating to the pink sesquioxide: $\ce{4 Er + 3 O2 -> 2 Er2O3}$, erbia.

with acids

Dissolves readily in dilute sulfuric acid to rose-red Er3+ solutions with evolution of hydrogen: $\ce{2 Er + 3 H2SO4 -> Er2(SO4)3 + 3 H2}$, the sulfate.

with halogens

Reacts with all the halogens to the trihalides: $\ce{2 Er + 3 Cl2 -> 2 ErCl3}$, violet, while the fluoride is pink.

Typical compounds

• Er₂O₃ erbium(III) oxide erbia, pink colourant for glass and porcelain glazes
• ErCl₃ erbium(III) chloride violet, soluble trihalide
• ErF₃ erbium(III) fluoride pink trihalide, dopant for fibre optics
• ErI₃ erbium(III) iodide violet iodide, one of the Los Alamos-listed halides
• Er₂(SO₄)₃ erbium(III) sulfate rose-red salt from sulfuric acid

Occurrence, production and use

Crustal abundance

3.5 milligrams per kilogram

Oceanic abundance

8.7×10-7 milligrams per liter

Occurrence and sources

• monazite (phosphate) and bastnaesite (fluorocarbonate) the principal minerals, with the other lanthanides

Extraction, production

Ion exchange and solvent extraction from monazite and bastnaesite

no balanced equation printed by the source

Historical first preparation of the metal by heating purified erbium chloride with potassium (Klemm and Bommer, 1934)

$\ce{ErCl3 + 3 K -> Er + 3 KCl}$

stoichiometry not printed, so no equation is written

Uses

Erbium is alloyed with vanadium to make it softer and easier to shape. Erbium is added to fiber optic cables as a doping agent where it is used as a signal amplifier. Erbium also has some uses in the nuclear power industry.

Erbia, the renamed material that Mosander discovered in 1843, is erbium oxide (Er2O3), one of erbium's compounds. Erbia has a pink color and is used to color glass and glazes. Other erbium compounds include: erbium fluoride (ErF3, erbium chloride (ErCl3 and erbium iodide (ErI3).

Erbium is finding nuclear and metallurgical uses. Added to vanadium, for example, erbium lowers the hardness and improves workability. Erbium oxide gives a pink color and has been used as a colorant in glasses and porcelain enamel glazes.

• Telecommunications and optics: erbium-doped glass fibre amplifiers for broadband signals in fibre-optic cables
• Glass and ceramics: erbium oxide in infrared-absorbing safety glass for welders and metal workers; pink colourant for glass, sunglasses, imitation gems and ceramic glazes ceramics and glass were among the United States end uses of rare earths in 2024 (usgs-mcs2025)
• Metallurgy: alloying addition to vanadium and other metals to lower hardness and improve workability
• Rare earth mining and separation: mined as bastnaesite (a rare-earth fluorocarbonate) at Mountain Pass, California, and as monazite (a phosphate) in heavy-mineral-sand concentrates; separated from the other rare earths by ion exchange and solvent extraction world mine production of rare earths 390,000 t of rare-earth-oxide equivalent in 2024 (USGS estimate), of which China 270,000 t (production quota), the United States 45,000 t, Burma 31,000 t, Australia, Nigeria and Thailand 13,000 t each; reserves over 90 million t, China 44 million t, Brazil 21 million t (usgs-mcs2025, PDF p149, printed p145)

Safety, toxicity

GHS classification, signal word Danger

• H228 Flammable solid Flammable solids

Discovery and name

Discovered by

Carl Gustaf Mosander

Discovered

1843

First isolated

Wilhelm Klemm and Heinrich Bommer

Named by

not in sources

Origin of the name

after Ytterby (Sweden), where it was mined

The pure metal is soft and malleable and has a bright, silvery, metallic luster. As with other rare-earth metals, its properties depend to a certain extent on the impurities present. The metal is fairly stable in air and does not oxidize as rapidly as some of the other rare-earth metals. Naturally occurring erbium is a mixture of six isotopes, all of which are stable. Nine radioactive isotopes of erbium are also recognized. Recent production techniques, using ion-exchange reactions, have resulted in much lower prices of the rare-earth metals and their compounds in recent years. Most of the rare-earth oxides have sharp absorption bands in the visible, ultraviolet, and near infrared. This property, associated with the electronic structure, gives beautiful pastel colors to many of the rare-earth salts.