Sulfite sulfate explained

A sulfite sulfate is a chemical compound that contains both sulfite and sulfate anions [SO₃]²⁻ [SO₄]²⁻. These compounds were discovered in the 1980s as calcium and rare earth element salts. Minerals in this class were later discovered. Minerals may have sulfite as an essential component, or have it substituted for another anion as in alloriite.^[1] The related ions [O₃SOSO₂]²⁻ and [(O₂SO)₂SO₂]²⁻ may be produced in a reaction between sulfur dioxide and sulfate and exist in the solid form as tetramethyl ammonium salts. They have a significant partial pressure of sulfur dioxide.^[2]

Related compounds are selenate selenites and tellurate tellurites with a varying chalcogen. They can be classed as mixed valent compounds.

Production

Europium and cerium rare earth sulfite sulfates are produced when heating the metal sulfite trihydrate in air.

Ce₂(SO₃)₃.3H₂O + O₂ → Ce₂(SO₃)₂SO₄ + 3H₂O

Ce₂(SO₃)₃.3H₂O + O₂ → Ce₂SO₃(SO₄)₂ + 3H₂O

Other rare earth sulfite sulfates can be crystallized as hydrates from a water solution.^[3] These sulfite sulfates can be made by at least three methods. One is to dissolve a rare earth oxosulfate in water and then bubble in sulfur dioxide. The second way a rare earth oxide is dissolved in a half equivalent of sulfuric acid. The third way was to bubble sulfur dioxide through a suspension of rare earth oxide in water until it dissolved, then let it sit around for a few days with limited air exposure. To make calcium sulfite sulfate, a soluble calcium salt is added to a mixed solution of sodium sulfite and sodium sulfate.^[4]

Control of pH is important when attempting to produce solid sulfite compounds. In basic conditions sulfite easily oxidises to sulfate and in acidic conditions it easily turns into sulfur dioxide.

Properties

In the sulfite sulfates, sulfur has both a +4 and a +6 oxidation state.^[5]

The crystal structure of sulfite sulfates has been difficult to study, as the crystal symmetry is low, crystals are usually microscopic as they are quite insoluble, and they are mixed with other related phases. So they have been studied via powder X-ray diffraction.

Reactions

When heated in the absence of oxygen, cerium sulfite sulfate hydrate parts with water by 400 °C. Up to 800° it loses some sulfur dioxide. From 800° to 850 °C it loses sulfur dioxide and disulfur resulting in cerium oxy disulfate, and dioxy sulfate, which loses some further sulfur dioxide as it is heated to 1000 °C. Over 1000° the remaining oxysulfates decompose to sulfur dioxide, oxygen and cerium dioxide. This reaction is studied as a way to convert sulfur dioxide into sulfur and oxygen using only heat.^{[6] [7]}

Another thermochemical reaction for cerium sulfite sulfate hydrate involves using iodine to oxidise the sulfite to sulfate, producing hydrogen iodide which can then be used to make hydrogen gas and iodine. When combined with the previous high temperature process, water can be split into oxygen and hydrogen using heat only.^{[8] [9]} This is termed the GA sulfur-iodine water splitting cycle.^[10]

Applications

Calcium sulfite sulfate hydrate is formed in flue gas scrubbers that attempt to remove sulfur dioxide from coal burning facilities. Calcium sulfite sulfate hydrate is also formed in the weathering of limestone, concrete and mortar by sulfur dioxide polluted air. These two would be classed as anthropogenic production as it was not deliberately produced or used.

List

name	formula	ratioSO3:SO4	mw	system	space group	unit cell	volume	density	optical	references
tricalcium disulfite sulfate dodecahydrate Orschallite	Ca3(SO3)2SO4•12H2O	2:1		rhombohedral	Rc	a=11.3514 c=28.412 a = 11.350 c = 28.321 Z=6	3170 3159.7	1.87	Uniaxial (+)nω = 1.4941 nɛ = 1.4960	^[11] ^[12] ^[13]
Hielscherite	Ca3Si(OH)6(SO4)(SO3)·11H2O	1:1		hexagonal	P63	a = 11.1178 c = 10.5381 Z=2	1128.06	1.82	Uniaxial (−)nω = 1.494 nε = 1.476	^[14]
pentamanganese tetrahydroxide disulfite disulfate dihydrate	Mn5(OH)4(H2O)2[SO<sub>3</sub>]2[SO<sub>4</sub>]	2:1	634.9	monoclinic	P21/m	a = 7.6117 b = 8.5326 c = 10.9273 β = 101.600° Z = 2	695.2	3.0321	pink	^[15]
	Y2(SO3)2SO4•2.5H2O	2:1
Barium sulfite sulfate3,7	Ba(SO3)0.3(SO4)0.7	2:7		orthorhombic	Pnma	a=8.766 b=5.46 c=7.126				^[16]
lanthanum disulfite sulfate tetrahydrate	La2(SO3)2SO4•4H2O	2:1
cerium disulfite sulfate	Ce2(SO3)2SO4	2:1
cerium disulfite sulfate tetrahydrate	Ce2(SO3)2SO4•4H2O	2:1
cerium sulfite disulfate	Ce2SO3(SO4)2	1:2
neodymium disulfite sulfate tetrahydrate	Nd2(SO3)2SO4•4H2O	2:1
	Nd(SO3)(HSO4)(H2O)3	1:1	374.41	triclinic	P	a=6.5904 b=6.9899 c=9.536 α=101.206 β=97.767 γ=92.823 Z=2	425.67	2.921	light violet	^[17]
	Nd(SO3)(HSO4)	1:1		triclinic	P	a=6.4152 b=6.6232 c=6.9955 α=91.726 β=92.438 γ=92.423 Z=2	296.55	3.610	light violet
ethylenediammonium bis-(neodymium sulfite sulfate hydrate)	C2H10N2[Nd(SO<sub>3</sub>)(SO<sub>4</sub>)H<sub>2</sub>O]2	1:1	738.87	monoclinic	P21/c	a=9.0880 b=6.9429 c=13.0805 β=91.55 Z=2	825.04	2.974	pink	^[18] ^[19]
	Sm2(SO3)2SO4•2.5H2O	2:1								^[20]
europium disulfite sulfate	Eu2(SO3)2SO4	2:1
europium sulfite disulfate	Eu2SO3(SO4)2	1:2
	Tb2(SO3)2SO4•2.5H2O	2:1
poly[diaqua-μ(4)-sulfato-di-μ(4)-''sulfito''-didysprosium(III)]	Dy2(SO3)2SO4•2H2O	2:1	617.21	monoclinic	C2/c	a = 11.736 b = 6.8010 c = 12.793 β = 102.686° Z=4	996.1	4.115	colourless	^[21]
	Ho2(SO3)2SO4•2.5H2O	2:1
	Er2(SO3)2SO4•2.5H2O	2:1
	Yb2(SO3)2SO4•2.5H2O	2:1
Complexes
	[OsO<sub>2</sub>(SO<sub>3</sub>)(SO<sub>4</sub>)(NH<sub>3</sub>)<sub>2</sub>]^2−	1:1								^[22]

Notes and References

1. Rastsvetaeva . R. K. . Ivanova . A. G. . Chukanov . N. V. . Verin . I. A. . Crystal structure of alloriite . Doklady Earth Sciences . July 2007 . 415 . 1 . 815–819 . 10.1134/S1028334X07050340 . 2007DokES.415..815R . 130051924 .
2. Web site: Richardson . Stephanie . Capture of Sulfur Dioxide using Sulfur Oxydianions: Synthesis and Characterization of Two Novel Compounds . 24 June 2020 . 2009.
3. Karppinen. M.. Leskelä. M.. Niinistö. L.. March 1989. Studies on lanthanoid sulfites. Part VIII. Thermogravimetric study of europium sulfite trihydrate. Journal of Thermal Analysis. en. 35. 2. 355–359. 10.1007/BF01904438. 97297578. 0368-4466.
4. Leskelä. Markku. De Matos. J.Everardo X.. Niinistö. Lauri. December 1987. Studies on lanthanoid sulfites. Part VII. Preparative and thermal study on rare earth sulfite sulfate hydrates. Inorganica Chimica Acta. en. 139. 1–2. 121–123. 10.1016/S0020-1693(00)84054-2.
5. Book: Alpers . Charles N. . Jambor . John L. . Nordstrom . D. . Sulfate Minerals: Crystallography, Geochemistry, and Environmental Significance . 2018 . Walter de Gruyter GmbH & Co KG . 978-1-5015-0866-0 . 95 . en.
6. Peterson. E. J.. Foltyn. E. M.. Onstott. E. I.. December 1983. Thermochemical splitting of sulfur dioxide with cerium(IV) oxide. Journal of the American Chemical Society. en. 105. 26. 7572–7573. 10.1021/ja00364a018. 0002-7863.
7. HAAS . N . PETERSON . E . ONSTOTT . E . Dilanthanum dioxymonosulfate as a recycle reagent and recycle substrate for the sulfur dioxide-iodine thermochemical hydrogen cycle . International Journal of Hydrogen Energy . 1990 . 15 . 6 . 397–402 . 10.1016/0360-3199(90)90196-6.
8. Onstott. E. I.. March 1991. Thermochemistry of iodine oxidation of sulfite in cerium and praseodymium oxide-sulfite-sulfate-hydrate compositions to yield hydrogen iodide by hydrolysis and disulfur by concomitant disproportionation and comparison to the behavior of lanthanum. The Journal of Physical Chemistry. en. 95. 6. 2520–2525. 10.1021/j100159a076. 0022-3654.
9. Onstott. E. 1989. Thermochemistry of iodine oxidation of sulfite in lanthanum oxide-sulfite-sulfate hydrates to yield hydrogen iodide. International Journal of Hydrogen Energy. en. 14. 2. 141–145. 10.1016/0360-3199(89)90004-9.
10. Web site: Onstott . E I . Bowman . M G . Michnovicz . M F . Hollabaugh . C M . Modification of the sulfur dioxide-iodine thermochemical hydrogen cycle with lanthanum sulfites and sulfates . 22 June 2020 . 15 July 1984.
11. Cohen. Abraham. Zangen. Mendel. 1984-07-05. STUDIES ON ALKALINE EARTH SULFITES – V. STRUCTURE AND STABILITY OF THE NEW COMPOUND Ca 3 (SO 3) 2 SO 4 ·12H 2 O AND ITS SOLID SOLUTION IN CALCIUM SULFITE TETRAHYDRATE. Chemistry Letters. en. 13. 7. 1051–1054. 10.1246/cl.1984.1051. 0366-7022. free.
12. Weidenthaler. C.. Tillmanns. E.. Hentschel. G.. 1993. Orschallite, Ca3(SO3)2 . SO4 . 12H2O, a new calcium-sulfite-sulfate-hydrate mineral. Mineralogy and Petrology. en. 48. 2–4. 167–177. 10.1007/BF01163095. 93169523. 0930-0708.
13. Zangen . Mendel . Cohen . Abraham . STUDIES ON ALKALINE EARTH SULFITES. VII. HYDROGEN BONDING AND THE LOCATION OF HYDROGEN ATOMS IN THE CRYSTAL STRUCTURE OF CaSO3·4H2O AND Ca3(SO3)2SO4 ·12H2O . Chemistry Letters . 5 June 1985 . 14 . 6 . 797–800 . 10.1246/cl.1985.797.
14. Pekov. I. V.. Chukanov. N. V.. Britvin. S. N.. Kabalov. Y. K.. Göttlicher. J.. Yapaskurt. V. O.. Zadov. A. E.. Krivovichev . S. V.. Schüller. W.. Ternes. B.. October 2012. The sulfite anion in ettringite-group minerals: a new mineral species hielscherite, Ca 3 Si(OH) 6 (SO 4)(SO 3)·11H 2 O, and the thaumasite–hielscherite solid-solution series. Mineralogical Magazine. en. 76. 5. 1133–1152 . 10.1180/minmag.2012.076.5.06. 2012MinM...76.1133P. 101147914. 0026-461X.
15. Ben Yahia. Hamdi. Shikano. Masahiro. Kobayashi . Hironori. 2013. Single crystal growth of the novel Mn₂(OH)₂SO₃, Mn₂F(OH)SO₃, and Mn₅(OH)₄(H₂O)₂[SO₃]₂[SO₄] compounds using a hydrothermal method]. Dalton Transactions. 42. 19 . 7158–66. 10.1039/c3dt50415h. 23525185 . 1477-9226.
16. Buchmeier. Willi. Engelen. Bernward. Lutz. Heinz Dieter. 1988-01-01. Kristallstruktur von Bariumsulfitsulfat, Ba(SO3)0,3(SO4)0,7 bzw. BaSO3,7. Zeitschrift für Kristallographie – Crystalline Materials. 183. 1–4. 43–50. 10.1524/zkri.1988.183.14.43. 101933384. 2196-7105.
17. Dovgan. Jakob T.. Polinski. Matthew J.. Mercado. Brandon Q.. Villa. Eric M.. 2018-09-05. pH Driven Hydrothermal Syntheses of Neodymium Sulfites and Mixed Sulfate-Sulfites. Crystal Growth & Design. en. 18. 9. 5332–5341. 10.1021/acs.cgd.8b00769. 104641887. 1528-7483.
18. Book: Rao, Chintamani Nagesa Ramachandra. Trends in Chemistry of Materials: Selected Research Papers of C.N.R. Rao. 2008. World Scientific. 978-981-283-383-9. 382–388. en.
19. Rao. K. Prabhakara. Rao. C. N. R.. April 2007. Coordination Polymers and Hybrid Networks of Different Dimensionalities Formed by Metal Sulfites. Inorganic Chemistry. en. 46. 7. 2511–2518. 10.1021/ic061988m. 17326625. 0020-1669.
20. Leskelä. Tuula. Leskelä. Markku. Niinistö. Lauri. May 1995. Thermoanalytical studies on samarium sulfite sulfate hydrate. Thermochimica Acta. en. 256. 1. 67–73. 10.1016/0040-6031(94)02170-S.
21. Zhang. Zai-Chao. Wang. Jia-Hong. Zhao. Pu-Su. 2011-05-15. Dy 2 (SO 3) 2 (SO 4)(H 2 O) 2 : the first lanthanide mixed sulfate–sulfite inorganic compound. Acta Crystallographica Section C Crystal Structure Communications. 67. 5. i27–i29. 10.1107/S0108270111009048. 21540523. 0108-2701.
22. Abisheva. Z.S.. Parshina. I.N.. Bochevskaya. E.G.. Ushanov. V.Zh.. November 1998. Chemical conversions of osmium (VI) sulfite complexes in ammonia–sulfate solutions. Hydrometallurgy. en. 50. 3. 269–278. 10.1016/S0304-386X(98)00059-0.