Tellurium

Typical wastewaters

• cadmium telluride photovoltaic manufacture and copper refinery anode slime processing
  tellurite TeO₃²⁻ and tellurate oxyanions, soluble through conventional treatment unless reduced to Te(0)
  the treatment studies used synthetic tellurite wastewater at 10 to 20 mg/L

1 · Identity

Symbol, number

Te, 52

Oxidation states in water

+6 (tellurate, TeO₄²⁻ and its protonated forms) and +4 (tellurite, TeO₃²⁻ and HTeO₃⁻) dissolved; 0 as insoluble elemental tellurium after reduction; -2 telluride only in strongly reducing sulfidic systems

Note

The element chapter covers the metalloid, TeO₂ and CdTe. In water the exact dissolved species (oxyanion or hydroxide) is still debated in the review.

2 · Occurrence in water

Natural sources

Weathering of tellurides and copper sulfide ores (element chapter); the ocean holds tellurate over tellurite with a surface maximum.

Anthropogenic sources

Copper refinery anode slime processing, cadmium telluride solar cell manufacture (about 40 percent of demand in the review, 60 percent in the element chapter's 2024 figure), thermoelectric production; Chinese coastal water and the Changjiang estuary show the elevated values.

3 · Speciation

Oxic water carries mainly Te(VI) as tellurate (70 to 87 percent of the total in coastal water), with tellurite Te(IV) as the minor and more toxic fraction; both are soluble. Reduction, biological or chemical, gives elemental Te(0), which is insoluble and settles or stays inside biomass. The review notes that whether the dissolved forms are oxyanions or hydroxides is still controversial.

Solubility

Tellurate and tellurite are soluble; Te(0) is insoluble.

Hydrolysis

Tellurous and telluric acids are weak acids; no protonation constants are quoted here.

Precipitates

Te(0); metal tellurides under sulfidic conditions, for which no source is quoted here.

4 · Role in treatment

5 · Removal and control

6 · Analytics

Sampling pitfalls

Acidification and storage can shift the Te(IV) to Te(VI) ratio; the review's coastal speciation data depend on prompt separation.

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 for tellurium in water anywhere read. Tellurite Te(IV) is the more toxic and more reactive form (the treatment papers call the oxyanions toxic and soluble and Te(0) less toxic and insoluble).

Bioaccumulation

Fish 1 to 12 ng/g (mean 2 to 3), mussels below 1.4 to 5.9, oysters 1.18 to 3.48, squid tissues 0.9 to 3.4 ng/g with bioaccumulation factors of 6 x 10^3 to 2 x 10^4 (review).

Identity

Name and symbol

Tellurium, Te

Atomic number

52 protons

Position

group 16 · period 5 · p-block · metalloid

CAS number

13494-80-9

Atomic structure

Atomic mass

127.6 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁴
[Kr] 5s²⁴d¹⁰⁵p⁴

Electrons per shell

2, 8, 18, 18, 6

Valence electrons

6 outer shell

Physical properties

State at room temperature

Solid

Melting point

722.66 K (449.51 °C)

Boiling point

1,261 K (987.85 °C)

Density

6.232 g/cm3

Appearance

silvery lustrous gray (crystalline),brown-black powder (amorphous)

Thermal conductivity

1.97 to 3.38 W/(m·K)

Electrical resistivity

not in sources

Electrical conductivity

not in sources

Crystal structure

hexagonal

Molar heat capacity

25.73 J/(mol·K)

Chemical properties

Oxidation states

+6, +4, -2

Electronegativity

2.1 (Pauling Scale)

Ionisation energy

9.01 eV
1st 869.3, 2nd 1,790, 3rd 2,698 kJ/mol

Electron affinity

1.971 eV

Atomic radius

empirical 138, covalent 138, van der Waals 206 pm

Ionic radius

Te²⁻ 221; Te⁴⁺ 97; Te⁶⁺ 56 pm

Reactivity

A brittle, silvery group 16 metalloid below selenium, a p-type semiconductor; grey tellurium resists air at room temperature but burns when heated, and it is oxidised by nitric acid, showing the -2, +4 and +6 states.

with water

Does not react with water.

with oxygen, air

Resists oxidation by air at room temperature; heated in air it burns with a greenish-blue flame to the dioxide: $\ce{Te + O2 -> TeO2}$.

with acids

Not attacked by non-oxidising acids; nitric acid oxidises it to the dioxide or tellurous acid: $\ce{3 Te + 4 HNO3 -> 3 TeO2 + 4 NO + 2 H2O}$.

with halogens

Combines with the halogens; fluorine gives the hexafluoride: $\ce{Te + 3 F2 -> TeF6}$, and chlorine the tetrachloride: $\ce{Te + 2 Cl2 -> TeCl4}$.

Typical compounds

• TeO₂ tellurium dioxide
  combustion product; oxidation-catalyst component
• H₂Te hydrogen telluride
  unstable toxic gas from zinc telluride and acid
• CdTe cadmium telluride
  thin-film solar cell semiconductor
• Bi₂Te₃ bismuth telluride
  thermoelectric material
• TeCl₄ tellurium tetrachloride
  typical Te(IV) halide
• H₆TeO₆ telluric acid
  Te(VI) oxoacid; tellurate salts

Occurrence, production and use

Crustal abundance

1×10-3 milligrams per kilogram

Oceanic abundance

Not Applicable

Occurrence and sources

Tellurium is occasionally found native, but is more often found as the telluride of gold (calaverite), and combined with other metals. It is recovered commercially from anode muds produced during the electrolytic refining of blister copper. The U.S., Canada, Peru, and Japan are the largest Free World producers of the element.

• anode slimes of electrolytic copper refining (up to about 8 percent Te)
  copper refineries in China, Japan, Russia, Sweden, Canada, United States; more than 90 percent of supply
• calaverite, sylvanite, gold and bismuth tellurides; rarely native
  gold telluride ores such as those of Transylvania; potential future sources
• crustal abundance
  about 0.001 ppm ¹; 0.001 mg/kg crust ²

Extraction, production

Recovery from copper anode slimes as copper telluride, then refining

the copper telluride intermediate is stated by USGS; neither source gives the leaching or reduction chemistry

Uses

Tellurium is a semiconductor and is frequently doped with copper, tin, gold or silver. Tellurium is also used to color glass and ceramics and is one of the primary ingredients in blasting caps.

Tellurium is primarily used as an alloying agent. Small amounts of tellurium are added to copper and stainless steel to make them easier to machine and mill. Tellurium is also added to lead to increase its strength and resistance to sulfuric acid (H2SO4).

Tellurium forms many compounds, but none that are commercially important. They include: tellourous acid (H2TeO2), tellurium tetrachloride (TeCl4), tellurium dichloride (TeCl2), tellurium trioxide (TeO3), tellurium monoxide (TeO) and sodium telluride (Na2Te).

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices.

• Solar energy: cadmium telluride thin-film solar cells; the leading US module maker reached almost 11 GW per year of capacity in 2024
  solar cells about 60 percent of global tellurium consumption in 2024 (usgs-mcs2025-tellurium)
• Thermoelectrics and electronics
  • bismuth telluride thermoelectric coolers and generators
  • photoreceptors, rewritable optical discs, blasting caps
  thermoelectric devices about 20 percent in 2024 (usgs-mcs2025-tellurium)
• Metallurgy
  • free-machining steel and copper alloys
  • lead alloys for vibration and acid resistance
  • chill control in cast iron, carbide stabiliser in malleable iron
  metallurgy about 15 percent in 2024 (usgs-mcs2025-tellurium)
• Chemicals (rubber, catalysts, glass)
  • vulcanising agent and accelerator in rubber processing
  • catalyst component for synthetic fibre production and oil refining
  • colouring agent in glass and ceramics
  other applications about 5 percent in 2024 (usgs-mcs2025-tellurium)
• Mining: tellurium follows copper concentrates to the refinery; supply is tied to copper output

Safety, toxicity

Tellurium and its compounds are probably toxic and should be handled with care. Workmen exposed to as little as 0.01 mg/m3 of air, or less, develop "tellurium breath," which has a garlic-like odor.

GHS classification, signal word Danger

• H360Df May damage the unborn child; Suspected of damaging fertility Reproductive toxicity
• H362 May cause harm to breast-fed children toxicity, effects on or via lactation
• H301 Toxic if swallowed Acute toxicity, oral
• H317 May cause an allergic skin reaction Sensitization, Skin
• H319 Causes serious eye irritation Serious eye damage/eye irritation
• H332 Harmful if inhaled Acute toxicity, inhalation
• H335 May cause respiratory irritation Specific target organ toxicity, single exposure; Respiratory tract irritation
• H360 May damage fertility or the unborn child Reproductive toxicity
• H413 May cause long lasting harmful effects to aquatic life to the aquatic environment, long-term hazard
• H336 May cause drowsiness or dizziness Specific target organ toxicity, single exposure; Narcotic effects
• H315 Causes skin irritation Skin corrosion/irritation
• H361 Suspected of damaging fertility or the unborn child Reproductive toxicity
• H371 May cause damage to organs Specific target organ toxicity, single exposure

Discovery and name

Discovered by

Franz-Joseph Müller von Reichenstein

Discovered

1782

First isolated

Martin Heinrich Klaproth

Named by

not in sources

Origin of the name

after Roman Tellus]], deity of the Earth

Crystalline tellurium has a silvery-white appearance, and when pure it exhibits a metallic luster. It is brittle and easily pulverized. Amorphous tellurium is found by precipitating tellurium from a solution of telluric or tellurous acid. Whether this form is truly amorphous, or made of minute crystals, is open to question. Tellurium is a p-type semiconductor, and shows greater conductivity in certain directions, depending on alignment of the atoms.

Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. In air, tellurium burns with a greenish-blue flames, forming the dioxide. Molten tellurium corrodes iron, copper, and stainless steel.