Yttrium

Typical wastewaters

• acid mine drainage passive remediation (Iberian Pyrite Belt) YSO₄⁺ ion pair in high sulfate AMD, retained by basaluminite as a monodentate inner-sphere complex
• coal mining acid mine drainage (solvent extraction recovery) yttrium with the heavy rare earths, over 75 percent extracted by Cyanex 272 South Africa
• acid mine drainage treatment residuals rare earths and yttrium adsorbed on hydrous manganese oxides in treatment sludge at near ore grade over 99 percent REY uptake by biotic HMO within 7 days
• rare earth industry wastewater Y³⁺ (10 to 110 mg/L test range) removed by biosorption 123.65 mg/g on Serratia marcescens

1 · Identity

Symbol, number

Y, 39

Oxidation states in water

+3 only (Y³⁺); no redox chemistry in water

Note

The element entry covers the metal and its slow reaction with water. In natural water yttrium is a hard trivalent cation whose ionic radius puts it among the heavy lanthanides (holmium, dysprosium), and it is treated with them by RIVM.

2 · Occurrence in water

Natural sources

Weathering of xenotime, monazite and the ion adsorption clays (element entry); released most in acid water. Dutch groundwater background 0.416 µg/L at pH 6.2 or above and 0.077 µg/L below pH 6.2 (RIVM Table 5.1).

Anthropogenic sources

Rare earth separation and phosphor, ceramic and laser manufacture (element entry); the Rhine estuary carries anthropogenic light rare earths (see La) and the RIVM report treats the estuary values as anthropogenic. Raw groundwater at some Dutch works carried enough for Y to reach 8 to 14 µg/L in drinking water at three works in 1994.

3 · Speciation

Trivalent Y³⁺ throughout the natural pH and Eh range; the free ion and sulfate pairs in acid water, carbonate complexes in neutral to alkaline water, and phosphate solids as the solubility cap, the pattern described for the lanthanides in the lanthanum entry. Yttrium sits with the heavy lanthanides, whose carbonate complexes are the strongest, so it is relatively more mobile than lanthanum in alkaline water. RIVM cites Liu and Byrne (1997) on rare earth and yttrium phosphate solubilities as the solubility control.

Solubility

Phosphate controlled; Dutch surface water below 0.22 µg/L.

Hydrolysis

Minor below pH 8; Y(OH)₃ forms under lime, so lime neutralisation of acid water strips yttrium with the iron and aluminium hydroxides.

Complexation

Sulfate in acid water, carbonate in alkaline water (lanthanide pattern); no yttrium stability constants read this session.

Precipitates

YPO₄, Y(OH)₃ under lime, YF₃ near fluoride rich discharges.

4 · Role in treatment

Not relevant or not given for this element.

5 · Removal and control

6 · Analytics

Sampling pitfalls

Filter before acidifying; colloid bound Y passes 0.45 µm filters. Do not use yttrium as the ICP-MS internal standard when yttrium is an analyte.

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.

Bioaccumulation

RIVM found bioaccumulation data for the rare earths limited and often contradictory and included no secondary poisoning assessment.

Ecotoxicity

RIVM (2000) environmental risk limits, not permit limits: MPA 6.2 µg/L fresh water (lowest LC₅₀ divided by 1000) and 0.72 µg/L salt water (lowest LC₅₀ divided by 1000); background 0.22 µg/L (detection limit); MPC 6.4 µg/L fresh and 0.94 µg/L salt; negligible concentrations 0.28 µg/L fresh and 0.22 µg/L salt. Data behind them: Daphnia magna 48 h EC₅₀ 6.2 mg/L and 21 d NOEC 0.3 to 0.7 mg/L, zebrafish 96 h LC₅₀ 14 mg/L; marine Acartia tonsa 48 h LC₅₀ 0.72 mg/L, Poecilia reticulata 96 h LC₅₀ 16.7 mg/L. Marine organisms were consistently more sensitive to the rare earths than freshwater ones.

Flags

• The RIVM MPCs are 2000 environmental risk limits from a very small data set with assessment factors of 1000; they are not discharge limits.
• Dutch groundwater and drinking water figures are 1991 to 1995 data.
• Carbonate speciation is written by analogy with the lanthanide pattern; no yttrium constants were read.

Gaps

• No yttrium specific stability constants or solubility product were read.
• No municipal or industrial wastewater concentration was read.
• No removal percentage for yttrium in any treatment other than the Dutch drinking water observation was read.
• No GCC discharge standard was read.
• World river average yttrium (Gaillardet et al. 2003) was not reachable.

Sources

Identity

Name and symbol

Yttrium, Y

Atomic number

39 protons

Position

group 3 · period 5 · d-block · transition metal

CAS number

7440-65-5

Atomic structure

Atomic mass

88.905 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹
[Kr] 5s²⁴d¹

Electrons per shell

2, 8, 18, 9, 2

Valence electrons

3 ns and (n-1)d

Physical properties

State at room temperature

Solid

Melting point

1,795 K (1,521.85 °C)

Boiling point

3,618 K (3,344.85 °C)

Density

4.47 g/cm3

Appearance

silvery white

Thermal conductivity

17.2 W/(m·K)

Electrical resistivity

α, poly: 596 nΩ·m

Electrical conductivity

1.68 MS/m

Crystal structure

hexagonal close packed

Molar heat capacity

26.53 J/(mol·K)

Chemical properties

Oxidation states

+3

Electronegativity

1.22 (Pauling Scale)

Ionisation energy

6.217 eV
1st 600, 2nd 1,180, 3rd 1,980 kJ/mol

Electron affinity

0.307 eV

Atomic radius

empirical 190, covalent 190, van der Waals 219 pm

Ionic radius

Y³⁺ 90 pm

Reactivity

A reactive transition metal that behaves like the heavier lanthanides: bulk metal is protected by a thin oxide film and looks stable in air, but turnings ignite above 400 C and the finely divided metal is very unstable in air.

with water

Reacts with water, slowly when cold and faster when hot, to yttrium hydroxide and hydrogen: $\ce{2 Y + 6 H2O -> 2 Y(OH)3 + 3 H2}$.

with oxygen, air

Bulk metal is relatively stable under a protective Y2O3 film; turnings ignite above 400 C and burn to the oxide: $\ce{4 Y + 3 O2 -> 2 Y2O3}$.

with acids

Dissolves in most strong dilute acids to yttrium(III) salts and hydrogen: $\ce{2 Y + 6 HCl -> 2 YCl3 + 3 H2}$; concentrated nitric and hydrofluoric acid attack it only slowly.

with halogens

Combines with the halogens above about 200 C to the trihalides: $\ce{2 Y + 3 Cl2 -> 2 YCl3}$.

Typical compounds

• Y₂O₃ yttrium oxide yttria; phosphor host, ceramics, stabiliser for zirconia
• YCl₃ yttrium chloride starting material for yttrium chemistry
• YF₃ yttrium fluoride reduced with calcium to make the metal
• Y₃Al₅O₁₂ yttrium aluminium garnet YAG laser host and simulated diamond
• Y₃Fe₅O₁₂ yttrium iron garnet microwave filters and acoustic transducers
• YBa₂Cu₃O₇ yttrium barium copper oxide high-temperature superconductor

Occurrence, production and use

Crustal abundance

3.3×101 milligrams per kilogram

Oceanic abundance

1.3×10-5 milligrams per liter

Occurrence and sources

Yttrium occurs in nearly all of the rare-earth minerals. Analysis of lunar rock samples obtained during the Apollo missions show a relatively high yttrium content.

It is recovered commercially from monazite sand, which contains about 3%, and from bastnasite, which contains about 0.2%. Wohler obtained the impure element in 1828 by reduction of the anhydrous chloride with potassium. The metal is now produced commercially by reduction of the fluoride with calcium metal. It can also be prepared by other techniques.

• ion-adsorption clays (weathered granite) Fujian, Guangdong, Jiangxi, Guangxi, Hunan in China and similar deposits in Myanmar; the main world source
• xenotime (YPO4, up to 50 percent yttrium phosphate) heavy-mineral placer sands; mined in China and Malaysia, present in Florida mineral-sand monazite concentrates
• monazite and bastnaesite Mountain Pass bastnaesite carries about 0.12 percent yttrium among its rare earths
• crustal and oceanic abundance about 33 ppm (BGS figure via RSC); 33 mg/kg crust and 0.000013 mg/L seawater (PubChem)

Extraction, production

Rare-earth separation to yttrium oxide

Ore concentrates are leached and the rare earths separated to Y2O3, the form in which most yttrium is traded; neither source states the separation chemistry

Calciothermic reduction of yttrium fluoride to metal

$\ce{2 YF3 (s) + 3 Ca (l) -> 2 Y (s) + 3 CaF2 (s)}$

RSC states yttrium fluoride reduced with calcium metal; calcium fluoride as the co-product is implied, not named

Uses

Although metallic yttrium is not widely used, several of its compounds are. Yttrium oxide (Y2O3) and yttrium orthovanadate (YVO4) are both combined with europium to produce the red phosphor used in color televisions. Garnets made from yttrium and iron (Y3Fe5O12) are used as microwave filters in microwave communications equipment. Garnets made from yttrium and aluminum (Y3Al5O12) are used in jewelry as simulated diamond.

Yttrium oxide is one of the most important compounds of yttrium and accounts for the largest use. It is widely used in making YVO4 europium, and Y2O3 europium phosphors to give the red color in color television tubes. Hundreds of thousands of pounds are now used in this application.

Yttrium oxide also is used to produce yttrium-iron-garnets, which are very effective microwave filters.

Yttrium iron, aluminum, and gadolinium garnets, with formulas such as Y3Fe5O12 and Y3Al5O12, have interesting magnetic properties. Yttrium iron garnet is also exceptionally efficient as both a transmitter and transducer of acoustic energy. Yttrium aluminum garnet, with a hardness of 8.5, is also finding use as a gemstone (simulated diamond).

Small amounts of yttrium (0.1 to 0.2%) can be used to reduce the grain size in chromium, molybdenum, zirconium, and titanium, and to increase strength of aluminum and magnesium alloys.

Alloys with other useful properties can be obtained by using yttrium as an additive. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. The metal has a low cross section for nuclear capture. 90Y, one of the isotopes of yttrium, exists in equilibrium with its parent 90Sr, a product of nuclear explosions. Yttrium has been considered for use as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes. Such iron has increased ductility.

Yttrium also can be used in laser systems and as a catalyst for ethylene polymerization reactions.

It also has potential use in ceramic and glass formulas, as the oxide has a high melting point and imparts shock resistance and low expansion characteristics to glass.

• Ceramics and refractories: Y2O3 as the stabiliser in zirconia ceramics; abrasives, bearings and seals, continuous-casting nozzles, jet-engine thermal-barrier coatings, oxygen sensors, cutting tools
• Electronics, lighting and lasers: yttrium-aluminium garnet (YAG) laser crystals for surgery, cutting, welding and communications; yttrium-iron garnets in microwave radar filters; phosphors for flat-panel displays and lighting, white LEDs; high-temperature superconductors
• Metallurgy: grain-refining additive and deoxidiser; strengthening additive in aluminium and magnesium alloys, heating-element alloys and superalloys
• Chemicals: catalyst in ethene polymerisation; catalysts generally
• Medicine: yttrium-90 radiotherapy for liver and other cancers
• Glass: Y2O3 in optical and camera-lens glass for heat and shock resistance

Safety, toxicity

GHS classification, signal word Danger

• H228 Flammable solid Flammable solids
• H250 Catches fire spontaneously if exposed to air Pyrophoric liquids
• H302 Harmful if swallowed Acute toxicity, oral
• H312 Harmful in contact with skin Acute toxicity, dermal
• H332 Harmful if inhaled Acute toxicity, inhalation
• H413 May cause long lasting harmful effects to aquatic life to the aquatic environment, long-term hazard
• H371 May cause damage to organs Specific target organ toxicity, single exposure

Discovery and name

Discovered by

Johan Gadolin

Discovered

1794

First isolated

Friedrich Wöhler

Named by

not in sources

Origin of the name

after Ytterby (Sweden) and its mineral ytterbite (gadolinite)

Yttrium has a silver-metallic luster and is relatively stable in air. Turnings of the metal, however, ignite in air if their temperature exceeds 400°C. Finely divided yttrium is very unstable in air.