Dysprosium

Typical wastewaters

• rare earth separation and processing (saponification wastewater) Dy³⁺ 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 dysprosium specific concentration read
• coal mine drainage (acid) Dy³⁺ and the DySO₄⁺ 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

Dy, 66

Oxidation states in water

+3 only (Dy³⁺)

Note

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

2 · Occurrence in water

Natural sources

Weathering of monazite, bastnaesite, xenotime and ion adsorption clays; a heavy lanthanide, enriched in coal mine drainage relative to conventional ore, more strongly carbonate complexed than the light row.

Anthropogenic sources

None read as a point source; magnet manufacture and recycling effluent is not described by any source read. Rare earth separation plant wastewater carries the whole row.

3 · Speciation

Trivalent Dy³⁺ 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 DySO₄⁺ 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 DyCO₃⁺ and Dy(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 dysprosium solid was read this session.

Hydrolysis

Hydrolysis of Dy³⁺ is minor in natural water; the hydroxide Dy(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

DyPO₄ (hydrated phosphate), Dy₂(CO₃)₃, DyF₃ near fluoride rich discharges, Dy(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; Dy 9,550); 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

RIVM (2000) environmental risk limits, not discharge limits: MPC 9.3 µg/L in fresh surface water and 3.8 µg/L in salt water (negligible concentrations 0.31 and 0.26 µg/L), derived as lowest LC₅₀ divided by 1000 plus a background set at the detection limit (0.22 µg/L). Acute data behind it: Daphnia magna 48 h EC₅₀ 9.1 mg/L, zebrafish 96 h LC₅₀ 25 mg/L; chronic: Daphnia magna 21 d NOEC below 0.2 mg/L (reproduction) and above 2.1 mg/L (mortality); zebrafish early life stage 30 d NOEC 2.6 to 3.8 mg/L. Field bioconcentration factor in amphipods (porewater basis) 9,550.

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 dysprosium specific river or groundwater concentration was read.

Sources

Identity

Name and symbol

Dysprosium, Dy

Atomic number

66 protons

Position

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

CAS number

7429-91-6

Atomic structure

Atomic mass

162.5 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁰
[Xe] 6s²⁴f¹⁰

Electrons per shell

2, 8, 18, 28, 8, 2

Valence electrons

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

Physical properties

State at room temperature

Solid

Melting point

1,685 K (1,411.85 °C)

Boiling point

2,840 K (2,566.85 °C)

Density

8.55 g/cm3

Appearance

silvery white

Thermal conductivity

10.7 W/(m·K)

Electrical resistivity

α, poly: 926 nΩ·m

Electrical conductivity

1.08 MS/m

Crystal structure

hexagonal close packed

Molar heat capacity

27.7 J/(mol·K)

Chemical properties

Oxidation states

+3

Electronegativity

1.22 (Pauling Scale)

Ionisation energy

5.939 eV
1st 573, 2nd 1,130, 3rd 2,200 kJ/mol

Electron affinity

not in sources

Atomic radius

empirical 192, covalent 192, van der Waals 229 pm

Ionic radius

Dy²⁺ 107; Dy³⁺ 91 pm

Reactivity

An electropositive late lanthanide (4f10 6s2) that is trivalent in almost all its chemistry; the metal keeps its lustre in dry air, tarnishes slowly in moist air and is readily attacked by mineral acids and by the halogens on heating.

with water

Reacts slowly with cold water and quickly with hot water to the hydroxide and hydrogen: $\ce{2 Dy + 6 H2O -> 2 Dy(OH)3 + 3 H2}$, the hydroxide losing water on heating to DyO(OH) and then Dy2O3.

with oxygen, air

Stable in dry air, tarnishes slowly in moist air, and burns readily when heated to the white sesquioxide: $\ce{4 Dy + 3 O2 -> 2 Dy2O3}$, dysprosia.

with acids

Readily attacked and dissolved by dilute and concentrated mineral acids with evolution of hydrogen; in dilute sulfuric acid it gives yellow Dy3+ solutions: $\ce{2 Dy + 3 H2SO4 -> Dy2(SO4)3 + 3 H2}$, the paramagnetic sulfate.

with halogens

Reacts vigorously with all the halogens above about 200 C to the trihalides: $\ce{2 Dy + 3 Cl2 -> 2 DyCl3}$, white, while the fluoride and iodide are green.

Typical compounds

• Dy₂O₃ dysprosium(III) oxide dysprosia, strongly magnetic white powder, neutron-absorbing cement
• DyF₃ dysprosium(III) fluoride green trihalide, reduced to make the metal
• DyCl₃ dysprosium(III) chloride white, soluble source of Dy3+
• DyI₃ dysprosium(III) iodide green iodide used in metal halide lamps
• Dy₂(SO₄)₃ dysprosium(III) sulfate noticeably paramagnetic salt from sulfuric acid

Occurrence, production and use

Crustal abundance

5.2 milligrams per kilogram

Oceanic abundance

9.1×10-7 milligrams per liter

Occurrence and sources

• monazite (phosphate) and bastnaesite (fluorocarbonate) with the other lanthanides in heavy-mineral sands and carbonatite deposits
• xenotime and fergusonite smaller quantities in these heavy rare earth minerals

Extraction, production

Ion exchange and solvent extraction from the rare earth minerals to dysprosium oxide

dysprosium oxide 99.5 percent averaged 260 dollars per kilogram in 2024 (usgs-mcs2025, PDF p148, printed p144)

Reduction of dysprosium trifluoride with calcium metal to the metal

$\ce{2 DyF3 + 3 Ca -> 2 Dy + 3 CaF2}$

no balanced equation printed by the source

Uses

There are no commercial applications for dysprosium. Since it easily absorbs neutrons and has a high melting point, dysprosium might be alloyed with steel for use in nuclear reactors. When combined with vanadium and other rare earth elements, dysprosium is used as a laser material.

Dysprosium oxide (Dy2O3), also known as dysprosia, is combined with nickel and added to a special cement used to cool nuclear reactor rods. Other dysprosium compounds include: dysprosium fluoride (DyF3), dysprosium iodide (DyI3) and dysprosium sulfate (Dy2(SO4)3).

While we have not found many applications for dysprosium, its thermal neutron absorption cross-section and high melting point suggest metallurgical uses in nuclear control applications and for alloying with special stainless steels. A dysprosium oxide-nickel cement has found use in cooling nuclear reactor rods. This cement absorbs neutrons readily without swelling or contracting under prolonged neutron bombardment. In combination with vanadium and other rare earths, dysprosium has been used in making laser materials. Dysprosium-cadmium chalcogenides, as sources of infrared radiation, have been used for studying chemical reactions.

• Permanent magnets: alloying addition to neodymium-iron-boron magnets for resistance to demagnetisation at high temperature in motors and generators of wind turbines and electric vehicles neodymium-iron-boron magnet block is a potential United States stockpile acquisition for fiscal years 2024 and 2025 (usgs-mcs2025, PDF p149, printed p145)
• Lighting: dysprosium iodide in metal-halide discharge lamps for intense white light
• Nuclear: dysprosium oxide-nickel cermet in reactor control rods, absorbing neutrons without swelling or contracting
• 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
• H250 Catches fire spontaneously if exposed to air Pyrophoric liquids
• H251 Self-heating; may catch fire Self-heating substances and mixtures
• H252 Self-heating in large quantities; may catch fire Self-heating substances and mixtures
• H260 In contact with water releases flammable gases which may ignite spontaneously Substances and mixtures which in contact with water, emit flammable gases
• H315 Causes skin irritation Skin corrosion/irritation
• H319 Causes serious eye irritation Serious eye damage/eye irritation
• H413 May cause long lasting harmful effects to aquatic life to the aquatic environment, long-term hazard

Discovery and name

Discovered by

Lecoq de Boisbaudran

Discovered

1886

First isolated

Georges Urbain

Named by

not in sources

Origin of the name

after Greek δυσπρόσιτος, "hard to get", for requiring 30 attempts to isolate

The element has a metallic, bright silver luster. It is relatively stable in air at room temperature, and is readily attacked and dissolved by dilute and concentrated mineral acids, to evolve hydrogen. The metal is soft enough to be cut with a knife and can be machined without sparking if overheating is avoided. Small amounts of impurities can greatly affect its physical properties.